Application of a three dimensional numerical model and soft computing models in discharge coefficient estimation for combined weir-gate structure

Combined triangular crested weir-rectangular gate is one of the most important structures which controlling the level of water surface, measuring discharge and avoiding the sedimentation behind the weir. In this study, 4 models with different geometric conditions were simulated via Flow-3D software. Then, dimensional analysis was done to evaluate the effect of involved dimensionless parameters on the discharge coefficient. These parameters are h/b, h/d and h/y, where h is the water head over the weir, b is the gate width, d is the gate height and y is the distance between the top of the gate to the bottom of weir. Moreover, four different intelligent system models prepared and the accuracy of these models for estimation of discharge were evaluated and compared with each other. Results show that Flow-3D is very accurate in 3D simulation of this structure. Besides, Statistical indices are good for simulation the water head and discharge coefficient, in this study (RMSE, MAE and MRAE for discharge coefficient are 0.0673, 0.221 and 0.295, respectively). Moreover, results show that in all models the dimensionless parameters of h/b, h/d and h/y has inverse proportion with discharge coefficient. Discharge coefficient of combined weir-gate of this study is in the range of 0.3-0.9. On the other hand, the results of four intelligent system models of MLP, M5P, RBF and GRNN show that the MLP model is the superior model among others and respectively M5P, RBF and GRNN are in the next grade.