# NDSolve printing error message NDSolve::ndode [closed]

Using NDSolve while solving system of ODE's. Here is my try

Eqn1 = -C  f'''''[x] + f'''[x] + f[x]  f''[x] - f'[x]  f'[x] + r^2 + λ  T[x] == 0

Eqn2 =
T''[x] + p1 f[x] T'[x] +
p2/(3 (1 - tw)) (12 (tw + (1 - tw) T[x] ) + tw)^2 (1 - tw) T'[x] T'[x] +
4 ((1 - tw) T[x] + tw)^3 (1 - tw) T''[x] == 0

BC1 = f == 0
BC2 = f' == 1
BC3 = f' == r
BC4 = f'' == 0
BC5 = f''' == 0
BC6 = T' == -B (1 - T)
BC7 = T == 0

param = {λ -> 1, p1 -> 10, B -> 10, tw -> 1.5, p2 -> 0.5,
C -> 1, r -> 1}

Sol =
NDSolve[{Eqn1, Eqn2, BC1, BC2, BC3, BC4, BC5, BC6, BC7} /. param,
{f, T}, {x, 0, 10},
Method ->
{"Shooting",
"StartingInitialConditions" ->
{f == 0, f' == 0, f'' == 1, f''' == 0, f'''' == 0, T = 0}}]


But I'm getting this error

NDSolve::ndode: Input is not an ordinary differential equation.

The specific reason for the error message is that "StartingInitialConditions" contains T = 0. It should be T == 0. The fact that f' == 0 is inconsistent with BC2 and that there are too few "StartingInitialConditions" for T also may cause difficulties. Certainly, with f' == 0 and T' == -10 added, the integration proceeds further before encountering

NDSolveValue::ndsz: At x == 9.991371232789929, step size is effectively zero; singularity or stiff system suspected. >>


This last issue suggests that the NDSolve Method may need to be reconsidered.

• Thanks dear for pointing out the syntax error. But NDSolve is facing issues to solve the odes.
– zhk
Mar 1, 2015 at 4:26
• Integration will fail, if 1 + 4*(1 - tw)*(tw + T[x] - tw*T[x])^3` vanishes within the domain of integration. Mar 1, 2015 at 5:06
• if I take p2 = 0, that should make it solvable but I still get 'singularity or stiff system suspected.
– zhk
Mar 1, 2015 at 6:37
• I see that you made progress in 76135. Congratulations. Mar 1, 2015 at 12:57
• yes I did but with asymptomatic boundary at 3. I would like to see the results for at least 12.
– zhk
Mar 1, 2015 at 13:13