Study on Hydraulic Characteristics of Triangular Labyrinth Side Weir
The labyrinth side weir has a large discharge capacity.It is widely used in flow control,farmland irrigation and drainage systems.In order to study the complex hydraulic characteristics for the triangular labyrinth side weir,the variation law of the discharge and the factors affecting the discharge,in this study we firstly carry out the numerical simulations regarding the hydraulic performance of a labyrinth side weir in 15 working conditions based on FLOW-3D software and RNG k-ε turbulence model.Its purpose is to obtain the hydraulic characteristics such as water surface flow pattern and velocity distribution of the side weir.Secondly,the dimensionless parameters affecting the discharge coefficient Cd of the labyrinth side weir are derived by Buckinghamπ theorem.Then the change rule between the Cd and the dimensionless parameters is explored.Finally,the calculation formula for discharge is obtained by developing artificial intelligence algorithm Genetic Programming(GP).The results show that the water in the main channel is in tranquil flow.When the weir crest angle θ is small,the secondary flow changes the flow pattern and direction of the water surface.The flow velocity changes sharply at the position close to the side weir,and vortexes occur inside the side weir.With the increase of θ,the water tongue above the side weir changes from symmetric distribution to the right side leakage,and the backflow inside the side weir gradually disappears.Cd decreases with the increase of the upstream Froude number(Fr)and the ratio of the overflow front to the upstream water depth(l/h1),and increases with the increase of the ratio of the weir height to the upstream water depth(p/hi).The greater the θ,the greater the change of Cd.The model evaluation results show that the calculation formula has the determination coefficient R2=0.913 and the root mean square error RMSE=0.045.Moreover,the predicted discharge coefficient Cd has a great fitting consistency with the experimental scatter diagram,with the data points evenly and symmetrically distributed around the fitting line.It shows that the results of GP algorithm are sufficiently accurate and can meet the accuracy requirement of the flow measurement in irrigation district.This work can provide theoretical basis and technical support for the application of labyrinth side weir in practical engineering.
triangular labyrinth side weirshydraulic parametersgenetic programming algorithmnumerical simulation
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