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Creating a circle with more boundary regions

Posted Nov 9, 2016, 4:50 a.m. EST Modeling Tools & Definitions, Parameters, Variables, & Functions 5 Replies

Arman Ameen
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Hi,

When you use the circle function in 2D modelling you end up with 4 regions based on the points that are the basis of the circle. These points are located at 0, 90, 180 and 270 degree. From this you get 4 "chooseable" boundaries later on that you put your parameters on, for example emissivity. Is there a way to make a circle that has a lot more points of reference and hence more selectable boundaries? For example I want to create a circle that has 36 reference points ( one point at every 10 degrees ) and subsequently I will end up with 36 choosable boundary regions to set my parameters.

Another question is if I already have a model that is defined as a 4 point circle or that has 4 boundary region parts, is it possible to split these regions into smaller pieces?

Thank you,
5 Replies Last Post Aug 16, 2017, 10:22 a.m. EDT
Robert Koslover Certified Consultant
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Posted: 8 years ago Nov 9, 2016, 9:39 a.m. EST
The easiest way is to make pie-wedges instead of full circles, and along with rotating them (while keeping the original) this will provide you with exactly what you need. In the "circle settings" box, change the "Sector angle" value from its default of 360 deg to a different value. This will give you a pie-wedge instead of a circle.
The easiest way is to make pie-wedges instead of full circles, and along with rotating them (while keeping the original) this will provide you with exactly what you need. In the "circle settings" box, change the "Sector angle" value from its default of 360 deg to a different value. This will give you a pie-wedge instead of a circle.
Arman Ameen
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Posted: 8 years ago Nov 9, 2016, 6:01 p.m. EST
Thank you.
Thank you.
Magnus Ringh COMSOL Employee

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Posted: 8 years ago Nov 10, 2016, 4:23 a.m. EST
Hi,

Alternatively, if you don't want the pie wedges, you can add a Point object at the perimeter of the circle. Then use a Rotate node with that point as the input object to add more points along the perimeter of the circle at rotational distances of 10 degrees.

Best regards,
Magnus Ringh, COMSOL
Hi, Alternatively, if you don't want the pie wedges, you can add a Point object at the perimeter of the circle. Then use a Rotate node with that point as the input object to add more points along the perimeter of the circle at rotational distances of 10 degrees. Best regards, Magnus Ringh, COMSOL
Yu Zhang
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Posted: 7 years ago Jul 14, 2017, 9:31 a.m. EDT
Dear Magnus Ringh:

I followed your approach, but the boundary is still a single boundary, not several independent boundaries that can be selected for applying different conditions? Could you please give me a further help? Thank you so much.



Hi,

Alternatively, if you don't want the pie wedges, you can add a Point object at the perimeter of the circle. Then use a Rotate node with that point as the input object to add more points along the perimeter of the circle at rotational distances of 10 degrees.

Best regards,
Magnus Ringh, COMSOL


Dear Magnus Ringh: I followed your approach, but the boundary is still a single boundary, not several independent boundaries that can be selected for applying different conditions? Could you please give me a further help? Thank you so much. [QUOTE] Hi, Alternatively, if you don't want the pie wedges, you can add a Point object at the perimeter of the circle. Then use a Rotate node with that point as the input object to add more points along the perimeter of the circle at rotational distances of 10 degrees. Best regards, Magnus Ringh, COMSOL [/QUOTE]
Magnus Ringh COMSOL Employee

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Posted: 7 years ago Aug 16, 2017, 10:22 a.m. EDT
Hi,

Just so that there are no doubts about the abilty to create extra boundary regions. A circle object in COMSOL Multiphysics is already divided into four boundary segments starting and ending at 0, 90, 180, and 270 degrees (for an unrotated circle). You can add a point object at the circle perimeter to create another boundary split at an angle of 30 degrees, for example, using the point coordinates

x: cos(30[deg])
y: sin(30[deg])

Then solving a simple equation on the circle with the boundary number as the boundary condition, you get a solution as in the attached image, with the value 1 on boundary 1, 2 on boundary 2, and so on, for the 5 boundary segments that the circle perimeter consists of.

Best regards,
Magnus Ringh, COMSOL

Hi, Just so that there are no doubts about the abilty to create extra boundary regions. A circle object in COMSOL Multiphysics is already divided into four boundary segments starting and ending at 0, 90, 180, and 270 degrees (for an unrotated circle). You can add a point object at the circle perimeter to create another boundary split at an angle of 30 degrees, for example, using the point coordinates x: cos(30[deg]) y: sin(30[deg]) Then solving a simple equation on the circle with the boundary number as the boundary condition, you get a solution as in the attached image, with the value 1 on boundary 1, 2 on boundary 2, and so on, for the 5 boundary segments that the circle perimeter consists of. Best regards, Magnus Ringh, COMSOL

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