Effect of Multi-gates Regultators Operations on Downstream Scour Pattern under Submerged Flow Conditions

Failures barrages 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 barrage 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 effects of operations of gates of mutlivents regulators on scour pattern are presented. The observed results on scour patterns are well explained in terms of bottom velocity patterns over the rigid bed upstream of the movable bed. The experimental program was carried under submerged flow conditions. Symmetric and unsymmetric operation of main gates and emergency gates are considered. An electromagnetic flow meter is used to measure the velocity components (in x and y directions) near bed at a predefined mesh over both the rigid bed and the movable bed. Both the pattern of the velocity vectors and the scour pattern for each run are plotted to qualitatively trace the interactive effects between the velocity pattern (relative magnitude and direction of the bottom velocity over the rigid bed) and the scour pattern (distribution of scour holes and the relative location of the maximum scour depth). It is observed that the scour pattern and hence the maximum depth of scour is a function of the bottom velocity pattern, 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 relative maximum scour depths are presented.