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3d Airfoil Modelling Problems

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Old   March 16, 2006, 07:54
Default 3d Airfoil Modelling Problems
  #1
Olly
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Hi

I'm trying to model a 3d airfoil using fluent but am having problems getting the solution to converge. The times that it has converged there is a negative gauge pressure everywhere except for a small point at the front of the wing.

I've modelled the wing in a wing tunnel with the following boundary conditions: Inlet - Velocity inlet set to 40ms Outlet - Outflow All other walls set as Symmetry

I'm using the k-epsilon solver, i've tried changing the mesh a few times from coarse to fine but am having no luck an ideas?

Thanks
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Old   March 16, 2006, 09:50
Default Re: 3d Airfoil Modelling Problems
  #2
Oleksiy Dushyn
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Hi,

- you should replace your symmetry doundary conditions by periodic ones;

- if you are simulating a static case do not make your mesh too fine otherwise you'll run to another problem with flow stability;

regards,

Alexey
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Old   March 17, 2006, 10:53
Default Re: 3d Airfoil Modelling Problems
  #3
Olly
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Thanks for the reply,

I changed the outflow to an outlet pressure and this seems to solve the negative gauge pressure up and down stream of the airfoil.

I'm now having problems trying to get it to converge at all. the residual plots just go up and then it doesn't converge, what does this mean?

Thanks
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Old   March 17, 2006, 11:44
Default Re: 3d Airfoil Modelling Problems
  #4
Oleksiy Dushyn
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As I've wtitten in my last posting if you want to get a good convergence you have to replace your symmetry BC by periodic ones.

Good luck
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Old   March 17, 2006, 12:12
Default Re: 3d Airfoil Modelling Problems
  #5
Olly
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Thanks again, i have replaced the symmetry bc with periodic ones but with no success.

What would cause the residuals to go up?

Thanks
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Old   March 17, 2006, 13:55
Default Re: 3d Airfoil Modelling Problems
  #6
Oleksiy Dushyn
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What initialization do you use?
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Old   March 17, 2006, 15:26
Default Re: 3d Airfoil Modelling Problems
  #7
Olly
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I initalise it from the inlet, is that what you mean?
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Old   March 19, 2006, 16:10
Default Re: 3d Airfoil Modelling Problems
  #8
Riaan
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1) use fmg-initialization

2) reduce your under-relaxation functions

3) does your mesh "CHECK" ok?

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