Solving differential equations in Mathematica 7.0
- To: mathgroup at smc.vnet.net
- Subject: [mg108581] Solving differential equations in Mathematica 7.0
- From: Wei-Li Tan <deathanubis at hotmail.com>
- Date: Wed, 24 Mar 2010 04:42:23 -0500 (EST)
Hi,all:
Here is the code I want to solve the equation
Eqn1 := f2*(D[z[x], {x, 1}])^2 + f1*(D[z[x], {x, 2}]) + P*(D[y[x],
{x, 2}]) + Psoil;
Eqn2 := z[x] - (D[y[x], {x, 2}]);
sol = NDSolve[{Eqn1 == 0, Eqn2 == 0, y[0] == disp, y'[0] == 0, y[L]
== 0, y'[L] == 0}, {z, y}, {x, 0, L},
MaxSteps -> Infinity, AccuracyGoal -> 10, StartingStepSize -
> 0.001, MaxStepSize -> 0.005,
MaxStepFraction -> 0.001]
f1,f2 are the function of z[x]; Psoil is the function of
y[x];P,L,disp are constant.
and the Mathematica return me the message:
NDSolve::ndsz: At x ==x1, step size is effectively zero; singularity
or stiff system suspected.
FindRoot::cvmit: Failed to converge to the requested accuracy or
precision within 100 iterations.
NDSolve::berr: There are significant errors {xi} in the boundary
value residuals.Returning the best solution found.
{{z -> InterpolatingFunction[{{0.,25}}, <>], y ->
InterpolatingFunction[{{0.,25}}, <>]}}
How should I do to debug the code and find the correct solution.
Any help on this matter will be greatly appreciated.
Thanks