THE INFLUENCE OF GATE OPERATION ON FUNCTIONING OF AN OVERFALL SPILLWAY

Abstract

Experimental investigations have been done on a five gated overfall spillway models operating minimum number gates to pass the flow in different combinations. The behaviour of flow thus affected by the gate operation for different magnitudes of flow and the resulting downstream bed movements have been analysed from the observed velocity and scour patterns comparing them with the uniform crest flow conditions for each cane. These studies have been made with a solid roller bucket and sloping apron jump basin functioning under a prepared tailwater rating curve, Rased on the analysis the best modes of operation have been concluded for each case,, The spreading of the jet on the spillway profile has been correlated to the 1roude Number of the jet entering the dissi.. pation basin, it has been found that the spreading effectively produces an uniform flow distribution in the basin when alternate gates are operated* From the data collected during experimenta. tion the discharge characteristics for free flow conditions of the spillway have been obtained and it has been confirmed that the crest coefficient of discharge increases with the head of flow and also with the number of bays operating..