Numerical Simulation Study On The Flow Around A Pile Of High Pile Wharf Under Unsteady Flow Conditions

Vertical high-pile wharf previously used for level changes little coastal harbor and estuary port.Due to the high efficiency,the vertical high-pile wharf is gradually expanding its scope of application.In the inland river area which has a large water level change and short flood period,the high piled wharf was also used.The existence of the pile column changes the flow structure.When the fluid flows around the cylinder,the flow velocity on both sides of the cylinder increases obviously,and the two sides of the cylinder can generate two rows of alternating vortex shedding.When the flow rate changes,the flow around the circular pile becomes more complex,and the turbulence intensity,pressure fluctuation and rise resistance coefficient fluctuation of the cylinder are all enhanced.These fluctuations which lead vibration and fatigue to the cylinder is very serious damage.Therefore,numerical simulation of flow around a circular cylinder under unsteady flow condition has important academic significance,but also has practical application value in determining the engineering parameters,optimizing the structure and reducing the cost of the high pile wharf.(1)The flow around a single cylinder,the fluctuating strength of the flow velocity has a certain effect on the drag coefficient of the cylinder,and the fluctuation range of the resistance coefficient increases with the increasing of the fluctuating intensity.After the flow field is stable,the upper and lower sides of the cylinder are alternately generating vortex shedding,forming a neat vortex.Under unsteady flow condition,the resistance variation range of the cylinder is larger than that of the steady flow.(2)The flow around double cylinders and three cylinders,Under the steady flow and unsteady flow the mean of the cylinder's lift and drag coefficient roughly equal corresponding to the conditions,but the drag coefficient vibration amplitude and varies in a wide range under unsteady flow.When the spacing is small,the lift and drag coefficients of parallel double cylinders and three cylinders lift and drag coefficient were larger than single cylinder,with increasing of the spacing ratio,the lift and drag coefficients of parallel double cylinders and three cylinders decrease and approache to the single cylinder,so in practical engineering the spacing ratio of tied double cylinders and three cylinders should be greater than 4.(3)The flow around two cylinders and three cylinders in tandem,when the spacing ratio is 2,the lift coefficient of two cylinders and three cylinders in tandem is 0 under the constant flow,there is no vortex shedding in the cylinders' wake region,the vortex shedding phenomenon is obvious under unsteady flow.Then the drag coefficient of two cylinders in tandem increases with the distance increaseing,the lift coefficient decreases with the increasing of distance.The flow of three cylinders in tandem is complexing than two cylinders,The lift and drag coefficients has no specific rules.The spacing ratio is less than 2 and greater than 4,the force of two cylinders in tandem and three cylindrical is smaller,the actual engineering can reference the spacing ratio.