The effect of submergence ratio on flow pattern around short T-head spur dike in a mild bend with rigid bed using numerical model

Spur dikes are hydraulic structures frequently applied to protect rivers’ banks. Since flow pattern around a spur dike located in a rivers’ bend is particularly complicated due to the existence of secondary flow and helical flow, the effect of submergence ratio on flow patterns around a short T-head spur dike located in a 90° bend has been monitored numerically in this study. The numerical data are verified with experimental data obtained under non-submerged conditions, which indicate the numerical results are in accordance with experimental data. In this research, the numerical simulation based on various submergence ratios is done using FLOW-3D software to analyze. The results showed an increase in dimensions and the number of vortices associated with an increase in submergence ratio so that for the amount of 50% submergence, two vortices form around outer wall and an area downstream of the wing of spur dike, at bed level. Moreover, the length and width of separation zones were estimated to be 1.6 and 1.5 times larger compared to non-submerged condition, respectively.