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Solving system of 2 nonlinear higher order coupled equation

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Poly
Poly le 30 Mar 2022
Modifié(e) : Torsten le 30 Mar 2022
syms w u2(x0) u0(x0) a A1 A2 Y
syms t om nu h a1 a2 p1
i=sqrt(-1);
% om=0.4;
% nu=0.1;
% h=1;
% a1=2;
% a2=0;
% p1=1;
% t=1;
U1(x0)=(i*p1/om)*((cosh(sqrt(i*om/nu)*x0))/(cosh(sqrt(i*om/nu)*h))-1)*exp(i*om*w*t);
A=w-om+(a1^2+a2^2)*i*nu;
B=A+a1*U1;
C= a1*diff(U1, x0);
D=i*a1*a2*U1-i*a2*A;
E=i*nu;
F=i*nu*a2;
G=(-nu/a1);
H=A*i/a1-i*nu*a1;
I=i*U1;
J=i*diff(U1,x0,2)+i*a1*A;
K=(i*nu*a2/a1);
L=A*a2/a1+a2*U1;
M=a2*diff(U1,x0);
eq1 = E*diff(u2,x0,3)-B*diff(u2,x0)-C*diff(u0,x0,2)+D*u0 == 0;
eq2 = G*diff(u0,x0,4)-H*diff(u0,x0,2)-I*diff(u0,x0)+J*u0-K*diff(u2,x0,3)+L*diff(u2,x0)+M*u2 == 0;
eq = [eq1; eq2];
bc1 = diff(u0,x0);
bc2 = diff(u0,x0,2);
bc3 = diff(u0,x0,3);
bc4 = diff(u2,x0);
bc5 = diff(u2,x0,2);
bc= [u2(1)==0; u2(-1)==0; u0(1)==0; u0(-1)==0; bc1(1)==0; bc2(1)==0; bc3(1)==0; bc4(1)==0;
bc5(1)==0; bc1(-1)==0; bc2(-1)==0; bc3(-1)==0; bc4(-1)==0; bc5(-1)==0];
var = dsolve([eq;bc])
[VF,Sbs] = odeToVectorField(eq);
odfcn = matlabFunction(VF, 'Vars',{x0,w,Y})
I don't know where I'm actually doing mistake. I need the equation u0 and u2 as a function of w. for other's you can put any value.

Réponses (1)

Torsten
Torsten le 30 Mar 2022
You won't get an analytical solution for this problem using "dsolve".
Use bvp4c instead.
  4 commentaires
Poly
Poly le 30 Mar 2022
I don't think it has any issue with real and complex part, the only problem I guess I'm facing maybe because of coupling equation. If I somehow manage to decouple above two equation, then it will be much easy to solve, I think.
Torsten
Torsten le 30 Mar 2022
Modifié(e) : Torsten le 30 Mar 2022
I don't think it has any issue with real and complex part,...
I also don't think that this makes the ODE more difficult to solve, but I'm not sure whether bvp4c can handle complex-valued ODEs directly or if you have to split in real and imaginary part manually.
If I somehow manage to decouple above two equation, then it will be much easy to solve, I think.
Maybe, but I don't think you can resolve the coupling.
Which seems obvious for me is that this system cannot be solved symbolically.
Make an attempt with bvp4c - I think this is the ony way that promises success.

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