# How to solve nonlinear coupled ode by Shooting method .

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Chandan Kumawat el 13 de Oct. de 2019
Comentada: darova el 2 de Nov. de 2019
Respected sir ,
I am getting problem to solve non linear coupled BVP by shooting method . Can you help me to solve that problem?
My problem is
F'''=(1/(1+epsilon1*(1-G)))*(A*F'+.5*t*A*F''+(F')^2-F*F''+epsilon1*G'*F''-lambda*G-delta*H+M*F'-(-1+epsilon1*G-epsilon1)*bita*F');
G''=(1/(1+epsilon2*G+Nr))*(Pr*(2*A*G+.5*A*t*G'+F'*G-F*G'-M*Ec*(F')^2-Ec*(1-epsilon1*G'+epsilon1)*(F'')^2)-epsilon2*(G')^2);
H''= Sc*(2*A*H+.5*A*t*H'+F'*H-F*H'+Rex*Zai*H);
where A=0 ; epsilon1= 0 ; epsilon2=1; lambda= 1; delta=1; bita=0; Nr=.1; Pr=5; M=.5;
Ec=.1 ; Sc=1; Rex= .3 ; Zai= .1 ;
and F(0)=0 , F'(0)=1 F'(infity)=0 G(0)=1 G(infity)=0 H(0)= 1 H(infity)=0
and F''(0) , G'(0) & H'(0) we have to guess
so tell me how to solve by shooting method with using rk -4 method .
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darova el 13 de Oct. de 2019
What have you tried? What ideas do you have? Did you see examples in MATLAB help?
Chandan Kumawat el 14 de Oct. de 2019
I general do it with general shooting method but i'm getting problem how to do initial guess.
Here i'm attaching code which i have tried .

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Chandan Kumawat el 14 de Oct. de 2019
It is okey but my problem still remain same that how i do appropriate guess for according to your code
F2(0) & G1(0) & H1(0)
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Chandan Kumawat el 2 de Nov. de 2019
here I'm not getting any option for accept your answer .
Thanks for solve my problem .
darova el 2 de Nov. de 2019
Whta is this?

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### Más respuestas (1)

darova el 14 de Oct. de 2019
Try bvp4c
Suggestion:
F0 = y(1);
%% ...
H1 = y(7);
% and use these variables to make your code more redable
dy(1) = F1;
%% ..
You can also use temporary variables to make your code simpler
dy(3) = 1/(1+e1*(1-G0))* ...
(A*F1 + 0.5*t*A*F2 + F1^2 - F0*F2 + e1*G1*F2 - lambda*G0 - delta*H0 + M*F1 - (-1+e1*G0-e1)*bita*F1);
%%
TEMP0 = 1/(1+e1*(1-G0));
TEMP1 = 0.5*t*A*F2;
TEMP2 = e1*G1*F2;
TEMP3 = (-1+e1*G0-e1)*bita*F1;
dy(3) = TEMP0 * (A*F1 + TEMP1 + F1^2 - F0*F2 + TEMP2 - lambda*G0 - delta*H0 + M*F1 - TEMP3);
See attached scripts
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Chandan Kumawat el 17 de Oct. de 2019
Thank you sir for give attention on my problem and now code is working well .
Can we solve it by ODE45 if yes then what values for F2(0) G1(0) & H1(0) should we take and how we will find that values .
darova el 17 de Oct. de 2019
I just changed main code
init = [0 1 -0.58 1 -1.52 1 -1.12];
% solinit = bvpinit([0 2],zeros(1,7));
% sol = bvp4c(@new,@bvpf,solinit);
[t,y] = ode45(@new,[0 2], init);
% plot(sol.x,sol.y)
plot(t,y)
legend('F','dF','d2F','G','dG','H','dH')
I took initial conditions from last calc. There is no rule for F2(0) G1(0) & H1(0) values, only guessing or something like bvp4c

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