抄録
A numerical method for simulating the mass diffusion in fragmentation and/or large deformation processes of a fluid has been developed. The Moving particle semi-implicit (MPS) method proposed by Koshizuka et al. and their moving particle interaction model for Laplacian operator are applied to the diffusion equation. Because of grid-less calculation procedures in the MPS method, the current method can analyze mass diffusion over free surfaces without the cumbersome effect of grid tangling. The viscosity of fluid is also considered. The calculation procedure of the current method is mainly separated into two stages: The first step is the original MPS method. Here the fluid is represented by moving particles and its convection is presented by the motion of those particles. The second step is the explicit method of mass diffusion. Mass diffusion among the moving particles is solved explicitly by using the Laplace model of the MPS in a given diffusion equation. A point source diffusion model has been solved by the current method and the Crank-Nicolson method is used to determine the optimal interaction radius of the Laplace model. Two transport phenomena with mass diffusion have been simulated: (1) a pouring diffusion model where pure water is poured into another cup filled partially with concentrated (non-pure) water and (2) a dam collapse with viscosity where mass resource spreading uniformly over the box floor. The dynamical change of mass transport phenomena with both convection and diffusion in large deformation of fluids were successfully simulated.
