Numerical volume integral with keeping parameters

Question

dont panic 2013-9-9

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HI ,

I wanted to calculate the magnetic potential of a bar magnet by numerical integration of the potential of a point source over the volume of the magnet. Below is my source code but I always get an error message.

Thank you for your help

a=0.0025; L=0.005; phis=0;

r1=0; r2=a; phi1=0; phi2=2*pi; z1=-L/2; z2=L/2;

%Function

f=@(r,phi,z,R,Z) (sin(phis-phi).*r)/(R.^2-2.*r.*R.*cos(phis-phi)+r.^2+(Z-z).^2).^(3/2);

[R,Z] = meshgrid(-0.05:s:0.05); mp=zeros(size( R ));

for k = 1:numel( R )

    g = @(r,phi,z) f(r,phi,z,R(k),Z(k));
    mp(k) = triplequad(g,r1,r2,phi1,phi2,z1,z2);

end

surf(R,Z,mp)

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Answer 1

Mike Hosea 2013-9-11

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Well, for starters, you need to change / to ./ in the definition of f. Second, however, you will need to use integral3 instead of triplequad.

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dont panic 2013-9-11

Thank you for your answer but I am using Matlab 2011a and as far as I can see matlab 2011a has no such ability. (but i might as well be wrong as i am new but the funktion browser had no entry for integral3 ) Is there a possibility to solve the problem with Matlab 2011a ?

thanks in advance

Mike Hosea 2013-9-11

Sorry, on second thought, you may not need INTEGRAL3. When I ran this, all I got were answers that numerically were not distinguishable from zero, and there is a singularity when R=0 and Z=0. There must be something wrong with your formulation.

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