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MathGroup Archive 2000

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Re: system of nonlinear ODE

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23732] Re: system of nonlinear ODE
  • From: Roland Franzius <Roland.Franzius at uos.de>
  • Date: Mon, 5 Jun 2000 01:09:24 -0400 (EDT)
  • References: <8gv85p$5mt@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Ioanna
I have changed a bit the figure a bit (don't know what's meant by Pr
here )

NDSolve[{Derivative[3][f][x] + 2.4*f[x]*
      Derivative[2][f][x] - 0.8*Derivative[1][f][x]**2 + 
     z[x] == 0, Derivative[2][z][x] + 
     2.4*f[x]*Derivative[1][z][x] == 0, z[0] == 0, 
   Derivative[1][z][0] == 0, Derivative[2][f][0] == 0, 
   f[0] == 0, Derivative[1][f][10] == 0}, {f[x], z[x]}, 
  {x, 0, 10}]


NDSolve::"ndv" : "For a boundary value problem, only nth order single
linear \
ordinary differential equations is supported."

This means Mathematica NDSolve accepts only initial value problems (your
f'(10)==0 is the problem) for systems

roland

Ioanna Pappa schrieb:
> 
> Hi
> I am trying to solve a system of two nonlinear ordinary differential
> equations with initial conditions.
> The system
> is
>                            f'''(x)+2.4f(x)f''(x)-0.8(f')**2+z=0
>                           z''(x)+2.4Pr[f(x)z(x)]'=0
>                  with z(0)=0, z'(0)=0, f''(0)=0, f(0)=0, f'(10)=0
> I use NDSolve end the message that gives me is:
> NDSolve::deql:
> The first argument must have both an equation and an initial condition.
> Can you help me;
> Gianna
> ipappa at mie.uth.gr

-- 
Roland Franzius

  +++ exactly <<n>> lines of this message have value <<FALSE>> +++


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