|
SRF Solution issue with Prism+Tetra mesh compare to Hexa
Hi friends,
i m solving a periodic section problem (9.72 deg section) using SRF model, inititally i solved the problem with the pure hexa (coarse- 0.1 million) i got consistent results but now i m trying to add vortex generator on blade, therefore i have to mesh domain with tetra+prism (0.6 million) and i did it, but i m not getting proper results, residuals are also fluctuating, and getting very high velocity on periodic patches. I tried with only tetra also but faced same issue. Even trying with different discretization scheme. Please suggest me the better discretization scheme. can i use hex-core mesh from tgrid to foam.... Thank you In advance.... |
inccorect results with tetra compare to hex mesh for the same case
Hi friends,
i m solving a periodic flow problem using SRF model, inititally i solved the problem with the hexa mesh (coarse- 0.1 million) i got good results for various cases, but when same case i m trying with tetra+prism mesh (fine-0.6 million), then i m not getting proper results, residuals are also fluctuating, and getting very high velocity on periodic patches...please help me out...any one has clue regarding these....kindly waiting for reply... nitin |
Greetings Nitin,
You're not sharing much information on your problem, so it'll be very hard for anyone to help you. The best I can do to help is give you some sources of information:
Bruno |
Hi thanks for your reply.. Actually im trying to match results of Case-II (tetra+prism mesh) with Case-I (Hexa mesh).
I m solving a periodic flow problem for fan (Axial entry & radial exit) and i have taken single blade periodic section (from total of 37 blades). Simulation details area as follows: Case I.) Initialy i tried with hexa mesh (periodic hexa mesh from ICEM): cell count: 0.09 million checkMesh: OK for all criterias Steady state flow Inlet: velocity inlet (Urel=20.4m/s) Outlet: pressure outlet (0) Model: SRFSimpleFoam (as i have only one cell zone i.e. rotating one) Turbulence Model: SST K-W Descretization schemes:- grad(p):Gauss linear; grad(Urel):Gauss linear; div(phi,Urel) Gauss upwind laplacianSchemes: Gauss linear corrected Output: impeller efficiency:57% Case II) In case-2, I tried with tetra+prism on blade mesh (Periodic mesh) checkMesh: Number of severly non orthogonal faces:46 and Non-orthogonality check: OK, also remaining checkmesh criterias are ok Cell count: 0.6 million "All remaining settings are same like Case-I" Output: Solution getting diverging and giving very high velocity throughout domain, even though Residuals are dropping below 0.01. kindly waiting for reply...Thanks in dvance Nitin |
Hi Nitin,
What does checkMesh tell you about the mesh that has tetrahedral cells? And are you using non-orthogonal correctors? Best regards, Bruno |
Hi Bruno, Thanks for your reply, quality check for Tet+Prism mesh is given below,,,,
administrator@ubuntu:~/nitin/ME/ME/results/0.2/1.3tetraFinePrism$ checkMesh /*---------------------------------------------------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ Build : 2.1.1-221db2718bbb Exec : checkMesh Date : Feb 27 2013 Time : 12:54:26 Host : "ubuntu" PID : 2233 Case : /home/administrator/nitin/ME/ME/results/0.2/1.3tetraFinePrism nProcs : 1 sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE). fileModificationChecking : Monitoring run-time modified files using timeStampMaster allowSystemOperations : Disallowing user-supplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create polyMesh for time = 0 Time = 0 Mesh stats points: 121835 faces: 1233760 internal faces: 1169262 cells: 594532 boundary patches: 7 point zones: 0 face zones: 1 cell zones: 1 Overall number of cells of each type: hexahedra: 0 prisms: 24630 wedges: 0 pyramids: 264 tet wedges: 0 tetrahedra: 569638 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces ... Patch Faces Points Surface topology outlet 2256 1297 ok (non-closed singly connected) inlet 2290 1263 ok (non-closed singly connected) blade 8210 2137 multiply connected (shared edge) hub 4986 2841 ok (non-closed singly connected) shroud 4280 2392 ok (non-closed singly connected) left1 21238 10836 ok (non-closed singly connected) right1 21238 10836 ok (non-closed singly connected) <<Writing 2134 conflicting points to set nonManifoldPoints Checking geometry... Overall domain bounding box (-0.0201298 0 -7.68958e-26) (0.0850515 0.306492 0.1787) Mesh (non-empty, non-wedge) directions (1 1 1) Mesh (non-empty) directions (1 1 1) Boundary openness (1.74928e-19 4.05201e-20 -7.65942e-20) OK. Max cell openness = 2.21344e-16 OK. Max aspect ratio = 13.0933 OK. Minumum face area = 5.08171e-08. Maximum face area = 8.40055e-06. Face area magnitudes OK. Min volume = 8.5903e-12. Max volume = 7.97833e-09. Total volume = 0.000920781. Cell volumes OK. Mesh non-orthogonality Max: 78.1445 average: 16.2617 *Number of severely non-orthogonal faces: 42. Non-orthogonality check OK. <<Writing 42 non-orthogonal faces to set nonOrthoFaces Face pyramids OK. Max skewness = 1.27209 OK. Coupled point location match (average 1.22399e-11) OK. Mesh OK. Time = 1 Mesh stats points: 121835 faces: 1233760 internal faces: 1169262 cells: 594532 boundary patches: 7 point zones: 0 face zones: 1 cell zones: 1 Overall number of cells of each type: hexahedra: 0 prisms: 24630 wedges: 0 pyramids: 264 tet wedges: 0 tetrahedra: 569638 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces ... Patch Faces Points Surface topology outlet 2256 1297 ok (non-closed singly connected) inlet 2290 1263 ok (non-closed singly connected) blade 8210 2137 multiply connected (shared edge) hub 4986 2841 ok (non-closed singly connected) shroud 4280 2392 ok (non-closed singly connected) left1 21238 10836 ok (non-closed singly connected) right1 21238 10836 ok (non-closed singly connected) <<Writing 2134 conflicting points to set nonManifoldPoints Checking geometry... Overall domain bounding box (-0.0201298 0 -7.68958e-26) (0.0850515 0.306492 0.1787) Mesh (non-empty, non-wedge) directions (1 1 1) Mesh (non-empty) directions (1 1 1) Boundary openness (1.74928e-19 4.05201e-20 -7.65942e-20) OK. Max cell openness = 2.21344e-16 OK. Max aspect ratio = 13.0933 OK. Minumum face area = 5.08171e-08. Maximum face area = 8.40055e-06. Face area magnitudes OK. Min volume = 8.5903e-12. Max volume = 7.97833e-09. Total volume = 0.000920781. Cell volumes OK. Mesh non-orthogonality Max: 78.1445 average: 16.2617 *Number of severely non-orthogonal faces: 42. Non-orthogonality check OK. <<Writing 42 non-orthogonal faces to set nonOrthoFaces Face pyramids OK. Max skewness = 1.27209 OK. Coupled point location match (average 1.22399e-11) OK. Mesh OK. End In fvSolution file i m using following settings for orthogonal corrector SIMPLE { nNonOrthogonalCorrectors 0; } Kindly waiting for your reply. Regards Nitin |
Hi Nitin,
Try setting "nNonOrthogonalCorrectors" to 2: Code:
nNonOrthogonalCorrectors 2;Nonetheless, these messages: Quote:
The first one... I don't know. Check if your other mesh had these issues as well or not. If possible, I would advise you to generate a new mesh with improved quality. Best regards, Bruno |
| All times are GMT -4. The time now is 23:28. |