Flow Discharge in Bottom Intakes with Porous Media

AbstractBottom intake is one of the most appropriate systems for diverting discharge in steep rivers. Bottom intake with porous media is a new system of diverting discharge which can be replaced by bottom rack intakes. To investigate the hydraulic flow characteristics on diverted discharge of this intake, an experimental model was designed in which the inflow, diverted discharge and remained flow of porous media intake can be measured. In the present research, measurements of the diverted discharge were performed for different rates of flow, grain size distributions as well as surface slopes of intake with clear water. According to the obtained results, by increasing the inflow discharge, the rate of diverted discharge increases gradually and then reaches to a constant value. Any increment of the surface slope above the intake also decrease the relation diverted flow. It is found that the grain size of the porous media has a great influence on the diverted flow. By increasing the grain size diverted flow increases, too. Dimensional analysis and experimental results were used to estimate the discharge coefficient of porous media. Analytical analysis on experimental data shows that the discharge coefficient of porous media intake is about 0.1. Also an empirical-theoretical relation is proposed to evaluate the diverted discharge of this kind of bottom intakes.