Decay of fluctuating wall-pressure field of Mach 5 turbulent boundary layer

The fluctuating wall-pressure field of a nominally two-dimensional, zero-pr essure 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-correla tion coefficient of the fluctuating wail-pressure signals with increasing s treamwise spacing. For small streamwise separations less than about five bo undary-layer thicknesses, the available data from this and other studies ca n be collapsed in terms of streamwise distance normalized by boundary-layer thickness. For larger separations the database if, too sparse to draw a de finitive conclusion. The maximum cross-correlation coefficient for incompre ssible, subsonic, and supersonic boundary layers can be collapsed in terms of a Strouhal number, for Strouhal numbers greater than about 5, In this ca se the Strouhal number is based on streamwise separation distance, narrowba nd frequency, and structure convection velocity within that narrow band. Fl uctuating pitot-pressure measurements were also made and analyzed in conjun ction with hot-wire data obtained in the same facility and with hot-wire ex periments at Mach 3. The boundary-lager large-scale structure angles, spanw ise scale, and intermittency distributions agree well with results at Mach 3. Based on the higher values of the cross-correlation coefficient in the M ach 5 flow, it appears that turbulent structures are somewhat larger than t hose at Mach 3.