Vortex Evolution in Flow Around Cylinder under Small Reynolds Number

In order to obtain the characteristic of flow field around cylinder under small Reynolds number,the evolution process of reverse symmetry eddy in unsteady flow around cylinder was numerically simulated based on finite volume method（FVM）,SIMEPLEC algorithm and laminar flow model under Re=40 by using the computational fluid dynamic（CFD） software Fluent.The multi-block grid technology and structured O type grid was used to generate the calculation region.This paper studies the dimension change and landscape orientation force change of the reverse symmetry eddy in the evolution process.The paper also researches the distribution and variation rules of pressure,velocity,wall shear stress and stream function during the evolution process.Numerical simulation results show that the evolution rule of reverse symmetry eddy is similar to nature biology,namely change is obvious at early period and is steady at late period.The landscape orientation force decreases firstly and then increases and finlly becomes steady.The minimum pressure location on cylinder wall located bearly behind the tangent point,and moves toward the tangent point in the evolution process.The velocity and the wall shear stress both present M type distribution characteristic,and the maximums both appear at about 57.3°.The stream function distribution presents center symmetry character and reaches minimum at about 45.8°.