Numerical Simulation Research On Flow Characteristics Of Cylindrical Piers With Water And Water-Sand Two Phase Flow

As one of the most common and important forms of blunt body flow,flow around circle cylinders is widely existed in the engineering field.When the fluid flows around the cylinder,the phenomenon of vortex shedding will occur at the end of the cylinder.The periodically changing forces caused by the periodic vortex shedding eddied will produce corresponding dynamic response and will make the cylinder structure vibrated or even destroyed.The diffusion of particles around the flow wake of cylinders is also a common phenomenon in the engineering field.For example,the movement of sand particles in the flow wake of a cylindrical pier is a typical movement of particles in the flow wake of a cylinder.Therefore,the research on the flow around cylindrical piers and the motion characteristics of the particles in the wake of cylindrical piers has important engineering value and practical significance.Based on the URANS method of FLUENT,numerical simulation of flow around infinite-length single cylindrical pier,finite-length single cylindrical pier and a double cylindrical piers of finite-length with spacing ratio 4 was carried out under the conditions of water and water-sand two-phase flow with Reynolds number of 1×106.The hydrodynamic characteristics such as time-averaged and transient flow field information and the motion characteristics of sand at different positions in the cylindrical wake area were analyZed.The main conclusions are as following:(1)Three-dimensional characteristics of flow around a finite-length single cylindrical pier are more obvious than those around an infinite-length single cylindrical pier with Reynolds number of 1×106.The wake area around the infinite-length single cylindrical pier presents a vortex shedding pattern similar to that of the smooth cylindrical tube,while the flow around the finite-length single cylindrical pier presents a special "horseshoe" vortex at the bottom wall surface,which makes the wake field more complex.(2)Under the condition of spacing ratio 4 with Reynolds number of 1－106,the upstream cylindrical pier still has an influence on the flow field of the downstream cylindrical pier and the force characteristics of the upstream and downstream cylindrical piers are obviously different.In a typical cycle,the vortex shedding frequencies of the upstream and downstream cylindrical piers are the same,which is manifested by the mode in which the vortices fall off together.(3)In the wake region of finite-length single cylindrical pier and a finite-length double cylindrical piers with spacing ratio 4,the velocity of the flow field changes sharply near the wake region of the cylindrical pier,and the followability of sand and fluid is poor.However,in the downstream flow field far from the cylindrical pier,the followability of sand and fluid is good,and the velocity distribution of sand and fluid is not significantly different.