       Re: NDSolve with Boundary Condition

• To: mathgroup at smc.vnet.net
• Subject: [mg107708] Re: [mg107694] NDSolve with Boundary Condition
• From: Patrick Scheibe <pscheibe at trm.uni-leipzig.de>
• Date: Wed, 24 Feb 2010 06:18:53 -0500 (EST)
• References: <201002231303.IAA16128@smc.vnet.net>

```Hi,

check

D[f[x, y], x] // InputForm

which gives

Derivative[1, 0][f][x, y]

Therefore, you can use something like

Derivative[1, 0][f][0, y] == blub

to give the values at the 0-boundary. If you want a working sample, read
the NDSolve documentation carefully.

Cheers
Patrick

On Tue, 2010-02-23 at 08:03 -0500, marjan wrote:
> Dear MathGroup members,
>
> I am trying to solve an numerical equation: sol = NDSolve[{D[Y[z, t],
> z, z] +
>      10^12 Sin[Y[z, t]] Cos[Y[z, t]] == D[Y[z, t], t]
> with boundary conditions: d(Y[a, t])/dz = 2*10^6  and   d(Y[b, t])/dz
> = 2*10^6 , but i don't know how to write the boundary condition in
> this equation. when I write it like D[Y[a, t], z] == 20*10^5, D[Y [b,
> t], z] == 20*10^5 Mathematica gives this error
>
> NDSolve::deqn: equation or list of equations expected instead of
> "false" in the first argument {D[Y[z, t], z, z] +
>      10^12 Sin[Y[z, t]] Cos[Y[z, t]] == D[Y[z, t], t] , False,False}
>