NUMERICAL-SIMULATION OF WIND-INDUCED ENTRAINMENT IN A STABLY STRATIFIED WATER BASIN

This study uses a two-dimensional eddy viscosity model to investigate the wind-induced entrainment in a two-layer stably stratified water ba sin. By changing the background stratification and surface shear stres s, the calculated entrainment coefficients E show that when Richardson number Ri is less than a critical Richardson number Ri(c), entrainme nt law is in the form of E proportional to Ri(-1). When Ri* > Ri(c), molecular diffusion can not be neglected. The value of Ri(c) is around the order of Pe(1/2), where Pe is the Peclet number. Furthermore, thr ee different mechanisms (upwelling, longitudinal dispersion and vertic al mixing) are observed in the numerical simulation. By analyzing the time scales of these mechanisms, the interaction among them can be exp lained. The interaction and the resulted entrainment coefficient are f ound to be dependent on the aspect ratio of stratified basin.