Oscillating Pressure Fields on a Free Surface

Abstract

The effect of a vertical barrier or lip on the wave generating capability of a pneumatic wavemaker is analyzed. For lip immersion approaching zero, the wave amplitudes approach the values predicted by Stoker in 1957. For finite lip immersion, wave amplitude is generally reduced below the amplitude from a wavemaker with no lip, but under certain conditions the amplitude can be greatly increased by the lip. Numerical results are presented. &&These results are used to show that the effect of sidewalls will be generally negligible in predicting the added mass and damping per unit length of a long air-cushion vehicle with sidewalls (captured_air-bubble vehicle). Such effects then being neglected, the added mass and damping are computed as functions of frequency and conditions of static support. The amplitude and phase of the mean free surface motion under the vehicle are also computed. It is found that the surface motion can actually be exactly opposite to that expected from quasi_static considerations.