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March 25, 2014, 02:19 |
OpenFOAM Aerofoil Simulation
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#1 | |
New Member
Join Date: Mar 2014
Posts: 3
Rep Power: 12 |
Hi all,
I'm new to CFD-Online and, in truth, pretty new to CFD as a whole. I'm working in OpenFOAM for a project I'm doing at university, and as part of it, I'm looking at obtaining the lift and drag forces on a NACA0012 aerofoil using OpenFOAM. I tried using simpleFoam with a Spallart-Almaras solver but it yielded vastly incorrect results, so I'm trying a kOmegaSST solver instead. Basically, I tried just modifying the Spallart-Almaras case (removing the NuTilda file in the 0 directory and replacing it with a k and an omega file, altering controlDict, etc.) but when I try to run the solver, it gets to the fourth iteration and throws up the following (rather spectacular) error: Quote:
Thanks! |
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March 27, 2014, 04:54 |
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#2 |
New Member
Syed Zahid
Join Date: Mar 2014
Location: Bangalore, Karnataka, INDIA
Posts: 5
Rep Power: 12 |
Dear Puglin
Please check your mesh and try again as your simulation shows a diverging nature. |
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August 19, 2014, 00:20 |
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#3 |
Member
D L
Join Date: Jun 2012
Posts: 49
Rep Power: 14 |
What you're running into is a printstack error; the values that are getting computed are beyond the limitations of a "double" type variable so it throws an error and kicks you out. There are lots of reasons for this: Mesh, schemes, Initial conditions, etc. Unlike other aerospace codes which do a reasonable way of finding their way back to a reasonable solution, OF in my experience is notoriously unforgiving.
Some things you might try, if you've got a converged Spalart-Almaras run already (assuming decomposed), you could do a reconstructPar and then add in the new k and omega variables with proper initialization. Or you could always run it through potentialFoam before invoking simpleFoam. Also doublecheck your fvSchemes and fvSolution. Use the simpleFoam airfoil test case as a template. Regarding correlation values for Cl and Cd, I've found the out-of-the-box turbulence models work fairly well in predicting Cl but Cd can be as much 50% high for low reynolds numbers (6e6 or less). Then again SA and kOmega (even k-epsilon) in most commercial codes perform the same way. OpenFoam is a bit finicky with aerospace type work. I'd suggest starting here for a good mesh. http://turbmodels.larc.nasa.gov/naca0012_val.html There's also some nice reading material there. |
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August 19, 2014, 06:36 |
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#4 |
Senior Member
Join Date: Mar 2014
Posts: 112
Rep Power: 12 |
Possibly a mesh problem. checkMesh
What is the y+ value? What is the aoa? If large, mesh resolution is more important. Keep working with sa model first because it is much more stable and easier to converge than komegasst for this kind of problem. And check your initial boundary conditions. Under normal circumstances openfoam can easily converge and correctly solve this problem. getting the correct drag or stall is a little harder though... |
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