| The phenomenon of turbulent around square column exists widely in engineering scientific fields covered in bridge engineering, marine engineering and urban construction, such as bridge pier, oil mining platform, city high-rise building, trash rack and so on. Because the fluid produces complicated flow phenomena including separation, reattachment and wide wake flow accompanied with vortex-shedding, conducting a comprehensive and deeper study is helpful to people to solve the problems in practical engineering.Following a brief review on the recent study about turbulent around square column by both domestic and foreign scholars, flow field characteristics of turbulent around the square column in water is theoretically studied based on the method combining physical model experiment with numerical simulation.In physical model experiment part, we focuse on the study of flow field characteristics in different inlet flows conditions. By analyzing the time-averaged velocity field around the square column and instantaneous velocity vectorgraph in downstream of the square column, we find that:(1) The influence of time-averaged velocity field in the upstream side of square column when inlet flow increases is chiefly presented as: the increasing of inlet flows less impact on the low- velocity zone, while has a great influence in the distribution of high-velocity zone;(2) A clockwise and counterclockwise vortex structure appears respectively in left and right side of square column, and two high- velocity zones far away from the walls are positioned close to the vortex structure; as the inlet flow increases, the velocity of high- velocity zone on both sides of square column is also increased, while its increase amplitude for feature velocity is decreased;(3) Two bilateral symmetry and counter rotating vortex struct ures form in downstream of the square column, and the backflow zone length has nothing to do with changings of inlet flow, it’s consistent in order of magnitude with the side length of square column and slightly larger than that;(4) In the aspect of instantaneous flow pattern, a series of cyclic swings occurred after square column; the strouhal number which is calculated by using swing period coincides well with the previous researcher’s result.In numerical simulation part, a 3D numerical model of current around a square is set up by MIK E3 software, whose dimension is the same as the physical mode l. The model is validated by water level and current velocity data of physical mode l experiment, and calculation results are consistent well with measured data. O n the base of verification, we numerical calculate the second condition of physical model. By comparing the results of numerical simulation with physical model experiment, our main findings are:(1) In the time-averaged velocity field of square column’s upstream area, both low velocity zone and high velocity zone of them have the same distributions, and the nearer to the inflow face, the lower the speed is, meanwhile, water flow gradually divided into left and right sides;(2) In the time-averaged velocity field of square column’s left and right area, both of them have clockwise and counterclockwise vortex structure s which appear respectively in two sides;(3) In the time-averaged velocity field of square column’s downstream area, a backflow zone and two b ilateral symmetry vortex structures are both formed, their distribution of velocity zone and length of backflow zone are same basically;(4) Through analyzing numerical simulation part’s instantaneous velocity vectorgraph in downstream of the square column in continuous time, the research shows that: in the downstream side of square column, occurs a series of cyclic swings accompanied with vortex-shedding; little differences between numerical simulation part and physical model experiment part are found in the swing period and strouhal number, which shows the correctness of data from physical model experiment. |
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