Three-dimensional Numerical Simulation Research On The Influence Of Permeable Spur Dike On Flow Characteristics Of Bends

The permeable spur dike is a new type of spur dike with a special dam structure,which is permeable to water flow.Compared with the traditional solid spur dike,the backwater in front of the dam is lower,the force on the dam body is smaller,and the local scour hole is shallower.The operation is safer and more reliable.so there is a better development prospect.In this paper,based on the curve experiment data of laying out tri-groin dike,the flow movement of the curve of laying out solid groin dike and permeable groin dike is simulated by using ANSYS FLUENT software.By analyzing the longitudinal velocity and water surface shape of the two types of spurs to the bends The difference in influence is compared,the improvement effect of different spur dikes on the bend flow is compared,and then the bend flow movement of the permeable spur dam with different body parameters is simulated,and the influence of the position,length and water permeability of the pervious spur on the characteristics of the bend flow,Draw the following main conclusions:(1)Regardless of whether the traditional solid spur dike or the permeable spur dike is placed in the curve,the direction of the water flow in the curve can be adjusted and the concave bank is no longer flushed,and the water level of the curve is redistributed.Compared with the curve without a spur dike,the curve is convex after the spur dike is installed.The bank flow rate increases,and the water level rises;the concave bank flow rate decreases,and the water level decreases.(2)Compared with the curve of a solid spur dike,the main flow velocity and the backflow velocity behind the dam are smaller,and the backwater height of the dam is lower,which is more conducive to the safety of the dam itself,the stability of the channel and the silt deposition in the dam field of concave bank.In addition,the lateral drop in front of the bend dam where the permeable spur dike is laid is also smaller,and the overall improvement effect of the permeable spur dike on the water surface of the curve is better than that of the traditional solid spur dike.(3)The closer the permeable spur dike is to the entrance of the bend,the greater the mainstream velocity,the longer the action area behind the dam,and the higher the backwater in front of the dam.As the length of the spur dike increases,the flow velocity in the backflow zone and the mainstream zone after the dam becomes larger and larger,and the cross-sectional circulation range gradually decreases.With the increase of the water permeability,the main flow velocity of the bend and the scope of the backflow zone after the dam have been continuously reduced,and the average lateral drop of the water surface has increased.The development of secondary flow;when the water permeability increases to 45%,there is almost no backflow after the dam.(4)The reasonable range of the parameters of the permeable spur dike under the current conditions in this article:the position is 1/6S and before the bend,the dam length is 0.2B-0.3B,and the water permeability is about 25%.