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Research

Pipe Flowrate Measurement: Problem Solving

A spray tank system is engineered to uniformly distribute a pest-control liquid across plants by using a pressurized mechanism. The tank, pressurized to 150 kPa, holds the pesticide at a height of 0.80 meters. Liquid flows from the tank through a 1.9 meter pipe with a diameter of 0.015 meters, angled at 0.698 radians, ultimately reaching a 0.007 meter nozzle that sprays the pesticide. Accurate calculation of the system&#39;s flow rate is crucial to ensure uniform application, and this is achieved by first determining the flow velocity within the connecting pipe.
The design requires an understanding of fluid mechanics principles. At the outset, the velocity of the fluid in the tank at Point 1 is zero, with the pressure set to 150 kPa. Point 2, located at the nozzle, is assumed to be open to the atmosphere, with a pressure of zero. The height difference between Points 1 and 2, calculated using the 0.698-radian pipe angle and pipe length, determines the elevation change component in the Bernoulli equation. This height difference is found by multiplying the pipe length by the sine of the inclination angle.
To connect the parameters at Points 1 and 2, a modified Bernoulli equation is used, accounting for energy losses due to friction and the nozzle&#39;s loss coefficient. The equation expresses the pressure, velocity, and elevation terms for both points as follows:
<img alt="Equation 1" src="/files/ftp_upload/18085/18085_PT_equation_1.svg" style="text-align: center; height: 30px;" />
Here, p represents pressure, &#961; the fluid density, V the velocity, g the gravitational acceleration, z1 the height of the pesticide inside the tank, and z2&#160; the nozzle height above the bottom of the tank. With values substituted for these terms, the flow velocity in the pipe at Point 1 is solved.
After calculating the pipe&#39;s flow velocity, the flow rate, Q, is determined by multiplying this velocity by the cross-sectional area A of the pipe:
<img alt="Equation 2" src="/files/ftp_upload/18085/18085_PT_equation_2.svg" style="text-align: center; height: 11px;" />
Where A is:
<img alt="Equation 3" src="/files/ftp_upload/18085/18085_PT_equation_3.svg" style="text-align: center; height: 25px;" />
This flow rate calculation ensures that the pesticide is delivered at a consistent and effective rate, optimizing pest control application.

Consider a spray tank system designed to evenly apply pest-control liquid to plants.
The system includes a pressurized tank at 150 kPa filled with ...

Pipe Flowrate Measurement

In pipe flow measurement, orifice, nozzle, and Venturi meters are commonly used to determine fluid flowrates by constricting the flow area, which increases fluid velocity and reduces pressure. This pressure difference, governed by Bernoulli&#39;s principle and adjusted for real-world conditions, is essential for calculating flowrate. Each meter type is suited to specific applications based on accuracy, efficiency, and compatibility with various flow conditions.
The orifice meter is a simple, cost-effective device consisting of a flat plate with a central hole that creates a measurable pressure drop. This device is popular in applications like water treatment, oil and gas processing, and general industrial use where moderate accuracy is acceptable. However, due to head loss from turbulent flow and area contraction, a discharge coefficient is used to correct the idealized flow equation. The flowrate through an orifice meter is proportional to the square root of the pressure difference, accounting for fluid density, orifice area, and the ratio of the hole diameter to the pipe diameter.
The nozzle meter improves on the orifice meter by using a contoured design that reduces flow separation and turbulence, resulting in a smoother flow and increased measurement accuracy. It is often used for high-velocity flows, such as in steam or gas pipelines, chemical processing, and power plants. With a higher discharge coefficient than the orifice meter, the nozzle meter provides improved precision with less energy loss.
The Venturi meter offers the highest accuracy among the three types. It is ideal for applications requiring minimal head loss and reliable measurements, such as water supply systems, natural gas pipelines, and wastewater management. Its smooth contraction and gradual expansion reduce flow separation, conserving energy and enabling accurate flowrate calculations even in low-pressure systems. The discharge coefficient for a Venturi meter, which depends on factors like the ratio of the throat to pipe diameter and flow characteristics, supports exact flow measurement but requires a more complex installation and is generally more costly.
Each meter type offers unique benefits, from essential flow monitoring to precise flow control, chosen based on the application&#39;s accuracy needs and specific conditions.

Flow measurement devices&#8212;such as orifice, nozzle, and Venturimeters&#8212;operate by narrowing the flow area. This increases fluid velocity and ...

Design Example: Designing a Residential Plumbing System

The design of residential plumbing systems requires carefully evaluating water demand, flow rates, and pressure dynamics to ensure both efficiency and reliability. The nature of water flow within pipes is defined by its Reynolds number, which classifies flow as either laminar (smooth) or turbulent.
<img alt="Equation 1" src="/files/ftp_upload/18086/18086_Equation_1.svg" style="text-align: center; height: 42px;" />
This dimensionless value depends on factors such as water velocity and pipe. Residential plumbing systems are designed to meet specific water demand and flow rate requirements based on occupancy and fixture needs.
Determining the nature of water flow &#8212; laminar or turbulent &#8212; requires calculating the Reynolds number, which depends on variables like pipe diameter and water velocity. In residential settings, flow is often turbulent, leading to higher energy loss due to friction, which impacts system efficiency. Energy losses, or head losses, arise as water moves through pipes. These losses are classified as either major or minor. Major losses from friction along pipe walls are calculated using the Darcy-Weisbach equation.
<img alt="Equation 2" src="/files/ftp_upload/18086/18086_Equation_2.svg" style="text-align: center; height: 42px;" />
The Darcy-Weisbach equation requires a friction factor, which is obtained from the Moody chart. This chart accounts for pipe roughness and flow characteristics, which significantly affect turbulent flow friction levels. Minor losses, in contrast, are caused by fittings, bends, and valves, each of which contributes resistance to flow. Each fitting is assigned a loss coefficient that quantifies its resistance and is factored into the total head loss.
<img alt="Equation 3" src="/files/ftp_upload/18086/18086_Equation_3.svg" style="text-align: center; height: 48px;" />
By adding major and minor losses, the overall head loss can be determined and managed so as to maintain adequate pressure, avoiding potential leaks or damage. Flow measurement devices like Venturi or orifice meters ensure the plumbing system provides the necessary flow rates. These meters measure flow rates by detecting pressure differences across constrictions in the pipe, confirming that water flow meets design specifications and household needs.

The residential plumbing system is designed by assessing the building&#39;s water demand and flow rate needs based on occupancy and fixture requirements.
...

Single Pipe Systems

In pipe flow analysis, problems are typically categorized into three types &#8212; Type I, Type II, and Type III &#8212; based on the known parameters and the desired outcome. Each type of problem addresses specific engineering requirements using fluid properties, pipe characteristics, and operational conditions.
In a Type I problem, fluid properties (density and viscosity), pipe characteristics (including diameter, length, and surface roughness), and the flow rate or average velocity are known. The objective is calculating the pressure drop or head loss needed to maintain the specified flow rate. For instance, in a heating system circulating hot water at 0.32 liters per second, knowing the system&#39;s fluid and pipe specifications allows engineers to determine the required pressure to achieve steady flow. Type I problems are common in designing HVAC systems, where maintaining consistent flow is essential for effective temperature control.
A Type II problem provides the applied pressure, fluid properties, and pipe details, to calculate the resulting flow rate. This type of analysis is used in applications such as garden irrigation, where engineers need to determine the water flow rate in a sprinkler system operating at a specified pressure, such as 276 kilopascals. Knowing the pipe dimensions and roughness, the flow rate reaching each sprinkler can be calculated to ensure adequate water distribution.
In a Type III problem, the known parameters include the pressure drop and desired flow rate, to determine the optimal pipe diameter to support efficient flow. This scenario is typical in cooling systems or industrial piping design, where engineers must size the pipe to achieve a flow rate of 0.19 liters per second, balancing efficiency with minimal energy loss. Choosing an appropriate pipe diameter in Type III problems ensures the required flow rate while minimizing pressure losses and pump energy demands.
By systematically categorizing pipe flow problems, engineers can streamline analysis and ensure optimal design and performance for fluid transport systems in heating, irrigation, and industrial applications.

In pipe flow problems, scenarios are grouped by known information and desired calculation and are typically classified as Type I, II, or III.
In a Type I ...

Minor Losses in Pipes

In pipe systems, minor losses refer to energy losses arising from components such as valves, bends, fittings, expansions, and other features that disrupt the steady flow of fluid. These disturbances cause energy dissipation through turbulence and resistance, which engineers quantify to manage system efficiency effectively.
Valves play a significant role in generating minor losses by obstructing or redirecting the fluid flow. When a valve is closed or partially closed, it restricts the flow path, creating additional resistance and inducing turbulence. The resulting energy dissipation depends on the valve&#39;s geometry, position, and flow path design. To quantify this effect, engineers use a loss coefficient, K, which scales with the square of the fluid velocity V as follows:
<img alt="Equation 1" src="/files/ftp_upload/18081/18081_Equation_1.svg" style="text-align: center; height: 30px;" />
where:
<ol style="list-style-type: circle;">
	<li>hLminor is the head loss due to the component,</li>
	<li>KL is the loss coefficient specific to the component geometry,</li>
	<li>V is the fluid velocity</li>
	<li>g is the acceleration due to gravity.</li>
</ol>
For ease of calculation, engineers often represent minor losses from fittings and valves as an equivalent length of straight pipe that would produce the same head loss.
At the entry point of a pipe, sharp edges or abrupt changes in flow area can cause the fluid to separate from the wall, creating turbulence and energy dissipation through viscous effects. This entrance loss contributes to the overall energy loss, depending on the pipe geometry and the flow velocity. When fluid exits a pipe, the kinetic energy disperses into the surrounding environment, creating an exit loss characterized by a unity loss coefficient, as all the kinetic energy is lost from the system.
Sudden expansions in the pipe create high-velocity jets that decelerate as they expand, dissipating energy through viscous effects. These expansions lead to additional energy losses as the fluid experiences abrupt pressure and velocity changes. Bends in the pipe also contribute to head loss, primarily due to flow separation and swirling motions induced by centripetal forces as the fluid changes direction. The frictional resistance over the length of the bend adds further to the overall head loss, with the degree of loss depending on the bend angle and radius.
Understanding these minor losses allows engineers to design pipe systems that manage energy dissipation effectively, optimizing flow efficiency and minimizing pressure drops across the system.

Minor losses in pipe systems arise from components like valves, bends, and fittings that disrupt fluid flow, causing energy dissipation through turbulence ...

Major Losses in Pipes

When a fluid flows through a pipe, it experiences energy losses due to frictional resistance along the pipe walls, known as major losses. These energy losses result in a pressure drop, which varies based on the flow conditions &#8212; whether laminar or turbulent &#8212; and the specific physical properties of the fluid and pipe.
Fluid flow can be classified as laminar or turbulent, primarily based on the Reynolds number. This dimensionless number reflects the relative influence of inertial to viscous forces in the fluid. In laminar flow (Re &#60; 2000), the fluid flows in parallel layers, or streamlines, with minimal cross-stream mixing. Here, the pressure drop mostly depends on the fluid&#39;s viscosity and is generally lower. In contrast, turbulent flow (Re &#62; 4000) is characterized by chaotic eddies and swirling motions. In this regime, the pressure drop is influenced not only by viscosity but also by the roughness of the pipe wall, as these irregularities disrupt the flow further, increasing energy losses.
The pressure drop in a pipe depends on several factors: fluid properties, flow velocity, pipe characteristics, and dimensionless numbers.
The Darcy-Weisbach equation is the standard approach for quantifying the pressure drop due to frictional losses in pipe flow:
<img alt="Equation 1" src="/files/ftp_upload/18080/18080_Equation_1.svg" style="text-align: center; height: 30px;" />
Where:
<ol style="list-style-type: circle;">
	<li>&#916;P is the pressure drop,</li>
	<li>f is the friction factor,</li>
	<li>L is the length of the pipe,</li>
	<li>D is the pipe diameter,</li>
	<li>&#961; is the fluid density,</li>
	<li>v is the flow velocity.</li>
</ol>
The friction factor f is crucial for calculating pressure drops, especially in turbulent flow. It depends on the Reynolds number and the relative roughness of the pipe. Engineers often refer to the Moody chart, which provides empirical values of friction factors across flow regimes and roughness levels.
The Colebrook equation
<img alt="Equation 2" src="/files/ftp_upload/18080/18080_Equation_2.svg" style="text-align: center; height: 30px;" />
Where:
<ol style="list-style-type: circle;">
	<li>f is the friction factor,</li>
	<li>&#1013;/D is the relative roughness</li>
	<li>Re is the Reynolds number.</li>
</ol>
offers a precise method to calculate f for smooth and moderately rough pipes, but it is implicit and requires iterative solutions. To avoid iteration, approximations like the Haaland equation:
<img alt="Equation 3" src="/files/ftp_upload/18080/18080_Equation_3.svg" style="text-align: center; height: 30px;" />
Where:
<ol style="list-style-type: circle;">
	<li>f is the friction factor,</li>
	<li>&#1013;/D is the relative roughness</li>
	<li>Re is the Reynolds number.</li>
</ol>
are commonly used in practice, providing reasonably accurate friction factor values without extensive calculation. Understanding these dynamics enables engineers to design pipe systems that manage flow efficiently, compensating for potential pressure losses over time as pipe roughness increases.

Consider &#160;a fluid flowing through a pipe; it encounters frictional resistance, causing energy losses known as major losses, resulting in a pressure ...

Multiple Pipe Systems

Multipipe systems consist of complex configurations of interconnected pipes designed to transport fluids efficiently across intricate networks. They are essential in engineering applications requiring precise control over flow distribution, pressure, and head loss. They are categorized into series, parallel, loop, and network configurations, each distinguished by unique flow characteristics and applications.
Series Configuration
In a series configuration, fluid flows sequentially from one pipe segment to the next, maintaining a constant flow rate throughout. This setup means each segment experiences the same flow rate, although head losses accumulate progressively across each section. The total head loss from an entry point A to an exit point B is the cumulative sum of head losses in each pipe, governed by the Darcy-Weisbach equation for head loss or similar empirical relationships. This configuration suits applications requiring a consistent flow rate along a fixed path, such as in specific water treatment processes.
Parallel Configuration
Parallel multipipe systems divide fluid flow across multiple paths, enabling a higher overall flow rate and reducing resistance across the network. Here, the total flow rate is the sum of the individual flow rates in each branch. However, a critical feature of parallel systems is that all paths experience the same pressure drop. Consequently, fluid particles in each path encounter identical head losses, regardless of the path taken. This arrangement is effective in systems needing efficient fluid distribution, such as in heating and cooling systems, where multiple paths ensure temperature control across large areas.
Loop and Network Configurations
In loop systems, the flow rate within one pipe is balanced by the combined flow rates of the other connected pipes, enabling fluid redistribution based on demand changes or localized resistance variations, such as in urban water distribution systems. Network configurations represent the most complex setup, involving numerous interconnected pipes with multiple inlets and outlets,such as in oil and gas pipeline networks. This flexibility allows for multiple flow directions, enhancing transport efficiency and adaptability to dynamic system demands.
Applications of Multipipe Systems
Multipipe systems are indispensable in several engineering sectors. Municipal water supply networks often use network configurations to ensure consistent pressure and reliable delivery across urban areas. In deepwater oil and gas pipelines, multipipe systems help manage the challenging pressures and flow conditions of underwater environments. Additionally, industrial cooling systems benefit from the controlled fluid distribution provided by parallel configurations, which improve heat dissipation and maintain optimal temperatures in manufacturing processes.

Multiple pipe systems consist of interconnected pipes that regulate fluid flow across complex networks.
They can be arranged in series, parallel, loop, or ...

Turbulent Flow

Turbulent flow is characterized by unpredictable fluctuations in velocity and pressure, which result in a chaotic fluid movement distinct from the orderly patterns of laminar flow. While laminar flow is governed by smooth, parallel layers with minimal mixing, turbulent flow exhibits highly irregular, three-dimensional patterns. This behavior arises due to instabilities in the fluid&#39;s velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent spots, appear once the flow reaches a critical speed. When the Reynolds number &#8212; a dimensionless quantity expressing the ratio of inertial to viscous forces in a fluid &#8212; exceeds a threshold of around 4,000, these spots coalesce, generating fully developed turbulence.
Structure of Turbulent Flow in Pipes
In pipe systems, turbulent flow comprises three distinct regions: the viscous sublayer, the buffer layer, and the outer layer. The viscous sublayer forms close to the pipe wall, a thin boundary where viscous forces dominate, and the flow behaves similarly to laminar flow. Here, velocity follows a near-linear profile influenced by fluid viscosity, providing a stable region within the otherwise chaotic turbulent flow.
Above the viscous sublayer lies the buffer layer, a transitional zone where viscous and turbulent forces contribute to fluid motion. This region is marked by a logarithmic velocity profile that conforms to the logarithmic law of the wall, representing a balance between viscous and turbulent interactions. Further from the wall, turbulent eddies drive fluid movement in the outer layer, promoting rapid mixing and random motion across the flow.
Engineering Applications of Turbulent Flow
The chaotic nature of turbulent flow makes it advantageous in numerous engineering applications where mixing and energy dissipation are crucial. For instance, wastewater treatment systems rely on turbulent flow to enhance the mixing of chemicals, promoting efficient contaminant removal. In hydraulic engineering, turbulent flow dissipates energy in spillways, preventing structural damage by controlling water velocity. The turbulent mixing process also reduces river sediment buildup, maintaining navigable waterways and protecting aquatic ecosystems.

Turbulent flow is a fluid movement marked by chaotic shifts in pressure and velocity.
Unlike laminar flow, turbulent flow displays complex, irregular ...

Turbulent Flow: Problem Solving

Carbonation is a process used to dissolve carbon dioxide gas in a liquid, commonly used in the production of carbonated beverages. Achieving efficient carbonation requires careful control of temperature, pressure, and flow conditions. By adjusting these parameters, carbonation efficiency can be maximized, producing a higher concentration of CO2&#160;in the liquid.
Temperature is a key factor in CO2 solubility. In this case, the CO2 gas and the liquid are cooled to 20&#176;C. Lower temperatures enhance the solubility of CO2, enabling a greater volume of gas to dissolve within the liquid. At this temperature, the CO2&#160;gas is pressurized to approximately 550 kPa. Elevated pressure increases the partial pressure of CO2&#160;over the liquid, further driving dissolution.
CO2 is pumped through a connecting pipe between two tanks, where the flow characteristics are crucial for maintaining steady carbonation. The high Reynolds number, defined as greater than 4000, indicates that the flow is turbulent rather than laminar. Turbulent flow improves gas-liquid contact by promoting mixing, which enhances CO2&#160;dissolution in the liquid. The Reynolds number (Re) is calculated using the equation:
<img alt="Equation 1" src="/files/ftp_upload/18079/18079_Equation_1.svg" style="text-align: center; height: 30px;" />
where:
<ol style="list-style-type: circle;">
	<li>&#961; is the density of CO2,</li>
	<li>v is the velocity of flow,</li>
	<li>D is the pipe diameter,</li>
	<li>&#956; is the dynamic viscosity of CO2.</li>
</ol>
The flow rate of CO2&#160;in this system is controlled by the pipe&#39;s cross-sectional area and the velocity of the gas. To maintain turbulent conditions, the flow velocity v is adjusted based on the desired Reynolds number, which allows the required pipe diameter to be calculated.
The Reynolds number equation can be rearranged to determine the pipe diameter for the required turbulent flow. The&#160;dynamic viscosity &#956; of CO2&#160;at 20&#176;C are obtained using physical property tables. The optimal pipe diameter can be calculated by substituting these values along with the target Reynolds number and flow velocity into the equation. This configuration ensures efficient CO2&#160;transport through the system, optimizing the liquid&#39;s carbonation conditions.

Consider a liquid that needs to be carbonated. Both the liquid and the carbon dioxide gas are cooled. The temperature is selected as 20 degrees Celsius to ...

General Characteristics of Pipe Flow II

When fluid enters a pipe, it first passes through the entrance region, where the velocity profile adjusts due to viscous effects. In this region, a boundary layer forms along the pipe walls and grows until it fully occupies the pipe&#39;s cross-section. Once the boundary layer merges, the flow becomes fully developed, with a steady velocity profile that remains consistent along the pipe&#39;s length.
The distance to reach a fully developed flow is called the entrance length and depends on the flow regime (laminar or turbulent) and the Reynolds number. Laminar flow typically has a shorter entrance length due to its smooth, gradual profile development, whereas turbulent flow requires a longer entrance length due to enhanced mixing and chaotic motion.
A pressure difference along the pipe&#39;s length drives fully developed flow in a constant-diameter pipe. In horizontal pipes, this pressure difference overcomes viscous forces, ensuring steady motion. The entrance region has a higher pressure gradient to account for acceleration as the velocity profile evolves. Once fully developed, the pressure gradient stabilizes, reflecting the energy needed to overcome viscosity.
Shear stress behaves differently in laminar and turbulent flows. In laminar flow, shear stress arises from molecular momentum transfer, resulting in smooth, orderly layers. Turbulent flow stems from momentum exchange between more significant, irregularly moving fluid particles, making it a macroscopic effect. These differences influence pressure distribution and flow characteristics.
For inclined pipes, gravity modifies the pressure gradient. Depending on the pipe&#39;s orientation, gravity can assist or resist flow, altering the force balance required for steady motion. The viscosity, pressure, and gravity interplay determine fluid behavior within the pipe.

As fluid enters a pipe, it first flows through an entrance region where the velocity profile adjusts, forming a boundary layer along the walls. This ...

Laminar Flow

Laminar flow represents a smooth, orderly fluid motion where particles move along parallel paths, resulting in minimal mixing between layers. Streamlined particle paths characterize this flow regime and occur under conditions where viscous forces dominate over inertial forces. The distinction between laminar, transitional, and turbulent flow is primarily determined by the Reynolds number, a dimensionless quantity calculated as:
<img alt="Equation 1" src="/files/ftp_upload/18076/18076_Equation 1.svg" style="text-align: center; height: 30px;" />
where &#961; is the fluid density, v is the flow velocity, D is the pipe diameter, and &#956; is the dynamic viscosity. A Reynolds number below approximately 2100 indicates laminar flow, while values above 4000 denote turbulent flow. Transitional flow occurs between these ranges as the fluid shifts from laminar to turbulent.
Velocity Profile and Entrance Length
In a pipe, fluid initially entering develops a velocity profile over a length known as the entrance length. During this phase, the flow transitions from a uniform profile at the inlet to a fully developed parabolic profile, where the velocity is highest at the center and gradually decreases toward the pipe walls due to viscous forces. The entrance length is a function of the Reynolds number and pipe characteristics, typically shorter in turbulent flow and longer in laminar flow. Once fully developed, the parabolic velocity profile remains stable unless disrupted by changes in pipe geometry, allowing consistent analysis of flow behavior along the pipe&#39;s length.
Energy Loss and Hagen-Poiseuille Law
Laminar flow is advantageous in minimizing energy loss, as the pressure drop along the pipe is dominated by viscous forces rather than turbulence. The relationship between pressure drop and flow rate in a fully developed laminar flow is defined by the Hagen-Poiseuille equation:
<img alt="Equation 2" src="/files/ftp_upload/18076/18076_Equation 2.svg" style="text-align: center; height: 30px;" />
where &#916;P is the pressure drop, &#956; is the dynamic viscosity, L is the pipe length, Q is the volumetric flow rate, and R is the pipe radius. This equation shows that the pressure drop in laminar flow is directly proportional to flow rate and fluid viscosity and inversely proportional to the fourth power of the pipe radius, highlighting the significant impact of pipe diameter on energy efficiency.
Applications of Laminar Flow
Laminar flow conditions are essential in applications that require smooth, predictable fluid motion with minimal mixing. Wastewater treatment systems, for example, benefit from laminar flow to avoid excessive energy loss and facilitate controlled fluid handling. In canal designs for irrigation, laminar flow promotes even distribution without turbulent disturbances, enhancing water delivery efficiency. Hydropower systems can also leverage laminar flow for more efficient energy conversion, particularly in sections where consistent, low-energy flow is needed.

Laminar flow refers to the smooth, orderly motion of fluid particles in which each particle follows parallel paths with minimal mixing between layers.
The ...

Laminar Flow: Problem Solving

Laminar flow occurs when a fluid moves smoothly in parallel layers with minimal mixing and turbulence. In fluid mechanics, ensuring laminar flow within a pipe is essential for precise control of flow characteristics, especially in engineering applications. The key factor in determining whether flow remains laminar is the Reynolds number, a dimensionless quantity that depends on the fluid&#39;s velocity, density, viscosity, and the pipe&#39;s diameter. A Reynolds number of 2100 or lower indicates laminar flow, while higher values lead to turbulence.
For air flowing through a pipe at standard atmospheric conditions and a given mass flow rate, the velocity of the fluid must be controlled to maintain laminar conditions. Since velocity depends on the flow rate and the cross-sectional area of the pipe, the pipe diameter plays a crucial role. By substituting the velocity expression into the Reynolds number formula and solving for the diameter, it is possible to determine the minimum required pipe size.
Using standard values for air density and viscosity at 300 Kelvin, the volumetric flow rate can be computed. This, in turn, allows for the calculation of the necessary pipe diameter. To ensure a Reynolds number of 2100 or lower, the minimum allowable diameter for the pipe is found to be approximately 0.46 meters. This calculation ensures that the flow remains smooth and predictable, avoiding turbulence that could disrupt performance.

Consider air flowing through the pipe at 300 Kelvin at standard atmospheric pressure, with a mass flowrate of 0.0163 kilograms per second. If the flow is ...

General Characteristics of Pipe Flow I

Pipe flow refers to the movement of fluids within fully enclosed conduits, typically cylindrical in shape, such as water pipes or hydraulic hoses. These conduits are designed to withstand high-pressure gradients that drive fluid movement, contrasting with open-channel flows, where gravity is the primary driving force. Rectangular conduits, like air conditioning and heating ducts, generally operate at lower pressures and are less suited for high-pressure applications.
The classification of fluid flow in pipes was pioneered by Osborne Reynolds through his foundational dye injection experiments. Reynolds identified three flow regimes &#8212; laminar, transitional, and turbulent &#8212; based on fluid velocity. At low velocities, the dye maintained a smooth streakline, indicating laminar flow, where fluid particles follow orderly, parallel paths. As velocity increased, the dye began to oscillate, marking the transitional regime, and at higher velocities, it dispersed unpredictably in the turbulent regime, where random, chaotic motion dominates.
These observations led to the development of the Reynolds number, a dimensionless quantity that indicates the balance of inertial and viscous forces in the flow. The Reynolds number is calculated based on fluid velocity, density, viscosity, and pipe diameter and serves as an indicator of flow type: laminar for values below 2100, turbulent for values above 4000, and transitional in the range between. In laminar flow, velocity remains steady over time, while turbulent flow exhibits unsteady, fluctuating velocities with random components perpendicular to the pipe axis. By calculating the Reynolds number, engineers can predict flow behavior in pipe systems, aiding in the design and optimization of pipelines, hydraulic systems, and fluid transport networks across various industries.

Pipe flow describes fluid movement through enclosed, fully-filled conduits, typically cylindrical pipes like water pipes or hydraulic hoses, engineered to ...

Design Example: Creating a Hydraulic Model of a Dam Spillway

Scaled hydraulic models of dam spillways provide a practical way to replicate and study the intricate flow dynamics of these structures. Often built to a 1:15 ratio, these models allow for observing critical water behavior, such as velocity distribution, flow patterns, and energy dissipation.
<img alt="Equation 1" src="/files/ftp_upload/18074/18074_Equation_1.svg" style="text-align: center; height: 38px;" />
Through this controlled setup, researchers can closely examine how water flows over the spillway, supporting a detailed analysis of its performance. A fundamental principle behind these models is using Froude number similarity, which preserves the proper balance between gravitational and inertial forces.
<img alt="Equation 2" src="/files/ftp_upload/18074/18074_Equation_2.svg" style="text-align: center; height: 38px;" />
This similarity is essential, as it ensures that free-surface flow characteristics, including wave formation, turbulence, and flow separation, behave as they would in the full-sized structure. By achieving this accurate representation, scaled models provide valuable insights into how water interacts with spillway features, helping to pinpoint areas where the design might benefit from adjustments to enhance safety or flow efficiency.
In the scaled model, adjustments are also applied to discharge rates, flow velocities, and timing to reflect real-world conditions without requiring extensive water volumes or prolonged test durations. The discharge rate, for example, is reduced by the scale factor to maintain manageable flow rates, enabling safe experimentation.
<img alt="Equation 3" src="/files/ftp_upload/18074/18074_Equation_3.svg" style="text-align: center; height: 36px;" />
Additionally, time is compressed so that events unfolding over an entire day in the full-scale structure can be examined in just a few hours within the model.
<img alt="Equation 4" src="/files/ftp_upload/18074/18074_Equation_4.svg" style="text-align: center; height: 48px;" />
This efficient scaling supports rapid testing and analysis of different flow conditions and potential structural responses. Overall, scaled modeling of spillways is crucial for assessing designs, identifying potential vulnerabilities, and confirming that the full-scale structure will perform reliably under various water flow conditions.

A hydraulic model of a dam spillway is often created by scaling down the design, typically to a 1:15 ratio, to replicate key flow characteristics such as ...

Dimensionless Groups in Fluid Mechanics

Dimensionless groups in fluid mechanics provide simplified ratios that help analyze fluid behavior without relying on specific units. The Reynolds number (Re), which represents the ratio of inertial to viscous forces, distinguishes between laminar and turbulent flows, making it essential in the design of pipelines and aerodynamic surfaces. The Froude number (Fr), the ratio of inertial to gravitational forces, is particularly useful in predicting wave formation and hydraulic jumps in open-channel flows and coastal engineering.
The Euler number (Eu) indicates the ratio of pressure forces to inertial forces and is used to calculate pressure drops in systems such as pipelines and across valves. The Cauchy number (Ca), representing the ratio of inertial to elastic forces, is critical in compressible fluid flow analysis and the study of shockwaves. The Mach number (Ma) compares the flow speed to the speed of sound, making it crucial for studies in supersonic flight and aeroelasticity.
The Strouhal number (St), which compares oscillatory frequency to inertial forces, finds applications in resonance studies, particularly vortex shedding around structures like bridge piers. Lastly, the Weber number (We), showing the ratio of inertial to surface tension forces, is vital in analyzing droplet formation, spray dynamics, inkjet printing, and fuel atomization processes. These groups enable the comparison of fluid behaviors across different scales and systems, supporting a broad range of fluid dynamics applications.

The dimensionless groups in fluid mechanics are ratios of physical quantities used to describe and analyze fluid behavior independently of units of ...

Correlation of Experimental Data

Dimensional analysis simplifies complex physical problems and guides experimental investigations, but it does not provide complete solutions. It identifies the dimensionless groups that influence a phenomenon, but experimental data is needed to establish the specific relationships and validate theoretical predictions.
For example, a spherical particle moving through a viscous fluid experiences drag. Dimensional analysis shows that the drag force depends on the particle&#39;s diameter, velocity, and the fluid&#39;s viscosity. These variables are grouped into dimensionless terms to form a relationship, but experimental data is needed to determine the exact nature of this relationship.
Researchers measure drag force while varying velocity to correlate the dimensionless groups, such as the Reynolds number. This correlation allows the relationship between drag and velocity to be expressed as a constant. Multiple tests verify this constant, confirming the dependency of drag on velocity.
If drag depends only on diameter, velocity, and viscosity, the relationship should be universal for any spherical particle in any fluid under consistent conditions. Multiple tests with different particles and fluids verify this universality, reducing the need for further experiments, as the derived constant remains valid under the specified conditions.

A key use of dimensional analysis is to efficiently manage, interpret, and correlate experimental data.
Dimensional analysis alone cannot fully solve a ...

Typical Model Studies

Fluid mechanics model studies often utilize scaled-down systems to predict fluid behavior in full-scale environments, such as river flows, dam spillways, and structures interacting with open surfaces. Maintaining Froude number similarity in river models is crucial, as it replicates surface flow features like wave patterns and velocities.
<img alt="Equation 1" src="/files/ftp_upload/18073/18073_Equation_1.svg" style="text-align: center; height: 48px;" />
Practical constraints, however, can introduce geometric distortions, impacting how accurately these models represent the real system. Adjustments, such as increased model roughness, help bridge this gap, aligning flow behaviors between the model and the actual river environment.
For hydraulic structures like spillways, the focus shifts to achieving high Reynolds numbers to maintain dynamic similarity. This approach emphasizes balancing inertial and gravitational forces to replicate the prototype&#39;s behavior closely.
<img alt="Equation 2" src="/files/ftp_upload/18073/18073_Equation_2.svg" style="text-align: center; height: 45px;" />
Larger models are generally preferred, as they capture critical force interactions more effectively in full-scale designs. Although exact similarity across all scales may not be feasible due to physical and financial limitations, these larger models still allow close approximations of essential conditions.
Verification tests and prototype comparisons are key for refining model accuracy. Adjusting variables and calibrating outcomes ensure that the model reliably mirrors actual fluid flow behaviors. This predictive capability supports planning and design adaptations, making these models indispensable tools for assessing performance before moving to full-scale implementation.

Typical model studies analyze scaled-down systems to predict fluid behavior, focusing on interactions with free surfaces and flow around immersed bodies.
...

Modeling and Similitude

Scaled modeling is a fundamental technique in engineering, enabling the study of large and complex systems by creating smaller, manageable replicas that recreate critical characteristics of the original. In hydrology and civil infrastructure, for example, scaled models of dams help analyze water flow, turbulence, and pressure. This method allows for accurate predictions of real-world behavior within a controlled environment, significantly reducing the cost and time involved in full-scale testing, which is often impractical. These models provide valuable insights into system performance under various conditions by ensuring that essential design elements match.
For the model to yield valid insights, it must maintain similitude, meaning the replica accurately reflects the prototype&#39;s behavior through geometric, kinematic, and dynamic similarity. Geometric similarity ensures the scaled model retains the same proportional dimensions as the actual structure, while kinematic similarity requires that motion characteristics match between model and prototype. Dynamic similarity further demands that forces acting within the model accurately replicate those in the real system, accounting for any scaling effects.
In fluid dynamics, the Froude number is a key dimensionless parameter that matches scaled models to their full-sized counterparts, especially for applications like ship design. The Froude number is defined as:
<img alt="Equation 1" src="/files/ftp_upload/18072/18072_Equation_1.svg" style="text-align: center; height: 60px;" />
where V represents velocity, g is the gravitational acceleration, and L is a characteristic length, often the ship&#39;s length. By equating the Froude numbers for both the model and the full-scale ships, the gravitational and inertial forces align, allowing the scaled model to accurately predict behaviors such as maneuverability, stability, and wave formation.

A scaled model of a dam is tested in a controlled environment to observe how it will manage water flow, turbulence, and pressure.
This setup predicts the ...

Determination of Pi Terms

The Buckingham Pi theorem is a valuable method in dimensional analysis, reducing complex relationships between variables into dimensionless terms. Relevant variables in analyzing the lift force on an airplane wing include lift force, air density, wing area, aircraft velocity, and air viscosity. Expressing each variable in terms of fundamental dimensions &#8212; mass, length, and time &#8212; provides a consistent foundation for constructing these dimensionless terms.
The theorem indicates that the number of Pi terms equals the total variables minus the number of fundamental dimensions. In this example, five variables and three dimensions result in two Pi terms. Air density, velocity, and wing area are selected as repeating variables, as they independently cover all dimensions. These repeating variables combine with lift force and viscosity to form dimensionless Pi terms.
<img alt="Equation 1" src="/files/ftp_upload/18069/18069_Equation_1.svg" style="text-align: center; height: 100px;" />
The first Pi term expresses the efficiency of lift generation, representing how lift depends on density, velocity, and area. The second Pi term accounts for the relative impact of viscosity, revealing how viscous forces interact with the wing in relation to inertia.
Each Pi term is verified as dimensionless, allowing complex aerodynamic behavior to be represented in simplified expressions. This approach enables the prediction and optimization of lift under various conditions, capturing the essential dynamics without needing to examine each factor individually.

To determine Pi terms using the Buckingham Pi theorem, consider the example of analyzing lift force on an airplane wing.
Relevant variables here include ...

Dimensional Analysis

Dimensional analysis is a valuable technique in fluid mechanics for simplifying complex problems by reducing them into dimensionless groups. These groups capture the essential relationships between the variables involved, allowing researchers and engineers to analyze fluid flow without dealing with each variable individually. This approach reduces the number of independent variables, allowing for easier analysis and better understanding of physical phenomena.
In fluid mechanics, dimensional analysis is used to understand the behavior of fluids in systems such as pipelines, channels, and other structures common in civil engineering. Consider the example of fluid flow through a long, smooth-walled, horizontal circular pipe, which is typical in the design of water distribution systems or sewage networks. The pressure drop per unit length along the pipe depends on variables such as pipe diameter, fluid density, fluid velocity, and viscosity. According to dimensional analysis, the pressure drop can be expressed as a function of these variables:
<img alt="Equation 1" src="/files/ftp_upload/18067/18067_Equation_1.svg" style="text-align: center; height: 12px;" />
This formulation involves five independent variables, which can complicate the analysis. To simplify this, we can use dimensional analysis to reduce the number of variables into two dimensionless groups, thus streamlining the problem. Two important dimensionless groups that emerge from this analysis are the Reynolds number, which characterizes the flow regime, and the friction factor, which correlates with the pressure drop.
<img alt="Equation 2" src="/files/ftp_upload/18067/18067_Equation_2.svg" style="text-align: center; height: 30px;" />
Engineers use the dimensionless groups to generate a universal curve that applies to any smooth-walled pipe and incompressible Newtonian fluid. This curve would allow them to predict the pressure drop for different pipe sizes and fluids without performing numerous experiments for each possible combination.
<img alt="Figure 1" src="/files/ftp_upload/18067/18067_PT_Figure.svg" style="text-align: center; height: 250px;" />
This approach minimizes the time and cost required for experimentation and allows for more straightforward design decisions. Whether designing water distribution networks or analyzing pressure losses in irrigation systems, dimensional analysis is critical for any civil engineer.

Dimensional analysis helps simplify fluid flow problems by using dimensionless groups, reducing complex variables into simpler terms that are easier to ...

The Buckingham Pi Theorem

The Buckingham Pi theorem provides a structured method to simplify fluid dynamics problems by reducing complex systems of variables to dimensionless terms.
<img alt="Equation 1" src="/files/ftp_upload/18068/18068_Equation_1.svg" style="text-align: center; height: 34px;" />
In analyzing flow through a pipe, variables that define the system include the pipe&#39;s diameter, the fluid&#39;s velocity, its density, and viscosity. These can be combined into a single dimensionless term, the Reynolds number (Re), which captures their essential relationship.
<img alt="Equation 2" src="/files/ftp_upload/18068/18068_Equation_2.svg" style="text-align: center; height: 38px;" />
The first step in applying the Buckingham Pi theorem is identifying the fundamental dimensions of each variable. In fluid mechanics, these are typically mass, length, and time. Here, the diameter represents length, velocity combines length and time, density encompasses mass and volume, and viscosity incorporates mass, length, and time.
<img alt="Equation 3" src="/files/ftp_upload/18068/18068_Equation_3.svg" style="text-align: center; height: 140px;" />
The theorem suggests that the number of independent dimensionless groups, known as Pi terms, is the difference in the number of variables k and the number of fundamental dimensions r. Only one dimensionless term is needed with four variables and three dimensions, simplifying analysis.
<img alt="Equation 4" src="/files/ftp_upload/18068/18068_Equation_4.svg" style="text-align: center; height: 32px;" />
This single term, the Reynolds number, compares inertial forces to viscous forces in the fluid. Establishing this ratio reveals whether the flow is likely to be smooth and orderly, known as laminar flow, or chaotic and irregular, known as turbulent flow. Lower values indicate laminar flow, where viscous forces dominate, and the fluid moves in parallel layers. Higher values reflect turbulent flow, where inertial forces lead to chaotic motion. The Buckingham Pi theorem&#39;s application in this context reduces complex interactions to a single term, making it easier to generalize flow behavior under varying conditions.

Consider the flow through a pipe, where key variables include the pipe&#39;s diameter D, fluid velocity V, density &#961;, and viscosity &#956;.
To ...

Navier&#8211;Stokes Equations

For incompressible Newtonian fluids, where density remains constant, stresses show a linear relationship with the deformation rate, defined by normal and shear stresses. Normal stresses depend on the pressure exerted on the fluid and the rate of deformation in specific directions, which determines how fluid flows under varying pressures. Shear stresses, on the other hand, act tangentially across fluid layers. They explain how adjacent fluid layers slide relative to one another, connecting tangential stress to velocity differences between layers. Normal and shear stresses define the internal forces within a fluid that influence its movement.
The Navier-Stokes equations are derived by incorporating these stress relationships into differential equations of motion.
<img alt="Equation 1" src="/files/ftp_upload/18062/18062_Equation_1.svg" style="text-align: center; height: 106px;" />
These equations balance inertial, pressure, and gravitational forces in a viscous fluid and are fundamental to predicting fluid behavior under various conditions. The inertia term in the Navier-Stokes equations accounts for fluid acceleration, representing the fluid&#39;s resistance to changes in velocity. This term is critical in capturing the momentum conservation of a moving fluid, as it demonstrates how fluids resist sudden shifts in speed or direction.
The pressure gradient term within the Navier-Stokes equations drives fluid movement by creating a net force from areas of high pressure to low pressure. Meanwhile, the viscous terms represent internal friction arising from molecular interactions within the fluid. Depending on the velocity gradients present, these viscous forces act to slow down the fluid movement.
Each directional Navier-Stokes equation captures internal forces like viscous stress and external forces like gravity. These equations allow for predicting fluid motion in various conditions, from simple to complex flows. For steady or laminar flow scenarios, where flow is smooth and orderly, the equations become more manageable, enabling more straightforward analysis. This simplification is useful in controlled scenarios like boundary layer flow, where flow near a surface has a structured layer, and in Couette flow, describing fluid between two parallel surfaces moving at different velocities.

In fluid motion under viscous conditions, shear stress is directly proportional to fluid deformation. In incompressible Newtonian fluids, this stress ...

Plane Potential Flows

Plane potential flows simplify fluid motion by assuming the fluid to be irrotational and incompressible. These characteristics allow these flows to be described by a velocity potential function, &#981;, representing the flow speed in a given direction, and a stream function, &#968;, that visualizes the flow path, both governed by Laplace&#39;s equation. These parameters help in estimating flow patterns, velocity distributions, and pressure fields around various hydraulic structures.
Uniform Flow
Uniform flow represents the simplest form of potential flow, with fluid moving in a straight line at a constant velocity. Streamlines are straight, parallel, and evenly spaced, clearly visualizing flow across channels or pipes with constant velocity. This flow type is essential in designing canals, pipelines and drainage systems, where the assumption of constant velocity aids in flow rate estimation and hydraulic design.
Source and Sink Flows
Source and sink flows describe radially symmetric flows originating from or converging to a point. In a source flow, fluid moves radially outward from a central point, while in a sink flow, it converges inward. These flows are modeled using a flow rate parameter to represent the strength of the source or sink. This model is widely used in groundwater hydrology, where source flows represent groundwater recharge, such as that from an injection well, and sink flows represent groundwater extraction in a pumping well.&#160; represent groundwater extraction from a pumping well., and sink flows simulate groundwater recharge .
Vortex Flow
Vortex flow involves fluid circulating a central point and appears in two forms: free and forced. In a free vortex, particles move in circular paths around a center point without external force, creating a whirlpool effect often observed in natural bodies of water. This model is used to design spillways and drainage systems that manage spiraling water flow to prevent clogging or turbulence. In a forced vortex, an external force drives the fluid&#39;s rotation, creating a scenario where the fluid rotates as a rigid body. Forced vortices are used in sedimentation tanks and certain hydraulic devices where uniform rotation aids in sediment separation and fluid mixing.
Flow Nets
In flow nets, streamlines represent the fluid flow path, while equipotential lines mark points of equal hydraulic potential. These lines intersect perpendicularly, creating a grid pattern that aids in identifying pressure distributions and potential seepage paths around structures. Flow nets are constructed to assess seepage in soil or porous media. Seepage rates are estimated by carefully analyzing the spacing and orientation of these lines and identifying potential areas of erosion or structural weakness.

Plane potential flows simplify fluid motion by assuming irrotational and incompressible flow, governed by a velocity potential function and a stream ...

Steady, Laminar Flow Between Parallel Plates

Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
Considering two horizontal plates aligned along the x-axis and spaced a distance &#39;2h&#39; apart, with the y-axis perpendicular to the plates, fluid motion is assumed to be parallel. Here, the continuity equation indicates no change in velocity along the x-axis, and the Navier-Stokes equations reduce as follows:
<img alt="Equation 1" src="/files/ftp_upload/18063/18063_Equation_1.svg" style="text-align: center; height: 30px;" />
The equations in the y and z directions show no pressure gradient along these axes, indicating that pressure varies hydrostatically in the y-direction, allowing integration to yield:
<img alt="Equation 2" src="/files/ftp_upload/18063/18063_Equation_2.svg" style="text-align: center; height: 12px;" />
For parallel plates with a pressure gradient along the x-axis, the equation simplifies:
<img alt="Equation 3" src="/files/ftp_upload/18063/18063_Equation_3.svg" style="text-align: center; height: 30px;" />
By integrating twice and applying boundary conditions (u = 0 at y = +h and y = -h), we obtain:
<img alt="Equation 4" src="/files/ftp_upload/18063/18063_Equation_4.svg" style="text-align: center; height: 30px;" />
This expression reveals that the velocity profile across the gap between the plates is parabolic, with maximum velocity at y = 0, midway between the plates. The volumetric flow rate through a unit width of the plates is obtained by integrating the velocity profile across the gap.
Understanding laminar flow between parallel plates has practical applications in groundwater flow, wastewater treatment, and lubrication. For instance, this model can approximate flow in soil layers, where water moves between soil particles like flow between plates. Knowing the flow rate and velocity distribution helps engineers design efficient drainage systems and predict groundwater movement.

Steady, laminar flow between two parallel plates describes fluid movement in a narrow, confined channel, often used to model simple fluid systems.
For ...

Cranial Nerves Exam I (I-VI)

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
During each section of the neurological testing, the examiner uses the powers of observation to assess the patient. In some cases, cranial nerve dysfunction is readily apparent: a patient might mention a characteristic chief complaint (such as loss of smell or diplopia), or a visually evident physical sign of cranial nerve involvement, such as in facial nerve palsy. However, in many cases a patient&#39;s history doesn&#39;t directly suggest cranial nerve pathologies, as some of them (such as sixth nerve palsy) may have subtle manifestations and can only be uncovered by a careful neurological exam. Importantly, a variety of pathological conditions that are associated with alterations in mental status (such as some neurodegenerative disorders or brain lesions) can also cause cranial nerve dysfunction; therefore, any abnormal findings during a mental status exam should prompt a careful and complete neurological exam.
The cranial nerve examination is applied neuroanatomy. The cranial nerves are symmetrical; therefore, while performing the examination, the examiner should compare each side to the other. A physician should approach the examination in a systematic fashion and go through the cranial nerves in their numerical order.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>I</td>
			<td>Olfactory</td>
			<td>Smell</td>
		</tr>
		<tr>
			<td>II</td>
			<td>Optic</td>
			<td>Visual acuity, afferent pupillary response</td>
		</tr>
		<tr>
			<td>III</td>
			<td>Oculomotor</td>
			<td>Horizontal eye movements (adduction), efferent pupillary response</td>
		</tr>
		<tr>
			<td>IV &#160;</td>
			<td>Trochlear</td>
			<td>Downward vertical eye movement, internal rotation of eye</td>
		</tr>
		<tr>
			<td>V &#160;&#160;</td>
			<td>Trigeminal&#160;&#160;&#160;</td>
			<td>Facial sensation, jaw movement</td>
		</tr>
		<tr>
			<td>VI &#160;</td>
			<td>Abducens</td>
			<td>Horizontal eye movement (abduction)</td>
		</tr>
		<tr>
			<td>VII</td>
			<td>Facial</td>
			<td>Facial movement and strength, taste, dampening of loud sounds, sensation; anterior wall of external ear canal</td>
		</tr>
		<tr>
			<td>VIII</td>
			<td>Acoustic</td>
			<td>Hearing, vestibular functioning</td>
		</tr>
		<tr>
			<td>IX</td>
			<td>Glossopharyngeal</td>
			<td>Movement of pharynx, sensation of pharynx, posterior tongue (including taste of posterior tongue), and most of ear canal</td>
		</tr>
		<tr>
			<td>X</td>
			<td>Vagal</td>
			<td>Movement and sensation of palate, pharynx, gag reflex, guttural sounds&#160;</td>
		</tr>
		<tr>
			<td>XI</td>
			<td>Spinal accessory</td>
			<td>Strength of sternocleidomastoids and trapezius muscles</td>
		</tr>
		<tr>
			<td>XII</td>
			<td>Hypoglossal</td>
			<td>Tongue protrusion and lateral movements</td>
		</tr>
	</tbody>
</table>
Table 1. The 12 Cranial Nerves and Their Basic Functions
Cranial nerve I (the olfactory nerve) is a purely sensory nerve that conveys the sense of smell, and is not routinely tested during most examinations. Cranial nerve II (the optic nerve) is the only cranial nerve that can be directly visualized as it exits from the central nervous system. Its axons convey visual information and compose the afferent limb of the pupillary reflex. Testing of the pupillary responses also assesses the function of cranial nerve III (the oculomotor nerve), parasympathetic fibers of which form the efferent limb of the pupillary reflex. Cranial nerve exam includes assessment of the extraocular movements, which are controlled by cranial nerves III, IV and VI. Cranial nerve III innervates the superior, medial, and inferior rectus muscles, as well as the inferior oblique muscle, which together function to move eyes medially and in the vertical plane. Cranial nerve IV (the trochlear nerve_ innervates the superior oblique muscles, which moves the eye downward and outward. Cranial nerve VI (the abducens nerve) innervates the lateral rectus muscles, which abducts the eyes. The function of the medial and lateral rectus muscles is straightforward: Lateral rectus is involved in abduction, meaning lateral movement along the horizontal plane. Medial rectus adducts moving the eye medially movement along the horizontal plane. The remaining muscles each causes movement in more than one direction and some combination of elevation/depression, abduction/adduction, intorsion/extorsion.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Muscle</td>
			<td>Innervation</td>
			<td>Primary action</td>
			<td>Secondary action</td>
			<td>Tertiary action</td>
		</tr>
		<tr>
			<td>Medial rectus</td>
			<td>CN III</td>
			<td>Adduction</td>
			<td>--</td>
			<td>--</td>
		</tr>
		<tr>
			<td>Superior rectus</td>
			<td>CN III</td>
			<td>Elevation</td>
			<td>Intortion</td>
			<td>Adduction</td>
		</tr>
		<tr>
			<td>Inferior rectus</td>
			<td>CN III</td>
			<td>Depression</td>
			<td>Extortion</td>
			<td>Adduction</td>
		</tr>
		<tr>
			<td>Inferior oblique</td>
			<td>CN III</td>
			<td>Extorsion</td>
			<td>Elevation</td>
			<td>Abduction</td>
		</tr>
		<tr>
			<td>Superior oblique</td>
			<td>CN IV</td>
			<td>Intorsion</td>
			<td>Depression</td>
			<td>Abduction</td>
		</tr>
		<tr>
			<td>Lateral rectus</td>
			<td>CN VI</td>
			<td>Abduction</td>
			<td>--</td>
			<td>--</td>
		</tr>
	</tbody>
</table>
Table 2. The function of the six extraocular muscles.
This first part of the cranial nerve exam concludes by testing cranial nerve V (the trigeminal nerve). This nerve has both motor and sensory components. It controls facial sensation, masticatory movements and forms the afferent limb of the corneal reflex. There are 3 major sensory branches of the trigeminal nerve - the ophthalmic, maxillary, and mandibular (also labeled V1, V2, and V3, respectively).

Anatomy and Physiology of the Cranial Nerves I -VI

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
During ...

Cranial Nerves Exam II (VII-XII)

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
The cranial nerve examination follows the mental status evaluation in a neurological exam. However, the examination begins with observations made upon greeting the patient. For example, weakness of the facial muscles (which are innervated by cranial nerve VII) can be readily apparent during the first encounter with the patient. Cranial nerve VII (the facial nerve) also has sensory branches, which innervate the taste buds on the anterior two-thirds of the tongue and the medial aspect of the external auditory canal. Therefore, finding ipsilateral taste dysfunction in a patient with facial weakness confirms the involvement of cranial nerve VII. In addition, knowledge of the neuroanatomy helps the clinician to localize the level of the lesion: unilateral weakness of the lower facial muscles suggests a supranuclear lesion on the opposite side, while lesions involving the nuclear or infranuclear portion of the facial nerve manifest with an ipsilateral paralysis of all the facial muscles on the involved side. Cranial nerve VIII (the acoustic nerve) has two divisions: the hearing (cochlear) division and the vestibular division, which innervates the semicircular canals and plays an important role in maintaining balance. During a routine neurological examination, special testing of the vestibular nerve is usually not performed.
Cranial nerve IX (the glossopharyngeal nerve) and cranial nerve X (thevagus nerve) arise from the medulla and have laryngeal and pharyngeal function; their function is tested by assessing speech and motility of the soft palate.Because cranial nerves IX and Xform the sensory and motor limbs of the gag reflex, eliciting for gag reflex can also test their function. Cranial nerve XI (the spinal accessory nerve) innervates the sternocleidomastoid muscle and the upper portion of the trapezius muscle. These muscles control side-to-side turning the head and shrugging of the shoulders. The cranial nerve exam concludes by testing cranial nerve XII (the hypoglossal nerve), which provides motor control of the muscles of the tongue.
During the neurological assessment, the clinician should always be trying to tie together the findings of the exam to get insight into the underlying disease. The important diagnostic clues might include signs of multiple cranial nerve involvement and unilateral vs. bilateral cranial nerve dysfunction. It will help the clinician formulate differential diagnoses to know whether the patient&#39;s symptoms occurred suddenly (as expected with a stroke), over about a day (as in Bell&#39;s palsy), or gradually over weeks to months (as with an expanding mass lesion).
Evaluation of cranial nerves I-VI is covered in another video of this collection. This video demonstrates the systematic examination of cranial nerves VII-XII (Table 1).
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>I</td>
			<td>Olfactory</td>
			<td>Smell</td>
		</tr>
		<tr>
			<td>II</td>
			<td>Optic</td>
			<td>Visual acuity, afferent pupillary response</td>
		</tr>
		<tr>
			<td>III</td>
			<td>Oculomotor</td>
			<td>Horizontal eye movements (adduction), efferent pupillary response</td>
		</tr>
		<tr>
			<td>IV &#160;</td>
			<td>Trochlear</td>
			<td>Downward vertical eye movement, internal rotation of eye</td>
		</tr>
		<tr>
			<td>V &#160;&#160;</td>
			<td>Trigeminal&#160;&#160;&#160;</td>
			<td>Facial sensation, jaw movement</td>
		</tr>
		<tr>
			<td>VI &#160;</td>
			<td>Abducens</td>
			<td>Horizontal eye movement (abduction)</td>
		</tr>
		<tr>
			<td>VII</td>
			<td>Facial</td>
			<td>Facial movement and strength, taste, dampening of loud sounds, sensation; anterior wall of external ear canal</td>
		</tr>
		<tr>
			<td>VIII</td>
			<td>Acoustic</td>
			<td>Hearing, vestibular functioning</td>
		</tr>
		<tr>
			<td>IX</td>
			<td>Glossopharyngeal</td>
			<td>Movement of pharynx, sensation of pharynx, posterior tongue (including taste of posterior tongue), and most of ear canal</td>
		</tr>
		<tr>
			<td>X</td>
			<td>Vagal</td>
			<td>Movement and sensation of palate, pharynx, gag reflex, guttural sounds&#160;</td>
		</tr>
		<tr>
			<td>XI</td>
			<td>Spinal accessory</td>
			<td>Strength of sternocleidomastoid and trapezius muscles</td>
		</tr>
		<tr>
			<td>XII</td>
			<td>Hypoglossal</td>
			<td>Tongue protrusion and lateral movements</td>
		</tr>
	</tbody>
</table>
Table 1. The 12 cranial nerves and their basic functions

Anatomy and Physiology of the Cranial Nerves VII -XII

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
The ...

Motor Exam I

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
Abnormalities in the motor function are associated with a wide range of diseases, from movement disorders and myopathies to strokes. The motor assessment starts with observation of the patient. When the patient enters the examination area, the clinician observes the patient&#39;s ability to walk unassisted and the speed and coordination while moving. Taking the patient&#39;s history provides an additional opportunity to observe for evidence of tremors or other abnormal movements, such as chorea or tardive dyskinesia. Such simple but important observations can yield valuable clues to the diagnosis and help to focus the rest of the examination. The motor assessment continues in a systematic fashion, including inspection for muscle atrophy and abnormal movements, assessment of muscle tone, muscle strength testing, and finally the examination of the muscle reflexes and coordination. The careful systematic testing of the motor system and the integration of all the findings provide insight to the level at which the motor pathway is affected, and also help the clinician to formulate the differential diagnosis and determine the course of the subsequent evaluation and treatment.

Motor Exam I: Evaluation of Muscle Tone and Strength

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
...

Motor Exam II

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
There are two main types of reflexes that are tested on a neurological examination: stretch (or deep tendon reflexes) and superficial reflexes. A deep tendon reflex (DTR) results from the stimulation of a stretch-sensitive afferent from a neuromuscular spindle, which, via a single synapse, stimulates a motor nerve leading to a muscle contraction. DTRs are increased in chronic upper motor neuron lesions (lesions of the pyramidal tract) and decreased in lower motor neuron lesions and nerve and muscle disorders. There is a wide variation of responses and reflexes graded from 0 to 4+ (Table 1).
DTRs are commonly tested to help localize neurologic disorders. A common method of recording findings during the DTR examination is using a stick figure diagram. The DTR test can help distinguish upper and lower motor neuron problems, and can assist in localizing nerve root compression as well. Although the DTR of nearly any skeletal muscle could be tested, the reflexes that are routinely tested are: brachioradialis, biceps, triceps, patellar, and Achilles (Table 2).
Superficial reflexes are segmental reflex responses that result from stimulation of a specific sensory input (cutaneous or conjunctival) and the corresponding motor response. These reflexes include the corneal, conjunctival, abdominal, cremasteric, anal wink and plantar (Babinski) reflexes. The plantar reflex is a polysynaptic reflex elicited by stroking the lateral aspect of the sole with the normal response being plantar flexion of the great toe. This reflex changes with the normal development of the nervous system. In infants the toe will dorsiflex, but by 2 years of age the toe responds by plantar flexing. With damage to the pyramidal system, there is an unmasking of the more primitive reflex and the toe becomes &#34;upgoing&#34; or a positive Babinski sign.
The evaluations of coordination and gait are performed as a part of the neurological motor examination and can help a clinician localize lesions or recognize movement disorders. The coordination of movements and gait has complex multi-level regulation and requires an integrated function of different components of the nervous system. This part of the neurological examination allows the examiner to assess the function of the cerebellum, the cerebellar connections, and other tracts including brainstem structures. Coordination is assessed by looking for smooth and accurate movement, and requires the integration of sensory feedback with motor output, most of which occurs in the cerebellum. An impaired ability to coordinate the rate, range, timing, direction, or force of voluntary movement is called ataxia. Testing coordination includes evaluation of rapid alternating movements and point-to-point coordination, both of which can be altered as a result of cerebellar dysfunction. As in other parts of the examination, observation is the first step in the evaluation of the patient. A careful observation of a patient&#39;s gait can help the clinician screen for problems including weakness, movement disorders, spasticity, and cerebellar disease. No neurologic examination is complete without the assessment of gait. Occasionally, the only sign of a serious neurologic disorder is an impaired gait.

Motor Exam II: Reflex, Coordination, Gait and Station Testing

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
There ...

Sensory Exam

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
A complete sensory examination consists of testing primary sensory modalities as well as cortical sensory function. Primary sensory modalities include pain, temperature, light touch, vibration, and joint position sense. Sensation of the face is discussed in the videos Cranial Nerves Exam I and II, as are the special senses of smell, vision, taste, and hearing. The spinothalamic tract mediates pain and temperature information from skin to thalamus. The spinothalamic fibers decussate (cross over) 1-2 spinal nerve segments above the point of entry, then travel up to the brainstem until they synapse on various nuclei in thalamus. From the thalamus, information is then relayed to the cortical areas such as the postcentral gyrus (also known as the primary somatosensory cortex). Afferent fibers transmitting vibration and proprioception travel up to medulla in the ipsilateral posterior columns as fasciculus gracilis and fasciculus cuneatus, which carry information from the lower limbs and upper limbs, respectively. Subsequently, the afferent projections cross over and ascend to the thalamus, and from there to the primary somatosensory cortex.
The pattern of a sensory loss can help to localize the lesion and determine the diagnosis. For example, testing the primary modalities allows the examiner to distinguish between a length-dependent peripheral neuropathy (e.g., in diabetic patients), a radiculopathy from a possible cervical or lumbar herniated disc, or a dermatomal sensory level (e.g., in a spinal cord lesion).
In order to localize the sensory deficit, knowledge of neuroanatomy and the peripheral nervous system is crucial. When seeing a patient with a peripheral sensory deficit, it can be helpful to think about what nerve root(s) may be involved. A spinal nerve root arises from every spinal segment and consists of both a sensory dorsal root and a motor ventral root, which provide innervation to a specific dermatome and myotome, respectively. There are 31 paired spinal nerve roots: eight cervical, 12 thoracic, five lumbar, five sacral, and one coccygeal.
For example, the C5 through T1 roots form a network called the brachial plexus that controls movement and sensation in the upper limbs, including the shoulder, arm, forearm, and hand. The brachial plexus gives rise to the radial, median, and ulnar nerves. The median nerve carries sensation from all fingers except the fifth finger and half of the fourth, which are carried by the ulnar nerve. These nerve territories extend proximally on the palmar side of the hand. The ulnar and radial nerves carry sensory information from the dorsal side of the hands.
In the lower extremities, T12-L4 form the lumbar plexus, and L4-S4 form the sacral plexus. These plexi give rise to peripheral nerves. A few of these peripheral nerves are the femoral, obturator, and sciatic nerves (motor and sensory) and the lateral femoral cutaneous nerve (sensory only). The sciatic nerve gives rise to the tibial and common peroneal nerves. Use of a dermatomal and peripheral nerve map can be helpful in localizing sensory dysfunction in both the upper and lower extremities.
If primary sensory modalities are normal, cortical sensation (or higher order aspects of sensation) can be tested as well. Cortical sensation is tested when there is reason to suspect a disorder of the brain. Cortical sensory testing can assist with localization of nervous system disorders. The cortical sensory examination includes tests for tactile localization (extinction), stereognosis, graphesthesia, two-point discrimination, and point localization. Cortical sensory testing is not routinely done during a screening neurological examination.

Sensory Exam: Pathways and Peripheral Nerve Distribution

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women&#39;s/Massachusetts General Hospital, Boston, Massachusetts, USA
A ...

Neck Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
Examination of the neck can be a challenge because of the many bones, joints, and ligaments that make up the underlying cervical spine. The cervical spine is composed of seven vertebrae stacked in gentle C-shaped curve. The anterior part of each vertebra is made up of the thick bony body, which is linked to the body above and below by intervertebral discs. These discs help provide stability and shock absorption to the cervical spine. The posterior elements of the vertebra, which include the laminae, transverse, and spinous processes and the facet joints, form a protective canal for the cervical spinal cord and its nerve roots.
The cervical spine supports the head and protects the neural elements as they come from the brain and from the spinal cord. Therefore, injuries or disorders affecting the neck can also affect the underlying spinal cord and have potentially catastrophic consequences. The significant motion that occurs in the neck places the cervical spine at increased risk for injury and degenerative changes. The cervical spine is also a common source of radicular pain in the shoulder. For this reason, the neck should be evaluated as a routine part of every shoulder exam.

Neck: Palpation, Motion, Strength, Impingement, Neurologic Test

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
Examination of the neck can be a challenge because of the many bones, joints, ...

Shoulder Exam I

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
Examination of the shoulder can be complex, because it actually consists of four separate joints: are the glenohumeral (GH) joint, the acromioclavicular (AC) joint, the sternoclavicular joint, and the scapulothoracic joint. The GH joint is primarily responsible for shoulder motion and is the most mobile joint in the body. It has been likened to a golf ball sitting on a tee and is prone to instability. It is held in place by the four rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis), along with the GH ligaments.
The shoulder exam begins with the inspection and palpation of the key anatomic landmarks, followed by an assessment of the patient's range of motion. The opposite shoulder should be used as the standard to evaluate the injured shoulder, provided it has not been previously injured.

Shoulder Exam I: Palpation and Range of Motion

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
Examination of the shoulder can be complex, because it actually consists of four ...

Shoulder Exam II

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The shoulder exam continues by checking the strength of the rotator cuff muscles and biceps tendons. The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) act as compressors, holding the humeral head in place against the glenoid. Injury and degeneration of the rotator cuff tendons are the most common sources of shoulder pain. 
The strength testing of the rotator muscle is performed by testing motions against resistance applied by the examiner. Pain with these resisted motions suggests tendonitis; weakness suggests a rotator cuff tear. The strength tested is followed by tests for impingement syndrome, shoulder instability, and labrum injury. It is important to test both of the shoulders and compare between the sides. The opposite shoulder should be used as the standard to evaluate the injured shoulder, provided it has not been injured as well.

Shoulder Exam II: Muscle Strength, Impingement and Instability

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The shoulder exam continues by checking the strength of the rotator cuff muscles ...

Elbow Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The elbow is a hinged joint that involves the articulation of 3 bones: the humerus, radius, and ulna. It is a much more stable joint than the shoulder, and because of that, the elbow has less range of motion. The elbow and its structures are prone to significant injuries, particularly with repetitive motion. Lateral and medial epicondylitis (also called tennis elbow and golfer&#39;s elbow) are two common diagnoses and often occur as a result of occupational activities.
When examining the elbow, it is important to remove enough clothing so that the entire shoulder and elbow can be inspected. It is important to compare the injured elbow to the uninvolved side. A systematic evaluation of the elbow includes inspection, palpation, range of motion (ROM) testing, and special tests, including maneuvers to evaluate ligamentous stability and stretch tests to accentuate pain caused by epicondylitis.

Elbow Exam: Palpation, Stretch and Collateral Ligament Testing

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The elbow is a hinged joint that involves the articulation of 3 bones: the ...

Wrist and Hand Examination

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The wrist is a complex joint made up of 8 carpal bones and their numerous articulations and ligaments. Overlying the wrist are the tendons and muscles of the hand and fingers. The hand is made up of 5 metacarpal bones, and the tendons that run to the hand overlie these bones. Finally, the fingers consist of 14 phalanges with their articulations held together by collateral ligaments and volar plates. Common mechanisms of both acute and chronic wrist injury include impact, weight bearing (which can occur in gymnastics), twisting, and throwing. Osteoarthritis of the hand commonly affects distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints, while rheumatoid arthritis (RA) is seen in the metacarpophalangeal (MCP) and PIP joints.
It is important to compare the injured wrist or hand to the uninvolved side. Key aspects of the wrist and hand exam include inspection, palpation for tenderness or deformity, testing the range of motion (ROM) and strength, neurovascular assessment, ligaments and tendon testing, and the special tests.

Wrist and Hand: Motor, Sensory, Ligament and Tendon Testing

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The wrist is a complex joint made up of 8 carpal bones and their numerous ...

Lower Back Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The back is the most common source of pain in the body. Examination of the back can be a challenge due to its numerous structures, including the bones, discs, ligaments, nerves, and muscles-all of which can generate pain. Sometimes, the location of the pain can be suggestive of etiology. The essential components of the lower back exam include inspection and palpation for signs of deformity and inflammation, evaluation of the range of motion (ROM) of the back, testing the strength of the muscles innervated by the nerves exiting in the lumbar-sacral spine, neurological evaluation, and special tests (including the Stork test and Patrick&#39;s test).

Lower Back Exam: Stork Test and Patrick&#039;s FABER Test

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The back is the most common source of pain in the body. Examination of the back ...

Hip Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The hip is a ball-and-socket joint that consists of the femoral head articulating with the acetabulum. When combined with the hip ligaments, the hip makes for a very strong and stable joint. But, despite this stability, the hip has considerable motion and is prone to degeneration with wear and tear over time and after injury. Hip pain can affect patients of all ages and can be associated with various intra- and extra-articular pathologies. Anatomic location of pain in the hip region can often provide initial diagnostic clues. Essential aspects of the hip exam include an inspection for asymmetry, swelling, and gait abnormalities; palpation for areas of tenderness; range of motion and strength testing; a neurological (sensory) exam; and additional special diagnostic maneuvers to narrow down the differential diagnosis.

Hip Exam: Trendelenburg, Hop, Leg Roll, Ober and FABER Tests

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The hip is a ball-and-socket joint that consists of the femoral head ...

Knee Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The knee is a hinged joint that connects the femur with the tibia. It is the largest joint in the body, and due to its location in the middle of the lower leg, it is subjected to a variety of traumatic and degenerative forces. Examination of the knee can be quite complex, owing to the fact it is an inherently unstable joint held together by various ligaments and supported by menisci, which act as shock absorbers and increase the contact area of the joint. In addition, the patella lies in front of the knee, acting as a fulcrum to allow the forceful extension of the knee needed for running and kicking. As the largest sesamoid bone in the body, the knee is a common source of pain related to trauma or overuse.
When examining the knee, it is important to remove enough clothing so that the entire thigh, knee, and lower leg are exposed. The exam begins with inspection and palpation of key anatomic landmarks, followed by an assessment of the patient's range of motion (ROM). The knee exam continues with tests for ligament or meniscus injury and special testing for patellofemoral dysfunction and dislocation of the patella. The opposite knee should be used as the standard to evaluate the injured knee, provided it has not been previously injured.

Knee Exam: Ligament, Meniscal and Patella Tests

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The knee is a hinged joint that connects the femur with the tibia. It is the ...

Ankle Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The ankle and foot provide the foundation for the body and the stability needed for upright posture and ambulation. Because of its weight-bearing function, the ankle joint is a common site of injury among athletes and in the general population. Ankle injuries occur as a result of both acute trauma and repetitive overuse (such as running). The ankle is a fairly simple joint, consisting of the articulation between the distal tibia and talus of the foot, along with the fibula on the lateral side. The ankle is supported by numerous ligaments, most notably the deltoid ligament on the medial side, and laterally by three lateral ligaments: the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). 
Physical examination of the ankle and the patient history (including the mechanism of the injury and the location of pain) provide diagnostic information that helps the physician to pinpoint specific structures involved in an injury, and are essential for determining the severity of the injury and the subsequent diagnostic steps. When examining the ankle, it is important to closely compare the injured ankle to the uninvolved side. Essential components of the ankle exam include inspection, palpation, range of motion (ROM), and strength. In addition, special tests can assess the integrity of ligaments.

Ankle Exam: Talar tilt, Anterior drawer, Squeeze, Thompson Tests

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The ankle and foot provide the foundation for the body and the stability needed ...

Foot Exam

Source: <a href="https://www.jove.com/author/Robert+E._Sallis">Robert E. Sallis</a>, MD. Kaiser Permanente, Fontana, California, USA
The foot is a complex structure composed of numerous bones and articulations. It provides flexibility, is the essential contact point needed for ambulation, and is uniquely suited to absorb shock. Because the foot must support the weight of the entire body, it is prone to injury and pain. When examining the foot, it is important to remove shoes and socks on both sides, so that the entire foot can be inspected and compared. It is important to closely compare the injured or painful foot to the uninvolved side. The essential parts of the evaluation of the foot include inspection, palpation (which should include vascular assessment), testing of the range of motion (ROM) and strength, and the neurological evaluation.

Foot Exam: Range of Motion, Strength and Sensory Exam

Source: Robert E. Sallis, MD. Kaiser Permanente, Fontana, California, USA
The foot is a complex structure composed of numerous bones and articulations. It ...

Science Education (Clinical Skills)

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