CODEWITHSUNDEEP
wolfram-mathematica
user2701450
user2701450

Reputation: 1

Wolfram Mathematica NDSolve error

I'm getting an error for the BC in this equation:

s = NDSolve[{D[h[t, x], t] + Sin[x Degree] h[t, x]^2 D[h[t, x], x] + 
     2/3 Cos[x Degree] h[t, x]^3 == 0, h[0, x] == 1, 
   D[h[t, 0], x] == 0}, h, {t, 0, 100}, {x, 0, 90}]

NDSolve::deqn: Equation or list of equations expected instead of True in the first argument {2/3 Cos[[Degree] x] h[t,x]^3+h[t,x]^2 Sin[[Degree] x] (h^(0,1))[t,x]+(h^(1,0))[t,x]==0,h[0,x]==1,True}. >>

Any tips?

Upvotes: 0

Views: 1809

Answers (1)

ogerard
ogerard

Reputation: 735

The last condition:

D[h[t, 0], x] == 0

is always True as you derivate on a constant. If what you mean is

D[ h[t,x], x]  /. x->0

that's something else.

For the time being, just remove it (and possibly find another sensible boundary condition compatible with the order of your equation).

NDSolve[{D[h[t, x], t] + Sin[x] h[t, x]^2 D[h[t, x], x] + 2/3 Cos[x] h[t, x]^3 == 0, h[0, x] == 1}, h, {t, 0, 100}, {x, 0, Pi/2}]

works with a few warnings about the underdetermined system.

Upvotes: 1

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