Decay of Fluctuating Wall-Pressure Field of Mach 5 Turbulent Boundary Layer

The fluctuating wall-pressure field of a nominally two-dimensional, zero-pressure gradient, adiabatic, turbulent boundary layer on the floor of a Mach 5 blowdown tunnel has been investigated experimentally. Various procedures are examined for scaling the streamwise decay of the maximum cross-correlation coefficient of the fluctuating wall-pressure signals with increasing streamwise spacing. For small streamwise separations less than about five boundary-layer thicknesses, the available data from this and other studies can be collapsed in terms of streamwise distance normalized by boundary-layer thickness. For larger separations the database is too sparse to draw a definitive conclusion. The maximum cross-correlation coefficient for incompressible, subsonic, and supersonic boundary layers can be collapsed in terms of a Strouhal number, for Strouhal numbers greater than about 5. In this case the Strouhal number is based on streamwise separation distance, narrowband frequency, and structure convection velocity within that narrow band. Fluctuating pitot-pressure measurements were also made and analyzed in conjunction with hot-wire data obtained in the same facility and with hot-wire experiments at Mach 3