Wave impact pressures on vertical cylinders

Abstract

Laboratory measurements of the pressure distributions on surface-piercing vertical cylinders due to breaking waves are presented. Breaking waves are generated in a repeatable fashion under program control, and both vertical and azimuthal distributions of pressures were measured over many repeats of the experiments. Despite the repeatability of the controllable experimental conditions, it is found that the highest impact pressures are subject to considerable variability, including pressure oscillations, from run to run. This high impact region is found to be localized in space and time, and the variability is attributed to the random dynamics of the breaking wave front and the entrapped air. Thus, despite the repeatability of the upstream incident wave hydrodynamics, it appears that the prediction of the largest pressures is essentially a stochastic problem. For those aspects of flow-structure interaction which do not depend on the higher-frequency impact pressures, these experimental results may be extrapolated to full scale through the use of the pressure impulse.