unsteady flow over cylinder

Rafal Z

I am making computation or non rotating circular cylinder to obtain von karman street. diameter of that cylinder is 1 cm.fluid is air , velocity 100 m/s. I am using k eps RNG model. vortex sheedind freq should be 500 hz in fluent manual is written that optimal no of iterations for unsteady flow is about 20. 500 hz means (i am not sure)that vorticies occurs 500 tines a second . i also know tat delta t should be at least 20 times smaller that period of vorticies 500hz is 0,002s so delta t is 0,0001

i tried with 100, 200,and more iteration but resusts are funny i thing that mesh is good. Y plus near wall is about 7 what else should i take into account or there is something very important that i do not know

please advise me A