Calculation of Wind Noise Measured at the Surface under Turbulent Wind Fields

Kraichnan (1956) provided theories to relate boundary layer turbulence to the total mean square pressure fluctuations at the boundary surface. This dissertation adopts methods from Kraichnan (1956) and George et al. (1984) to develop calculations that incorporate measured outdoor spectra of the turbulence and different models of the outdoor wind velocity profile for the investigation of the pressure fluctuation measurements outdoors with the microphone mounted at the ground surface and beneath the ground surface with a foam covering. The measured outdoor turbulence spectra can fit to a revised von Karman spectrum form. Pressure fluctuation spectra due to turbulence-shear interactions were calculated for a logarithmically varying form of wind velocity profile and a multiple exponentially varying form. The developed multiple exponential profile model can provide pressure spectral predictions at the surface under wind fields with an arbitrary mean velocity profile. The influence from the atmospheric stability condition and surface details were investigated.;Theoretical predictions were compared with experimental pressure measurements. Foam covered microphone measurements can be well predicted under all conditions at low and middle wave numbers. There are large variations on the measured pressure spectral levels for the microphone flush mounted at the surface. The high pressure levels cannot be predicted from the calculation of the pressure fluctuation due to the interaction of the gradient of the horizontal velocity profile and the vertical turbulence. There may be other contributions from the interaction between the ambient gradient of mean velocity and the transverse or longitudinal velocity fluctuations.