Re: NDSolve Unable to find initial conditions that satisfy the
- To: mathgroup at smc.vnet.net
- Subject: [mg116598] Re: NDSolve Unable to find initial conditions that satisfy the
- From: Oliver Ruebenkoenig <ruebenko at wolfram.com>
- Date: Mon, 21 Feb 2011 05:34:32 -0500 (EST)
On Sun, 20 Feb 2011, Ali K. Ozdagli wrote: > Any help? > > On Fri, Feb 11, 2011 at 8:25 PM, Ali K. Ozdagli <ozdagli at gmail.com> wrote: > >> Hello all, >> >> When I write the following to mathematica >> >> NDSolve[{0.04*u[z, t] == -3*(D[u[z, t], z])^(1/3) + 0.02*z*D[u[z, t], z] - >> D[u[z, t], t], Derivative[1, 0][u][1, t] == 0, u[z, 0] == 0}, u, {z, 1, 2}, >> {t, 0, 1}, MaxSteps -> 10^4, AccuracyGoal -> 8, SolveDelayed -> True]; >> >> Although the solution is relatively easy, u[z,t]=0, it gives the following >> errors: >> >> NDSolve::ibcinc: Warning: Boundary and initial conditions are inconsistent. >>>> >> >> NDSolve::icfail: Unable to find initial conditions that satisfy the >> residual function within specified tolerances. Try giving initial conditions >> for both values and derivatives of the functions >> >> >> >> I do not see any inconsistency in the boundary conditions and don't know >> why mathematica cannot find a solution. >> >> Any help is appreciated. >> >> Best, >> >> Ali >> >> > > > Ali, if you use NDSolve[{0.04*u[z, t] == -3*(D[u[z, t], z])^(1/3) + 0.02*z*D[u[z, t], z] - D[u[z, t], t], Derivative[1, 0][u][1, t] == 0, u[z, 0] == 0}, u, {z, 1, 2}, {t, 0, 1}, MaxSteps -> 10^4, AccuracyGoal -> 8]; you get the following message: The differential order of the functions in the initial or boundary \ conditions should be strictly less than in the differential equations. This means that for the present eqn the boundary condition must not contain a derivative. Oliver