Publications Details

Improved measurements of large-scale coherent structures in the wall pressure field beneath a supersonic turbulent boundary layer

Beresh, Steven J.; Henfling, John F.; Spillers, Russell W.; Pruett, Brian O.

Data have been acquired from a spanwise array of fluctuating wall pressure sensors beneath a wind tunnel wall boundary layer at Mach 2, then invoking Taylor's Hypothesis allows the temporal signals to be converted into a spatial map of the wall pressure field. Improvements to the measurement technique were developed to establish the veracity of earlier tentative conclusions. An adaptive filtering scheme using a reference sensor was implemented to cancel effects of wind tunnel acoustic noise and vibration. Coherent structures in the pressure fields were identified using an improved thresholding algorithm that reduced the occurrence of broken contours and spurious signals. Analog filters with sharper frequency cutoffs than digital filters produced signals of greater spectral purity. Coherent structures were confirmed in the fluctuating wall pressure field that resemble similar structures known to exist in the velocity field, in particular by exhibiting a spanwise meander and merging of events. However, the pressure data lacked the common spanwise alternation of positive and negative events found in velocity data, and conversely demonstrated a weak positive correlation in the spanwise direction.