Experimental investigation of the hydraulic performance of porous bottom intakes

Abstract

Due to the technical problems of bottom intake racks, porous intakes made of rock, gravel, or sand can be a suitable alternative. This research used an experimental model to investigate the performance of porous bottom intake (PBI). To this end, the effects of various parameters, including the main channel slope, grain size distribution of porous media, the geometry of the intake structure, and the water depth in the main channel, have been investigated on the diverted flow rate during sediment-free flow. The performance of one and three-sided designs has also been compared under the same conditions. A comparison of different slopes of the main channel showed that the discharge coefficient and diverted flow of the slope of 1 % are 25 % and 15 % greater than the slope of 1.68 %, respectively. The proportion of the flow that goes through the intakes compared to the overall flow of the main channel varied between 3.5 % and 8 %. Comparing the one- and three-sided PBI models shows that, on average, the flow rate inside three-sided PBI is 72 % higher than one-sided PBI. Finally, a formula has been proposed to calculate the discharge coefficient of PBI using nonlinear multivariate regression, experimental data, and dimensional analysis. The absolute error of this formula for training and testing data is less than 0.1 for more than 95 % of the data.