Modelling transverse mixing layer in shallow open-channel flows

Numerical computations are conducted of the flow across a turbulent mixing layer in an open channel of small depth using three turbulence models: a single-length-scale model, a modified single-length-scale model, and a two-length-scale model. The performance of these turbulence models is evaluated by comparing the numerical results with the available experimental data. The single-length-scale turbulence model is shown to be biased toward the small-scale turbulence. The coefficients of this single-length-scale turbulence model have been modified in an attempt to improve the performance of the model. The results of the modified single-length-scale model are in agreement with the laboratory data 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 experimental data than those obtained by the single-length-scale model treating both components together as a whole.