SIMULATION OF HORIZONTAL TURBULENCE IN SHALLOW RECIRCULATING FLOWS

Abstract eng:
The Large Eddy Simulation method is employed in this study to compute shallow recirculating flows in an open channel. The depth- averaged equations are solved to calculate the large-scale horizontal turbulence. Sub-depth-scale viscosity and sub-grid-scale viscosity are determined by a modified Smagorinsky model. The computations were conducted for a range of friction effect from deep to shallow water depth. Flow parameters, such as the length of the main recirculating zone, the length of the secondary recirculation area, the wake width, the recirculation flow rate, the Reynolds stresses, the mean and fluctuations of a tracer concentration, are computed and are compared with the experimental data. The simulations are in agreement with the experimental data when optimal value of the Smagorinsky coefficient, Cs, is selected for the simulations. The optimal value of this coefficient is not constant but depends on the bed-friction number effect. It decreases rapidly from Cs = 0.26 to 0.14 as the bed-friction number increases from S = 0.027 to 0.25, respectively.

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