# Problem in unstructured circular cylinder case

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 January 3, 2011, 17:58 Problem in unstructured circular cylinder case #1 Senior Member   Tarak Join Date: Aug 2010 Location: State College, PA Posts: 110 Rep Power: 8 Hii, I'm trying to run the circular cylinder case for Re=3900 using unstructured grid (prism/tetras) generated by ICEM. I'm using a hybrid DES/LES model. Although I'm being able to run the case using Upwinding scheme, the solution blows off after some time as I switch to CD scheme. Does it have to do anything with the mesh quality, given the checkMesh output as: Checking geometry... Overall domain bounding box (0 0 0) (0.579999987 0.4199999906 0.07999999821) Mesh (non-empty, non-wedge) directions (1 1 1) Mesh (non-empty) directions (1 1 1) Boundary openness (2.796323021e-17 1.133420052e-17 -2.412554847e-16) OK. Max cell openness = 2.744236741e-16 OK. Max aspect ratio = 5.985448358 OK. Minumum face area = 1.860038895e-07. Maximum face area = 0.0001631631359. Face area magnitudes OK. Min volume = 7.890352088e-11. Max volume = 7.346122294e-07. Total volume = 0.01946299762. Cell volumes OK. Mesh non-orthogonality Max: 63.07437883 average: 7.798812186 Non-orthogonality check OK. Face pyramids OK. Max skewness = 0.8103598145 OK. Mesh OK. Are the parameters such as aspect ratio, skewness ok for OF to handle tetra domainated meshes? Can someone advice any other settings (for schemes etc) which he/she would prefer for this case. Thanks, Tarak

 January 4, 2011, 04:42 #2 Senior Member   Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 8 Hi Tarak, as I understand it unstructered grids increase the unboundedness of schemes. I have had some succes using the blended scheme for the convection term, however, in my case (low-Re DNS) this gave so much numerical diffusion that the solution turned laminair (for 5 percent upwind). You can also try to use really low CFL (<0.5). Hope this helps.

 January 5, 2011, 01:48 #3 Senior Member   Tarak Join Date: Aug 2010 Location: State College, PA Posts: 110 Rep Power: 8 Hii Steve, Thanks for the reply. Can you please tell me how to use blending of Upwind and CD schemes in OF. Thanks, Tarak

 January 5, 2011, 04:13 #4 Senior Member   Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 8 this is for 5 percent upwind: div(phi,U) Gauss blended 0.95;

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post goodegg Main CFD Forum 12 January 22, 2013 12:47 pXYZ Main CFD Forum 14 July 25, 2011 10:05 saisanthoshm88 ANSYS Meshing & Geometry 15 December 27, 2010 12:14 fpz Main CFD Forum 7 June 20, 2005 21:30 Srinivas FLUENT 3 March 15, 2005 20:57

All times are GMT -4. The time now is 16:22.

 Contact Us - CFD Online - Top