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Axilleas Tsompanos September 2, 2004 10:20

Separation point on cylinder
 
Hello there,

I am simulating the flow around a 2d cylinder at Re=100. I need to find the separation points of the up and down surface. I tried to plot the friction coefficient and the tangential velocity along the cylinder but i am not satisfied with the results. Is there a better way to do it?

Regards, Achilleas Tsompanos

guill. September 3, 2004 14:36

Re: Separation point on cylinder
 
Separation is best viewed using the friction coefficient... What do you mean with "not satisfied"? Your problems may come from your viscous model and your grid density: Re=100 is very slow motion!

Axilleas Tsompanos September 4, 2004 12:22

Re: Separation point on cylinder
 
Dear friend,

The viscous coeff is always positive quantity. So when separation ocurs naturaly the friction changes direction. Therefore you are looking for a value of the coeff as near to zero as possible. However when it reataches the value drops close but not very close to zero. So my problem with skin friction coefficient is that it is not always clear when it reattaches. Do you suggest denser grid in the aft area? Re=100 is a good starting point to verify certain aspects of the solution (grid, solver, etc). The flow ofcourse is laminar.

Regards

guill. September 5, 2004 20:29

Re: Separation point on cylinder
 
Hi again, I am not an expert on the subject... but i'd say at Re=100, the flow is laminar, ok, though very unstable in the wake of the cylinder (you have a Von Karman vortex) and hence it is very difficult to predict the reaatachment using the steady solver... May be a good idea to use the unsteady one with a finer mesh density on the expected reattachment point!


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