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March 4, 2007, 15:07 |
Convergence issue
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#1 |
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I have a model of a straight pipe, I am using to get a fully developed profile to use in my pipe junction.
I am using an SST model. Funnily, I seem to have no convergence even after about plenty of iterations. The behaviour is bouncy but it does not even try to go down even a tiny bit. I tried playing with the timestep. But that didn't work. But funnily enough, when I refine the mesh, I get convergence as low as E-12 in just 5 iterations. So what can my problem be? I use CFX mesh to create the mesh. While trying to keep the Y+ less than 1. Thanking in anticipation |
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March 4, 2007, 18:41 |
Re: Convergence issue
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#2 |
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Something is really very wrong when you get convergence to 1e-12 in 5 iterations. This cannot be a converged solution!
When you use SST and find a lot of flow separation at delicate locations you won't ever get convergence. Have you exported residual values to your res-file? What do these tell you? Have you tried k-e with scalable wall functions? This should converge quite fast as it clips to y+=11. What do you define on the in- and outlet in terms of turbulence? Astrid |
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March 7, 2007, 11:37 |
Re: Convergence issue
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#3 |
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Well, my inlet velocity is 210 m/s. I did a little calculation for my branch of diameter- 16 inches. And found out that the trubulence intensity would be around 2.3%.
My outlet is a pressure out, at 0 atm. I will try to see how K-epsilon does. Have I exported residual values to your res-file? I am not really sure what that is, and how it may help? Would you please help me understand? Thanx for replying Astrid! |
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