Interactions between an incident bore and a free-standing coastal structure

This dissertation describes experiments carried out to examine the problem of tsunami impact on coastal structures. Using a 16.6 m long and 0.61 m wide tank situated in the Harris Hydraulics Laboratory at the University of Washington, bores were generated using a lift gate and made to impinge on structures of simple geometry.; Measurements were made of water level using wave gauges and a laser profiler. Flow velocities were obtained at single points with a laser doppler velocimeter and a two dimensional flow field was constructed using particle image velocimetry. A six degree of freedom load cell recorded forces on the structures.; The energy and momentum in the flow was analyzed. The contribution of the potential energy was found to be approximately equal to that of the kinetic energy. The turbulence in the bore and the wake of the structure was also analyzed. Turbulent kinetic energy was found to be negligible. The dynamics of the bore interaction with the structures and tank side walls yielded highly unsteady momentum flux in the region of the structures.; The forces on the structures were examined and related to the Froude number, bore height, tank width and structure geometry. Resistance coefficients in the range of 1--2 were observed. The resistance decreased with increasing Froude number and relative bore height. The variation of the resistance coefficients with bore height was more pronounced for circular columns than for square columns. Resistance coefficients increased with decrease in the ratio between flow depth and column width owing to more redirection of the flow.