Flow Characteristics of River Channels under Different Types of Ice Cover

Abstract

Abstract A RSM numerical model together with a laboratory measurement with Micro ADV were adopted to investigate flow through a straight rectangular flume under four conditions: no ice cover, continuous ice cover, discontinuous ice cover and inshore ice cover. Under the combined action of ice cover roughness and bed roughness, the flow structure is complex. The water depth with ice sheet conditions is generally larger than that without ice cover. The presence of ice cover makes the vertical profile no longer satisfies the classical logarithmic distribution. The stream-wise velocity increases gradually from the bottom of the riverbed and reaches its maximum at a point between the ice sheet and the riverbed, which is called the inflection point. After passing the inflection point of flow velocity, the flow velocity gradually decreases, eventually decreasing to 0 at the ice sheet. There is a large velocity gradient at the interface between the ice cover and the current. Comparison between the numerical prediction and laboratory measurement shows that the RSM model can well predict the flow structure of ice cover. Furthermore, the turbulent kinetic energy and dissipation rate are analyzed based on the RSM prediction. The increasing of turbulent kinetic energy and dissipation rate at the interface between ice cover and water surface indicates that ice cover causes more intense internal mixing and energy dissipation of water flow.