Numerical prediction for many floating debris transported in city model due to tsunami-induced flows

A three-dimensional computational method based on multiphase modelling is employed to predict the behaviors of floating tsunami debris in coastal residential areas. The present computational method enables us to deal with the interactions between free-surface flows and the movements of floating objects, as well as the collisions among the objects and fixed structures. The present method was first applied to simple stability problems of floating cylinders and then it was applied to the 1/250 scale tsunami experiments. Finally, two types of numerical experiments were performed using larger number of floating objects in more compli- cated conditions. As a result, it was shown that the present method is effective to predict the behaviors of floating objects transported by tsunami between buildings on non-uniform grand surfaces

Validity of Pressure-Velocity Correction Algorithm (C-HSMAC method) for Incompressible Fluids with Passive Scalar Convection

In the computations of incompressible fluids, it is essentially important to obtain accurately the velocity components that satisfy the incompressible condition (∇・u = 0) as well as the pressure variables which are consistent with the velocity fields. For this purpose, a pressure-velocity correction method (C-HSMAC method) has been proposed by Ushijima et al. (2002) with a finite volume method (FVM) for incompressible fluids. The purpose of this paper is to estimate the effects of the unsatisfied incompressible condition on the passive scalar convection and to confirm that the C-HSMAC method is able to suppress them. The C-HSMAC and usual SMAC methods were applied to the passive scalar convection in the cavity having an oscillating top wall. It was concluded that the unsatisfied incompressible condition may cause the unphysical scalar overshoots in the SMAC method. In contrast, the C-HSMAC method enables us to control |∇・u| with the given threshold ϵD and to suppress such overshoots. In addition, it was demonstrated that the C-HSMAC method allows us to obtain reasonable results without overshoots even in combination with a higher-order scheme for convection terms with finer cell divisions