Introduce of Crown Wheel Spillway and Study of Its Discharge Coefficient under Free Flow Regime

Flood is a stochastic phenomenon and successful and construction of economic dam in flood discharge system is very important. In recent years, non-linear overflows, as a solution, helped designers and engineers of water sciences. In this study, new non-linear overflow weirs as Crown Wheel spillways are introduced. Discharge coefficient tests were performed under various scenarios geometry of the overflow in order to investigate the ability of the hydraulic overflow flood discharge. To study the effect of the slope floor of inlet and outlet keys (Z) on the current discharge coefficient, the slope of 1 : 0.5, 1 : 1 and 1 : 1.5 (Horizontal : Vertical) were designed and built. Then in each of the three phase variation in the slope floor of inlet and outlet keys (Z), four types of spillway with a crest length of two, four, six and eight cycles were designed, built and tested. The results indicated that by increasing the slope of inlet and outlet keys (Z), discharge flow rate will be increased. This also increases the number of cycles at low heads, leading to an increase in the flow discharge coefficient. In large heads, the feature of vortex breaking in overflows with the less number of cycles is noticeable. The results showed that the coefficient of discharge in Crown Wheel spillway is to 2.2 bigger than in a circular vertical sharp edged weir. Due to the small dimensions of this type of overflow compared to similar types, this nonlinear overflows can be considered as an efficient and economic flood discharge system for introduction to the scientific community of the country.