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Question regarding the calculation of area
Posted 21.03.2019, 05:26 GMT-4 General, Geometry, Modeling Tools & Definitions Version 5.4 1 Reply
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Hi all,
I have a 3D geometry and I was trying to get the boundary area of certain portion as an input for the further calculation.
As suggested, there are two ways to get the area value: 1. Use measure under the geometry tag to get the boundary area. 2. Use intergration function for this boundary (such as expression intop(1)) to get the area.
However, I found the values from these two method are a bit different. For example, for a circular plane, from integration method it got 9.7193E-12 [m^2], but from the measure methode it showed 1.0169E-11 [m^2]
Why there is a difference? And which one should I trust?
Thank you
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Hi,
There can be small differences in the vales for the two ways to compute an area. The Measure tool always uses the visualization mesh (with the detail level set to Fine). The integration operator acts on the computational mesh, which uses second-order curved mesh elements and can be refined to increase the accuracy. Values computed using the integration operator will then have a slightly higher accuracy. You can test the two methods on a unit circle, for example, and then compare them to the exact area of the circle (pi). Another advantage with the integration operator is that you can use it directly in the model as intop1(1).
Best regards,
Magnus Ringh, COMSOL