Numerical Simulation Of Forced Oscillating Of A Cylinder With Different Cross-Sections

The problem of vortex-induced vibration is a classic subject in fluid mechanics.VIV is common in engineering and daily life,and it has become the focus of scholars.Vortex-induced vibration is a special form of cylinder flow that causes fatigue damage to the cylinder,which will affect the safety and stability of the structure.In engineering applications,the phenomenon of vortex-induced vibration is widespread,especially in the field of ocean engineering and wind engineering,the study of vortex-induced vibration is very necessary and important.The research on vortex-induced vibration can be divided into self-excited vibration and forced vibration.In this paper,the computational fluid dynamics method is used to numerically simulate the cylinders with different cross-section shapes under Reynolds number Re=200.The flow field is calculated by using the finite volume method to solve the N-S equation of the two-dimensional incompressible viscous fluid to obtain the flow field data.The periodic vibration of the cylinder is programmed by the DEFINE＿CG＿MOTION of UDF,and the dynamic layer method in dynamic mesh technology is used to realize the forced vibration of the cylinder,so as to realize the flow field simulation of the moving cylinder.Firstly,the flow around the cylinder and the forced vibration of the cylinder are simulated to verify the correctness of the simulation method and the programmed program.Then the transverse forced vibration of the opposite column and the hexagonal column under uniform flow is simulated.The different frequency ratios of the dimensionless amplitude ratio A*=0.2 and 0.4 are selected to study the lift coefficient and resistance of the cylinder.The coefficients,the FFT spectrogram,and the vortex shedding mode were analyzed,and the phenomenon of beat vibration and locking was captured.The results show that the forced vibration of the square column is different from the forced vibration of the cylinder.The flow field changes sharply when the square column vibrates,and the lift coefficient and the drag coefficient are large.The locking intervals of the cylindrical and hexagonal columns increase with the increase of the amplitude ratio,while the square columns remain basically unchanged.The range of the lock interval is located at a frequency ratio greater than one,as opposed to a cylindrical and hexagonal column.The vortex shedding mode of the square column has 2S mode and P+S mode.The forced vibration of the hexagonal cylinder is similar to that of the cylinder.The closer the cylinder shape is to the cylinder,the better the vibration stability.Passive control is carried out by turning the sharp corner of the square column into rounded corners,and three different rounding parameters of r/D=1/4,1/5 and 1/8 are selected for the flow calculation.The large lift coefficient and drag coefficient are reduced.The rounded square column with different parameters is selected to simulate the forced vibration.Compared with the sharp square column,the lift coefficient and the drag coefficient are significantly reduced.The range of the locking interval is basically symmetrical about F=1.The trend of the lock interval is similar to that of a cylinder.The vortex shedding mode of the rounded square column is 2S mode,and the vortex wake is narrowed.After the square column is rounded,the flow stability can be significantly improved.