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NDsolve question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg29119] NDsolve question
  • From: Supriyo Sinha <supriyo at stanford.edu>
  • Date: Wed, 30 May 2001 05:50:33 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

I'm relatively new to Mathematica (I normally use MATLAB), 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

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