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

LUSGS understanding

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

Reply
 
LinkBack Thread Tools Display Modes
Old   February 14, 2007, 10:12
Default LUSGS understanding
  #1
Gustavo
Guest
 
Posts: n/a
I've been reading a bit of LUSGS schemes on Blazek's book and I'm facing some difficulties to understand it ...perhaps someone can enlight me...

On LUSGS we basically want to factorise (on three matrixes) the implicit operator (A) on the deltaW, like (D+L).D^(-1).(D+U) being L a lower triangular, U an upper triangular e D a diagonal. These (L, D, U) have different definitions for structured and unstructured meshes. In a general way, calling R the residual, we could split the equation A.deltaW=-R, where A stands for the implicit and R(residual) the explicit operators, in two parts. These would be

D.deltaW(1-ijk) =-R(n-ijk) - LdeltaW(1) D.deltaW(n-ijk)=D.deltaW(1-ijk)-UdeltaW(n)

If I have correctly understood, as we are marching the solution on space by layers (i+j+k=constant, or layer composition on unstructured grids) we first solve the first equation for the whole grid as a forward step, as we would already have LdeltaW(1) from the previous steps, discovering deltaW(1-ijk) (just having to invert matrix D for this), and then we solve the second on a similar way but sweeping the whole grid on the opposite direction as now we would already have UdeltaW(n), from previous steps, and D.deltaW(1-ijk) from the previous equation. First of all, is this correct, is this the way it works ?

If so, then on the beggining of the first equation calculation, let's say i+j=0 , how would I have LdeltaW(1) , the same for the second with UdeltaW(n) ?? From boundary conditions, perhaps ??
  Reply With Quote

Reply

Thread Tools
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 On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Problems in understanding BuoyantBoussinesqSimpleFoam Anne Lincke OpenFOAM 8 September 14, 2011 04:16
Ambiguity in understanding interfaces in CFX saisanthoshm88 CFX 9 February 2, 2011 14:05
basic understanding of sHM colinB OpenFOAM Native Meshers: snappyHexMesh and Others 1 October 6, 2010 08:17
Problem understanding rhoPisoFoam MatP OpenFOAM Running, Solving & CFD 1 May 15, 2010 13:21
Understanding of channelOodles and oodles solver fs82 OpenFOAM 1 September 23, 2009 10:36


All times are GMT -4. The time now is 02:44.