Wave Induced Pressures on Submerged Plates

In the analysis, the plate is imagined to be rigidly suspended at an arbitrary fixed depth and then replaced by a vortex sheet the strength of which varies both temporarily and spatially. The velocity potential of this sheet is adjusted such that, when combined with the potential of the oncoming waves, boundary conditions on the plate, the free surface, and the bottom are approximately satisfied. The final vortex strength distribution can be determined allowing the velocity field and thus the pressure distribution on each side of the plate to be calculated. The experimental program was conducted using a 4x4x40ft (1.2x1.2x12-m) flume with a generator capable of producing waves having a broad frequency and amplitude spectrum in varying water depths. A flat plate of sandwich type construction was instrumented with small pressure transducers with outputs that were processed and recorded on an oscillographic recorder. Results are presented as instantaneous differential pressure distributions for associated wave positions, sequentially as the wave progresses. An advantage of the analytic approach is that pressure distributions as well as total forces may be readily obtained.