Mohammad Vaghefi

Spur dikes are used widely as flow control structures in rivers. The main direction of flow is changed by a spur dike and which is accompanied by formation of separation and reattachment zones around the spur dike. In this article attention was focused on the study of 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 of separation and reattachment zones in a 900 bend using the SSIIM numerical models. The spur dike installed at the middle of outer bank in 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 at downstream of spur dikes can be increased. For all submergence ratios, from the bed level upwards the crest level of spur dike, the length of flow separation zone decreases but the length of flow reattachment zone increases. By changing the dike submergence, the vortices dimensions around the dike change due to changes in the flow separation and reattachment zones.