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August 21, 2012, 10:24 
Problem with timestep error on Rans ke model.

#1 
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Rafael Valenzuela Musura
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Hi everyone
I'm having some problems with my simulation. What i'm doing is a delta wing through wind at 5ºC. What I want to do is to study de vortex geometry formed at the leeward side of the delta wing. For that i'm usin RANS, pisoFoam, ke model. With a y+ value of 30, so i'm usin the wallfunctions. The mesh is a cube with the delta wing positioned near the front face (inlet, named "entrada") and two conic volumes that melt with the back (outlet, named "salida"), the contour has to be open space like if the delta wing were levitating in the air, so non wall function is applied for the contour named "contorno" and i give them the same properties as the inlet ("entrada"). Wall functions are applied over the delta wing for epsilon, k, and nut. i'm attaching the 0, the contstant and the system folder without the mesh because it has over 6e6 cells. The quality is ok, gmsh and checkMesh said so. Soon I'll attach some pictures of the geometry. MY QUESTION IS: What am I doing wrong with the BC or some of the other files in constant and system folder or is just a mesh problem? Thank you very much. PD: If some one has any ke simulation files, would you send them to me please? Last edited by rafamusura; August 21, 2012 at 18:42. Reason: definition error 

August 21, 2012, 14:23 

#2 
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Rafael Valenzuela Musura
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Here I attach the mesh view


August 21, 2012, 14:33 

#3 
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Rafael Valenzuela Musura
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My question is what am I doing wrong in the system files or with the pressure that generates the high timestep continuity error


August 21, 2012, 15:00 

#4 
New Member
Rafael Valenzuela Musura
Join Date: Feb 2012
Posts: 27
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Hi everyone
I'm having some problems with my simulation. What i'm doing is a delta wing through wind at 5ºC. What I want to do is to study de vortex geometry formed at the leeward side of the delta wing. For that i'm usin RANS, pisoFoam, ke model. With a y+ value of 30, so i'm usin the wallfunctions. The mesh is a cube with the delta wing positioned near the front face (inlet, named "entrada") and two conic volumes that melt with the back (outlet, named "salida"), the contour has to be open space like if the delta wing were levitating in the air, so non wall function is applied for the contour named "contorno" and i give them the same properties as the inlet ("entrada"). Wall functions are applied over the delta wing for epsilon, k, and nut. But when I run the code it crashed inmediately without any information only crazy caracters, i'm attaching the 0, the contstant and the system folder without the mesh because it has over 6e6 cells. The quality is ok, gmsh and checkMesh said so. I'm solving the problem but i think the timestep continuity error is too high. I'm attaching the 0, constant and system folder, images of the mesh and a file with the log generated by openFoam. Time = 0.0336 DILUPBiCG: Solving for Ux, Initial residual = 0.0107502, Final residual = 0.000280403, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00391993, Final residual = 0.000106919, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.00883818, Final residual = 0.000195784, No Iterations 2 DICPCG: Solving for p, Initial residual = 1.83261e16, Final residual = 1.83261e16, No Iterations 0 time step continuity errors : sum local = 6.63806e+32, global = 3.95053e+30, cumulative = 1.03367e+32 DILUPBiCG: Solving for epsilon, Initial residual = 4.79003e09, Final residual = 4.79003e09, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 5.31403e19, Final residual = 5.31403e19, No Iterations 0 ExecutionTime = 8039.58 s ClockTime = 8091 s Time = 0.0339 DILUPBiCG: Solving for Ux, Initial residual = 0.0109797, Final residual = 0.000390804, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00381153, Final residual = 0.000152027, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.00965729, Final residual = 0.000251777, No Iterations 2 DICPCG: Solving for p, Initial residual = 2.05904e16, Final residual = 2.05904e16, No Iterations 0 time step continuity errors : sum local = 6.64336e+32, global = 3.94975e+30, cumulative = 1.07317e+32 DILUPBiCG: Solving for epsilon, Initial residual = 4.79003e09, Final residual = 4.79003e09, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 5.09973e19, Final residual = 5.09973e19, No Iterations 0 ExecutionTime = 8104.96 s ClockTime = 8157 s Time = 0.0342 DILUPBiCG: Solving for Ux, Initial residual = 0.00955455, Final residual = 0.000285136, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00319492, Final residual = 9.09444e05, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.00881291, Final residual = 0.000391108, No Iterations 2 DICPCG: Solving for p, Initial residual = 2.03742e16, Final residual = 2.03742e16, No Iterations 0 time step continuity errors : sum local = 6.64862e+32, global = 3.95421e+30, cumulative = 1.11271e+32 DILUPBiCG: Solving for epsilon, Initial residual = 4.79003e09, Final residual = 4.79003e09, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 4.90337e19, Final residual = 4.90337e19, No Iterations 0 ExecutionTime = 8169.98 s ClockTime = 8222 s Time = 0.0345 DILUPBiCG: Solving for Ux, Initial residual = 0.00777732, Final residual = 0.000356118, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00291982, Final residual = 0.000111127, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.00717223, Final residual = 0.000263995, No Iterations 2 DICPCG: Solving for p, Initial residual = 1.96088e16, Final residual = 1.96088e16, No Iterations 0 time step continuity errors : sum local = 6.65354e+32, global = 3.96524e+30, cumulative = 1.15236e+32 DILUPBiCG: Solving for epsilon, Initial residual = 4.79003e09, Final residual = 4.79003e09, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 4.72676e19, Final residual = 4.72676e19, No Iterations 0 ExecutionTime = 8235.81 s ClockTime = 8288 s Time = 0.0348 DILUPBiCG: Solving for Ux, Initial residual = 0.00845433, Final residual = 0.000324603, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00300571, Final residual = 7.6532e05, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.00998808, Final residual = 0.000212127, No Iterations 2 DICPCG: Solving for p, Initial residual = 1.99572e16, Final residual = 1.99572e16, No Iterations 0 time step continuity errors : sum local = 6.66062e+32, global = 3.98281e+30, cumulative = 1.19219e+32 DILUPBiCG: Solving for epsilon, Initial residual = 4.79003e09, Final residual = 4.79003e09, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 4.56481e19, Final residual = 4.56481e19, No Iterations 0 ExecutionTime = 8300.7 s ClockTime = 8354 s Time = 0.0351 DILUPBiCG: Solving for Ux, Initial residual = 0.00852669, Final residual = 0.000562289, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00322229, Final residual = 9.61648e05, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.0105383, Final residual = 0.00019362, No Iterations 2 DICPCG: Solving for p, Initial residual = 2.11936e16, Final residual = 2.11936e16, No Iterations 0 time step continuity errors : sum local = 6.67132e+32, global = 4.00495e+30, cumulative = 1.23224e+32 DILUPBiCG: Solving for epsilon, Initial residual = 4.79003e09, Final residual = 4.79003e09, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 4.42232e19, Final residual = 4.42232e19, No Iterations 0 ExecutionTime = 8365.5 s ClockTime = 8419 s Time = 0.0354 PLEASE HELPE WITH THIS PROBLEM! 

August 21, 2012, 16:20 

#5  
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Bruno Santos
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Greetings Rafael,
FYI: I've moved your posts from that older thread where you posted, to this thread, because ... the other one was an old thread!!! And don't repeat the same questions over and over! Use the "Edit" button! You can edit a post of yours and modify anything in it. Now, about your problem:
Bruno
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August 21, 2012, 18:25 

#6 
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Rafael Valenzuela Musura
Join Date: Feb 2012
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Hi Bruno
1 Well I'm basing the simulation with the pitzdaily tutorial, because is the only ke incompresible tutorial i've. But I changed the boundary conditions as said on: http://www.cfdonline.com/Wiki/Turbu...ary_conditions, but I think I have made a mistake on the distribution of them, i mean if I asignate a nut fixed valua to some patch that deosn't have to have it. 2 Basing the controldict of pitzdaily there are some fuctions that i've deleted so the simulation run properly, but solwly and with very high timestep error like on the erleir post. Is not something that came large ina a short period it has been growing constantly since time=0 3 Actualy I'm using the openFOAM2.1.1 5 Yes I was able to run the pitzdaily tutorial. 

August 22, 2012, 17:22 

#7 
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Bruno Santos
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Hi Rafael,
What I meant by the last question was this: it would be easier to help you if you could provide a complete and simplified version of your case. For example, the tutorial "compressible/sonicFoam/ras/prism" has a very good and simple mesh that can be used for trying to replicate your case. You can change that case to use pisoFoam. Then change from 2D to 3D, by increasing the 3rd dimension resolution and with "symmetryPlanes" instead of empty patches. From there it'll be easier to gradually increase the level of complexity of the case to reach a similar situation. Otherwise, this is just a guessing game Best regards, Bruno
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Last edited by wyldckat; August 22, 2012 at 17:23. Reason: forgot to mention the need to increase the 3rd resolution... 

August 24, 2012, 07:57 

#8 
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Rafael Valenzuela Musura
Join Date: Feb 2012
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Hi Bruno
I've made some changes and simplified the problem. Now I've started the simulation with a sapartallmaras model, and it looks ok (image attached). But i have another problem, if I don't want to have a U value=0 at the contour walls, but if I change the initial boundary confitions for the contor walls for the same as the inlet the simulation crashed. Do you have any ideas for solbing this problem, I think i'm loosing something here. Another question is the fvSolution file, when I tried to simulate the vortex with ke there was pcibg solver and for spalar is a GAMG and smoothsolver, I would like to know the diference between them and where is information about the comands that are included in gamg ans smoothsolver and it's values. Thankyou very much 

August 24, 2012, 17:57 

#9  
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Bruno Santos
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Quote:
Quote:
Code:
OpenFOAM GAMG smoothSolver
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August 25, 2012, 11:01 

#10 
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Rafael Valenzuela Musura
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Hi Bruno first of all thankyou for your help, I have making some simulations with the spalartallamaras model, but I have some convege problems the code doesn't converge although the solution doesn't varies so maybe i'm missing something on the fvsolution. I'm using the same of the tutorial airfoil.
Thanks 

August 26, 2012, 07:50 

#11 
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Bruno Santos
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Hi Rafael,
If you can't share the case, it becomes very complicated to help you This is why I've been telling you to "create a simple case"! My guess is that it is the mesh the one to be blamed. Run checkMesh to see if anything bad is indicated. Good luck! Bruno
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August 27, 2012, 12:35 

#12 
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Rafael Valenzuela Musura
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Hi Bruno, I'm really sorry because I haven't been able to explain what is really what i'm asking so today I will try to put in order my ideas.
1) I have been reading some books, and I don't know if using the ke turbulence model is appropiete for this case, because what I really want is to get the conic geometry of the vortex generated leeward. I believe that the ke is for HiRe flows, so if I take a chord avarege of the delta wing and I calculate the Re number with wind 10m/s I get a Re of about 1.14e6 wich is turbulent but only for the wing. Another thing is that ke is unable to show me the vortex generated over the wing, the picture attached in the above reply is from the spalartallamaras. *Bibliography tells me that with this angle of attack the vortex is steady so lets suppouse RANS is ok. My question is: Do you think i'm wrong using ke model, and I should use the Spalart Allamaras o the komega model.? 2) Second question, when I ran the spalart allamaras model the residuals converge to a realitve high rage e1 to e3 (picture attached) so I would like to know how do I have to do for this residuals to get lower, is something about the mesh resolution or is something in the fvSchemes and fvSolution files that I should change. If the information I give you isn't enough I could share you the case folders to take a look at them. Thank you very much and sorry for my incapacity to explain myself. 

August 27, 2012, 17:03 

#13 
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Bruno Santos
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Hi Rafael,
Unfortunately I don't know enough to help you decide which turbulence and wall function models to use . My best suggestion is to look for threads here at the forum related to aerodynamic models. As for the simple case, my objective was to try and help you to "get better help". I could also test the case myself and in my limited experience I could find one or two problems, but I would probably end up not knowing the final solution. Last but not least, I should have pointed you to the following thread on my first response to you: How to give enough info to get help Good luck! Bruno
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August 30, 2012, 10:54 

#14 
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Rafael Valenzuela Musura
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Hi Bruno
Finally I could make it fine with the simulations, but I only have one more question. I'm trying to get a inlet wind profile with the atmboundarylayervelicity BC but it seems no to work anymore in OF2.1.1, so i tried with swak4Foam utility for using the groovyBC but I don't have any idea of how to make it work. If you know something about it please give me a hand. Thanks a lot. 

August 31, 2012, 05:31 

#15 
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Bruno Santos
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Hi Rafael,
Best regards, Bruno
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Tags 
boundary, initial condition, ke, kepsilon, rans 
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