NUMERICAL SIMULATION OF MORPHOLOGICAL CHANGES IN COASTAL LAKES INDUCED BY TSUNAMI USING DUALSPHYSICS

Abstract

 In the Great East Japan Earthquake, the ground behind the coastal levees was scoured by the tsunami, causing the levees to breach and increasing the damage from flooding. Elucidating the mechanism of damage caused by scour will help to strengthen the tenacity of coastal levees. The open source fluid analysis code DualSPHysics implements a non-Newtonian fluid model and has shown applicability to scour phenomena such as dam failure. However, there are few examples of analyses of scour caused by embankment overtopping, and the parameters of non-Newtonian fluid flow are not well understood in many cases. In this study, the hydraulic experiments of Mitobe et al. were reproduced using DualSPHysics, and the issues and possible improvements of the non-Newtonian fluid model for scouring phenomena were discussed. The results show that the reproducibility of scouring phenomena can be improved by dividing the ground behind the beach ridge into three layers, setting the density and kinematic viscosity of the non-Newtonian fluid in each layer, and setting the layer thickness for all tsunami inflow rates.