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ytc1-Visitor
1-Visitor
September 8, 2010
Question

Mathcad 'Odesolve' to solve boundary value problem

  • September 8, 2010
  • 3 replies
  • 6614 views

Hi,

I tried to solve a boundary value problem of a nonlinear sytem of differential equations, but with no success. The 'odesolve' command keeps saying not able to converge to solution. It is a boundary value problem, so naturally there are 7 prescribed initial conditions and 6 prescribed conditions at the other end (See attached mathcad file), but it keeps saying not able to converge and suggest to change initial guess values. However, there is no way to change them in the solve block. Instead I have reprogram the problem using cumbersome 'c' language using ISML library to carry out multiple shooting strategy to solve the problem, and it works. It seems that the 'odesolve' command does not support multiple shooting strategy to solve highly non-linear system of ordinary differential equations with boundary conditions prescribed at the terminal ends of integration.

Is there any workaround to force the 'odesolve' command to converge in mathcad. Experts out here care to comment and give your view.

    3 replies

    M
    MikeArmstrong1-Visitor
    1-Visitor
    September 8, 2010

    Re-post the worksheet in M11 format for a wider audience.

    Mike

    V
    24-Ruby IV
    ValeryOchkov24-Ruby IV
    24-Ruby IV
    September 8, 2010

    I know (it seems to me) the OdeSolve-function solves correct the boundary task for one ODE but not correct for n ODEs.

    V
    24-Ruby IV
    ValeryOchkov24-Ruby IV
    24-Ruby IV
    September 8, 2010

    >it seems to me

    See the attach

    F
    f.kohlhepp1-Visitor
    1-Visitor
    September 8, 2010

    Is there any workaround to force the 'odesolve' command to converge in mathcad.

    You can try the command line solvers (rkfixed,rkadapt, etc.) and the "bvalfit" function that is supposed to turn boundary value problems into initial condition problems. I've never had a lot of luck . . .

    Y
    ytc1-VisitorAuthor
    1-Visitor
    September 8, 2010

    Thanks for your response. But still I have no much luck with the 'bvalfit' function. Anyway, I give it one more try and see how it goes. Another thing with the 'odesolve' function is that it does not seem to give you an option to use multiple shooting algorithm, which could be essential in solving highly non-linear boundary value problem.

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