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Old   August 23, 2011, 05:38
Default starting vortex
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Does anybody know, for starting vortex past an Airfoil, which BCs and also which strategies for time-dependent velocity should be used?
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Old   August 24, 2011, 15:15
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Are you talking about the starting vortex simulation wise (i.e. starting from a non-physical initial field) or about the physical starting vortex from an accelerated airfoil??

huge difference =

Cheers!
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Old   August 25, 2011, 03:59
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I want to see what happend to the fluid past an Airfoil, if there is an acceleration in the fluid,
I do not know how I should increase the velocity and which BCs should I use?
Is special strategy necessary?

many Thanks!
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Old   August 25, 2011, 07:09
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so you are trying to simulate the flow from an airfoil at rest up to some given speed? like an airplane taking off?

I have seen that done a few times, almost always with a moving mesh approach, but I'm no expert on this...

What happens if you do sth like this: inflow BC: freestream, starting from u=0 to some u (of course, make sure your time discretization can handle this!!), outflow: extrapolation outflow. That would be my first try...
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Old   August 25, 2011, 09:00
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I run this case with different BSc, but I could not get a good result. Do you think I should add a source term in NA-ST equations? or do you have another Idea?
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Old   August 25, 2011, 10:18
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Quote:
Originally Posted by blume83 View Post
I run this case with different BSc, but I could not get a good result. Do you think I should add a source term in NA-ST equations? or do you have another Idea?
could you describe what you mean by "not good results"?? with what did you compare your results? what scheme are you using?
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Old   August 25, 2011, 15:24
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I compare my results with the experiment. I expect to have a vortex at the trailing edge (that agrees Helmholz theory too), but my results are the same as the results optained without the initial acceleration. I use DG (discontinous Galerkin) method.
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Old   August 25, 2011, 15:41
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