Effect of T-shaped spur dike on flow separation in a 90° bend using SSIIM model

Spur dikes are used widely as flow control structures in rivers. The main direction of the flow is changed by a spur dike, which is accompanied by formation of separation and reattachment zones around the spur dike. This study was focused  on the effect of a submerged single T-shaped spur dike and the  influence of the distance between non-submerged T-shaped spur  dikes, in determining the separation and reattachment zones in  a 90° bend using the SSIIM (sediment simulation in intakes  with multi-block option) numerical model. The spur dike was installed at the middle of the outer bank in a movable-bed channel. It was observed that by increasing the submergence ratio, the length of separation and reattachment zones can be reduced, and by increasing the distance between two spur dikes the length of reattachment zone downstream of spur dikes can be increased. For all submergence ratios, from the bed level upwards to the crest level of the spur dike, the length of flow separation zone decreases, but the length of flow reattachment zone increases (dike crest level is equal to water depth level on the dike). By changing the dike submergence, the dimensions of the vortices around the dike can be changed due to variations in the flow separation and reattachment zones.