Numerical study on influences of planar flow and bed scour in double dike closure

In large water power engineering construction, double dikes can be used to reduce difficulties in river closure under high flow and big drop. But in practice it was often not easy to control the hydraulic conditions to obtain satisfactory situation where both dikes could share water fall in balance during closing process. 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, and the corresponding bed scour pattern were necessary to drop sharing of the downstream embankment. The intensive sediment scour on deep alluvial river bed may decrease total drop of the flow and cause significant fluctuations in drop distribution between the two dikes, which increase the difficulties in flow stabilization and hydraulic control.