trouble solving partial DE
- To: mathgroup at smc.vnet.net
- Subject: [mg39919] trouble solving partial DE
- From: karlo jolic <kjolic at swin.edu.au>
- Date: Tue, 11 Mar 2003 02:39:02 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
Hi everyone
I keeping getting the following error:
NDSolve::"deql": "The first argument must have both an equation and an \
initial condition."
when i try to solve the following second order partial differential
equation
(wherein the function u is a function of variables x and t):
NDSolve[{m*D[u[x, t], t, t] + 6*Pi*n*r*D[u[x, t], t] -
0.5*mu*i*ndash*pm*((L - u[x, t])^2/(R^2 + (L - u[x, t])^2)^1.5
-
1/(R^2 + (L - u[x, t])^2)^0.5 - (L + u[x, t])^2/(R^2 + (L +
u[x, t])^2)^1.5 +
1/(R^2 + (L + u[x, t])^2)^0.5) == 0,
u[L, 0] == L,
D[u[L, 0], t] == 0},
u, {x, 0, L}, {t, 0, 1}]
I have specified 2 initial conditions already, so i can't understand why
i get the error.
does anyone know whats the problem?
Thanks
Karlo
PS I'm relatively new at mathematica.