| Piano Key Weir is a new type of labyrinth overflow weir,with super strong discharge capacity,and its upstream and downstream upstream suspension design overcomes the defect that the traditional labyrinth weir base covers a large area,so that it can be more widely placed In the dam or spillway,effectively solve the problem of insufficient flood discharge capacity of various reservoirs.Due to the complicated flow state of the Piano Key Weir,the numerous shape parameters and the size of the discharge capacity directly depend on the size of the shape parameters,it is of great significance to study its hydraulic characteristics and shape parameters.In this paper,combined with model test of Piano Key Weir,using FLOW-3D software,RNG turbulence model and free surface capture technology of VOF method are used to simulate and study the influence of upstream and downstream overhang ratio on the discharge characteristics of Piano Key Weir and the erosion characteristics of Piano Key Weir downstream.The main research contents and results are as follows:(1)Through experiments and numerical simulations,the discharge characteristics of an asymmetrical Piano Key Weir with an overhang ratio of 2.5 were studied.Combined with the grid independence and convergence analysis,the feasibility of this numerical simulation method for the simulation of the discharge of the Piano Key Weir is verified by comparing the information such as the flow rate,the head above the weir,the water surface line,and the flow pattern.The flow characteristics,velocity distribution and pressure distribution characteristics of Piano Key Weir under symmetrical arrangement.(2)The flow of six kinds of Piano Key Weir when the overhang ratio is 1.0,1.5,2.0,2.5,3.0 and ? are calculated by simulation,and the change rule and influence mechanism of the discharge capacity with the overhang ratio parameter are analyzed.The results show that theoverhang ratio is an important shape parameter that affects the discharge capacity of the Piano Key Weir.Under the water head on the same weir,the larger the overhang ratio,the larger the discharge flow of the Piano Key Weir.When the head above the weir is 0.7,the maximum weir of the Piano Key Weir with an overhang ratio of ? is about 25% more than when the overhang ratio is 1.The analysis of the discharge capacity of the overflow fronts between the six types of Piano Key Weir shows that the difference in the discharge capacity of the side overflow fronts determines the size of the discharge capacity of the different inverted Piano Key Weir,and the longer the upstream overhang The water head near the upstream part of the side overflow front edge is more close to the head on the weir,thereby increasing the side discharge flow.(3)A mathematical model of sediment was used to discuss the scour pattern downstream of the piano weir.According to the Jüstrich scouring test results,the turbulence model,sediment mathematical model and grid were calibrated,and the flow,water level,and crater shape were verified by comparison.Finally,a reasonable numerical simulation calculation scheme was determined.Furthermore,the effects of different flow rates and sand particle sizes on the crater morphology,recirculation area,velocity field,turbulent kinetic energy,and shear stress on the bed surface were simulated and compared.The particle size decreases with the increase of the particle size of the sand;the maximum mound height will decrease with the increase of the flow rate until it approaches the original height of the river bed,and the change with the increase of the particle size of the sand is not obvious. |
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