Fundamental study of a particle method for thermal-hydraulic analysis

Oka, Yoshiaki*; Koshizuka, Seiichi*

In order to enhance safety and economy of fast breeder reactors further more, numerical methods, which enables us to analyze large deformation of the domain due to, for instance, moving boundaries with satisfactory accuracy, should be developed. Since the fluid is represented by a group of particles in a particle method, it is easy to trace fluid flows by using the motion of particles. Fragmentation and coalescence as well as the large deformation of the fluid can be analyzed without any special techniques. The particle method the authors have been developing, however, needs much more computation time than that of the finite difference method in large problems at the moment. Thus improvement of the computation speed is focused on here as a fundamental study of the particle method. The dominant routine for the computation time in the code is the calculation of incompressibility because of implicit discretization. In the present study a correction parameter is optimized and listing of neighboring particles is incorporated, which has realized extensive improvement of the computation speed. The improved code is applied to a problem of propagation of surface waves at the coast where the water depth decreases uniformly. The waves are generated by oscillating motion of a vertical wall. This proves that moving boundaries can be dealt with in the particle method even if a free surface is involved.