Experimental Study on the Influence of Dune Dimensions on Flow Separation

Abstract

Using laboratory experiments and a numerical model, this study examined the influence of dune dimensions on the separation of flow. Different conditions, depending on the dune height, material, and angle and flow depth and velocity, were considered. Experiments were conducted in a horizontal flume with one side wall being transparent for application of optical measuring devices. A train of two-dimensional (2D) fixed dunes were installed on the bottom of the flume starting just downstream of the entrance on the flume. Dunes were prepared with well-sorted gravel particles. Experiments were carried out using four types of dunes with different lee slopes. The numerical model used was sediment simulation in intakes with multiblock option (SSIIM), which is an open-source computational fluid dynamics model. Both experimental observations and numerical results were in agreement about the influence of dune characteristics on the flow separation, with particular regard to dune height, particle size, angle on the leeside, and flow velocity.