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#1 |
Member
Nikesh Bhattarai
Join Date: Nov 2011
Location: Sacheon, South Korea
Posts: 82
Rep Power: 14 ![]() |
Hi all,
I am simulating a simple 2D flat plate flow in OpenFoam using simpleFOAM to validate a new turbulence model that I would like to implement here. This new turbulence model is a slight modification of the kOmegaSST model which includes few new terms into the nut equation. Results from kOmegaSST model are all OK! However, when I use this new model for the same grid, my initial pressure residuals oscillate around a pretty high value, at around 0.03 while the initial U,k and omega residuals are all at a reasonable convergence criterion, at around 10^-5. This is not making much sense to me. Because, after some iterations(about 6~7,000) when I extract the results (even without reaching the convergence tolerance) and compare, they don't yet seem so weird or deviating highly from that of the SST's results. I have checked my code numerous times, doesn't seem to have any problems in there. Could there be a problem with the solvers I chose? I am as well wondering how the p-residual is calculated in simpleFOAM. I would highly appreciate any insights into this! Thanks! Nikesh These are my settings and I've used the same for kOmegaSST (in the pic attached). |
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#2 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 27 ![]() |
hi
Test for one or two order lower p tolernces than U,... 1e-9 or 1e-10 |
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#3 |
Member
Nikesh Bhattarai
Join Date: Nov 2011
Location: Sacheon, South Korea
Posts: 82
Rep Power: 14 ![]() |
Thanks!
Tried, yet not much of a difference. |
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#4 |
Member
AndreiCFD
Join Date: Nov 2012
Posts: 47
Rep Power: 14 ![]() |
Hi
Basically I am having the same problem.... I just want to ask you if you managed to do it in the end. I am simulating the flow over an aerofoil using k omega sst and simpleFoam with wall functions.......... Have you got any ideas? Thanks Andrei |
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#5 |
Member
Nikesh Bhattarai
Join Date: Nov 2011
Location: Sacheon, South Korea
Posts: 82
Rep Power: 14 ![]() |
Hii Andrei,
Well, I am still stuck with the same problem. Obviously higher p-residual means mass is not being conserved so well somewhere in the cells. You might want to look into your boundary conditions once more. Basically that is what I am trying to do too. And the schemes and type of mesh you are using for airfoil flow. |
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#6 |
Member
AndreiCFD
Join Date: Nov 2012
Posts: 47
Rep Power: 14 ![]() |
Hi
Ok I understand . I am using k omega sst , wall functions and simpleFoam solver ..... I have changed my boundary conditions many times still nothing......for example how you o file looks like and something that I don't understand : how do you calculate the turbulent kinetic energy K and the rate of dissipation W(omega)....... thanks Andrei |
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#7 |
Senior Member
Daniel P. Combest
Join Date: Mar 2009
Location: St. Louis, USA
Posts: 621
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Nick,
There are some strategies that I would try to get these residuals down to something you would like.
There are a lot of other strategies that you can try, but this one might be sufficient. Without knowing more details like divergence schemes; mesh structure and checkmesh results; y+ values; and boundary conditions there is not much to add on my part. I would look at the thread http://www.cfd-online.com/Forums/ope...-problems.html and then move on to a search of the forum. There are many threads about simpleFoam convergence...but my list of threads is not in front of me right now. good luck. Last edited by chegdan; March 10, 2013 at 19:01. Reason: spelling |
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#8 |
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,208
Rep Power: 27 ![]() |
how can decrease the initial residuals for p in unsteady problems when relaxations are not applicable?
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#9 |
New Member
Thodoris
Join Date: Apr 2016
Location: Greece
Posts: 26
Rep Power: 10 ![]() |
Hello guys,
I am running a simulation of a flow over two wings. My simulation is 3d.I check the mesh and there is no error. I am using freestream bc and wall functions. Solver is simplefoam and turbulence model spalart almaras dudes. The problem is when I ran with coarse mesh the solution converge but when I ran with finer mesh the pressure residuals don't fall under 10^-5 they stop at about 2*10^-4.I used snappyhexmesh for the mesh. Any advice would be useful thank you in advance. Thodoris |
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#10 | |
Member
AndreiCFD
Join Date: Nov 2012
Posts: 47
Rep Power: 14 ![]() |
Quote:
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#11 |
New Member
Thodoris
Join Date: Apr 2016
Location: Greece
Posts: 26
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Andrei,
Thank you a lot for your answer.I am trying to calculate the cl, cd but i am having troubles because of my geometry, which consists two wings in the same but opposite angle of attack (+- 8 degrees) so i am having problems with the normals. I hope you have an idea to face this problem.I am attaching my geometry. Thank you very much in advance. |
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#12 | |
Member
AndreiCFD
Join Date: Nov 2012
Posts: 47
Rep Power: 14 ![]() |
Quote:
Cheers |
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