# Meshing a cylindrical volume

 Register Blogs Members List Search Today's Posts Mark Forums Read

 March 18, 2010, 15:19 Meshing a cylindrical volume #1 Member     Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 16 Hi I want to mesh a 3d pipe. How can I do that? What I tried was: I meshed one face (275 cells) and tried to sweep that face along the axis of the pipe to form the volume. But the mesh density is v high. Gambit takes a default value of 1 in the axial direction. How can I control the axial density of the mesh? I am new to Gambit. Please help. Geometry: Dia: 50 mm Length: 12.7 m Approx nodes reqd: 38000.

 March 18, 2010, 23:03 #2 Member     Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 16 Or.. I should put the question like this... How can I mesh a 3d pipe in Gambit using hex elements?

 March 19, 2010, 00:55 #3 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41 Build first the geometry. Then deal with the mesh. Once your pipe is build, mesh one cap with quad-pave, and then mesh the volume with the desired element size. __________________ In memory of my friend Hervé: CFD engineer & freerider

 March 19, 2010, 01:56 #4 Member     Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 16 I did mesh one cap with quad-pave. What option do I choose to control the element size. Is 'cooper' the best option and do I specify the interval count/size appropriately in the axial direction?

 March 19, 2010, 02:54 #5 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41 Yes Cooper is the best option (if your volume enables it). If the cap is meshed, (and you are using Cooper), then the surface mesh for caps are fixed. The "mesh-freedom's degree" remaining is the axial one, so giving the element size for the volume mesh, will be the element size for the axial direction. Else you can mesh one edge in axial direction, and it will govern the volume mesh densiy (you can try to give a very fine element size for the volume mesh, but as the axial edge is already meshed, this volume element size will be ignored, since you don't enable the delete lowe mesh option) __________________ In memory of my friend Hervé: CFD engineer & freerider

 March 20, 2010, 10:00 #6 Member     Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 16 Thanks Max... that was really helpful

 March 22, 2010, 17:13 #7 Member     Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 16 Hi, I have another problem now. I want to split the inlet of my mesh into two equal parts-upper and lower for two different fluid inlets. How can I do that? I created a semi-circular face first and then swept it to make myself a "semi-cylinder". Then I mirrored it to get myself two semi-cylindrical geometries with mesh. But the problem is that the two new faces generated due to this (interface between the two semi-cylinders) is taken as a wall when I export the mesh to fluent. I only want two inlets and one outlet to allow mixing of the fluids. Thanks, Pranab

 March 23, 2010, 00:46 #8 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41 your "interfaces" seem to be not connected. You can connect them in gambit (Surface/Connect) __________________ In memory of my friend Hervé: CFD engineer & freerider

 March 23, 2010, 05:07 Similar Problem #9 New Member   Jon Join Date: Mar 2010 Posts: 10 Rep Power: 16 post removed! Last edited by Sidewinder; March 29, 2010 at 08:00.

 March 23, 2010, 14:58 #10 Member     Pranab N Jha Join Date: Nov 2009 Location: Houston, TX Posts: 86 Rep Power: 16 I did get my geometry and mesh right (finally). But I used very basic method to do that. -I created two semi-circular faces (like a circle) at both ends of the pipe. -I made faces out of the pair of upper and lower circles. -I joined the two faces to make the pipe volume. Then I specified the inlet conditions for the two fluids at the two inlet faces. But I would like to know how I can mirror a half cylinder to form two cylinders (described in my earlier post) and neglect the interface as I do not need it. I will give Max's suggestion a try and see.

 March 24, 2010, 00:55 #11 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41 you can copy your volume, enables reflect option and give the right direction's vector. Also enable copy mesh unlinked option. Depending on your coordinate system, you may have to aligne your reflected volume for "glueing" it with the original one. Then connect the interfaces each other. Watch out sometimes, the connect operation delete the volume mesh, and you will have to remesh it __________________ In memory of my friend Hervé: CFD engineer & freerider

 March 24, 2010, 05:56 #12 New Member   Jon Join Date: Mar 2010 Posts: 10 Rep Power: 16 post removed! Last edited by Sidewinder; March 29, 2010 at 08:01.

 March 24, 2010, 06:10 #13 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41 post a picture, or mail me your geometry __________________ In memory of my friend Hervé: CFD engineer & freerider

March 24, 2010, 08:17
#14
New Member

Jon
Join Date: Mar 2010
Posts: 10
Rep Power: 16
post removed!
Attached Images
 mesh_2.JPG (80.5 KB, 28 views)

Last edited by Sidewinder; March 29, 2010 at 08:00.