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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Interpolation method in numerical integration

Posted 2015年2月19日 GMT-5 13:11 Results & Visualization Version 4.4 3 Replies

Hannes Pfeifer
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Dear all,

I have a question regarding the integration mechanism in Comsol.

If one integrates an expression with Comsol, for example on a 3D simulation volume, as a derived value in results or using mphint2 in Matlab with Comsol, does Comsol interpolate the integrated expression between the mesh nodes and if yes what method does it use to do that?
(like: linear interpolation/nearest neighbor/natural neighbor/ ...)

Within the reference manual the only information regarding that is uses a "standard numerical integration method (quadrature)", but I don't know what that means regarding the points where it wants to evaluate the expression to perform the numerical integration.

Thanks already in advance for your help.

Best regards,
Hannes
3 Replies Last Post 2015年2月23日 GMT-5 06:12
Gunnar Andersson COMSOL Employee

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Posted: 10 years ago 2015年2月20日 GMT-5 07:15
If one integrates an expression with Comsol, for example on a 3D simulation volume, as a derived value in results or using mphint2 in Matlab with Comsol, does Comsol interpolate the integrated expression between the mesh nodes and if yes what method does it use to do that?
(like: linear interpolation/nearest neighbor/natural neighbor/ ...)


When integrating over a solution data set, the most common situation, Gaussian quadrature is used. The interpolation within each element is performed using the shape function, which usually is linear or quadratic.



[QUOTE]If one integrates an expression with Comsol, for example on a 3D simulation volume, as a derived value in results or using mphint2 in Matlab with Comsol, does Comsol interpolate the integrated expression between the mesh nodes and if yes what method does it use to do that? (like: linear interpolation/nearest neighbor/natural neighbor/ ...)[/QUOTE] When integrating over a solution data set, the most common situation, Gaussian quadrature is used. The interpolation within each element is performed using the shape function, which usually is linear or quadratic.
Hannes Pfeifer
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Posted: 10 years ago 2015年2月20日 GMT-5 08:11
Hi Gunnar,

thank you very much for your answer.
That really helps me a lot.

Do you also know, what method mphinterp uses for interpolation. I guess some polynomial, but after which order does it usually stop?

Best,
Hannes
Hi Gunnar, thank you very much for your answer. That really helps me a lot. Do you also know, what method mphinterp uses for interpolation. I guess some polynomial, but after which order does it usually stop? Best, Hannes
Gunnar Andersson COMSOL Employee

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Posted: 10 years ago 2015年2月23日 GMT-5 06:12
Do you also know, what method mphinterp uses for interpolation. I guess some polynomial, but after which order does it usually stop?


It also uses the shape function order.


[QUOTE]Do you also know, what method mphinterp uses for interpolation. I guess some polynomial, but after which order does it usually stop?[/QUOTE] It also uses the shape function order.

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