Re: desperate, please help.
- To: mathgroup at smc.vnet.net
- Subject: [mg27362] Re: desperate, please help.
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 22 Feb 2001 02:25:07 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <97003k$tq@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
Mathematica can't solve differential algebraic equations.
More over that is a bit difficult because only
for special input values a solution exist.
Don't type stuff like ÷ into equations, don't make
assignments like F = .9*163 in differential equations,
don't mix the case in k[x] and K[x], use always an argument
(not a single K or r) and try to elimimate T[x],F,C,K[x]..
with Eliminate[] before you call NDSolve[].
Regards
Jens
Thjqase wrote:
>
> I need help numerically solving a differential equation coupled with several
> algebraic equations. New to Mathematica. Here's code:
>
> NDSolve[{v'[x] == -F÷r, T[x] == 330 + 43.3*x, F = .9*163, C == 9.3,
> k[x] == 31.1Exp(7906*(T - 360)/(T*360))
> , K[x] == 3.03*Exp(-830.3*((T - 333)/(T*333))),
> r[x] == -k*C*(1 - (1 + 1/K)*x),
> v[0] == 0}, {v}
> , {x, 0, .7}]
>
> Error code is:
>
> NDSolve::"deql": "The first argument must have both an equation and an \
> initial condition."
>
> Any suggestions? What am I doing wrong? My head is sore from banging it against
> the wall.
>
> TIA.