The purposeful design of triangular flip bucket angle and width of the spillway chute using genetic algorithm

The criteria for hydraulic design of flip buckets are based on the analytical and experimental methods obtained from physical models. Due to the importance of spillways in the safety of dams, these structures should be secure and highly efficient. In the present study, in order to increase the efficiency of the spillway, it has been attempted to optimally design wide- triangular flip bucket angle and chute spillway by applying genetic optimization method. To achieve the aforementioned objectives, firstly, the equations derived for dynamic pressure head on the flip bucket, the exit jet length, and scour depth have been used as the parameters of objective function (Hojjati, 1392). Thereafter, the weights of objective function parameters have been calibrated using data related to the spillway of Karoon 3 dam, and eventually triangular flip bucket angle and chute spillway have been designed with the help of genetic optimization algorithm. Taking into consideration the design parameters of Karoon 3 spillway, the spillway length and angle of triangular flip bucket were obtain as 17.4 meters and 30 degrees, respectively by means of genetic algorithm. However, their difference with , the spillway length and angle of triangular flip bucket of Karoon 3 dam has been obtained as 16% and 0%, respectively wich indicates that the genetic algorithm enjoys high potential for designing the aforementioned parameters. The width of downstream and deflector angle have been obtained 3.6 meters and 30 degrees, respectively with 70% decrease of discharge, 45.4% increase of Froude number, and consistency of the weights of objective function and flip bucket height. Also by assuming the weight constant, increasing Froude number and decreasing the width of spillway, the flow rate increases and results in the increase of the parameters used in the objective function. With the design parameters of Karoon 3 dam remaining constant and the significant increase of weights associated with the parameters of pressure and scour depth independently of each other; spillway width was designed very largely which is not cost-effective. As well, with the design parameters of Karoon 3 dam remaining constant and the decrease of weights associated with the exit jet length in a way that all the three parameters can be viewed equally effective in minimizing the objective function, maximum dynamic pressure and scour depth have been reduced as much as 7% and 16%, respectively; however, the jet length has undergone a reduction of 12% and its width has undergone an increase of 38% which is not fully desirable. As a result, the weight reduction of jet length is not cost effective due to the slight change of scour depth and the maximum increase of pressure on the flip bucket and also the big increase of spillway width. Therefore, it seems preferable that the effect of jet range parameter outweigh the other two parameters because increasing the jet range results in the further depreciation of flow energy which is the main focus of the ski jump dissipator construction.