Maestrello and Lindei 



Fig. 3. Longitudinal Cross-Correlation of the Wall 

 Pressure 



vection velocity is very low Uc/Ue = 0.13 and the correlation is very 

 weak. The correlation between x/6 = 0,33 and x/5 = 0.25, where 

 x/6 = 2,25 corresponds to the maximum static pressure ratio is 

 negative. The shock induces the boundary layer to separate and the 

 recirculation within the separation region permits the sign of the 

 pressure to change. Kistler argued that the fluctuating pressure 

 in the separated region arises from the combined action of the turbu- 

 lent shear layer and the recirculating flow. The picture, however, 

 is not yet clear enough to develop a model for time dependent loading, 

 since the geometry of the separated region is the primary variable 

 in estimating the pressure ainplitude and resulting phase. 



No measurement of the lateral cross-correlation was made 

 during the test; however, for the purpose of computing the response 

 of the panel, it is assumed that the pressure decays similarly to 

 that in the case of zero pressure gradient e" ^ ' °2 where (X2 = 0.26 

 and T) is the spatial separation [Maestrello 1968] . This choice 

 overestimates the lateral cross-correlation, since the flow field is 

 far from being homogeneous. However, the overestimation may not 

 be exceeded by a factor of 2. 



482 



