結晶形状に準拠した座標系による氷晶成長の2 次元数値シミュレーション

Abstract

Ice crystal growth by diffusion of water vapor from supercooled liquid water is simulated with equations written in a surface-following coordinate system. This two-dimensional system, similar to “terrain-following coordinate system” used in meteorology and oceanography, consists of the one axis pointing vertical and the other following the crystal geometry. It facilitates the introduction of the boundary condition on the surface of ice crystal so that simplifies the algorithm for computer programming. By introducing the system, the growth of one branch of snow crystal is simulated smoothly in contrast to the previous simulations adopting the ordinary rectangular coordinate system where it becomes bumpy. Also, while the rectangular coordinate system shows different growth rate and shape of ice crystal with grid resolution, those obtained from the surface-following coordinate system depend little on grid resolution.