Numerical Solution of Free Surface Flow in Homogeneous Rockill Dam under Non-hydrostatic Pressure Distribution Condition

Document Type : Research Paper


1 PhD of hydraulic structures, Dept. of Irrigataion and Reclamation Engineering, Faculty of Agriculture and Engineering Technology, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran

2 Full Professor, Dept. of Irrigataion and Reclamation Engineering, Faculty of Agriculture and Engineering Technology, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran

3 yasooj university


Due to environmental considerations, application of rockfill in designing of hydraulic structures, such as rockfill dams is increased. According to hydraulic principles, by increasing water surface and bed slope as well as significant curvature of streamlines, the vertical pressure distribution is deviated from hydrostatic state. Therefore, because of severe energy loss and big difference between upstream and downstream water surface elevation in rockfill porous media, pressure distribution is expected to be non-hydrostatic. In this study, using the distribution of non-hydrostatic pressure, the energy equation and considering the quadratic form of friction loss for non-Darcy flows, the equation representing the longitudinal profile of the water surface inside the rockfill dam is presented. In order to check the accuracy of this equation, experiments on homogeneous rockfill dams consisting of round river materials with average diameters of 1.68, 2.27, 4.07 and 4.84 cm and in two lengths of dams (50 and 100 cm), were performed in the hydraulic laboratory of the department of Irrigation and Reclamation Engineering, University of Tehran. Numerical solution of the equation representing the free surface flow inside the rockfill dam in comparison with the laboratory observations show that the equation is well able to calculate the longitudinal profile of the water surface in rockfill dams at low and high discharges. Statistical analysis of the results shows that the average relative error of estimates is 3.96%.


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