A Novel Approach for Measurement of Peak Expiratory Velocity

It is well known that behind the orifice in a pipe, flow velocity increases and pressure decreases simultaneously. The generated sound appears that is caused by the pressure fluctuations that occur as the flow passes through the orifice. Then the flow velocity is averaged over a pipe cross-section a...

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Bibliographic Details
Published in:Journal of Applied Fluid Mechanics 2017-01, Vol.10 (1), p.379-387
Main Authors: Wu, Chung-Ching, Yu, Fan-Ming
Format: Article
Language:English
Subjects:
Compressibility
Compressibility effects
Correlation analysis
Flow velocity
Fluctuation
Inlet temperature
Mach number
Measuring instruments
Microphones
Orifice meters
Orifices
Peak expiratory velocity
Wall-pressure spectra
pipe flow
PSD
Pipe
Pipes
Power spectral density
Pressure
Regression analysis
Sound
Sound pressure
Spectra
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Summary:It is well known that behind the orifice in a pipe, flow velocity increases and pressure decreases simultaneously. The generated sound appears that is caused by the pressure fluctuations that occur as the flow passes through the orifice. Then the flow velocity is averaged over a pipe cross-section and is considered as a constant, it can be seen that the amplitude of sound increases with increases in the expiratory velocity. An experimental study of the quantitative analysis of sound pressure level correlated with expiratory velocity in a pipe was conducted using an apparatus that includes an air pump in conjunction with a pipe, a microphone, and an orifice plate, among other instruments. The regression and analysis of the results shows that the pressure fluctuation of sound spectra can be correlated to the expiratory velocity of a pipe. The experiment is conducted under conditions where the air passing through the orifice has an averaged expiratory velocity ranging from 0.88 m/sec to 1.35 m/sec, an inlet temperature of 298.15 K, and where the outlet pressure is that of the atmosphere. In this experiment, the Mach number is very low, and the compressibility effects can be ignored. The obstacle orifice plate was placed in the center of the pipe, and a microphone was mounted flush downstream to acquire the sound pressure data on the pipe wall. The measured results show that the approach for measuring the expiratory velocity using a microphone can be justified, and there exists a good correlation between the Power Spectral Density (PSD) of sound pressure fluctuation and the peak expiratory velocity.
ISSN:1735-3572
1735-3645
DOI:10.18869/acadpub.jafm.73.238.25515