cylinder, drag, onvergency

num

Hi,

I have simulated the flow around a circular cylinder using the following configuration (steay, SPALART-ALLMARAS, C,H-MESH (the c-topology defines the inlet), Char. Rey-Number: 140000). But there occur several problems:

1. the convergence history (global residual) is fluctuating - it also happens with a laminar configuration or another turbulence model.

2. I applied the following boundary conditions: inlet=static quantities imposed (to define the velocity Vx=100 [m/s] and pressure 101300 [Pa]). OUTLET=static pressure impoed, SOLIDS WALLS=adiabatic, EXTERNALS=settings from the inlet. Do you principally agree with these settings

4. I would like to calculate the drag - a was thinking about F=m*a but I am not sure how to connect it with my problem.

5. The flow behind a cylinder is not steady - could you explain to me what will I have to do to make it unsteady (boundary condition, mesh generation) -- (I want no rotation!).

Thanks.