TURBULENCE MEASUREMENTS RELEVANT TO JET NOISE
TORONTO UNIV DOWNSVIEW (ONTARIO) INST FOR AEROSPACE STUDIES
Pagination or Media Count:
Liththills equation for aerodynamic noise was reformulated in terms of its spectral characteristics using the one-dimensional fourier cosine transform. The final formalism is more revealing in that both the Doppler effect of moving eddies and the extent to which retarded time differences can be neglected are explicit in the final equation. Also the convection effect can be distinguished as a combined effect of Doppler shift and amplification. Experimentally, two-point space-time correlation of both the turbulent velocities and the square of these velocities were measured in the mixing region of a 4 inch model jet about 142 fps with constant temperature hot-wire anemometers. These measurements included the ordinary u-component and also the components at 45 deg. and 60 deg. to the jet axis. Results for the u-component agree well with those of previous investigators. Using the moving axis transformation of these space-time correlation functions to-gether with the mean velocity measurements, an estimate of the basic directivity, the intensity, and the spectrum of both the shear and the self noise generated by a unit volume of jet turbulence was obtained.
- Fluid Mechanics