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Topic: Infinite expression, NDSolve
Replies: 1   Last Post: Oct 16, 2012 10:49 PM

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 grasley@gmail.com Posts: 2 Registered: 10/16/12
Infinite expression, NDSolve
Posted: Oct 16, 2012 3:25 AM

Dear All,

I am trying to use NDSolve to solve the heat equation for 1-D radial flow in cylindrical coordinates, with the initial condition of a spatially constant temperature, and boundary conditions of zero flux at r=0 (axisymmetry) and a constant temperature at a radius of 1. Here is the code:

NDSolve[{D[T[r, t], t] == 1/r*D[r D[T[r, t], r], r],
Derivative[1, 0][T][0, t] == 0, T[1, t] == 20, T[r, 0] == 0}, T, {r,
0, 1}, {t, 0, 10}]

Power::infy: Infinite expression 1/0. encountered. >>

Infinity::indet: Indeterminate expression 0. ComplexInfinity encountered. >>

Power::infy: Infinite expression 1/0. encountered. >>

Infinity::indet: Indeterminate expression 0. ComplexInfinity encountered. >>

NDSolve::ndnum: Encountered non-numerical value for a derivative at t == 0.`. >>

I've tried using nonzero (i.e. very small values) for the initial time and in place of r=0 in the boundary condition, but to no avail. Any ideas?

Thanks!

Date Subject Author
10/16/12 grasley@gmail.com
10/16/12 Kevin J. McCann