Hot Wire Anemometry

Overview

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI

Hot-wire anemometers have a very short time-response, which makes them ideal to measure rapidly fluctuating phenomena such as turbulent flows. The purpose of this experiment is to demonstrate the use of hot-wire anemometry.

Procedure

Measure the width of the slit, W, and record this value in table 1.
Verify that the data acquisition system follows the schematic in Figure 2.
Connect the positive port of the pressure transducer (see Figure 2 for reference) to the plenum pressure tap ().
Leave the negative port of the pressure transducer open to the atmosphere. Hence, the reading of this transducer will be directly
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Results

The experimental measurements are listed in Table 2 and shown in Figure 5. A linear regression of these data produced the following result for equation (6):

(9)

Which can be used to determine the velocity as a function of the voltage:

Application and Summary

Given that turbulence exhibits high frequency velocity fluctuations, hot-wire anemometers are suitable instruments for its characterization due to their high time-resolution. In the present experiment, we demonstrated the process of calibrating a hot-wire anemometer. To this end, we compared the voltage signal of the anemometer with known values of velocity at the vena contracta of a well-characterized jet. These measurements were used to determine the calibration constants for the linear response of the anemome

References

Chapra, S.C. and R.P. Canale. Numerical methods for engineers. Vol. 2. New York: McGraw-Hill, 1998.
King, L.V. On the convection of heat from small cylinders in a stream of fluid: determination of the convection constants of small platinum wires with applications to hot-wire anemometry. Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character 214 (1914): 373-432.
White, F. M. Fluid Mechanics, 7th ed., McGraw-Hill, 2009.
Munson, B.R., D.F. Young, T.H. Okiishi. Fundamentals of Fluid Mechanics. 5^th ed., Wiley, 2006.
Buckingham, E. Note on contraction coefficients of jets of gas. Journal of Research, 6:765-775, 1931.