An immersed boundary method for complex terrain flow analysis

We present modified immersed boundary method (IBM) for complex terrain flow analysis which is done on coarse grid and based on large-eddy simulation (LES). The main idea is that IBM force to make fluid velocity perpendicular to terrain surface zero and to revive tangential fluid velocity near the terrain surface is applied at Lagrangian point on terrain surface. For smoothing out the effect of IBM force on coarse grid, IBM force at Lagrangian point is distributed on collocated grid and gathered at the position of fluid velocity on staggered grid. For validation of our method, we conduct complex terrain flow analysis for mountainous terrain which is mock-up model of coastal region in Gyeongju and compare our simulation results with wind-tunnel experiment results and other simulation using ANSYS. Our simulation results show better agreement with wind-tunnel experiment results than ANSYS simulation results and properly capture various flow characteristics occuring in complex terrain.