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rocketman1151 October 26, 2011 13:49

GAMBIT Meshing of Pipe with Holes Perpendiculer to Flow Stream
Hello All:

I am new to GAMBIT and have a project I am working on that involves a spray bar. It consists of a pipe with fluid entering one end and exiting out the other. Along the pipe are multiple sets of holes so that part of the fluid sprays out through the holes as well as out the end of the pipe. I am to use circular o-grid meshing and the question is two-fold: First, how to model the holes in the side of the pipe. Secondly, how to handle the intersection of the main o-grid mesh through the pipe with circular o-grid meshes from the holes (if that is the right way to do it). If I don't need to use an o-grid mesh for the holes, what is the best way to mesh them? Thank your for the help!


-mAx- October 27, 2011 01:48

you have always many ways for meshing geometry.
Can you post a picture of your model (or a sketch).
The quickest way to mesh such stuff is using tetra-hexcore with size function (and perhaps Boundary Layer).
But the first thing to ask you is: do I need hexa mesh?
Hexa mesh isn't so trivial and overall not automatic (volume decomposition)

rocketman1151 October 28, 2011 10:10

basic sketch of spraybar
1 Attachment(s)
OK, if I attached it correctly, you should be able to open the basic spraybar sketch. I will model only one tube (the sketch refers to multiple design) and the segment of interest in the sketch is the vertically oriented one as the other segment is the inlet line. I will model two sets of holes near the top of the spraybar. The holes will be drilled through the tube, so each set will comprise two holed at 180 degrees apart circumferentially. The sets will be located about one-two inches apart and the first one will be located about one inch from the top of the pipe, which will be open (i.e. not restricted). I am supposed to use o-grids for the flow through the pipe as well as for the intersecting holes located on the sides of the pipe. It is how to best model the holes and how to handle the intersecting o-grid meshes. Thanks for the help!

-mAx- October 28, 2011 10:16

it is already built in Gambit?

rocketman1151 October 30, 2011 22:04

No, I am just at the beginning of learning how to use Gambit/Fluent in preparation for modeling the spraybar. I was hoping to get some pointers before moving out and setting it up.

-mAx- November 2, 2011 02:02

Then build your geometry first. Then mesh it.
For building your model, you just need to create cylinders, and move them at their right places (translate-rotate).
Finally you may unite all the cylinders together.

rocketman1151 November 26, 2011 18:39

OK, what I did was create the pipe using quarter circles and then joining them together to make the two ends and then placing lines between them to form the wireframe. I then made the holes using points on the lines and creating two sets of two-arcs on opposite sides of the pipe wireframe and then making faces from them. The idea is then to subtract the faces from the pipe volume so that they form the holes on opposite sides of the pipe. I then am supposed to use an o-grid through the pipe and square grid intersecting the o-grid at the "hole" Does that make sense? Any thoughts on how to handle the intersection of the o-grid and square grid? Thanks.

-mAx- November 30, 2011 03:39

you cannot substract a surface from a volume.
you can substract a volume from another volume, or a face from another face.
I think you wanted to say "split"

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