Cylindrical weir shapes offer a steady-state overflow pattern, where the type of weirs can offer a simple design and provide the ease-to-pass floating debris. This study considers a coefficient of discharge (Cd) prediction for oblique cylindrical weir using three diameters, the first is of D1 = 0.11 m, the second is of D2 = 0.09 m, and the third is of D3 = 0.06.5 m, and three inclination angles with respect to channel axis, the first is of θ1 = 90 ͦ, the second is of θ2 = 45 ͦ, and the third is of θ3 = 30 ͦ. The Cd values for total of 56 experiments are estimated by using the radial basis function network (RBFN), in addition of comparing that with the back-propagation neural network (BPNN) and cascade-forward neural network (CFNN). Root mean square error (RMSE), mean square error (MSE), and correlation coefficient (CC) statics are used as metrics measurements. The RBFN attained superior performance comparing to the other neural networks of BPNN and CFNN. It is found that, for the training stage, the RBFN network benchmarked very small RMSE and MSE values of 1.35E-12 and 1.83E-24, respectively and for the testing stage, it also could benchmark very small RMSE and MSE values of 0.0082 and 6.80E-05, respectively.

The main purpose of broad crested weir used in open channels is to raise and control upstream (U/S) water level. The most important problems for downstream of hydraulic structures are the local scour formed at the downstream of hydraulic structures. Scour control process considered as the main objective to ensure safety and economical design of hydraulic structures to prevent any serious failure in the future. In this study, four models of Single-Step-Broad-Crested weirs with different angles were tested under different flow intensity for duration of 6 hours. Acoustic Doppler Velocimeter (ADV) was used to investigate the velocity field. The results showed that, the model C reduces local scour hole volume was about 87.6%, 55.58% and 44.8% and the maximum depth of scour reduced 73.43%, 32.56% and 24.22% as compared with model D at each discharge.

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