Turbulent Bursts and Wall Pressure Events in Disturbed Flows

The correlation between near-wall turbulent bursts and large-amplitude wall-pressure events has been extensively studied for equilibrium flows. This paper presents the results of an experimental investigation on this relationship for a non-equilibrium flow. The flow configuration was the reattached turbulent boundary layer downstream of a backward facing step. For this flow, a disturbance layer propagates across the boundary layer causing the peak turbulent stress to occur in the overlap and outer regions. Farabee (1986) has shown that these outer-layer structures contribute to the wall pressure in the low-frequency range while the near-wall structures contribute to the high-frequency range. This investigation extends the earlier work by examining the intermittent features of temporal records for turbulence and wall-pressure data. Wavelet filtering techniques were utilized to isolate the near-wall structures. The correlations between clusters of burst and wall-pressure events were made using detection techniques developed for this application. Comparative results between the equilibrium and disturbed flows will be presented.