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Re: NDsolve question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg29138] Re: NDsolve question
  • From: Erich Mueller <emuelle1 at uiuc.edu>
  • Date: Wed, 30 May 2001 23:28:25 -0400 (EDT)
  • Organization: University of Illinois at Urbana-Champaign
  • References: <9f2gjo$881$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Mathematica is case sensitive.  You used lower case letters in defining
your constants, and upper case letters in your equations.

Erich

On Wed, 30 May 2001, Supriyo Sinha wrote:

>
> Hi,
>
> I'm relatively new to Mathematica, but I heard
> that Mathematica is better at solving differential equations.  Anyways,
> I'm trying to solve a set of six coupled differential equations (each
> equation is coupled to a maximum of two other equations).  When I try to
> evaluation, I get the following error message:
>
> NDSolve::ndnum: Differential equation does not evaluate to a number at Z =
> 0..
>
> The code I'm trying to run is the following:
>
> Betapump = 2.23038
> Beta1 = 2.0744
> Beta2 = 1.92669
> Beta3 = 1.78431
> Beta4 = 1.66273
> Beta5 = 1.54011
> g1 = 0.97536
> g2 = 0.95079
> g3 = 0.92583
> g4 = 0.90336
> g5 = 0.87948
> NDSolve[{Kp'[Z] == -1*K1[Z]*Kp[Z] - Betapump*Kp[Z],Kp[0] == 1,K1'[Z] ==
> G1*(K1[Z]*Kp[Z]-K1[Z]*K2[Z])-Beta1*K1[Z],K1[0] == (0.1)^12,K2'[Z] ==
> G2*(K2[Z]*K1[Z]-K2[Z]*K3[Z])-Beta2*K2[Z],K2[0] == (0.1)^12,K3'[Z] ==
> G3*(K3[Z]*K2[Z]-K3[Z]*K4[Z])-Beta3*K3[Z],K3[0] == (0.1)^12,K4'[Z] ==
> G4*(K4[Z]*K3[Z]-K4[Z]*K5[Z])-Beta4*K4[Z],K4[0] == (0.1)^12,K5'[Z] ==
> G5*(K5[Z]*K4[Z])-Beta5*K5[Z],K5[0] == (0.1)^12},{Kp[Z], K1[Z], K2[Z],
> K3[Z], K4[Z], K5[Z]}, {Z, 0, 500}]
>
> All the equations are pretty similar.  I would actually prefer to use
> DSolve to get an equation, but I will settle for the interpolated solution
> given by NDSolve and plot it.
>
> Any help would be GREATLY appreciated.
>
> Thanks,
> Supriyo
> supriyo at stanford.edu
>
> ---------------------------------------------------------------------
> "The presence of an enthusiast makes me as cold as ice, while I think
> I should become passionately excited if I had much to do with a dull
> and phlegmatic person."
>
> 			- Gregory Aleksandrovich Pechorin
> 			  M. L. Lermontov's A Hero of Our Own Times
>
> "...the only consolation you have left is to whip yourself..."
>
> 			- F. Dostoyevsky's Notes From the Underground
>
>
>


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