Improved models of surface tension and air resistance for multiphysics particle method

Abstract

ABSTRACT A multiphysics particle method is being developed to simulate the dynamic behaviors of fluid and solid involving their freezing and melting which occur in a severe accident at a nuclear reactor. So far, the conventional particle method code for fluid dynamics has been expanded so that thermodynamics, melting, and freezing can be treated. In this study, new models for the surface tension and air resistance were developed. The developed surface tension model is based on the potential model, where the magnitude of the normal force to the surface is corrected to agree with the theoretical value. A simulation of droplet collisions was conducted to verify the developed model. The simulation results were compared with experimental results and their good agreement was confirmed. The developed air resistance model is based on the assumed pressure distribution around a sphere located in an air stream, hence, the direct simulation of the air phase is not necessary, reducing the computational time. The breakup of a droplet in air was simulated for verification and it was confirmed that reasonable results are obtained using the developed model when the parameters of the analysis object are appropriately chosen.