I need help, How to solve bvp4c error?

Hello, I want to solve the following bvp using bvp4c:

• The differential equation is: y''''(x)-A(x)y''(x)+B(x)y(x)=f(x)with the boundary conditions: y(0)=y'(0)=0 and y(200)=y'(200)=0
• The coefficients are:
• f(x)=diff(psi,4,'x')*(-2*alpha*exp(-alpha*x)) +diff(psi,3,'x')*(6*alpha^2*exp(-alpha*x))++diff(psi,2,'x')*exp(-alpha*x)*(2*1i*alpha^2*diff(psi,'x')-4*alpha^3)-4*alpha^3*exp(-alpha*x)
• A(x)=(2*alpha^2+1i*alpha*diff(psi,'x')) and B(x)=(alpha^4+1i*(alpha^3*diff(psi,'x') +alpha*diff(psi,3,'x'))).
• were the parameter psi is a known function of x and alpha is a unknown constant parameter.
• I rewrite the differential equation as a system of first order equations of the form dydx=F(x,y).
• I use the following code:
• function dydx=stream(x,y,psi,alpha) % stream = EDO/BVP the streamfunction corresponding to a turbulent gaz flow % dydx = stream(x,y psi,alpha) evaluates derivative.
• dydx=[y(2) y(3) y(4) diff(psi,4,'x')*(-2*alpha*exp(-alpha*x)) +diff(psi,3,'x')*(6*alpha^2*exp(-alpha*x))+diff(psi,2,'x')*exp(-alpha*x)*(2*1i*alpha^2*diff(psi,'x')-4*alpha^3)-4*alpha^3*exp(-alpha*x)+(2*alpha^2+1i*alpha*diff(psi,'x'))*y(3)-(alpha^4+1i*(alpha^3*diff(psi,'x')+alpha*diff(psi,3,'x')))*y(1)];
• end
• function res = streambc(ya,yb,~)% streambc ODE/BVP streamfuction boundary conditions.% res = streambc(ya,yb) evaluates residual.
• res=[ya(1);ya(2);yb(1);yb(2)];
• end
• function yinit = streaminit % streaminit ODE/BVP streamfuction initial guess.% yinit= streaminit(x) evaluates initial guess at x.
• yinit=[0;1;0;-1];
• solinit=bvpinit(linspace(0,200,101),@streaminit);
• sol= bvp4c(@courant,@streambc,solinit);
• x=linspace(0.0,200,101);
• y = deval ( sol, x );
• plot ( x, y(1,:) );
• end
• by running this code, a message appears: "Not enough input arguments"I don't know what I could add as input arguments! Could you please help me understand and solve the problem? I will be very grateful.

Answer 1

[Torsten]

1. You pass a handle called "courant" to bvp4c, but you supply the derivatives in a function called "stream".

2. If you want to pass psi and alpha to stream, the call to bvp4c must read sol=bvp4c(@(x,y)stream(x,y,psi,alpha),@streambc,solinit);

Best wishes

Torsten.

[Nadjah]

Hello, thank you for your response. I made the corrections that you have brought, but the same message still appears, "Not enough input arguments"!

[Torsten]

Of course the lines

solinit=bvpinit(linspace(0,200,101),@streaminit);

sol= bvp4c(@courant,@streambc,solinit);

x=linspace(0.0,200,101);

y = deval ( sol, x );

plot ( x, y(1,:) );

have to be outside the function streaminit.

Did you take this into account ?

Best wishes

Torsten.

[Nadjah]

  Thank you for your comments. I modified my code and I rested my question because I get other errors.