From help-request at octave dot org Fri Jan  7 05:33:58 2005
Subject: ODE system solving
From: "homer_jay at katamail dot com" <homer_jay@katamail.com>
To: help at octave dot org
Date: Fri, 07 Jan 2005 11:35:28 +0000

hi everybody

i need to solve a differential equation system, 1 first order equation and 1 second order equation.

they are in the form

w"=f(z,w,w',T,T')
T'=f(z,w,T)

w,w',w",T,T' are function of z.
i have 3 initial condition w0,w'0, T0.
in the rfirst equation i make the substitution 

w --> y1
w'--> y2, so w" --> y2'
T --> y3, so T' --> y3'

the system became a 3 first order equation system, is it right?
this is the m-file section:

SysO(1)=y(2); 

SysO(2)=y(1)*y(2)/(3*Nup)-(g/(3*Nup))+(2*tau/(3*Nup*rho*Rz))+((y(2)^2)/y(1)*3*Nup)-(1/Nup)*dNup*y(2)*(-2*hc*(y(3)-Ta)/(Rz*rho*Cp*y(1)));

SysO(3)=-2*hc*(y(3)-Ta)/(Rz*rho*Cp*y(1));


as you can see, the second equation (SysO(2)) is dependent of T': in fact the last term of the second equation is the same of the third equation.
the question is: is this m-file correct?

of course in the m-file i have all the other equations (Rz, Nup....). they are function of w and T.

in solving the system i receive a "tolerance not met" error message. can you help me?!?!?

thanks

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