Experimental and numerical study of critical submergence for dual intakes

Abstract

Estimation of the critical submergence for water intakes is important for avoiding air-entrainment from free surface vortices. Critical submergence can be defined as the minimum submergence required for a water intake for preventing the entry of air core of free surface vortex causing air entrainment. The present paper discusses an experimental study on the critical submergence for dual water intakes placed laterally on the side wall of an open channel under uniform flow conditions. The parameters that likely affect the critical submergence of dual intakes are identified and discussed. Intake Froude number and the approach flow Froude number are found to be the most significant parameters that affect the vortex formation at the dual intakes. Velocity field at the vicinity of the intakes were measured using Acoustic Doppler Velocimeter (ADV).Vortex formation was observed at downstream intake at critical submergence when both intakes carried same discharge. Flow at dual intakes at critical submergence was simulated using a Three Dimensional Multiphase CFD model. The size and form of the air-entraining vortex from CFD simulations were identified using volume fraction analysis. Volume fraction study was used to identify the critical submergence. The results obtained from CFD results were validated using experimental data and found to be in good agreement. The results obtained from the present paper may highly benefit the hydraulic engineers for the rational design of water intakes.