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Old   October 24, 2010, 21:42
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Daniel
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Hello everyone,

I am new at snappyHexMesh, and I am trying to use the program to generate a 2-D mesh of an airfoil. I have been following the wingMotion series of tutorials, but the problem I run into is that I must avoid extruding a projection of the mesh as is done in wingMotion2D_simpleFoam. The reason is that I have modified the geometry (wing_5degrees.obj) file to include a second patch for a flap, which would be lost in the extrusion since autoPatch requires a geometrical feature to separate two patches - no such feature is present, I have merely set the trailing 20% of the airfoil as a flap.

When snappy is run, it generates a 3D mesh about 50 cells deep on the z-axis, for the wing (and flap) patch(es). Why does snappy choose this number, and how can it be reduced? I tried making the geometry thinner, but that did not make a difference. Is is possible to extrude while maintaining the patches in the axis along which the extrusion is taking place?

Thanks in advance,

Dan
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Old   October 27, 2010, 03:20
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Ivan Flaminio Cozza
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Hi Daniel,

I'm working too in 2D (or extruded) meshing with SHM, in my opinion it is the best choice for cylindrical bodies (I mean, bodies that are "geometrically" extruded in the third direction, like a unswept wing). If I understood, SHM put many cells in z dir. as the refining procedure is just splitting the cells like this:

if I have one exa and I want to reach the next level of refinement, divide by two ALL the edges of the exa, and the result is 4 new exas.

So, up to now SHM meshes are inerently 3D, if you want it 2D you have to do something, like extruding!


Quote:
Originally Posted by dancfd View Post
Hello everyone,

I am new at snappyHexMesh, and I am trying to use the program to generate a 2-D mesh of an airfoil. I have been following the wingMotion series of tutorials, but the problem I run into is that I must avoid extruding a projection of the mesh as is done in wingMotion2D_simpleFoam. The reason is that I have modified the geometry (wing_5degrees.obj) file to include a second patch for a flap, which would be lost in the extrusion since autoPatch requires a geometrical feature to separate two patches - no such feature is present, I have merely set the trailing 20% of the airfoil as a flap.

When snappy is run, it generates a 3D mesh about 50 cells deep on the z-axis, for the wing (and flap) patch(es). Why does snappy choose this number, and how can it be reduced? I tried making the geometry thinner, but that did not make a difference. Is is possible to extrude while maintaining the patches in the axis along which the extrusion is taking place?

Thanks in advance,

Dan
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Old   October 27, 2010, 16:26
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Daniel
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Hi Ivan,

Thanks for the response. I understand the inherent 3-D nature of sHM, and that extruding will make it 2-D, however I cannot extrude the mesh without losing my patch. Thanks again,

Dan
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