please, I need help! I don't find the solution to my ODE using bvp4c solver.

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Nadjah 2015-1-15

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评论： Torsten 2015-1-19

exo3_bvp.m

Hello,

I have already asked my question, and remarks pushed me to revise my program, but I still get errors.
I have a fourth order ODE/BVP. It describes the stream function in the flow of turbulent gas above a liquid fluid film flowing over an inclined plane.
I use the bvp4c solver to solve this EDO/BVP. This is the solver that used the author of the article on which I work.
Two errors are displayed compiling program.
I attach the program that I do. Could you please help me understand and solve the problem? I will be very grateful.

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Torsten 2015-1-16

In the program documentation, you write that alpha is an unknown parameter.

Is this true ?

Best wishes

Torsten.

Nadjah 2015-1-16

Yes, it is true.

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Answer 1

Torsten 2015-1-19

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a) If alpha is to be determined by bvp4c, then

1. Change the call to bvp4c from

sol = bvp4c(@odes,@bcs,solinit,alpha);

to

sol = bvp4c(@odes,@bcs,solinit);

2. You will Need to supply a forth boundary condition in function "odes".

Take a look at the example

Compute Fourth Eigenvalue of Mathieu's Equation

under

http://de.mathworks.com/help/matlab/ref/bvp4c.html

b) The x-array in your function "odes" is supplied by bvp4c. So you can't redefine it as

x=0:0.001:200;

Calculate derivatives of your function psi1 before calling bvp4c on your preferred x-grid and use interp1 to interpolate the derivatives at the points required by bvp4c in "odes".

Best wishes

Torsten.