Experimental Study on Hydraulic Characteristics of Porous Bottom Intake in Clear Water

Bottom intakes are hydraulic structures widely adopted for diverting water in steep rivers. The problems of vibration، corrosion، deformity، and clogging of the bottom racks by sediment، freezing and foliage inspire a new system of bottom intake in which a filled trench of porous media replaces the bottom racks. In the present paper we have analyzed the data obtained from a systematic series of experiments carried out in a laboratory two-story flume. Measurements of the diverted discharge were performed for different rates of flow، grain size distributions، surface slopes and dimensions of intake as well as important factors. Also the relationships presented in previous studies، are compared with the results of new experiments and the characteristics of the physical behavior of these equations are investigated. Due to lack of the validity in previous models، a new equation for estimating discharge coefficient and flow diversion in porous bottom intake is presented، by using dimensional analysis and multivariate regression with experimental observations. The robustness of the proposed relationship is confirmed by the principles of hydraulic behavior of this intake and the comparison between the calculated discharges through the proposed relationship and those measured in an extensive series of experiments، characterized by ranges of the relevant flow parameters much larger than those investigated in the present contribution.