Research On Overcurrent Characteristics Of Multi-level Curved Weir

In order to further implement the concept of "clear waters and green mountains are as good as mountains of gold and silver",promote the implementation of the "rural revitalization" strategy,promote the harmonious development of man and nature,and increase water landscapes.In the treatment of small and medium-sized rivers,the multi-level curved weir has a unique structure design and beautiful geometric shape,which can create a curved water drop and waterfall landscape effect,increase water hydrophilicity,and is widely used.Due to the many geometric parameters of the multi-level curved weir and the complex body structure,there are few studies on the flow capacity of the multi-level curved weir,especially in the application of practical engineering.It is necessary to study the flow capacity and basic hydraulic characteristics of the weir.In this paper,through the combination of physical model test method,numerical simulation method and theoretical analysis method,the flow capacity and hydraulic characteristics of multi-stage curved weir under different arc angles and different number of stages are discussed,which enriches the new weir.At the same time,the flow coefficient formula of the new weir type is fitted,which provides a certain reference value for related projects.The main research results are as follows:(1)By comparing the water level,velocity and flow results of the model test and numerical simulation,it is shown that the numerical simulation method of the multi-level curved weir using the FLOW-3D software is feasible,and the error are not more than 5%.(2)Through the physical model test,it can be seen that the water flow pattern of the multi-level curved weir is related to the upstream water level.The low head is a ternary flow,there are main flow and side flow,and the high head is a binary flow.When the water flow over the weir is a falling water flow,it has a waterfall landscape effect,and the water flow behind the weir fluctuates greatly,producing a large number of bubbles;when the water flow over the weir is excessive water flow,there is a cavity between the water tongue and the curved weir step,and the downstream air bubbles are reduced;when the water flow over the weir is a sliding water flow,the gap between the tongue and the steps is full of water flow,the fluctuation behind the weir is small,and the bubbles disappear.When the water head above the weir is constant,the arc angle has a great influence on the overflow water surface line,among which the 90° weir upper water surface line is the highest,and the 135° curved weir overflow water surface line is the lowest;The third-order,fourth-order and fifth-order curvilinear weir flow surface lines are basically the same.The numerical simulation results show that the distribution of the flow field on the multi-level curved weir is uneven,the flow velocity on both sides of the arc is greater than that at the center of the arc,and the maximum flow velocity appears at the last step.With the increase of the water head above the weir,the flow velocity before the weir increases gradually.(3)The analysis of the test results shows that under the condition of a certain weir height,the flow capacity of the multistage curved weir is inversely proportional to the arc angle ?,and proportional to the number of stages m.The flow capacity of the multi-stage curved weir is smaller than that of the equal-width broken line weir,and the flow efficiency is inversely proportional to the arc angle.The fifth-order curve weir with 90° has the strongest flow capacity.When the downstream water level is lower than the weir height,it will not affect the flow capacity.When the downstream water level is higher than the weir height,the influence of the submerged coefficient should be considered.(4)Through theoretical analysis,the main factors affecting the flow coefficient of the multi-level curved weir are determined,and the calculation formula of the multi-level curved weir flow coefficient is fitted.The error between the measured value and the calculated value is within 5%,and the fitting effect is better.Figure [45] table [13] reference [66]...