A network model is implemented to study the transition of flow in porous media. In this way, a real porous medium is simulated according to an orthogonal pipe network which was formed by some spheres that are connected to each other using a set of pipes. In this model the pipes play the role of existing ducts in porous medium, and the nodes (spheres) indicate existing holes in the place of duct junctions. The effects of variety in some hydraulic parameters are investigated in this model. Afterward, this network is analyzed by the combined pressurized-free surface network (CPFNET) method. The CPFNET model results were similar overall to the observed experimental data. Moreover, sensitive analyses were used based on several parameters. Due to all of them, the accuracy of this method is specified.

Stepped spillways have a wide range of applicability as a hydraulic structure in large dams to dissipate energy of high-velocity flows at a downstream area of dams as well as release overflows into the downstream. In this study, the numerical simulation of the flow over the stepped spillway was investigated by using Flow3D software as an analytic flow field. The RNG k-ε model was applied as the turbulence model, and Volume of Fluid (VOF) model was used to determine the free surface flow profiles. At the first stage, the model was verified by reliable experimental data. Then, in order to investigate the various features of skimming flow regime, 112 numerical spillway models was designed, which 96 models were stepped spillway models and 16 models were smooth spillway models (i.e., WES profile). In these numerical experiment, two step sizes, six configuration, four passing discharge and four profile slopes (15, 30, 45 and 60 degrees) with various relative discharges were considered to investigate the energy dissipation and discharge coefficient rates. The results indicated that discharge coefficient rate and energy dissipation rate have inverse relationship. Also it was observed that when relative discharges increased, energy dissipation rate decreased and discharge coefficient rate increased.