Computations of suspended sediment transport in a shallow side-cavity using depth-averaged 2D models with effects of secondary currents

Abstract

Two-dimensional (2D) depth-averaged shallow flow models’ integrated effects of secondary currents are applied to open channel flows with a side cavity, and the accuracy of predictions of the flow structures as well as the behavior of suspended sediment transport is examined. The flow in a side-cavity is characterized by formations of a steady recirculation with a vertical axis and associated secondary current due to a centrifugal force (a secondary current of the first kind). The flow structures become completely three-dimensional and suspended sediment transports are affected by such complicated flow features. In this study, we applied depth-averaged shallow flow equations including effects of secondary currents, instead of 3D flow equations considering computational efficiency. We applied 4 different types of models for shallow flow equations and compared the performances of each model. First, these models were applied to a simple flow in a torus-shape channel with rigidly rotating flow, in order to consider the fundamental characteristics of suspended sediment transport. Then the models were applied to open channel flows with a rectangular side cavity, in order to consider both flow structures and sediment transport affected by the secondary current. The computations were performed under the same conditions of the laboratory tests and applicability of each model was discussed through the comparison between computational and experimental results. The model considering the lag of development of secondary current behind the streamline curvature, and the deformation of mean velocity profiles affected by secondary currents showed excellent performance for predicting flow phenomena with recirculation.