visualization-of-high-speed-liquid-jet-impaction-on-a-moving-surface

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

University of British Columbia

Three dimensional large eddy simulations, microphone "pop" measurements, and high-speed videos of the airflow and lip opening associated with the syllable "pa" are presented. In the simulations, the mouth is represented by a narrow static ellipse with a back pressure dropping to 110th of its initial value within 60 ms of the release. The simulations show a jet penetration rate that falls within range of the pressure front of microphone pop. The simulations and high-speed video experiments were within 20% agreement after 40 ms, with the video experiments showing a slower penetration rate than the simulations during the first 40 ms. Kinematic measurements indicate that rapid changes in lip geometry during the first 40 ms underlie this discrepancy. These findings will be useful for microphone manufacturers, sound engineers, and researchers in speech aerodynamics modeling and articulatory speech synthesis.

Characteristics of air puffs produced in English "pa": experiments and simulations.

Health care facility ventilation design greatly affects disease transmission by aerosols. The desire to control infection in hospitals and at the same time to reduce their carbon footprint motivates the use of unconventional solutions for building design and associated control measures. This paper considers indoor sources and types of infectious aerosols, and pathogen viability and infectivity behaviors in response to environmental conditions. Aerosol dispersion, heat and mass transfer, deposition in the respiratory tract, and infection mechanisms are discussed, with an emphasis on experimental and modeling approaches. Key building design parameters are described that include types of ventilation systems (mixing, displacement, natural and hybrid), air exchange rate, temperature and relative humidity, air flow distribution structure, occupancy, engineered disinfection of air (filtration and UV radiation), and architectural programming (source and activity management) for health care facilities. The paper describes major findings and suggests future research needs in methods for ventilation design of health care facilities to prevent airborne infection risk.

Preventing airborne disease transmission: review of methods for ventilation design in health care facilities.

A 1D fluid model is implemented for the purpose of fluid-structure interaction (FSI) simulations in complex and completely collapsible geometries, particularly targeting the case of obstructive sleep apnea (OSA). The fluid mechanics are solved separately from any solid mechanics, making possible the use of a highly complex and/or black-box solver for the solid mechanics. The fluid model is temporally discretized with a second-order scheme and spatially discretized with an asymmetrical fourth-order scheme that is robust in highly uneven geometries. A completely collapsing and reopening geometry is handled smoothly using a modified area function. The numerical implementation is tested with two driven-geometry cases: (1) an inviscid analytical solution and (2) a completely closing geometry with viscous flow. Three-dimensional fluid simulations in static geometries are performed to examine the assumptions of the 1D model, and with a well-defined pressure-recovery constant the 1D model agrees well with 3D models. The model is very fast computationally, is robust, and is recommended for OSA simulations where the bulk flow pressure is primarily of interest.

Sheldon Green

Department of Mechanical Engineering

University of British Columbia

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Sheldon Green

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Mechanical Engineering

University of British Columbia

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Department of Mechanical Engineering