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

Multigrid or Krylov subspace for poisson eqn

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 4, 2006, 22:44
Default Multigrid or Krylov subspace for poisson eqn
  #1
zonexo
Guest
 
Posts: n/a
Hi,

I am currently solving my poisson eqn from my FVM fractional step scheme using the Krylov subspace solver. On some high-aspect ratio grids, convergence is slow and it sometimes fails.

My poisson eqn is formed from c-grid of an airfoil. Hence is the multigrid method a better way to solve? Or it depends solely on the actual solver itself?

Thanks
  Reply With Quote

Old   May 5, 2006, 04:26
Default Re: Multigrid or Krylov subspace for poisson eqn
  #2
rt
Guest
 
Posts: n/a
1) In general Multi-grid methods are more robust for damping high frequency modes of error, it is attractive when we have fine grid or large number of grids in computational domain. Also as your grid (C-type) is structured, the FAS (multi-grid with full appriximation method) is probably better choice and more easy to implement.

2) But, as you stated that your problem is related to high aspect ratio, not grid refinement, i think one probable source of convergence rate decay (or oscilation) is decreasing accuracy and enlarging truncation error due to large aspect ratio (generally large aspect ration is not suitable). So i recommend using double precision arithmatice (if you use SP) and application of high order methods (specially compact method).

  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
what is the "Krylov subspace iterations " ztdep Main CFD Forum 1 October 4, 2006 01:51
Various Norms and Krylov subspace deepak Main CFD Forum 2 September 5, 2006 23:25
multigrid sureshkumar Main CFD Forum 0 June 9, 2006 02:20
UDFs for Scalar Eqn - Fluid/Solid HT Greg Perkins FLUENT 0 October 11, 2000 04:43
Multigrid applied to k-e models Paulo Zandonade Main CFD Forum 9 May 24, 1999 09:10


All times are GMT -4. The time now is 07:42.