Numerical simulation of wind-induced entrainment in a stably stratified water basin

Abstract

This study uses a two-dimensional eddy viscosity model to investigate the wind-induced entrainment in a twolayer stably stratified water basin. By changing the background stratification and surface shear stress, the calculated entrainment coefficients E show that when Richardson number Ri _* is less than a critical Richardson number Ri _c, entrainment law is in the form of E ∝ 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, three different mechanisms (upwelling, longitudinal dispersion and vertical mixing) are observed in the numerical simulation. By analyzing the time scales of these mechanisms, the interaction among them can be explained. The interaction and the resulted entrainment coefficient are found to be dependent on the aspect ratio of stratified basin.