Author(s): Mete Koken, Ezgi Budak
Linked Author(s): Koken Mete
Keywords: Open channels, coherent structures, detached eddy simulation, spur dike, secondary flow
Abstract:
Results of three-dimensional (3D) Detached Eddy Simulation (DES) are used to investigate the changes in flow and large-scale coherent structures within a high-curvature open channel, with and without an isolated spur dike located on the outer bank of the channel. The flow of an 1800 bend is simulated, in which the ratio between the bend curvature to the channel width is 1.25. The channel contained a flat bed, which represents the initiation of the scour process. The Reynolds number and Froude number are calculated using the channel depth at the inflow and the flume-averaged velocity were around 125,000 and 0.68, respectively. The crossstream secondary flow and anisotropic effects play a crucial role in the redistribution of the streamwise momentum and influence significantly the distribution of the bed shear stress, which in turn, determines the capacity of the flow to entrain sediment. The presence of the isolated spur dike complicates the flow filed within the channel more, causing additional coherent structures to form around it. The eddy content is very rich within the flow field as compared to the case without the spur dike. It is shown that the secondary flow cell forming along the outer bank in the curved channel is not present once the spur dike is introduced. Moreover, there are differences in the bed shear stress distribution because of the inclusion of spur dike. In overall, the bed shear stress values get smaller within the curved reach whereas the patch of large shear stress values are shifted towards the inner bank once the spur dike is introduced. (2611, 80, 367)
Year: 2017