# Which one is a correct smallest geometry unit?

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

January 16, 2019, 11:47
Which one is a correct smallest geometry unit?
#1
New Member

Zari Musavi
Join Date: Oct 2013
Posts: 9
Rep Power: 8
Hi everyone,

I am preparing a 3D geometry to be modeled in Fluent later.

I am in doubt what could be the smallest unit that I can choose.

The physical system is a chamber having hundreds of small tubes as inlets from two ends, as it shown in the attachment "Geometry 3D".

The cross section at each end looks like the attached image "Geometry 2D".

As you can see it is very periodic or symmetric.

I considered the following two cross sections at inlet boundaries. The first is one inlet tube + part of 9 neighbors, shown as the attachment "unit 1".

and the second is one inlet + part of the 4 neighbor inlets, shown as the attachment "unit 2".

Q1: Which one do you think is correct or is enough?

Q2: Do you have other suggestions for the smallest geometry unit to model this system?

Q3: I have thought to set all side-boundaries as symmetric. Do you think a periodic boundary would be better?

Zari
Attached Images
 Geometry 3D.PNG (132.5 KB, 9 views) Geometry 2D.png (94.1 KB, 13 views) unit 1.png (13.6 KB, 10 views) unit 2.png (11.3 KB, 5 views)

January 16, 2019, 11:52
#2
Senior Member

Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 3,638
Rep Power: 45
You can go even smaller like so. The trick is to recognize all the lines of symmetry and choose the nearest ones. Actually you can go even smaller than the square I have drawn by slicing along the diagonal and simulating a triangular shaped domain. However, I like to avoid these triangular/wedge shapes because meshing them becomes funky.

Periodic or symmetry should work. Symmetry is a stronger constraint and would be preferred. Symmetry is also easier since you don't need a conformal mesh.
Attached Images
 unit 1.png (13.9 KB, 10 views)

 January 16, 2019, 13:48 #3 New Member   Zari Musavi Join Date: Oct 2013 Posts: 9 Rep Power: 8 Thanks LuckyTran, If I choose the smaller unit, similar to you draw, the effects from the other inlets might be neglected. All circular shapes are inlets and the space between them is walls.

January 16, 2019, 13:53
#4
Senior Member

Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 3,638
Rep Power: 45
Oh I didn't realize it was counterflow. It's hard to understand you. Then maybe something like so.
Attached Images
 unit 12.png (13.9 KB, 8 views)

 Tags geometry, geometry definition, smallest modeling, symmetrical

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post [ANSYS Meshing] CATIA Geometry Generation and Meshing danielsullivan ANSYS Meshing & Geometry 0 April 3, 2017 22:11 EphemeralMemory ANSYS Meshing & Geometry 2 December 8, 2016 14:02 [snappyHexMesh] snappyHexMesh - geometry does not appear in Mesh czhongrong OpenFOAM Meshing & Mesh Conversion 1 January 20, 2016 06:26 fatb0y CFX 3 January 14, 2012 20:42 Jack Keays FLUENT 9 June 16, 2000 00:39

All times are GMT -4. The time now is 18:01.