Transport of Yellow Sand in Stratified Flow over an Isolated Mountain Ridge

The transport of yellow sand over mountain regions in the presence of internal gravity waves has been investigated numerically. The motion of yellow sand particles has been simulated in a Lagrangian frame of reference by solving the time-dependent Reynolds averaged Navier-Stokes equations. An implicit time integration in a fitted body grid arrangement was used to simulate the stratified flow over an isolated ideally bell-shaped mountain. The transport and deposition of particles of various sizes, and of the altitudes where particles were released have been analyzed. Particular attention was given to transport patterns of different sized particles in various atmospheric conditions. The results show that the particle size and the re-lease altitude are both important factors in determining the trajectories of the particles. Small particles tend to be transported a long distance over the mountains, whereas heavier particles settle down around the re-lease source. Due to the existence of an internal gravity wave, the particle release altitude affects the trajec-tory of the particles. The analysis and results provide a very useful tool for the study of atmospheric flow and transport of pollutants over real topographies.