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Oscillating Residuals for flow around an airfoil -ANSYS FLUENT. What should I do? |
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June 12, 2018, 08:15 |
Oscillating Residuals for flow around an airfoil -ANSYS FLUENT. What should I do?
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#1 |
New Member
öobleck
Join Date: May 2018
Posts: 5
Rep Power: 8 |
I am using a structured mesh on a D-field having length of 12.5 chord lengths for an airspeed of 33m/s.
I tried both for ke-realisable and kw-sst, the residuals are wildly oscillating. I even tried giving URFs but it didnt work. As the iterations proceed, back flow is occuring and turbulent viscosity ratio is being limited. I am attaching an image of my mesh. |
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June 12, 2018, 11:52 |
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#2 |
Senior Member
Join Date: Dec 2016
Posts: 152
Rep Power: 10 |
The mesh looks really good, and it seems odd to me that your residuals would be oscillating even after you enabled a turbulence model. Is this a steady-state or transient simulation?
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June 12, 2018, 12:08 |
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#3 |
New Member
öobleck
Join Date: May 2018
Posts: 5
Rep Power: 8 |
Its a steady-state simulation.
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June 12, 2018, 12:11 |
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#4 |
Senior Member
Join Date: Dec 2016
Posts: 152
Rep Power: 10 |
Alright, so you're residuals are all oscillating, but how about other quantities? Did you set any report definitions?
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June 13, 2018, 06:35 |
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#5 |
New Member
öobleck
Join Date: May 2018
Posts: 5
Rep Power: 8 |
I am interested in calculating the coefficients of lift, drag and moment. These I defined in the monitors tab. As for the Report Definitions tab, I haven't given anything.
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June 13, 2018, 13:11 |
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#6 |
Senior Member
Join Date: Dec 2016
Posts: 152
Rep Power: 10 |
Report Definitions are what the Monitor tab monitors. If you are monitoring your solution, you probably already set Report Definitions without even knowing it haha.
When you simulate, I assuming you are looking at the Solution Monitors every iteration to see how they perform. Are they oscillating as well, or do they seem to be okay? |
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June 14, 2018, 12:10 |
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#7 |
New Member
öobleck
Join Date: May 2018
Posts: 5
Rep Power: 8 |
I got the problem of back flow and viscosity limitation corrected.
I had missed an edge while defining inlet and outlet. I ran using ke realizable for first order and second order. The first order converged but the second order residuals has become more or less constant. What shall I do? |
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June 14, 2018, 12:16 |
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#8 |
Senior Member
Join Date: Dec 2016
Posts: 152
Rep Power: 10 |
For that, I would check out the topic of "Convergence" on the forum. It's not the easiest thing to judge, and you might actually be looking at a perfectly good simulation and not even know it. I know that's not the answer you were looking for, but it's the best one I can provide.
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April 2, 2024, 15:16 |
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#9 | |
Senior Member
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Quote:
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Tags |
fluent 17.2, residual oscillations., structured mesh |
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