| Due to the great practical significance of stably stratified flows in the environment, people need practical methods for computing them, including the turbulent transport processes associated with such flows.; The literature survey on this topic shows that k-&egr; turbulent closure models underestimate the effects of negative buoyancy on vertical turbulence in a stably stratified cloud compared to the experimental data. This appears to be associated with modeling the influence of stratification on ground-level boundary conditions. A buoyancy-extended k-&egr; model needs to be developed for density-stratified flows.; The previous reports in our research group showed that the approach flow turbulence may be severely damped due to the effect of density stratification, and air entrainment due to ambient turbulence may essentially stop at sufficiently high gradient Richardson number. Under such circumstances, mixing due to molecular diffusion may dominate turbulent air entrainment.; The principal objective in this work is focused on developing a buoyancy-extended k-&egr; model. The revised model is used in the finite element model (FEM3C) and is compared with past experimental data and planetary boundary layer (PBL) model on stratified and neutral density flows. Based on the comparisons, it is concluded that the revised k-&egr; turbulent closure model has a good improvement over the PBL model and is much more applicable to the stably stratified flows around obstacles such as the structure of tank and dike. |
