The coherence of a pressure field induced on a prismatic obstacle placed in a turblent flow

The results of wind tunnel trials with a flow of 8.5 m/sec passing over a square oblond placed broadside to the flow are presented. Turbulence was generated in the flowfield by placing a grid with different mesh sizes upstream, and monitored with X-wire anemometry. The pressure field was measured with 16 microphones placed at various points on the surface of a two-dimensional slice of the obstacle. It was found that pressure fluctuations at the stagnation point lacked the Strouhal frequency component. The Strouhal component dominated the pressure fluctuations on the sides of the solid surface. A spectral peak was observed in the fluctuations and was assumed as independent of the broadband noise. Although the peak diminished with increasing turbulence, it did not vanish even when the turbulent component reached 17.5 percent.