Meshing union of shapes

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4 years 8 months ago #2495 by dfoiles
Hello everyone,

I am trying to create a mesh of a nanorod in water. I am intending for the nanorod to be a cylinder with two hemispherical endcaps inside a larger cylinder of water inside a larger cylinder of PML. However, when I run my script, I get an error. I have determined that the problem is when I try to add the endcaps of the nanorod to its main cylindrical body. Specifically, I get the error

File "<string>", line 2
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 1-2: malformed \N character escape
Start Findpoints

at which point, Netgen will hang permanently. I would really appreciate it if you could help me figure out why I am getting this error.

Thank you

File Attachment:

File Name: NanorodQuestion.py
File Size:1 KB

Thank you
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4 years 8 months ago - 4 years 8 months ago #2501 by matthiash
Replied by matthiash on topic Meshing union of shapes
Hello,

you can just add the whole sphere to the cylinder. It seems the mesher has problems identifiying the edge of the cylinder with the one of the hemisphere.
Code:
from ngsolve import * from netgen.csg import * def Nanorod(aeff,ratio): geo = CSGeometry() radius = aeff*(2/(3*ratio-1))**(1/3) length = 2 * radius * ratio cyl_length = length/2 - radius physical_space = length + 100 domain = physical_space + 150 sphere1 = Sphere(Pnt(0,-cyl_length,0),radius) sphere2 = Sphere(Pnt(0,cyl_length,0),radius) cyl1 = Cylinder(Pnt(0,-2*cyl_length,0),Pnt(0,2*cyl_length,0),radius) cyl2 = Cylinder(Pnt(0,-2*physical_space,0),Pnt(0,2*physical_space,0),radius+100) cyl3 = Cylinder(Pnt(0,-2*domain,0),Pnt(0,2*domain,0),radius+200).bc('outer') box2 = OrthoBrick(Pnt(-physical_space,-physical_space,-physical_space),Pnt(physical_space,physical_space,physical_space)) box3 = OrthoBrick(Pnt(-domain,-domain,-domain),Pnt(domain,domain,domain)).bc('outer') plane1 = Plane(Pnt(0,-cyl_length,0),Vec(0,-1,0)) plane2 = Plane(Pnt(0,cyl_length,0),Vec(0,1,0)) middle = cyl1*plane1*plane2 AuNP = (middle+sphere1+sphere2).mat('gold') water = (cyl2*box2 - AuNP).mat('water') pmldom = (cyl3*box3 - water).mat('pml') geo.Add(AuNP) geo.Add(water) geo.Add(pmldom) ngmesh = geo.GenerateMesh() mesh = Mesh(ngmesh) return mesh mesh = Nanorod(40,1.6) Draw(mesh)


Best,
Matthias
Last edit: 4 years 8 months ago by matthiash.
The following user(s) said Thank You: dfoiles
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4 years 8 months ago #2503 by dfoiles
Replied by dfoiles on topic Meshing union of shapes
That did the trick. Thank you very much for your help and quick reply.
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