CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Complex Mesh In Gambit.

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 24, 1999, 18:54
Default Complex Mesh In Gambit.
  #1
Ranjeet
Guest
 
Posts: n/a
Has anybody meshed a complex volume in gambit with structred mesh on few of the faces and unstructred mesh inside the volume.? need few tips?
  Reply With Quote

Old   March 25, 1999, 03:43
Default Re: Complex Mesh In Gambit.
  #2
Jonas Larsson
Guest
 
Posts: n/a
Yep, I've meshed a 1.5 stage turbine using a hybrid grid on the hub/shroud surfaces (quads around the blades and tris further out) and "cooper" (ie structured) in the radial direction. Works well, although bugs in the boundary layer handling makes it difficult to get all boundary layers correct. If you are having problems with boundary layers get the 1.0.4 release due out in a week or two, it is much better than 1.0.3 at boundary layers, although several problems still remain.

  Reply With Quote

Old   March 25, 1999, 11:09
Default Re: Complex Mesh In Gambit.
  #3
Ranjeet
Guest
 
Posts: n/a
It seems the mesh You are talking about is a 2-D mesh.What I am trying to do is say a cube is there and You mesh quads on few of the faces and tris inside the volume.Here Gambit gives me error that some x nodes not meshed and so it cant mesh the geometry.I have been playing around with this for a week now. need help?
  Reply With Quote

Old   March 25, 1999, 14:07
Default Re: Complex Mesh In Gambit.
  #4
John C. Chien
Guest
 
Posts: n/a
(1). there is no simple method to generate complex geometry and 3-D mesh automatically !!! (2). but if you plan ahead, and divide (cut) the computational domain into smaller blocks ( the surface patches will be smaller and simpler than one large complex surface), the nodal distribution, the surface mesh generation and the volume mesh generation will be easier to handle. (3). it is always a practical method to build the geometry and the mesh from ground up ( create points, curves, surfaces, volumes, and associated meshes).(4). I have used more than 500 surface patches to generate a complex 3-D geometry and mesh, using the very old FLUENT/preBFC module. ( the generation before Geomesh and Gambit) The mesh generator was tgrid module.( it can handle hybrid mesh) (5). The current generation like Gambit can handle the geometry and mesh generation in two ways: one is the traditional ground up method, and the other is CAD like top down solid modeling. There are many rules involved in the automatic mesh generation using the solid model top down approach. (6). My suggestion is: a). the first ground up method will always give you the answer with a lot of control over the geometry and the mesh, if you can spend more time to study the geometry of your problem and simplify it by subdivision of the computational domain. b). In order to use the second method, you really have to study every commands and the procedures of the user's guide in order to take advantages of the top down method. (7). So, in the ground up method, you control the mesh generation. On the other hand, you have to understand and follow the program's rules in order to use the top down method. (8). a few weeks or a few months is not uncommon to generate a complex 3-D mesh. (9). I have not started using the new Gambit program, but I think, if you follow the rule exactly, your chance of getting the final 3-D mesh should be relatively high. In this area, be patient.
  Reply With Quote

Old   March 25, 1999, 21:50
Default Re: Complex Mesh In Gambit.
  #5
ranjeet
Guest
 
Posts: n/a
Thanks for the reply,I hope now I will be able to tackle this.
  Reply With Quote

Old   March 26, 1999, 03:29
Default Re: Complex Mesh In Gambit.
  #6
Jonas Larsson
Guest
 
Posts: n/a
Nope the mesh I'm talking about is a full 3D mesh of a 1.5 stage axial turbine (two stators and one rotor). I meshed it using a mix or tris and quads on the hub surface and then extending them in the 3rd direction using the "cooper scheme". I have also started adding rim-seals and cavities using fully unstructured tets.
  Reply With Quote

Old   March 26, 1999, 11:18
Default Re: Complex Mesh In Gambit.
  #7
Ranjeet
Guest
 
Posts: n/a
In my case its the other way round, I have to make 2 sides as rot.periodic and two sides of the geometry as trans. periodic so I need quads on the outer surface and tris in the core.
  Reply With Quote

Old   March 26, 1999, 13:25
Default Re: Complex Mesh In Gambit.
  #8
John C. Chien
Guest
 
Posts: n/a
(1). If the outer boundary of the domain is covered by six sided bricks(hex.), then, in order to grow the four-sided cell(tet.) inside this closed boundary, you need a transition layer of five-sided cells(pyramid.) (2).you need to find out whether the program can do this automatically or not.
  Reply With Quote

Old   March 26, 1999, 15:53
Default Re: Complex Mesh In Gambit.
  #9
Ranjeet
Guest
 
Posts: n/a
That I have checked with the Gambit tech support and they say that Gambit automatically makes these pyramids. That is it supports quads on surface and tets inside the volume.
  Reply With Quote

Old   April 29, 1999, 18:18
Default Re: Complex Mesh In Gambit.
  #10
Kevin Cahill
Guest
 
Posts: n/a
The error message you are getting is typical of a mismatch in number of elements on your outter and inner surfaces. You will have to "play" with the number of tets on your inner surface and try remeshing the voulme until gambit can handle the transition. Remember that you need more tets on the tet-meshed surface than hexs on the hex-meshed surface. Try a ratio of about 2:1, but the spacing between the surfaces is also important. Keep trying. I have been throught this cycle, and it will work with a little luck.
  Reply With Quote

Reply


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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Gambit problems Althea FLUENT 22 January 4, 2017 04:19
mesh missing after export in gambit morteza08 ANSYS Meshing & Geometry 1 July 26, 2010 02:10
mesh missing after export in gambit morteza08 Main CFD Forum 0 July 23, 2010 03:19
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55
Icemcfd 11: Loss of mesh from surface mesh option? Joe CFX 2 March 26, 2007 19:10


All times are GMT -4. The time now is 08:48.