Analysis On The Impact Of Complex Inflow On Square Piers

With the rapid development of economy and society,the influence of the shape of the pier from square to round and oval is a worthy engineering problem.In the actual engineering,the piers are in the nonuniform flow field,and the current research on the flow of the bluff body is concentrated in the uniform flow condition.The flow from the uniform flow into a non-uniform flow,the structure of the flow field structure and,the drag force and the lift force will change greatly.In order to investigate the effects of linear shear flow on characteristics of flow past a square cylinder,a numerical model for shear flow past a square cylinder was established by introducing the convective outflow boundary condition into the characteristic-based operator-splitting finite element method.A linear shear flow past a square cylinder at Re=100,k=0.0~0.5 is researched.The numerical results show that the shear parameter k has a significant effect on the two rows of vortices in the wake of flow past the square cylinder,and a larger k value inhibits the vortex shedding from the cylinder.When k≥0.4,the formation region of vortices behind the cylinder becomes a triangular zone.As the value of k increases,the stagnation point shifts towards the lateral separation point.When k≥0.3,the location of the stagnation point remains unchanged.The significant change in the mean drag coefficient occurs in the range 0.2≤k≤0.25.When k≥0.2,the mean lift coefficient is negative.The results of linear shear flow past two equal-sized square cylinders in tandem arrangement show that the ratio of S/D and shear constant k have a great impact on the flow field structure,the force parameters,the surface pressure and the drag and lift phase diagram.The stability of the flow field of the tandem cylinders under uniform flow conditions is related to whether the negative region in the region is continuous.And this relationship does not take place under shear flow.The critical spacing is S/D=4~5 and S/D=3~4,respectively,when k = 0 and 0.1 are obtained by combining the flow field structure and pressure cloud.The results of the flow past oval piers show that with the increase of L/D,the mean drag coefficient increases first and then decrease,and the magnitude of the lift coefficient and Strouhal number decrease.