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Surface maximum

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I have simulated a structure and want to find the maximum field enhancement of a particular surface. I have taken a 2D cut plane to define the surface. I simply take surface maximum and put the equation for maximum field enhancement. The problem is the calculated maximum surface field enhancement and the simulated maximum field enhancement shown in color bar is different. However, they should be same as both are showing the maximum. Any reasoning why?


4 Replies Last Post Sep 7, 2021, 3:50 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 3 years ago Sep 6, 2021, 2:43 a.m. EDT

The probable reason is that the values are not obtained at exactly the same locations in the elements. Typically, the maximum evaluation will show a slightly higher value. By default, it is sampled in more points.

You can adjust the settings in the Quality section for the plot and the Advanced section for the maximum evaluation to investigate these effects.

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Henrik Sönnerlind
COMSOL
The probable reason is that the values are not obtained at exactly the same locations in the elements. Typically, the maximum evaluation will show a slightly higher value. By default, it is sampled in more points. You can adjust the settings in the *Quality* section for the plot and the *Advanced* section for the maximum evaluation to investigate these effects.

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Posted: 3 years ago Sep 6, 2021, 4:00 a.m. EDT

Thank you Henrik for your reply. I have checked both options. I found that using no smoothing in the advanced setting gives similar results obtained in the maximum value of the plot. I have changed the element refinement in the maximum evaluation option but results did not change. Since there is large difference between the plot with normal setting (55) and calculated maximum (70), I am not sure which one is more reliable. Can you please suggest?

Thank you Henrik for your reply. I have checked both options. I found that using no smoothing in the advanced setting gives similar results obtained in the maximum value of the plot. I have changed the element refinement in the maximum evaluation option but results did not change. Since there is large difference between the plot with normal setting (55) and calculated maximum (70), I am not sure which one is more reliable. Can you please suggest?

Henrik Sönnerlind COMSOL Employee

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Posted: 3 years ago Sep 7, 2021, 2:20 a.m. EDT

If you use the same value of Refinement in both places, I would expect that you see the same value using either method. If the difference in result is large when changing the refinement value, then there must be large gradients within the elements. There is also another possibility: If the cut plane is coincident with an element face, then the value can be taken from either of the two adjacent elements based on some roundoffs. That could cause a strong dependency on the refinement.

What kind of variable are you trying to evaluate?

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Henrik Sönnerlind
COMSOL
If you use the same value of Refinement in both places, I would expect that you see the same value using either method. If the difference in result is large when changing the refinement value, then there must be large gradients within the elements. There is also another possibility: If the cut plane is coincident with an element face, then the value can be taken from either of the two adjacent elements based on some roundoffs. That could cause a strong dependency on the refinement. What kind of variable are you trying to evaluate?

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Posted: 3 years ago Sep 7, 2021, 3:50 a.m. EDT

Thanks again. I am evaluating electric field enhancement in a defined plane. I am interested to evaluate the maximum enhancement anywhere in the defined plane. Thus, taking the surface maximum of the plane should give the same result as found in the surface plot.

Thanks again. I am evaluating electric field enhancement in a defined plane. I am interested to evaluate the maximum enhancement anywhere in the defined plane. Thus, taking the surface maximum of the plane should give the same result as found in the surface plot.

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