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MathGroup Archive 1995

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DAE Solver in Mathematica?

  • To: mathgroup at christensen.cybernetics.net
  • Subject: [mg940] DAE Solver in Mathematica?
  • From: achillgc at ttown.apci.com (Geoff C. Achilles)
  • Date: Wed, 3 May 1995 00:19:24 -0400
  • Organization: Air Products & Chemicals

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[0]  == 400,
           c[0]  == 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)


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