Shooting Method Boundary Conditions not Implementing

I am trying to implement RK4 using the shooting method for the following boundary layer equations,
n = 0.4;
Bo = 0.01322917839;
dy = zeros(5,1);
dy(1) = y(2);
dy(2) = ((2*n+1)*y(3)*y(2)*Bo^(2/(n+1))/(n+1))/0.2e1;
dy(3) = y(4);
dy(4) = y(5);
dy(5) = ((-y(4)^2*n+2*y(3)*y(5)*n+2*y(1)*n-y(4)^2+y(3)*y(5)+2*y(1))/y(5)^(n-1)/n/(n+1))/0.2e1;
Where,
y(1) = theta
y(2) = theta'
y(3) = f
y(4) = f'; and
y(5) = f''
Subject to the following Boundary Conditions,
3 initial conditions are given: eta=0, f(0)= f'(0)=0,theta(0)=1
The boundary conditions that needs to be satisfied are: f'(eta=inf)= 0 and theta(eta=inf)=0 as eta=30.
I have tried the following code but the graph I get is not as it's supposed to be.
function Shooting_Method_code1
clc
clear all
x = [0.5 0.5];
options = optimset('Display', 'iter');
x1 = fsolve(@solver,x);
end
function F = solver(x)
options = odeset ('RelTol', 1e-8, 'AbsTol', [1e-8 1e-8 1e-8 1e-8 1e-8]);
[t,u] = ode45(@equation, [0,1], [1 x(1) 0 0 x(2)], options);
s = length(t);
F = [u(s,1)-0, u(s,4)-0];
figure(1)
plot(t,u(:,1), t, u(:,4))
end
function dy = equation(t,y)
dy = zeros(5,1);
n = 0.4;
Bo = 0.01322917839;
dy = zeros(5,1);
dy(1) = y(2);
dy(2) = ((2*n+1)*y(3)*y(2)*Bo^(2/(n+1))/(n+1))/0.2e1;
dy(3) = y(4);
dy(4) = y(5);
dy(5) = ((-y(4)^2*n+2*y(3)*y(5)*n+2*y(1)*n-y(4)^2+y(3)*y(5)+2*y(1))/y(5)^(n-1)/n/(n+1))/0.2e1;
end
Please help.

8 Comments

You provide f'(0)=0 while in your mathematical description you claim f'(0)=1.
Torsten, that was an errror and has been corrected.
The boundary conditions seem to be satisfied for the solution you get.
Why do you write that the graph is not as it is supposed to be ?
theta.jpg F'.jpg
The graphs should look something like this. I think the problem is the span from of the graph, but increasing tspan causes the code to fail.
I am not too familiar with bvp4c, could you please help out with it?
function main
xmesh = linspace(0, 30, 1000);
solinit = bvpinit(xmesh, [0; 0; 0; 0; 0]);
sol = bvp4c(@equation, @bcfcn, solinit);
plot(sol.x,sol.y(4,:))
end
function dy = equation(t,y)
dy = zeros(5,1);
n = 0.4;
Bo = 0.01322917839;
dy = zeros(5,1);
dy(1) = y(2);
dy(2) = ((2*n+1)*y(3)*y(2)*Bo^(2/(n+1))/(n+1))/0.2e1;
dy(3) = y(4);
dy(4) = y(5);
dy(5) = ((-y(4)^2*n+2*y(3)*y(5)*n+2*y(1)*n-y(4)^2+y(3)*y(5)+2*y(1))/y(5)^(n-1)/n/(n+1))/0.2e1;
end
function res = bcfcn(ya,yb)
res(1) = ya(1)-1.0;
res(2) = ya(3);
res(3) = ya(4);
res(4) = yb(1);
res(5) = yb(4);
end

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on 3 Jul 2019

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