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Re: NDSolve initial value problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99203] Re: NDSolve initial value problem
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 29 Apr 2009 06:41:32 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <gt90l4$l1t$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

the parts of Piecewise[] outside of the interval y in[-1,1]
are total useless and will not help to make consistent
boundary conditions.

Regards
   Jens

Murat Havzal wrote:
> Dear Mathematica users;
> 
> 
> 
> I am trying to solve liquid heat/mass transfer equation with mixed boundary
> conditions.
> 
> My code looks like this:
> 
> 
> 
> pe=0.5;
> 
> u[y]=1-y^2;
> 
> 
> 
> sol=NDSolve[
> 
> {
> 
> pe*u[y]*D[T[x,y],x]==D[T[x,y],y,y],
> 
> 
> 
> T[0,y]==Piecewise[{{-y,y<=-1},{0,-1< y<1},{1,1<=y}}],
> 
> 
> 
> T[x,1]==1,
> 
> (D[T[x,y],y]/.y->-1)==-1
> 
> 
> 
> },
> 
> T,{x,0,1},{y,-1,1},SolveDelayed->True];
> 
> 
> 
> This returns inconsistent initial boundary conditions error.
> 
> I also tried to make the piecewise initial condition, a numerical function
> namely:
> 
> 
> 
> initial[y_?NumericQ]:=Piecewise[{{-y,y<=-1},{0,-1< y<1},{1,1<=y}}]
> 
> 
> 
> 
> 
> However this did not work, too. I understand that there is a similar
> question already asked about this subject,
> 
> and I tried my best to convert it to my problem but couldn't. I couldn't
> find the code but I also tried to give the
> 
> initial piecewise function as a interpolating function, it returned the same
> response.
> 
> Any help would be appreciated.
> 
> 
> 
> Thanks.
> 
> 
> 
> Murat Havzal
> 
> 


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