       Re: DAE Solver in Mathematica?

• To: mathgroup at christensen.cybernetics.net
• Subject: [mg957] Re: DAE Solver in Mathematica?
• From: saarinen (Sirpa Saarinen)
• Date: Thu, 4 May 1995 02:54:07 -0400
• Organization: Wolfram Research, Inc.

```In <3npp74\$ohp at news0.cybernetics.net> achillgc at ttown.apci.com (Geoff C. Achilles) writes:

>I am trying to solve a system of differential and algebraic equations
>using Mathematica.  NDSolve seems like the logical function, but it
>doesn't seem to like algebraic equations.  I post a trivial example
>below to illustrate my problem.  Converting the algebraic equation to a
>differential equation is an alternative (but is difficult in my
>particular case).  Is there a package out there for solving DAE's?

>Example calculation:

>NDSolve[ { T'[t] == -c[t],
>           c[t]  == 1,
>           T  == 400,
>           c  == 1 },
>         { T[t], c[t] }, { t, 0, 10 } ]

>Obviously my case is more complicated and the algebraic equations
>(c[t]) are time dependent, but the basic setup is the same.  This
>particular format gives and error message saying that c[t] isn't in the
>form of an ODE - because it isn't an ODE.  Any suggestions?

>Geoff (achillgc at ttown.apci.com)

Yes, there are packages for solving DAEs and you can get them from
netlib. The most famous one is the one written by Linda Petzold.
Send mail to netlib at ornl.gov for information.

Mathematica will have DAEs implemented in some future version as well
but not in the current one (V 2.2).

Sirpa Saarinen
saarinen at wri.com

```

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