Passive Water Intake Screen to Reduce Entrainment of Debris and Aquatic Organisms Under Various Hydraulic Flow Conditions

In order to minimize problems associated with the operation of surface water intakes, passive wedge-wire screens are increasingly being used. Deflectors of special design are placed inside the intake heads to reduce local maximum inlet velocities and to ensure a uniform velocity distribution over their surface. The use of computer software based on Computational Fluid Dynamics (CFD) methods enabled simulations and optimization of the intake head design. Subsequently, a series of laboratory tests was conducted. Several scenarios were considered, varying the flow rates in the hydraulic flume and taking into account both the presence and absence of the deflector. Velocities around the intake head were measured, and the amount of particles in the water attracted to the head surface under the analyzed conditions was assessed. The results confirm the clear effect of the deflector on the velocity distribution. Its use originates reduced velocities near the head surface, as well as a smaller amount of debris deposited on the screen, while maintaining efficiency. At the same time, lower inlet velocities close to the head surface reduce the risk of entrainment and potential injury or mortality of young fish, fry, and eggs.