Simulation of a round jet and a plume in a regional atmospheric model

The mean flow characteristics of a turbulent round jet and a plume are simu lated in a high-resolution regional atmospheric model. The model used for t he study is the Advanced Regional Prediction System (ARPS). It is observed that the predicted flow characteristics are very sensitive to the turbulenc e closure scheme used. Among the three closure options in ARPS, namely, the constant eddy viscosity scheme, the Smagorinsky diagnostic closure, and th e 1.5-order total kinetic energy scheme, the constant eddy viscosity scheme predicts the jet characteristics in better agreement with experiments. For the plume, all three schemes are unsatisfactory. It is shown that a modifi cation of the constant eddy viscosity scheme incorporating a length-scale v ariation as suggested by theory predicts plume characteristics in good agre ement with experiments. The simulations are carried out at one fixed grid-b ox size and flow inlet conditions; extending the present simulation results to other cases is discussed.