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Re: Re: finite differencing of a PDE system

  • To: mathgroup at smc.vnet.net
  • Subject: [mg67748] Re: [mg67656] Re: finite differencing of a PDE system
  • From: "Chris Chiasson" <chris at chiasson.name>
  • Date: Thu, 6 Jul 2006 06:53:21 -0400 (EDT)
  • References: <e8888u$92q$1@smc.vnet.net> <200607031038.GAA16538@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

First, thank you to my previous responders:
Gregor
Oliver Ruebenkoenig

I changed my discretization of the interior PDEs so that they detect
when they're on the boundary and appropriately change from center
difference to forward or backward difference.

current situation:

CoefficientArrays creates a 155001x155001 (m) matrix and a 155001x1
(-b) matrix if I just feed it the finite difference equations
generated from the interior PDEs.

CoefficientArrays creates a 163779x155001 (m) matrix and a 163779x1
(-b) matrix if I feed it the interior and boundary conditions.

LinearSolve[m,b] only works for a square m.

questions:

How do I include the Dirichlet boundary conditions for the stress?

poor solutions:

I could try LinearSolve with the homogeneous equations, but I have a
feeling the m matrix will be singular or that there will otherwise be
no solution. It certainly wouldn't be a solution corresponding to my
boundary conditions.

I could also try a least-squares fit (pseudo-inverse). That seems like
it should be unnecessary.

Thanks again for any input you may give,
-- 
http://chris.chiasson.name/


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