       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>

```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
>
> 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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