Experimental and numerical investigation on effect of trash rack on flow properties at power intakes

Abstract

In the present experimental and numerical research, the flow behavior in a reservoir and horizontal water intake was analyzed in the presence of surface vortices. To do so, velocity field, vortex strength, and Reynolds number in different horizontal sections in the reservoir and the energy loss and entrained air volume at horizontal intake pipe at three different relative submerged depths (S/D = 1, 1.5 and 2) and five intake Froude numbers (Fr = 0.8, 1.0, 1.2, 1.4, and 1.6) were investigated by installing two trash racks with 64% and 70% openings and one intake without trash rack. The velocity field and vortex strength were measured using Particle Tracking Velocimetry. Reynolds number, velocity, energy loss, and entrained air volume at horizontal intake pipe were computed by numerical simulations. The commercially available computational fluid dynamics program Flow‐3D, was used for the numerical modeling. Numerical simulations were validated by the experimental data. The experimental tests revealed that trash rack presence has a significant effect on reducing the vortex strength and velocity on the water surface. The vortex strength was decreased by 11% and 16% in the trash racks with 70% and 64% opening, respectively. Energy loss clearly increased with the installation of a trash rack. Energy loss in the trash rack with 70% opening was approximately 19–26%. In addition, some relationships were provided for calculation of vortex strength, velocity, and local energy loss in the water intake, which are in good agreement with the studies in the literature.