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

deforming grid

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 6, 2005, 13:58
Default deforming grid
  #1
sourabh
Guest
 
Posts: n/a
I want to model a deforming grid problem with fixed no. of points, In finite volume framework withe explicit marching. Can I get any suggestion or referece something. Thank you for reading.
  Reply With Quote

Old   October 7, 2005, 03:53
Default Re: deforming grid
  #2
ganesh
Guest
 
Posts: n/a
Dear Sourabh,

Yes, it is definitely possible to model such a problem. However, it would be more intersting and clear if you could also specify the context of your problem, ie. what kind of problem you are in fact trying to solve. In general most unsteady flow problems that involve moving boundaries can be solved using a variety of methods, which include moving grid/deformin-grid formulations. If your work matches with the above to any extent you casn check the following papers for an initial reference.

And as far as deforming grids are concerned, with explicit marching the major changes to a non-deforming grid case are in the following.

1. The flux formula, the grid moves so the convection velocity is modified 2. The boundary conditions on the moving boundary, for which the grid is deforming 3. The FVM update formula and hence the marching, to incorporate the changing volumes.

J.T. Batina,AIAA Jl. Implicit flux split schemes for unsteady aerodynamic analysis involving unstructured dynamic meshes

Trepanier etal., AIAA Jl. Unsteady euler solutions for arbitarily moving bodies and boundaries

Venkatakrishanan and Mavriplis , AIAA paper 1995

These give some details for implicit marching also.

Hope this helps

Regards,

Ganesh
  Reply With Quote

Old   October 7, 2005, 09:30
Default Re: deforming grid
  #3
Jessy
Guest
 
Posts: n/a
For time-varying grids, you have to solve an additionnal conservation law for the cell volume. This is the so-called Geometrical Conservation Law (GCL) which is deduced from the general integral form of the Euler equations for a constant state (density = cst, velocity = cst, pressure =cst). You can find quite a lot of papers dealing with the GCL and the formulation of the numerical methods in this general framework.
  Reply With Quote

Old   October 8, 2005, 07:47
Default Re: deforming grid
  #4
ganesh
Guest
 
Posts: n/a
Dear Jessy,

Thaks for making the point, which I missed completely. However, it is to be noted that there has been a lot of controversy about the GCL and its use. While there has been only a little theoretical work on the GCL (Farhat etal 2002,2000), there have been several numerical experiments on the same. While some do not find any difference in the absence of the GCL, others have reported numerical instabilities and non-physical oscillations. However, in problems of aeroelasticity wherein there is an energy transfer/interplay between the fluid& structure, it is imperative that the GCL be used.(Farhat,1999). Although this is the case, I strongly support the fact that GCL is a must for any moving grid computation, to be on the safer side, both numerically and theoretically.

Regards,

Ganesh
  Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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
Deforming grid - ALE method CFD Student Main CFD Forum 1 October 10, 2006 11:33
Recommend structured grid deforming algorithm zonexo Main CFD Forum 0 April 17, 2006 04:24
GRID TO GRID INTERPOLATION in FLUENT calogero FLUENT 3 June 4, 2003 09:32
Combustion Convergence problems Art Stretton Phoenics 5 April 2, 2002 06:59
Troubles modelling flow through a grid Hans Klaufus CFX 1 June 28, 2000 17:43


All times are GMT -4. The time now is 23:47.