Strongly stably stratified grid turbulence using second-moment closure

A second-moment closure model is used to investigate the strongly stably st ratified water flow downstream from the turbulence-generating grid, with th e aim of examining the validity of the second-moment closure model to revea l the countergradient transport of heat and momentum. The Reynolds number b ased on the streamwise mean velocity and the grid spacing is 2.5 x 10(3). C omputations are carried out for two temperature gradients, namely, two temp erature differences of 15 and 30 K between the upper layer and the lower la yer Computational results of the closure model are compared in detail with the results of the direct numerical simulations. It is found that the secon d-moment closure model is capable of demonstrating the countergradient tran sport of heat in the strongly stably stratified condition. However, the clo sure models need to be improved in the future to obtain better agreement wi th the results of the direct numerical simulations.