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March 13, 2010, 12:21 |
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#21 |
Senior Member
Steve Hansel
Join Date: Jun 2009
Location: Colorado, USA
Posts: 112
Rep Power: 17 |
I have yet to get reasonable numbers with turbDyMFoam. (Probably because I have no idea what to use for turbulence parameters.) I suggest starting with icoDyMFoam and see what you get. I find I get pretty reasonable results on a lot of VAWTs.
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March 13, 2010, 12:28 |
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#22 |
Senior Member
Herman
Join Date: Nov 2009
Posts: 122
Rep Power: 17 |
Hi hansel, thanks for your quikly reply.
Sorry but, icoDyMFoam is a solver for LAMINAR flows, isn't it? I can't understand how can I get reasonable results... |
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March 15, 2010, 09:02 |
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#23 |
Member
Nick Gardiner
Join Date: Apr 2009
Location: Chichester, UK
Posts: 94
Rep Power: 17 |
Hi enry
I'm fairly new to this but is magUInf the right value? |
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March 15, 2010, 10:23 |
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#24 |
Senior Member
Herman
Join Date: Nov 2009
Posts: 122
Rep Power: 17 |
Hi Nick,
I found my error... Since the mesh is 2D, OF tranform it into 3D mesh, even if it solve with 2D solver. So to compare 2D FLUENT's results with pseudo-3D OF's results I have to divide OF results by thickness that OF create. |
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March 15, 2010, 10:42 |
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#25 |
Member
Nick Gardiner
Join Date: Apr 2009
Location: Chichester, UK
Posts: 94
Rep Power: 17 |
enry
So how did they compare? Mostly I'm simulating vertical axis marine current turbines and also use CFX while I explore this option. |
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March 15, 2010, 11:24 |
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#26 |
Senior Member
Herman
Join Date: Nov 2009
Posts: 122
Rep Power: 17 |
Hi Nick,
the curves overlap! Results is very very similar. I haven't done any error percentage until now, but I'm satisfied. |
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March 15, 2010, 11:29 |
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#27 |
Senior Member
Steve Hansel
Join Date: Jun 2009
Location: Colorado, USA
Posts: 112
Rep Power: 17 |
Enry, would you post what you used for transport properties and RASProperties? I've never manage to get good numbers form turbDyMFoam.
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March 15, 2010, 11:31 |
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#28 |
Member
Nick Gardiner
Join Date: Apr 2009
Location: Chichester, UK
Posts: 94
Rep Power: 17 |
Hi again Enry
Sounds good. How did the processing times compare? |
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March 15, 2010, 11:37 |
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#29 |
Member
Nick Gardiner
Join Date: Apr 2009
Location: Chichester, UK
Posts: 94
Rep Power: 17 |
Another question Enry!
Are you using parallel? Can you get forces etc. in parallel? If so how?! Cheers Nick |
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March 15, 2010, 11:52 |
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#30 |
Senior Member
Herman
Join Date: Nov 2009
Posts: 122
Rep Power: 17 |
@Nick: Sorry, not yet, but I think that I will run calculation in parallel untill next month.
@Hansel: RASProperties: RASModel RNGkEpsilon; You can use also realizable K-E. Standard K-E don't work. TransportProperties: transportModel Newtonian; nu nu [0 2 -1 0 0 0 0] 1.46e-05; CrossPowerLawCoeffs { nu0 nu0 [0 2 -1 0 0 0 0] 1e-06; nuInf nuInf [0 2 -1 0 0 0 0] 1e-06; m m [0 0 1 0 0 0 0] 1; n n [0 0 0 0 0 0 0] 1; } BirdCarreauCoeffs { nu0 nu0 [0 2 -1 0 0 0 0] 1e-06; nuInf nuInf [0 2 -1 0 0 0 0] 1e-06; k k [0 0 1 0 0 0 0] 0; n n [0 0 0 0 0 0 0] 1; } ControlDict: applicationClass turbDyMFoam; startFrom latestTime; startTime 0; stopAt endTime; endTime 8; deltaT 0.0001; writeControl adjustableRunTime; writeInterval 0.5; cycleWrite 0; writeFormat ascii; writePrecision 6; writeCompression uncompressed; timeFormat general; timePrecision 6; runTimeModifiable yes; adjustTimeStep yes; maxCo 0.3; maxDeltaT 1.0; functions ( forces { type forces; functionObjectLibs ("libforces.so"); //Lib to load patches (blades); // change to your patch name rhoName rhoInf; rhoInf 1.225; //Reference density for fluid CofR (0 0 0); //Origin for moment calculations outputControl timeStep; outputInterval 1; } forceCoeffs { // rhoInf - reference density // CofR - Centre of rotation // dragDir - Direction of drag coefficient // liftDir - Direction of lift coefficient // pitchAxis - Pitching moment axis // magUinf - free stream velocity magnitude // lRef - reference length // Aref - reference area type forceCoeffs; functionObjectLibs ("libforces.so"); patches (blades); rhoName rhoInf; rhoInf 1.225; CofR (0 0 0); liftDir (0 1 0); dragDir (1 0 0); pitchAxis (0 0 1); magUInf 6; lRef 1; Aref 1; outputControl timeStep; outputInterval 1; } ggiCheck { // Type of functionObject type ggiCheck; phi phi; // Where to load it from (if not already in solver) functionObjectLibs ("libsampling.so"); } ); // ************************************************** *********************** // Fv schemes and Fv solutions are those imposed into turbFoam cavity tutorial. |
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March 15, 2010, 12:17 |
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#31 |
Senior Member
Herman
Join Date: Nov 2009
Posts: 122
Rep Power: 17 |
Hi nick, sorry, I read only your last reply .
FLUENT is faster than OF, because In FLUENT I impose a time step, wile in OF I set adjustTimeStep in order to have CFL<0.3-0.4. I can say that FLUENT is maybe three - four times faster than OF. |
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March 15, 2010, 12:32 |
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#32 |
Senior Member
Steve Hansel
Join Date: Jun 2009
Location: Colorado, USA
Posts: 112
Rep Power: 17 |
Thanks for the info, Enrico. One last question (I think). How fine was your mesh at the turbine's surface?
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March 15, 2010, 12:40 |
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#33 |
Senior Member
Herman
Join Date: Nov 2009
Posts: 122
Rep Power: 17 |
Hi hansel,
I create a mesh that can give me a value of mean y+ about 30. Mesh resolution so depend of course on simulation set up. My first cell is about 1/800 turbine diameter. I advice you to get some simulation in order to establish your mesh resolution near the blades. |
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July 9, 2010, 14:32 |
Wind Turbine
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#34 |
New Member
Join Date: Jul 2010
Posts: 17
Rep Power: 16 |
Hey guys,
I've read this thread and some others and its been helpful. I am trying to simulate a wind turbine at a high rpm in OF1.7. Now, I read online that simpleSRFFoam is not good for this. So my options are pimpleDymFoam or MRFSimpleFoam. I gather that pimpleDymFoam moves the mesh whereas MRFSimpleFoam does not (it adds a source term). I guess when I think of a wind turbine simulation, I usually imagine just creating a mesh for a single blade and then using periodic boundary conditions but from the looks of it none of you guys are doing that - why is that? And I'm still not sure which one is better - MRFSimpleFoam or pimpleDymFoam. If anyone has plots of results from these versus experimental data, I would love to see it. Thanks! |
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July 9, 2010, 21:11 |
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#35 | |
Senior Member
Steve Hansel
Join Date: Jun 2009
Location: Colorado, USA
Posts: 112
Rep Power: 17 |
Quote:
Will OF1.7 rotate meshes? |
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July 9, 2010, 21:21 |
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#36 |
New Member
Join Date: Jul 2010
Posts: 17
Rep Power: 16 |
If you used pimpleDymFoam, i think that moves the mesh doesnt it?
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December 13, 2010, 04:44 |
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#37 |
Member
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Hi Foamers,
I inserted an obstacle in the icoFoam/cavity case and to see what happens when it rotates I've included dynamic mesh effects on icoFoam. The thing is: The square rotates correctly, but the problem is that the mesh rotates with it, and that produces an invalid mesh (severe non-orthogonality). I would like the mesh to just stretch and contract as the square rotates. I mean, I don't want the points attached to the square to rotate. To better explain: When you look at the mesh in the wireframe form on paraView, I want the horizontal wires to keep their y(vertical) position and move (expand or contract) horizontally as the square rotates, and I want the vertical wires to keep their x (horizontal) position and move (expand or contract) vertically as the square rotates. How can I implement this? I'm on OpenFoam 171 and had to modify icoFoam to create icoDyMFoam. How can I install the 1.5-dev? There I believe lives icoDyMFoam and the GGI utility. Thanks and regards! All the best |
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April 2, 2013, 17:05 |
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#38 |
Member
R. P.
Join Date: Jul 2010
Posts: 73
Rep Power: 16 |
Hi all,
I made a 2D mesh using the blockMeshDict and now I wish to rotate producing a half geometry. For example, rotating (180 degree) 2D cylinder we obtain a half 3D cylinder. There is a tool called rotateMesh (http://www.openfoam.com/features/mesh-manipulation.php) but how can I use it ? Any idea ? Thanks. |
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openfoam 1.5, rotating mesh |
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