The Influence Of Different Positions Of The Spur Dike On The Flow Pattern And Numerical Simulation

As a kind of bank protection structure in water conservancy projects,the spur dike uses its water-carrying function to change the structure of the water flow and avoid the river bank from being corroded by the water flow.This paper mainly sets up different types of spur dikes in the bends of the flume to study the influence of the setting of the spur dikes on the flow characteristics of the 180° open channel bends.The experiment includes two parts:physical model and mathematical model,to study the influence of different spur dikes in the bend on the flow characteristics.In the physical model part,the automatic water level measurement system combined with the manual measurement method and the flow rate measurement system are used to obtain the water level and flow velocity data of the measured section in the bend.The experimental data is used to analyze the changes of the water surface along the way,the horizontal drop of the water surface,and the vertical drop of the water surface.And the flow rate changes along the way.In the mathematical model part,numerical simulation is carried out through the ANSYS CFD module,the Geometry software is used to establish a three-dimensional numerical model with the same size as the physical model,and the model is imported into the Mesh software to divide the unstructured grid,and the Fluent software is used to set the solution conditions for the solution calculation,And use Tecplot and CFD-Post software to post-process the data,and compare and verify the data results with the data obtained from the sink physical model.The simulation results mainly compare and analyze the flow velocity in the bend,the scale of the backflow zone behind the dam,and the distribution and change law of turbulent kinetic energy.The main findings and conclusions are as follows.(1)Under different experimental conditions,the water level of the concave bank in the bend is higher than the water level of the convex bank,and the water level on the convex side of the bend varies more than the water level on the concave side.The water level on the convex side of the bend was higher than that on the concave side.(2)After the placement of the Ding dam,the overflow section of the river near the Ding dam shrinks,and the mainstream is biased towards the convex bank,forming a high velocity zone before and after the head of the dam,extending a larger influence area upstream and downstream of the Ding dam,and the velocity of the water near the convex bank increases significantly,which may have a certain scouring effect on the convex bank;the velocity of the water before and after the concave bank of the Ding dam decreases very significantly,which plays an obvious protective role for the concave bank.(3)The placement of different angles of Ding dams at the same location in the bend mainly affects the magnitude of water level and velocity in the bend,while the flow pattern along the bend tends to be the same;the placement of Ding dams at the same angle at different locations in the bend results in very different flow patterns along the bend,and the water level and velocity at each observation section are also different.At different locations in the bend,the 135° angle dam has the least influence on the flow of water,and the flow pattern in the bend is relatively stable,so it is appropriate to use a downward-facing dam in the project.(4)The position of the dam in the bend,in a certain range with the increase in the angle in the bend,the influence of the dam on the distance of the water flow also grows,the more obvious the phenomenon of congestion in front of the dam,the change in the water level of the bend also increases,the water surface cross ratio drop is shown to first increase and then decrease.The influence range of the mainstream area behind the dam gradually decreases,and the maximum flow velocity also decreases;however,the influence range of the water flow in front of the dam gradually increases.(5)After the deployment of the Ding dam,the water flow in the bend appears to separate,forming a vortex zone mainly counterclockwise behind the dam.When comparing different lengths of Ding dams,a dam length/river width of 0.1250 shows a relative reduction in the extent of the main flow zone and maximum flow velocity values within the bend of the Ding dam,and the scouring effect on the convex banks of the river is also significantly reduced.In the middle of the bend,it is advisable to set the dam length/river width at 0.1875 or increase the density of the dam length/river width at 0.1250,which can better protect the river bank.The data measured in the physical experiments in the paper are single point data,which do not visually reflect the flow of water in the bend,and the experimental process is long,with many consumables and huge workload.The numerical simulation results are visual and reflect the flow of water throughout the bend,further enhancing the study of water flow in the bend and reducing the workload significantly.Combining the two research methods,the data obtained is realistic and vivid,and is a good contribution to the study of the characteristics of the water flow after the placement of a Ding dam in the bend.