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Old   February 17, 2012, 09:08
Default Steady or Transient
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Chanchai
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Hi everybody
I am trying to obtain Cl and Cd for my half wing 3d simulation and also want to see a wingtip vortex core but when i run the simulation, first i choose steady state for simulation but my solution is not convergence the continuity residual is going around e-1 and then oscillation around some point(other residual is around e-6). Now i change to transient simulation this time the continuity residual is going to e-6 (same boundary condition with steady). Is the value from transient simulation correct? and Which one should i choose Steady or Transient?
If Steady, Do i have to re-mesh (because of my continuity residual is too high)?

My object is to obtain lift curve slope and drag curve slope of the wing
and see wingtip vortex at position behind the wing


thanks
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Old   February 17, 2012, 13:38
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Ries Bouwman
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Hi,

That is a good question.


From a physical point of view, I'd say your problem is a transient one (hence the residual situation).


That does not mean you can not get useful answers using steady state! It is faster and sometimes even more accurate (depending on turbulence model used etc).


In the industry, I have seen both approaches being used successfully. It realty depends what you want exactly. Don't forget that CFD is the tool, not the goal. You are the engineer/scientist! You decide.


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