A COMPARISON OF NUMERICAL-MODEL EXPERIMENTS OF FREE-SURFACE FLOW OVERTOPOGRAPHY WITH FLUME AND FIELD OBSERVATIONS

A numerical model is used to simulate free surface shallow water flow over bottom topographical features. The model, in which turbulence clo sure is achieved at the level of the turbulence energy equation, allow s for the inclusion of both the hydrostatic and hydrodynamic contribut ions to the pressure field and, accordingly, is successful in reproduc ing flow separation on the downstream side of an asymmetrical sandwave structure. Experiments are described in which the geometrical and flo w parameters are chosen so as to correspond to recently reported flume and field observational studies. The experimental flume studies repre sent a particularly detailed and well-conducted determination of mean and turbulent flow properties in highly controlled laboratory conditio ns. Good overall agreement is found between the model and experimental evaluations of the mean fluid velocity, the turbulence energy, the ki nematical shear stress and the extent of the flow separation zone. The second application of the model involves a comparison with a recently acquired field data set based on observations made in the Taw Estuary , Devon, England. In addition to measuring the dynamical properties of the flow, a determination was also made of suspended sediment concent rations. With appropriate modification to the model, evaluations of co ncentration profiles are also compared with those obtained in the fiel d observations. The overall agreement is again of an encouraging quali ty thus lending support to the application of the numerical model in d ifferent coastal environments.