Rahim Gerami Moghadam; Behrouz Yaghoubi; Mohammad Ali Izadbakhsh; Saeid Shabanlou
Abstract
Generally, Hydraulic jumps usually happen at the downstream of hydraulic structures like ogee spillways. In addition, one of the parameters affecting the proper design of stilling basin is calculation of the hydraulic jump length. In this study, a hybrid method (ANFIS-DE) was proposed for modeling hydraulic ...
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Generally, Hydraulic jumps usually happen at the downstream of hydraulic structures like ogee spillways. In addition, one of the parameters affecting the proper design of stilling basin is calculation of the hydraulic jump length. In this study, a hybrid method (ANFIS-DE) was proposed for modeling hydraulic jumps on sloping rough beds for first time. This approach forecasts values of the jump length by combining the Adaptive Neuro-Fuzzy Inference System (ANFIS) and the Differential Evolution (DE) algorithm. First, the variables affecting the hydraulic jump length including the ratio of bed roughness, the Froude number, the ratio of sequent depths and the bed slope were identified. Then, by combining the input parameters, five different numerical models were introduced. Furthermore, the k-fold cross validation (k=4) was utilized so as to verifying the numerical models. The results of the analysis of different numerical models indicated that the model with four input parameters (superior model) simulated the length of the hydraulic jump with higher accuracy. For the best model, the mean absolute percent error (MAPE), the correlation coefficient (R) and the root mean square error (RMSE) were predicted 4.875, 0.978 and 0.807, respectively. Finally, two parameters including the ratio of sequent depths and the Froude number were identified as the most important parameters in modeling the hydraulic jump length on sloping rough beds.
Hamed Azimi; Majeid Heydari; Saeid Shabanlou
Abstract
Dam break is an important phenomenon which significantly affects the environment as well as the inhabitants of the downstream areas of the dam. In the present study, the hydraulic break of Malpasset dam as a result of sudden flooding was simulated numerically using the FLOW-3D software. The two-equation ...
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Dam break is an important phenomenon which significantly affects the environment as well as the inhabitants of the downstream areas of the dam. In the present study, the hydraulic break of Malpasset dam as a result of sudden flooding was simulated numerically using the FLOW-3D software. The two-equation k-ε turbulence models and RNG k-ε turbulence model were used to simulate the flow field turbulence. Also, the free-surface variations of the flow were simulated using the VOF (Volume of Fluid) scheme. The results obtained from the numerical model were in good agreement with those predicted by the EDF model. Based on the simulation results, the maximum pressure occurred at the lower layers of the flow and reduced as the free surface of the flow was approached. The maximum pressure increased at each point in time. The maximum longitudinal velocity occurred at the front of the advancing wave resulting from break of the dam, and subsequently decreased due to the increasing depth at the downstream of the dam. Additionally, the effects of obstacles with different shapes on the flow pattern arising from dam break (due to sudden flooding) were also investigated. Examination of these effects revealed that the cubic obstacle placed obliquely in the flow direction produced the maximum separation region at its downstream. Conversely, this separation region was eliminated completely when a cylindrical obstacle was used. The maximum and minimum Froude numbers were obtained for the flow encountering the perpendicular cubic obstacle and the flow impacting the cylindrical obstacle, respectively.
Majid Heydari; Shima Abolfathi; Saeid Shabanlou
Abstract
There are found numerous methods to measure flow in open channels. The simulation of water flow in channel requires mathematic calibration of the structures in channel so that the water level and the discharge become compatible with demand. Sluice gate is one of the most important structure which can ...
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There are found numerous methods to measure flow in open channels. The simulation of water flow in channel requires mathematic calibration of the structures in channel so that the water level and the discharge become compatible with demand. Sluice gate is one of the most important structure which can perform in free and submerged flow. In this research, there were experiments on a sluice gate mounted in lab flume of 12.5 m, 0.6 and 0.65 length, width and height, respectively, in the slope of 0.0002. Some equations of measuring the discharge from the sluice gate extracted from Energy equations and Momentum were calibrated using two metaheuristic algorithms of simulated annealing and ant colony. After the sensitivity analysis of algorithm was done, the optimal coefficients of discharge obtained for the Conventional equation of discharge in free and submerged flow was obtained 0.686, and 0.881. Also, in calibration of Energy-Momentum method for submerged flow, the optimal contraction coefficient was 0.533. finally, the methods were assessed and compared for which the statistical indexes show the favorability of results.
Majid Heydari; Jalal Sadeghian; Saeid Shabanlou
Abstract
Manning roughness coefficient is one of the most important parameters in designing water conveyance structures. Unsuitable selection of this coefficient brings up some mistakes. This research aims to present a method to determine the Manning roughness coefficient based on a combination of optimization ...
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Manning roughness coefficient is one of the most important parameters in designing water conveyance structures. Unsuitable selection of this coefficient brings up some mistakes. This research aims to present a method to determine the Manning roughness coefficient based on a combination of optimization algorithm of simulated annealing (SA) with gradually varied flow equations. Therefore, in a lab rectangular flume of 12 m, 60 cm and 65 cm in length, width and height with fixed channel bed slope of 0.0002, nine series of water level profiles were carried out. Then, an objective function based on observed and calculated water level gradient was defined to decide on manning roughness coefficient while it was minimized with simulated annealing optimization method. The values of objective function parameters were discussed by sensitivity analysis and the most optimal objective function was obtained. To measure the accuracy of coefficient obtained, Statistics indices of R2, Root mean square error (RMSE), Mean bias error (MBE), d were used. The results showed that manning roughness coefficient has a great accuracy.