Large-eddy simulation of stably stratified flow past a rectangular cylinder in a channel of finite depth

Large-eddy simulation is performed to investigate an incompressible stratified flow with a linear temperature gradient past a rectangular cylinder with side ratio b/h=0.6, where b and h are its breadth and depth, respectively. Simulations are performed for Reynolds number Re=8,400 with respect to a series of stratification numbers K. Results show that transition of stratification effect occurs at around K=2 due to the occurrence of second-order stationary internal waves. Both Strouhal number St and drag coefficient CD decrease with stratification number K when K<2 due to suppression of vertical motion, but increase with K when K>2 because of the stationary internal waves. The relationship between the fields of temperature and other flow parameters are studied and a coincidence of temperature field with internal wave is observed at high stratification number. Finally the stratification effect on the vortex street is discussed.