Evaluation of Effective Factors on Flow Discharge in Bottom Intakes with Porous Media in Clear Water

Applying bottom racks to divert water from the river bed is one of the most common methods in water diversion works. Problems due to rack installation on diversion channel have led to propose new idea of bottom intake with porous media. In the present investigation by conduduction of several experiments and by using laboratory equipments, , diverted discharge were measured for different grain size distributions of porous media, three lengths and three heights for intake and rates of flow. According to the obtained results, as the the grain size increased, diverted flow was also increased, but as the increasing uniformness coefficient of grain intake was increased, diverted flow decreased between 4 to 6 percent. diverted discharge increased with an increase of the length and height of intake. For example increasing intake length from 15 cm to 45 cm for intake model with H=10 cm, d50=15.3 mm and Qt=14.82 lit/s, caused 25% increase in diverted discharge. Minimum and maximum values of relative diverted discharge in investigation was found to be 13 and 90 percent respectively. Comparison of the results of this research with previous research findings, showed that the rate of diverted discharge under new conditions decreased. By analysis of experimental data and using dimensional analysis and multivariate regression, a new equation for estimation of discharge coefficient with the value of R2=0.897 was developed.