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Comparison between integration in COMSOL and MATLAB
Posted 06.06.2018, 14:54 GMT-4 Structural & Acoustics, Heat Transfer Version 5.3a 1 Reply
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I have an expresion I need to integrate. I have been integrating this expression in MATLAB. However I find that when I integrate the same expression in COMSOL I get a slightly different value (see image).
In COMSOL I calculate
FF = solid.freq*2*pi/2/(solid.Ws_tot)/solid.rho*d(solid.Ws,T), and
Cii = volume integral of { solid.rho*solid.freq*2*pi/2/(solid.Ws_tot)/solid.rho*d(solid.Ws,T)*solid.freq*2*pi/2/(solid.Ws_tot)/solid.rho*d(solid.Ws,T) }
and in MATLAB I calculate
Cii(i) = sum ( rho * meshvol .* FF(:,i) .* FF(:,i) );
where meshvol, rho and FF are those exported from COMSOL and i indexes eigenmodes.
Is there a method to get identical results?
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There is no easy way. Comsol uses the shape functions when integrating which gives a higher accuracy than summing in Matlab does.
There are no good ways to get the weights that Comsol uses for improving the integration in Matlab (or other tools). Why can't you simply use the integration from Comsol?
-------------------Lars Gregersen
Comsol Denmark