Effects of Multi-gates Operations on Bottom Velocity Pattern under Submerged Flow Conditions

Failures of barrages or regulators or parts of them may be expected when excessive scour patterns are observed downstream of such structures. Severe and excessive scour may be largely due to unsymmetric operation of gates especially when a multi-vents barrages or regulator is being considered. Previous investigations proved that the scour patterns downstream hydraulic structures are functions of the bottom velocities among other relevant factors such as Froude number, operation of gates, .... etc. In this paper, the results of an experimental investigation on the effect of operations of gates of mutli-vents regulator on the pattern of bottom velocity (velocity near bed) are presented. The experimental program was carried under submeregd flow conditions. Symmetric and asymmetric operation of main gates, emergency gates and mixed operation of main and emergency gates are considered. An electromagetic flow meter is used to measure the velocity components (in x and y directions) near bed at a predefined mesh over both rigid and movable beds. The pattern of the velocity vectors for each run is plotted to indicate the relative magintude and direction of the bottom velocity, which in turn, could be used to predict the pattern of scour downstream of rigid bed of the multi-vents regulator. It is observed that the velocity pattern is a function of the operation of gates, type of gates (main or emergency), Froude number at the vena contracta, and submergence ratio. The qualitative and quantitative effects of all these parameters on the bottom velocity are presented in the present research paper.