Laboratory Evaluation of the Effect of Floating Debris Accumulation at Crown Wheel Weirs on the Hydraulic Characteristics under Cumulative Test

In this research the effect of floating debris accumulation in the debris flow at the weir entrance on hydraulic coefficients of crown wheel weir is discussed. For this purpose, an effort was made to create different amount of blocking at the opening of crown wheel weir, by using experimental setups and by use of woods with various slenderness coefficients. In order to study the effect of weir opening shape on the Hydraulic Profile, several conditions were created by changing the gradient keys (z) and number of cycles (n) of crown wheel. Regardless of the shape of inlet to intake, results showed that increasing the slenderness coefficient decreases the possibility of blocking in overflow openings and consequently, reduces the upstream head water and increases the coefficient of dischargespill flow. In oter words by changing the slenderness coefficient from 15 to 20 and 25 respectively, the discharge flow on an average increased from 8.02 to 14.44 percent. . Moreover, the key slope (z) and cycle numbers (n) of crown wheel weir, affected the amount of blocking and consequently characteristics of hydraulic flow such that the best performance belonged to key slope of equivalent to1.5 which was observed in weirs with 8, 6, 4 and 2 number of cycles, respectively.