On planar flow and its influences in double dike closure by numerical simulation

Double dikes can be used to reduce the difficulties in river closure under high flow and big drop. It is required that both dikes share water fall during the closing process. But in practice it was often not easy to control the hydraulic conditions to obtain satisfactory situation. A series of 3-D numerical experiments by CFD simulation on two-dike closure in simplified straight boundaries were conducted in this paper. The results demonstrated that two recirculation zones in reverse direction in the flow plane, which were formed due to main stream diversion between the dikes, were necessary to drop sharing of the downstream embankment. The diverting spur wall had been found through computational tests to contribute to this kind of stable flow pattern. The location and size of the wall could influence formation and stability of the pattern. The distance between two dikes had a minimum value for maintaining the recirculation but had less influences on total drop and its allocation on the two embankments in the presence of the two stable return flow.