Experimental Assessment of the effect of positive Variation of weir in cross section on discharge coefficient of triangle weirs structures

Weirs are always one of the most important components of water transmission networks, due to its simple structure and function. These components play an important role in the hydraulic structures by regulating the water surface, measuring the flow discharge and increasing the water level. And as a result, provide water heights needed to divert the desired flow into the lateral channels. Also, these structures are used as flow measuring devices of the important applications of overflows, the secure flow of floods behind the dams. The purpose of this study is to investigate the investigation the effect of positive Variation of weir in cross section on discharge coefficient of triangle weirs structures and provide a relationship for estimating the discharge coefficient based on geometrical hydraulic parameters. The discharge coefficient was defined as a function of Froude number (Fr), angle of vertex, ratio of water head to height of weir (H/P) and ratio of water head to effective length (H/Le). To achieve this aim, several experiments were done in the water and sediment laboratory, located in Gorgan agricultural sciences and natural resources university . The experiments were accomplished by 4 different angles of vertexes and 3 different slopes. Then, an equation was set by using Gene Expression Programming (GEP) to estimate the discharge coefficient by more accuracy. The findings showed that the discharge coefficient would decrease by increasing trend in the side slopes in the constant Froude number. Also, by increasing the ratio of H/P a decreasing and increasing trend in the discharge coefficient was seen, respectively. The results show that GEP predicted the coefficient of triangle weirs structures with R2 of 0.9676 and 0.8591 and RMSE of 0.0706 and 0.0247 for training and testing stages, respectively. This model gave better results compared by regression equation with R2 of 0.9253 and 0.8029 and RMSE of 0.0467 and 0.084 for training and testing parts, respectively. In the other words, the error of coefficient triangle weirs structures prediction was decreased about 47.10% using GEP approach. The results show that GEP intelligence approach is an adequate model to coefficient triangle weirs structures. Also, the results of traditional regression equations were improved using this method. In the other words, these results indicated that GEP is reliable to evaluate the coefficient discharge of triangle weirs structures by more accurate estimation. So; use of this way is suggested in future studies related to this topic.