Author(s): Hiroshi Nagashima; Nozomu Yoneyama
Linked Author(s): Nozomu Yoneyama
Keywords: Tsunami driftage; Three dimensional numerical analysis; Six-degree-of-freedom motion
Abstract: This study aims to develop a three-dimensional numerical analysis method for the prediction of driftage behavior during a tsunami attack. The main features of this method are as follows: First, this method can simulate the six-degree-offreedom motion of driftage in a three-dimensional flow field. Second, the volume of fluid (VOF) method is applied to flow involving the free surface. Third, the intersectional shape of driftage and each calculation cell is clearly calculated by vector analysis, and the fractional area volume obstacle representation (FAVOR) method is applied to the recognition of the existence of driftage in each cell. Fourth, the interaction between fluid flow and driftage motion is considered. The method was applied to two types of hydraulic experiments carried out by subjecting a wooden body to an abrupt flow of water. The obtained numerical solutions of driftage motion agreed well with the experimental results. Therefore, the new method can successfully predict the behavior of driftage during a tsunami attack. Furthermore, we applied the new method to a hydraulic experiment of a flap gate breakwater. The computed flap gate motions agreed well with the experimental ones. Therefore, this method is also applicable to the motion analysis of a flap gate breakwater during a tsunami attack.