Determination of the outflow proportion of bottom intake with trash rack by controlling the amount of opening between racks with computational fluid dynamics approach

Tyrolean weir has a hydraulic trash rack that is installed through the river stream for water-intake. In this paper, hydraulic flow of this structure is simulated three-dimensionally, and its perfor-mance is studied through a change of the amount of the opening between trash racks. The modeling and analysis is done with AN-SYS CFX 16.0. The accuracy of numerical model and the results are confirmed by comparing the parameters such as discharge of the weir output and wetted trash rack length with models and re-sults of the prior researchers. To generalize the results, Tyrolean weir is investigated in cases of three different input discharge and three different inclinations of the trash rack from the horizon (0%, 10% and 20%). The results show that increasing the inflow in a given inclination of the weir surface, less part of the water-intake is as a slip of water over the network and pouring of that in the weir. For instance, 35% opening is required to water-intake of 50% of maximum input discharge of 12 lit/ (s.m).