MODELING TRANSVERSE MIXING LAYER IN SHALLOW OPEN-CHANNEL FLOWS

Numerical computations are conducted of the flow across a turbulent mi xing layer in an open channel of small depth using three turbulence mo dels: a single-length-scale model, a modified single-length-scale mode l, and a two-length-scale model. The performance of these turbulence m odels is evaluated by comparing the numerical results with the availab le experimental data. The single-length-scale turbulence model is show n to be biased toward the small-scale turbulence. The coefficients of this single-length-scale turbulence model have been modified in an att empt to improve the performance of the model. The results of the modif ied single-length-scale model are in agreement with the laboratory dat a but not with the field data. The two-length-scale turbulence model, by treating the small-scale and the large-scale turbulence as separate components, has produced results in better agreement with the experim ental data than those obtained by the single-length-scale model treati ng both components together as a whole.