Some Statistical Properties of the Pressure Field Radiated by a Turbulent Boundary Layer

The radiation field generated by a supersonic turbulent boundary layer is examined. A short description of the experimental technique for measuring the pressure fluctuations is given. One finds that for a given free‐stream Mach number the fluctuations scale with the wall shearing stress τ_w, the nondimensional radiation intensity $\overline{{\mathrm{p\prime }}^2}{\mathrm{/\tau }}_{\mathrm{w}}^2$ increases with Mach number and is two orders of magnitude smaller than the intensity measured on the wall. From the measurements of some statistical properties such as space‐time correlation and energy spectrum, one concludes that the streamwise propagation of the radiated pressure is different from that of the wall pressure at lower Mach numbers, and that the radiated field contains relatively much more energy in the low‐wavenumber region than does the near field. Some attempt is made to explain these results.