Hi, all

I'm testing mathematica for 30 days. I've several questions: the first one: Is here the right place to do that? If not, please tell me, where I can do that!

Actually I test PDE solutions ( transient heat conduction). Has anyone an idea, why the following PDE example from the Help Documentation works

NDSolve[{D[u[t, x], t] == D[u[t, x], x, x], u[0, x] == 0,

u[t, 0] == Sin[t], u[t, 5] == 0}, u, {t, 0,

10}, {x, 0, 5}]

while the following example ( I've changed one boundary condition- I hope, that was the only change- ) doesn't:

NDSolve[{D[u[t, x], t] == D[u[t, x], x, x], u[0, x] == 0,

u[t, 0] == Sin[ t], D[u[t, 5], x] == 0}, u, {t, 0, 10}, {x, 0,

5}]

what is my mistake?

hopefully, later on I want solve the following problem:

a one dimensional bar (constant heat conductivity, density, heat capacity) is heated ( or cooled) at one end with a given, time dependent fluidtemperature distribution (as a function or at discrete times with interpolation). The heat transfer coefficient is assumed to be constant.

The other end of the bar is assumed to be isolated( dT/dx=0)

After my first insights in mathematica examples, I think this could be done with mathematica and in an CDF document ( with or without mathematica?) with the following options:

changing the material coefficients ( perhaps from mathematica databases or a own one)

changing the given, time dependent fluidtemperature distribution

and, at top: changing the initial and the possible boundary conditions ( I've seen a comparable CDF document: beam deflection with different boundary conditions)

choosing between different solution presentations:

3D plot ( temperature distribution as function of space and time)

2d plot temperature vs bar length ( at different times)

table form temperature vs bar length ( at different times)

maybe, that this example is too complicated for a newbie?

but anyway, thank you so much for any help!

Peter