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Diff. Equ

  • To: mathgroup at
  • Subject: [mg43692] Diff. Equ
  • From: Prechtl Josef <e9426270 at>
  • Date: Tue, 30 Sep 2003 16:42:41 -0400 (EDT)
  • Organization: Vienna University of Technology, Austria
  • Sender: owner-wri-mathgroup at

I'm trying to solve a set of ordinary diff. equations (the independant
parameter is s), for which certain boundary conditions have to be
fulfilled: one boundary condition at s=0, the second one at an unknown s1.
I am trying to solve this equation with a 'shooting' method, trying to
vary one parameter (in my case it is tetastrich) in the system of diff.
equation, and have a look if the boundary equations are fulfilled at the
second boundary. This is implemented in Solution[] via FindRoot.
SolutionFind[..,tetastrich] should solve the diff. equation for a given
tetastrich (basically it uses NDSolve[]). Obviously, in order to do that,
this routine needs to be evaluated already with a certain numerical value
of tetastrich; however, in my case this seems not to be the case, since I
always get the error message:
NDSolve::"ndinn": "Initial condition \!\(1.`\\ tetastrich\) is not a

Thanx for any useful comment in advance!!

Solution[druck_, v_] :=
  FindRoot[Evaluate[SolutionFind[druck, v, tetastrich]], {tetastrich, 0}]

SolutionFind[druck_, v_, tetastrich_] :=
  With[{min =
            Evaluate[-Teta[s, druck, v, tetastrich]], {s, 0, 0,
              2\[Pi]}][[2]]}, {R[s, druck, v, tetastrich] == 0 /. min,
      Teta[s, druck, v, tetastrich] == \[Pi] /. min}]

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