How to draw a spiral block/boundary?

[Yasunaoka]

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Question

Hi guys, I recently wanted to draw a spiral p=e^θ（(as shown by the green line on the diagram) or a series of points on that spiral over a 2D circular mesh so that I can specify the initial condition variable c=1 in the region. i have tried a few objects but didn't succeed. Does anyone know how to implement this elegantly please? Any help is much appreciated!

[GiudGiud]

Hello

Do you want the mesh to have a spirally shape? Or simply cover part of the domain with a spiral?
You are looking for 2D surface right? Or a 1D spiral curve?

Use this generator
https://mooseframework.inl.gov/source/meshgenerators/ConcentricCircleMeshGenerator.html
Then this one to transform the circles into spirals
https://mooseframework.inl.gov/source/meshgenerators/ParsedNodeTransformGenerator.html
You'll have to figure out the transformation in cartesian coordinates

Guillaume

[Yasunaoka]

Sorry, I may have missed the point, I currently do have a circular mesh AnnularMeshGenerator already:

So far, I have gotten the following linear initial condition via BoundingBoxIC

But now I'm trying to get the spiral pattern shown in the green line below, and I'm not finding the right way to do it.

[GiudGiud]

if you want the mesh to rigorously align with the spiral, you could rotate the mesh (not evenly, with the parsedTransform) first.
then use a ParsedGenerateSideset to select the spiral sideset

If you are OK with a jagged edge, then you could simply use the ParsedGenerateSideset to approximately draw the spiral bit within the mesh

[Yasunaoka]

That's exactly what I want! That's great! Thank you so much!