| As a common discharge structure,side weirs are widely used in flow control,farmland irrigation and drainage systems.In recent years,with the significant increase of extreme weather and rainstorm flood,new requirements have been put forward for the discharge capacity of discharge structures.Because the labyrinth side weir has a large discharge capacity,it can be used as an effective solution to improve its discharge capacity.At the same time,the labyrinth weir has both positive water flow and lateral water flow.After the water flow passes through the top of the weir,it will be concentrated and discharged.The water tongues that collide with each other make the hydraulic characteristics of the labyrinth weir more complicated than the linear weir.Therefore,this paper first uses FLOW-3D to simulate the three-dimensional flow field of triangular labyrinth side weir and semi-circular labyrinth side weir,and analyzes the hydraulic characteristics of different side weirs in detail.On the basis of this data set,the MATLAB program is used to develop the side weir discharge capacity prediction model.Finally,based on the global sensitivity analysis method,the influence mechanism of geometric parameters of different side weirs is analyzed.The following conclusions are as follows.1、For the labyrinth side weirs,from the main channel to the entrance of the side weir,the Froude number the whole flow process is subcritical flow,when the water flows through the crest of the weir,the flow regime changes complicated,and the Froude number is increased.For the triangular labyrinth side weir,when the angle of the crest of the weir a=30°,the water tongue on the crest of the weir is symmetrically distributed,and as a increases,the length of the overflow front of the side weir becomes shorter,and due to the inertia of the water flows,the water is discharged to the right of the side channel,which is especially significant when the angle of the crest of the weir a=150°.For the semi-circular labyrinth side weir,the change of water depth at the crest of the weir and the velocity of traveling flow is very sensitive,at this time,Fr>1,which indicates that the water flow over the weir is supercritical flow.2、When the single model Extreme Learning Machine(ELM)is used to predict the discharge coefficient of the triangular labyrinth side weir and the semi-circular labyrinth side weir,the average error of the model is 5.76%and 2.03%respectively in the testing stage.After optimizing the hyperparameters of ELM through Bayesian network,the average errors of the optimized model Bayesian Extreme Learning Machine(BELM)in the testing stage are 4.19%and 1.19%,respectively,and the errors are reduced by about 27.26%and 41.38%,respectively,indicating that BELM has high accuracy,stability and generalization prediction ability when predicting the discharge capacity of labyrinth side weirs.3、The sensitivity analysis of Sobol’s method shows that for the triangular labyrinth side weir,the weir top angle θ,the ratio of weir height to weir head(p/h1),the ratio of side weir width to main chan nel width(LIB),the ratio of overflow front length to weir head(l/h1),and the Froude number in the upstream of the channel(Fr),and the first-order sensitivity coefficient(Si)are 0.1491,0.081 8,0.0568,0.0652 and 0.099,respectively.The global sensitivity coefficients(Si)are 0.4218,0.2393,0.1777,0.4152 and 0.4393,respectively.For the semi-circular labyrinth side weir,the ratio of weir head to semi-circular diameter(h1/D),the ratio of main channel width to semi-circular diameter(B/D),the ratio of side weir height to semi-circular diameter(P/D),and upstream Froude number(Fr),and the first-order sensitivity co efficient S1 are 0.1903,0.1131,0.0881 and 0.0143,respectively,and the global sensitivity coefficient Si are 0.5909,0.3972,0.3397 and 0.4274,respectively. |
PDF Full Text Request