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Not spotting where/how index exceeds number of array elements

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I'm trying to solve a Navier-Stokes setup in a cylindrical coordinate system and am bumping up against an array indexing challenge. Any help folks might be able to offer to straighten matters out would be most appreciated. I'm including my live editor content below.

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Vladimir Sovkov
Vladimir Sovkov el 14 de Dic. de 2019
Is this what you want? Live script vesion is attached.
xmesh = linspace(0.01,0.05,5);
solinit = bvpinit(xmesh, @guess);
sol = bvp4c(@bvpfcn, @bcfcn, solinit);
plot(sol.x, sol.y, '-o')
function bound = bcfcn(ua,ub)
bound = [ua(1)-0.1, ub(1)];
end
function g = guess(r)
g = [1*(0.05-r)/(0.05-0.01), -1/(0.05-0.01)];
end
function dudr = bvpfcn(r,u)
dudr = [u(2), u(2)./r];
end
  4 comentarios
Vladimir Sovkov
Vladimir Sovkov el 20 de Dic. de 2019
Editada: Vladimir Sovkov el 20 de Dic. de 2019
No prob.
I do not understand why you replace your initial equation by . It seems to me that must have been with the "plus" sign, and, consequently, dudr = [u(2), u(2)./r] in the program, isn't it? Otherwise, you are solving the equation .
Brian Taff
Brian Taff el 21 de Dic. de 2019
You are correct, I had mistyped the original equation in the live editor's documentation. It should have been stated as u'' + u'/r = 0.
The downstream function calls do, in fact, solve this equation and the results were as intended.

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