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Old   March 20, 2004, 16:31
Default Meshing a Sphere
  #1
Ajay
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Hi I am trying to mesh a simple concentric sphere geometry . I want a Quad Map type of Mesh on the surface of the sphere and have tried many different ways to get it done but in vain.could any one shed some light as to how this could be done ? thanks , Ajay
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Old   March 20, 2004, 18:44
Default Re: Meshing a Sphere
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stk
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i had problems too with quad meshing.i will tell you a quick solutiojn,but for further quad meshing knowledge you have to see gambit documentation. Try to cut this geometry in two semi spheres and mesh them apparently. afterwards merge them. i did this when i had a complex geometry in a boundary box for quad mesh mapping.
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Old   March 20, 2004, 20:27
Default Re: Meshing a Sphere
  #3
Ajay
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I have tried this but dint work for me , I went through the gambit manual too it says that for quad it needs 4 end vertices and also in their note they have that a cylinder is an exception and can be meshed even if it doesnt satisfy the 4 end vertices rule. Problem is in getting the edges in a sphere and how to get 4 end vertices. It is puzzling to think as to why GAMBIT doesnt have an automated quad mesh scheme for such elementary geometry such as a sphere ! thanks for the suggestion , i am working on the same lines. -Ajay
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Old   March 21, 2004, 07:12
Default Re: Meshing a Sphere
  #4
mateus
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Hi!

If you cut the sphere face with a qube. You should get 4 edges on each side of the sphere. You connect the vortices from the bottom 4 edges to the top edges, and make new faces from new edges. This way you get 6 faces that can be meshed with quad map. I didn't try this -I hope it works for you.

good luck

MATEUS

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Old   March 21, 2004, 09:53
Default Re: Meshing a Sphere
  #5
zxaar
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here is a sample .jou file that makes mesh on a sphere, hope the idea will help. save it in some .jou file , and run it from gambit from run journal menu.

jou ----- volume create radius 3 sphere face create width 8 xyplane rectangle face cmove "face.2" multiple 1 offset 0 0 2 face cmove "face.2" multiple 1 offset 0 0 -2 volume split "volume.1" faces "face.3" connected bientity volume split "volume.1" faces "face.4" connected bientity vertex create onedge "edge.13" uparameter 0.25 vertex create onedge "edge.13" uparameter 0.75 vertex create onedge "edge.13" uparameter 0.5 vertex create onedge "edge.14" uparameter 0.5 vertex create onedge "edge.14" uparameter 0.25 vertex create onedge "edge.14" uparameter 0.75 edge create straight "vertex.15" "vertex.19" edge create straight "vertex.13" "vertex.14" edge create straight "vertex.17" "vertex.18" edge create straight "vertex.16" "vertex.20" edge create project "edge.15" face "face.6" vector 1 0 0 edge create project "edge.17" face "face.6" vector 0 1 0 edge create project "edge.18" face "face.6" vector -1 0 0 edge create project "edge.16" face "face.6" vector 0 -1 0 edge delete "edge.15" "edge.17" "edge.16" "edge.18" lowertopology face delete "face.5" "face.2" "face.7" lowertopology edge split "edge.13" vertex "vertex.21" connected edge split "edge.23" vertex "vertex.23" connected edge split "edge.24" vertex "vertex.25" connected edge split "edge.14" vertex "vertex.26" connected edge split "edge.14" vertex "vertex.24" connected edge split "edge.14" vertex "vertex.22" connected face create wireframe "edge.14" "edge.19" "edge.13" "edge.22" real face create wireframe "edge.27" "edge.20" "edge.24" "edge.21" real face create wireframe "edge.26" "edge.22" "edge.25" "edge.21" real face create wireframe "edge.28" "edge.19" "edge.23" "edge.20" real face create wireframe "edge.14" "edge.28" "edge.27" "edge.26" real face create wireframe "edge.25" "edge.13" "edge.23" "edge.24" real window modify volume invisible volume create stitch "face.9" "face.12" "face.10" "face.11" "face.13" \ "face.14" real window modify shade window modify volume visible volume delete "volume.3" lowertopology face connect "face.3" "face.4" "face.8" "face.1" "face.10" "face.9" "face.11" \ "face.12" "face.13" "face.14" real window modify noshade volume unite volumes "volume.2" "volume.4" "volume.1" edge mesh "edge.19" "edge.22" "edge.21" "edge.20" successive ratio1 1 size \ 0.14594537 edge mesh "edge.13" "edge.28" "edge.14" "edge.26" "edge.27" "edge.25" \ "edge.24" "edge.23" successive ratio1 1 size 0.13509259 volume mesh "volume.2" map size 1
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Old   March 21, 2004, 12:39
Default Re: Meshing a Sphere
  #6
Ajay
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Thanks a lot !

I tried copying the above mentioned into a file and naming it with .jou (i left out the jou---- ) and running it in gambit. GAMBIT gives this error ERROR (960)- Keyword must have a string value could u mail me the .jou filefto my email id arao@uh.edu thanks a lot once again. Ajay
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Old   March 22, 2004, 07:48
Default Re: Meshing a Sphere
  #7
STK
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tell me you want a mesh over the sphere (between sphere and domain),on the surface of the sphere, or inside the sphere? i will send the dbs, but tell me first what do you want exactly.
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Old   March 22, 2004, 12:13
Default Re: Meshing a Sphere
  #8
Ajay
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ok here are the details inner sphere 1 mm radius outer 2.4 cm radius the volume to be meshed is the volume got by subtracting the big sphere minus the small sphere Quad mapping is required and i have specification for the number of nodes too ! In the azimuthal and polar direction nummber of nodes must be 216 and in the radial direction 66 nodes . in the radial direction the mesh must be graded with very fine mesh near the inner sphere and courser as it gets near the outer bigger sphere. Thanks, Ajay
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Old   March 22, 2004, 12:49
Default Re: Meshing a Sphere
  #9
Avijit
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Hi,

I have almost the same problem as Ajay's. I want a mapped meshing fr a sphere in a cylinder. actually I want to mesh a cylinder with a spherical hole. I am simulating flow over a sphere and want to find its drag coefficient at various reynolds numbers. It would be great of u guys if u send me the picture file of the mapped mesh as i dont have assces to Fluent, I am using ANSYS Flotran (7.1).

thanks a lot

Avijit
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Old   March 29, 2004, 09:14
Default Re: Meshing a Sphere
  #10
Karthick
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