Effect of dual intake direction on critical submergence and vortex strength

Intake direction is one of the most important factors which have significant effect on vortex formation at intakes. Due to the importance of withdrawal direction to vortex formation, the present study examined the effect of different intake angles on strength of vortices and critical submergence. Experiments were performed on dual and single intakes with three withdrawal directions (with angles of 0°, 45° and 90°). To calculate the strength of formed vortices, the tangential velocity component of vortices was measured using an ADV. Results showed that, by varying the intake angle from vertical to horizontal, strength of vortices decreased by 31% and 35% for single and dual intakes, respectively. An empirical relationship between the circulation number and Froude number for various submergence depths was developed for each withdrawal direction of the dual intakes. Furthermore, the critical submergence of single and dual intakes was investigated and results indicated that the critical submergence is considerably affected by changing the withdrawal directions.