PHYSICAL AND NUMERICAL INVESTIGATION OF THE SKIMMING FLOW OVER A STEPPED SPILLWAY

In the last two decades experimental research on stepped chute hydraulics has been very active. In this paper, the developing flow region over the stepped spillway was investigated using a physical and a numerical model. The numerical model is based on the 2D Navier-Stokes equations, where the free surface is represented using a refined Volume-Of-Fluid (VOF) algorithm, the internal obstacles are described by means of the Fractional Area-Volume Obstacle Representation (FAVOR) method. The numerical results were compared with experimental data obtained in a large scale model using the particle image velocimetry technique. The stepped channel is 0:50 m wide and 2.0 m high, with step height of 0.05 m and bottom inclination of 51.3 degrees corresponding to a slope (V:H) of 1:0.8. At the upstream region of the chute the free surface is smooth and glassy and no air entrainment occurs, the numerical model is suitable for obtaining the characteristics and the influence of the presence of the steps. Typical flow phenomena in the cavity of the steps, in the shear layer and in the main flow are described. Velocity and turbulence intensities profiles are presented. The agreement between the numerical results and laboratory measurements was satisfactory.