CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

Best Way to Mesh a Channel with Spheres Constituting The Bed

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 5, 2021, 11:37
Cool Best Way to Mesh a Channel with Spheres Constituting The Bed
  #1
Member
 
Will Crawford-Jones
Join Date: Jan 2021
Posts: 43
Rep Power: 3
wcj1n18 is on a distinguished road
Hello,

I'm intending on modelling sediment transport. As such, I have a rectangular channel with 1000s of hexagonally-packed spheres constituting the bed- these will all be stationary for now. Any advice on what the best means of meshing such a set up would be? So far I have tried trimmed mesh. This works well for the bulk of the channel but near the bed it becomes 'messy' (see attached images). I don't mind too much how difficult it is to do, but just want to ensure I get solution convergence to ensure the simulations are less computationally expensive. As an example, would people advise Immersed Boundary Method (though I don't think this is possible with Star-CCM+)? Is it possible to set up a trimmed mesh for the bulk of the channel but a polyhedral mesher for the part where the spheres are? I don't want to do DEM simulations as I will only be modelling on mobile sphere, the rest of them are stationary. For the mobile sphere I intend on using DFBI, overset mesh.

Any comments/ discussion are welcome

Thanks

Will
Attached Images
File Type: jpg Mesh_1.jpg (182.4 KB, 17 views)
File Type: jpg Mesh_2.jpg (164.2 KB, 17 views)
File Type: jpg Mesh_3.jpg (143.1 KB, 17 views)
File Type: jpg Mesh_4.jpg (117.5 KB, 16 views)
wcj1n18 is offline   Reply With Quote

Old   November 8, 2021, 13:32
Default
  #2
Member
 
Pietro
Join Date: Jun 2021
Location: London
Posts: 40
Rep Power: 3
pi120 is on a distinguished road
Hi Will,

Do you really need so many spheres?

You might need a better prism layer mesh surrounding your sediment spheres. I would at least impose 10 layers, with low prism layer stretching (1.1 or 1.2). Ideal would be to have the last prism layer cell half the size of the first cell outside the prism layer.

I would probably set it up all with the polyhedral or the trimmed mesher. But it is possible to have a polyhedral mesh for the sphere and trimmed mesher for the rest as well.
You just need to create two different regions, one for the low region close to the spheres and the other for the bulk.
To do so you need to separate the two bodies when modelling your CAD geometry. After that you need to generate the parts, and click on "assign parts to region", "create one region for each part".
Finally create two meshes, assign the bulk region to the trimmed mesher and the sphere region to the polyhedral.

hope this helps
Pietro
pi120 is offline   Reply With Quote

Old   November 8, 2021, 13:48
Default
  #3
Member
 
Will Crawford-Jones
Join Date: Jan 2021
Posts: 43
Rep Power: 3
wcj1n18 is on a distinguished road
Hi Pietro,

Thanks for the suggestions. I'll respond to each part separately:

Do you really need so many spheres?

I may well reduce this number later on.

You might need a better prism layer mesh surrounding your sediment spheres. I would at least impose 10 layers, with low prism layer stretching (1.1 or 1.2). Ideal would be to have the last prism layer cell half the size of the first cell outside the prism layer.

Thanks for the suggestion. I may try something like this.

I would probably set it up all with the polyhedral or the trimmed mesher. But it is possible to have a polyhedral mesh for the sphere and trimmed mesher for the rest as well.
You just need to create two different regions, one for the low region close to the spheres and the other for the bulk.

To do so you need to separate the two bodies when modelling your CAD geometry.

How do I separate the bodies? Do you mean when I create the geometry (which I am using Star-CCM+ for) I create two separate bodies that can be separate regions but combined as one domain? I shall look into this anyway

After that you need to generate the parts, and click on "assign parts to region", "create one region for each part".
Finally create two meshes, assign the bulk region to the trimmed mesher and the sphere region to the polyhedral.

Thanks for the help

Will
wcj1n18 is offline   Reply With Quote

Old   November 8, 2021, 13:54
Default
  #4
Member
 
Pietro
Join Date: Jun 2021
Location: London
Posts: 40
Rep Power: 3
pi120 is on a distinguished road
Yes you need to do it when creating the geometry. I use the split feature in SolidWorks usually so not sure how to do it in star but shouldn't be too hard.

I suggest you to generate your mesh on a simplified geometry (just 1 or 2 spheres), manage to get the right sizes for the boundary layer, and then apply them to the real thing.
pi120 is offline   Reply With Quote

Reply

Tags
immersed boundary method, mesh 3d, open channel flow, sphere geometry, trimmed mesh

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
[ICEM] how to mesh a pack bed reactor with contact spheres using ICEM? NIU ANSYS Meshing & Geometry 4 November 16, 2021 06:24
[ICEM] Bad Quality Hybrid Mesh External Flow tim13 ANSYS Meshing & Geometry 0 March 8, 2020 03:22
[snappyHexMesh] No layers in a small gap bobburnquist OpenFOAM Meshing & Mesh Conversion 6 August 26, 2015 10:38
[snappyHexMesh] Layers:problem with curvature giulio.topazio OpenFOAM Meshing & Mesh Conversion 10 August 22, 2012 10:03
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 12:55


All times are GMT -4. The time now is 19:14.