Study Of Cylinder Wake Vortex Fluidic Control Based On Lattice Boltzmann Method

When fluid flows through the cylinder structure,it produces alternating vortex.When the vortex frequency is close to the natural frequency of the structure,it will easily cause the cylinder resonance to cause structural damage.Therefore,it is of great engineering value to study the problem of cylindrical vortex suppression.The mechanism of flow around circular cylinder is complicated and involves many fluid problems.It can not be perfectly simulated by current computational fluid mechanics.Lattice Boltzmann method(Lattice Boltzmann Method,LBM)is a method based on the molecular dynamic theory,using a simplified dynamic model of Boltzmann equation,with many discrete lattices as the computing nodes,and obtaining the macroscopic physical quantities by statistical averaging the particle to simulate the fluid numerically.Compared with other traditional CFD methods,the LBM has many advantages,such as the physical model is more essential,the boundary processing is simple,and it is easy to large-scale parallel.So,it is a valuable topic to explore the application of the LBM method in the field of marine engineering.In this work,a numerical simulation program written in FORTRAN language is based on LBM method.The program is applied to the study of jet suppressing the vortex shedding of flows around circular cylinder.According to the numerical simulation of the jet with the same and opposite direction of the flow,the difference effects of suppressing vortex shedding are analyzed.The main work of this paper includes the following aspects:(1)In this paper,a new optimal treatment scheme for multi-grid grid coarse and fine grid junction structure is proposed.The scheme solves the problem of original method which has complicated program structure,wastes memory and is easy to accumulate the error from interpolation.(2)According to Multi-Relaxation Lattice Boltzmann method,the basic numerical simulation program is compiled.By adding a self circulation module,the improved multi-grid method can be embedded into the basic computing program.And write the multi-block of modules,turbulence modules,jet modules and other modules to achieve the corresponding function.Using OpenMP rewriting the program code to achieve parallel computing,enhance the computational efficiency.(3)Using the program to simulate the classical example,and compared the numerical simulation results with the existing data to verify the validity of the numerical program.(4)The interference of the stationary point jet on the flow around the cylinder at different jet velocities is studied.The influence of jet on the hydrodynamic parameters such as drag coefficient,lift coefficient and so on is analyzed.The mechanism of the stationary point jet to suppress the cylindrical vortex after analyzing the flow field diagram.(5)The influence of the front standing jet on the flow around the cylinder at different jet flow velocity.The variation of the hydrodynamic parameters,such as the drag coefficient and the lift coefficient of the cylinder under different velocity jets,is analyzed.The effect of the stagnation jet on the cylinder tail vortex distribution before analysis is observed.The numerical results of former obvious inhibition effect exists stagnation jet issuing of cylindrical vortex.