Re: NDSolve series of ode with equilibrium conditions

• To: mathgroup at smc.vnet.net
• Subject: [mg21944] Re: NDSolve series of ode with equilibrium conditions
• From: Eckhard Hennig <hennig at itwm.uni-kl.de>
• Date: Sat, 5 Feb 2000 00:49:18 -0500 (EST)
• Organization: ITWM
• References: <87avsu\$o1r@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```David Grymonpre schrieb in Nachricht <87avsu\$o1r at smc.vnet.net>...
>
>I am having a problem using NDSolve.  I have a series of  linear ODE's
>such as:
>
>y1'[t]== f(y1[t], y2[t], ...y40[t])
>.
>.
>.
>y40'[t]== f(y1[t], y2[t], ...y40[t])
>
>with initial conditions for each equation.  I need to add several
>equilibrium equations where one variable is a function of several of the
>other variables such as:
>
>y1[t]=K*y2[t]*y3[t]  where K is a constant.
>
>As of now, the system is quite complex (as far as lines of code for the
>problem) and I am trying to find a way to include these equilibrium
>equations in my system.  The code works when the equilibrium equations
>are not included.  How do I include the additional equilibrium
>equations?  I am using version 3.0.

David,

the system of equations you want to solve is a DAE (differential-algebraic
equation) rather than a system of ODE's. Unfortunately, NDSolve cannot
handle this type of equations. However, our circuit analysis toolbox Analog
Insydes includes a numerical DAE solver (NDAESolve) that may help you to
our web site (see my signature). In addition, if you send me your equations,
I can show you how to use NDAESolve.

Best regards,

Eckhard Hennig

-----------------------------------------------------------
Dipl.-Ing. Eckhard Hennig      mailto:hennig at itwm.uni-kl.de
Institut fuer Techno- und Wirtschaftsmathematik e.V. (ITWM)
Erwin-Schroedinger-Strasse,  67663 Kaiserslautern,  Germany
Voice: +49-(0)631-205-3126    Fax: +49-(0)631-205-4139
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