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Partition an Imported Face into Circular/Rectangular Regions
Posted 2025/09/16 9:44 GMT-4 Geometry, Modeling Tools & Definitions, Modeling Workflow Version 6.3 5 Replies
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Hello everyone,
I’m working with imported geometries in COMSOL (typically STL/MPHTXT files), and I would like to partition specific faces into smaller circular or rectangular regions of defined size. The ultimate goal is to assign different boundary conditions on these partitions later in my simulation workflow.
Here’s what I’m aiming for:
Workflow: Import the geometry. Partition a selected face (for example, Face 2/3 in my attached geometry) into circular or rectangular regions (e.g., a circle of 1mm radius centered on a certain point on Face 2). Use these partitions to define boundary conditions in the physics modules and mesh them separately. Ideally, automate or repeat this sequence via MATLAB.
Challenge: I’m able to find the “Partition Faces” operation in the Geometry module, but it only seems to offer splitting via work planes, extended edges, or curves between existing vertices. I don’t see an option to directly create arbitrary-shaped partitions (like circles or rectangles) purely on an existing face, especially on imported surfaces.
Is there a way to do this?
Thank you very much for your time and assistance!
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See the attached edited file for an example approach. I created a workplane parallel to one of your surfaces and drew a closed polygon in it. You could just as easily use circles, rectangles, or other curves or polygons. Then, I was able to set a floating potential specifically inside that polygon. So does this approach address/solve your problem?
-------------------Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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Note that you do not necessarily need separate partitions to apply boundary conditions to, for example, a circle. You can write expressions like
if((X-Xc7)^2+(Y-Yc7)^2<R7^2,myvalue,0)
Here Xc7, Yc7, and R7 are parameters describing the seventh circle if it happens to be in an XY-plane. You can of course also make it neater with an expression like
if(insideCircle(Xc7,Yc7,R),myvalue,0)
and define a function insideCircle()
This example is relevant for a Neumann condition. You can do the same for Dirichlet conditions, as described in
https://www.comsol.com/blogs/how-to-make-boundary-conditions-conditional-in-your-simulation
-------------------Henrik Sönnerlind
COMSOL
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See the attached edited file for an example approach. I created a workplane parallel to one of your surfaces and drew a closed polygon in it. You could just as easily use circles, rectangles, or other curves or polygons. Then, I was able to set a floating potential specifically inside that polygon. So does this approach address/solve your problem?
Thank you, this is exactly what I was looking for. I didn't know that drawing on a workplane would actually create partitions on a face. This is very helpful.
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Note that you do not necessarily need separate partitions to apply boundary conditions to, for example, a circle. You can write expressions like
*if((X-Xc7)^2+(Y-Yc7)^2
I was able to create partition and get my model to work but I am interested in learning this approach.
I am using the electric currents module and want to apply terminal and ground conditions to two circular partitions on a face. I replaced the ground another terminal to act as a sink (since the ground condition has no option to provide the equations).
I am giving a conditional statement like the one you mentioned but it is actually selecting the entire surface instead of a circular region.
Appreciate any help debugging this.
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For more detailed help, I suggest that you contact support.
However, I think that one problem here can be that terminals are overriding features. So you can only have one Terminal node active on a certain boundary. That is, if you want to have several conditional terminals, you need to pile up all expressions into one Terminal node.
-------------------Henrik Sönnerlind
COMSOL
