Power of infinity, NDSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg128400] Power of infinity, NDSolve*From*: grasley at gmail.com*Date*: Tue, 16 Oct 2012 03:21:56 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Dear All: I am trying to solve the 1-D heat equation with NDSolve in cylindrical coords (radial flow only). The boundary conditions are a fixed outer temperature at r=1 and a zero flux at r=0, with an initial condition of a constant temperature. Unfortunately, I am getting a power of infinity error. 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}] 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 have tried using non-zero initial radial points and nonzero initial times, but to no avail. Any ideas?