How to mesh on a semi-circumference

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1

Dear all,

I wonder how to mesh on a semi-circumference
[tex]x^2+y^2=0.5^2,\quad y\geq 0.[/tex]

In fact, I can code like

geo.AddCircle(c=(0,0), r=0.5, maxh=0.01, leftdomain=1, rightdomain=1)

to get a mesh on an entire circumference.

I can also code like

p1,p2,p3,p4,p5= [ geo.AppendPoint(x,y) for x,y in [(0.5,0), (0.5,0.5), (0,0.5), (-0.5,0.5), (-0.5,0)] ]
geo.Append (["spline3", p1, p2, p3], maxh=0.01, leftdomain=1, rightdomain=1)
geo.Append (["spline3", p5, p4, p3], maxh=0.01, leftdomain=1, rightdomain=1)

to get a mesh on the semi-circumference. However, this method seems little awkward and also has some restricts in combined meshes, which may cause the global mesh failure.

So, is there a simple method to mesh on the semi-circumference just like meshing on an entire circumference? Please help me. Thank you very much.

Best,

Di Yang

2

Hi Di Yang,

with the CSG2D tools you can add, subtract, etc. primitives to form a semi-circumference without splines:

[code]from ngsolve import *
from netgen.geom2d import CSG2d, Circle, Rectangle

geo = CSG2d()
circle = Circle( center=(0,0), radius=0.5, mat=“circle”, bc=“bnd” )
rect = Rectangle( pmin=(-2,-1), pmax=(2,0), bc=“cut” )
geo.Add(circle - rect)

mesh = Mesh(geo.GenerateMesh(maxh=0.3))
mesh.Curve(2)
Draw(mesh)[/code]

Best
Michael

3

(which internally generates the exact same splines :wink: )