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-   -   Trimmer vs Polyhedral memory (http://www.cfd-online.com/Forums/star-ccm/109360-trimmer-vs-polyhedral-memory.html)

chris12345 November 15, 2012 13:46

Trimmer vs Polyhedral memory
 
Hello,

I was wondering, I want to increase my overall background region mesh. I am though limitied my virtual memory, I usually use polyhedral but I am consedering using Trimmer cells.

My question now, which cell type takes more virtual/RAM memory? My aim is to refine my background mesh.

Thank you

//Chris

abdul099 November 15, 2012 19:58

The installation guide (can be found in the CCM+ directory) says:

Memory requirements for meshing:
Trimmed mesh: About 0.5 GB / million cells.
Polyhedral mesh: About 1GB / million cells.

Memory requirements for solving (serial, two-equation turbulence model, and I assume no multiphase flow, no energy equation, no chemical reaction etc...):

Polyhedral mesh:
Segregated: ~1GB / million cells
Coupled explicit: ~ 2GB / million cells
Coupled implicit: ~ 4GB / million cells

Trimmed mesh:
Segregated: ~0.5GB / million cells
Coupled explicit: ~ 1GB / million cells
Coupled implicit: ~ 2GB / million cells

I can confirm the requirements for meshing, solving segregated schemes and solving coupled implicit on trimmed meshed. The other schemes haven't been tested by me, but I assume it's close to reality.

So when you're tight on memory, a trimmed mesh with segregated solver seems to be the best choice - as long as your physics is suitable to run on a trimmed mesh (sometimes a polyhedral mesh could be better, especially when your flow is not aligned to your mesh lines).

chris12345 November 16, 2012 05:48

thanks for the reply abdul.

Im actually doing a study on a hovering helicopter. Im thinking of using polyhedral cells on my overset region (the main rotor) and the background region I'm thinking of using trimmed cells.

I want to use polyhedral cells but I need more cells around my wake, but I cant since im contrained over my memory usage.

What do you think about this set up?

//Chris


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