BVP4C code not giving an output & boundary condition issues.

Hi, I'm really new to matlab so the attached code could be completley wrong but I've attached it anyway. It doesn't give an output and I have no idea how to fix it, for refrence to the problem im just recreating the unbounded shear layer problem in Introduction to hydrodyanmics, Drazin and Reid. I'm using the boundary conditons y(-1)=1 and y(1)=A=2, say. Although I can give other boundary conditions which also must be satisfied anyway, we have y'(-1)=(-1+(1+c)a)/(1+c) and y'(1)=(A-(1-c)a)/(1-c).

Any help would be brilliant and if you could alter the problem to satisfy/add the other conditions it would be amazing.

Thanks.

Answer 1

[Stephan]

Hi,

your function does not return anything. Try:

sol = main;
subplot(2,1,1)
plot(sol.x,sol.y)
grid
subplot(2,1,2)
plot(sol.x,sol.yp)
grid

function sol = main
xlow=-1; xhigh=1;
solinit=bvpinit(linspace(xlow,xhigh,2000),[0,0]);
sol=bvp4c(@bvp4ode, @bvp4bc, solinit);
end

function dydx=bvp4ode(~,y)
a=0.4;
dydx=[y(2) (a^2)*y(1)];
end

function res=bvp4bc(ya,~)
A=2;
res=[ya(1)-1 ya(2)-A];
end

Best regards

Stephan

[Alexander Kimbley]

Yes I get an output but I'm not entirley sure what I'm looking at and from what I can see the first two boundary conditions aren't satisfied.

Thanks.

[Torsten]

I don't understand what exactly your question is.