Turbulent Boundary Layer Pressure Field-Induced Vibrations in a Thin Flexible Plate Under Water.

Two point Turbulent Boundary Layer pressure spectra at the wall were determined empirically in a low noise water tunnel. The measured pressure spectra were used in a linear theory to predict the response of a thin stainless steel rectangular plate attached to the water tunnel. The predicted responses were found to agree well with the measured responses of the plate. The in-situ plate response characteristics were also determined empirically by driving the plate separately at several points with a miniature shaker and measuring its response with accelerometers mounted on the plate. The accuracy of the predicted response was found to be controlled by the accuracy of the plate modal model. Due to the reverberant acoustic field in the water tunnel and a complicated supporting structure, the plate modal model could be determined only approximately. The plate modal damping factors were very high, its resonance frequencies were close and the associated mode shapes were complex. These factors made it very difficult to accurately determine the plate modal properties. The wall pressure spectra were also measured for the case when a step discontinuity was present in the wall. These spectra were markedly different from those measured on a smooth wall.