Correction and laboratory investigation for energy loss coefficient of square-edged orifice plate

A lot of studies have shown that the hydraulic characteristics of orifice plate are mainly controlled by its contraction ratio, but the thickness of square-edged orifice plate also has many impacts on energy loss characteristics. The primary objective of this study was to investigated the effects of square-edged orifice plate thickness on energy loss characteristics. In this paper, the effects of square-edged orifice plate thickness on energy loss characteristics are investigated by numerical simulation using CFD. Orifice plate discharge tunnel is axial symmetric, two dimensional numerical simulations of orifice plate discharge tunnel flow was used. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed. The results of the present research demonstrate that energy loss coefficient decreases with increase of the orifice plate thickness. The results of model experiment are consistence with the results calculated by using rectified equation in present paper. The CFD simulations and Model experiment for the flow through an orifice plate are carried out. For square-edged orifice plate energy dissipater, the relative orifice plate thickness T/D has remarkable impacts on its energy loss coefficient ξ. The Traditional equation (8) is corrected by numerical results. The equation (9) for calculating energy loss coefficient of square-edged orifice plate energy dissipater considering the influence of thickness is proposed and this equation is available in the condition of d/D = 0.4–0.8, T/D = 0.05–0.25, and Re > 105(Re is Reynolds number). Comparing with the physical model experimental data, the relative errors of equation (9) is smaller than 15%.

Experimental study of the effect of horizontal screen diameter on hydraulic parameters of vertical drop

The horizontal screen is one of the energy dissipater structures used on the brink of vertical drop. These structures increase the energy dissipation and the turbulence in the flow by causing the air entrainment. In the present study, the effect of the diameter of the screen with constant porosity at three different diameters on the hydraulic parameters of the vertical drop was investigated. The experiments were performed in the relative critical depth range of 0.13 to 0.39. The results showed that by increasing the relative diameter of the horizontal screen, the relative wetting length and turbulence length increased, the residual energy remained constant and the pool depth decreased. Compared to the stilling basin, the horizontal screen significantly reduces turbulence length and residual energy. The results also showed that the application of horizontal screens at the brink of the drop, with and without a downstream rough bed, could be a suitable alternative for a stilling basin.