Bore impact upon vertical wall and water-driven, highmass, low-velocity debris impact

Abstract

This dissertation proposes a method to predict the peak lateral force on a vertical wall from an impacting bore. The formula has been developed based on the analysis of data from large-scale experimental tests on bore impact. The lateral forces are much larger than traditional lateral loads on vertical walls. It is shown, the data indicate that the formula can be used for prototype scale following Froude scaling. Additionally, a computational tsunami bore generation study utilizing the Reynolds Average Navier-Stokes equations is presented. Three bore generating scenarios are reviewed and results are presented, providing guidance on how best to generate bores for further numerical studies. In the latter part of the dissertation, the application of a simple one-dimensional model to obtain impact force magnitude and duration, based on acoustic wave propagation in a flexible projectile, is explored. The focus herein is on in-air impact. Based on small-scale experiments, the applicability of the model to predict actual impact forces is investigated. The tests show that the force and duration are reasonably well represented by the simple model, but they also show how actual impact differs from the ideal model. The one-dimensional model is extended to consider water-driven debris as well. When fluid is used to propel the 1-D model, an estimate of the 'added mass' effect is possible. In this extended model the debris impact force depends on the wave propagation in the two media, and the conditions under which the fluid increases the impact force are discussed. The results indicate that the model provides an accurate estimation of the peak impact force and its duration. For the tested scenario, the maximum impact force does not depend on the total mass of the debris.