Maestrelto and Linden 



6.0 7.0 8.0 



Fig. 1, Static Pressure Fluctuations and Mean Pressure 

 Distribution Downstream of the Shock 



effective decay downstream. Fig. 1. In the present case, the wedge 

 angle induces a shock in the boundary layer large enough to cause a 

 separation: farther downstream, the flow becomes reattached and 

 goes back to the flat plate condition. This transition takes place 

 within a few boundary layer thicknesses. 



Downstream of the shock, the ratio of the mean pressure 

 distribution p^jj/pj and the ratio of the rnns pressure fluctuation 

 Psd/P& vary with a consistent relationship and both reach a maximum 

 at x/6 — 2.3, where subscripts s and sd, mean upstream and 

 downstream of the shock, respectively. Fig, 1. Beyond x./5=^ 6 

 the effect of the shock on the static pressure vanishes. Kistler 

 [ 1963] indicates a similar behavior between mean and fluctuating 

 pressure in the spearated region ahead of a forward-facing step at 

 the same Mach number and upstream Reynolds number. The differ- 

 ences in the flow geometry only alter the magnitude of the pressure, 

 in that the ratio of the mean pressure to the fluctuating pressure 

 p /p'. =• 14 in the present experiment while Kistler found that 

 pJpI = 32. 



The normalized power spectral density measured upstream 

 and downstreajTi of the shock are shown in Fig. 2. The spectra are 



Tr(co) d = 1 in order to demonstrate the 



deviation from the zero pressure gradient ease. For the spectra 

 just downstream of the shock more energy is concentrated in a 

 narrow low frequency band while further downstream at x/6 « 4, 

 the energy is distributed over a much broader bandwidth and 

 approaches the shape and level of the spectrum taken upstream of 



480 



