Pipe Flow with Multiple Regions for Computer Cluster

wcj1n18 · July 5, 2021, 10:37

Hello,

I need to do a simulation with a large number of cells and hence want to use the university's supercomputer. As a practice run I want to simulate pipe flow with it split, cross-sectionally, into multiple (80) regions, each region being assigned to a different core on the supercomputer. I understand that I would then have to partition by region.

How do I split one region (simply a cuboid) into multiple regions? Another approach I have tried is using the 'split' feature in solidworks. When imported to Star-ccm+ these are automatically separated into 80 parts. Each of these can then easily be assigned to separate regions. The problem then is that each of these sub-regions have walls between them, which I do not want. I also tried deleting the unwanted surfaces prior to creating the regions, however, once I try to mesh this I encounter an error ("Failed meshing part 1 of 80, An edge attached to part surface "..." is free"). This is because each sub-region that is being meshed is not 'sealed', because I have deleted one of the faces. I understand that I could perhaps solve this in the "Repair Surface" feature but don't know how to do this.

I think the first approach makes the most sense, i.e., split a region into multiple regions, but how do I do this?

Thanks

Will

ashokac7 · July 6, 2021, 06:21

Why are you splitting region into multiple? We don't need to do that for large mesh either. Software takes care of parallelization. We just need to assign a number of cores we want to use for simulation.

wcj1n18 · July 6, 2021, 07:31

I was of the understanding that this is what partitioning was, i.e. the sub-domain that each core deals with. When I've tested across 40 cores in the computer cluster it doesn't seem any quicker than if I just use a few cores, so I was thinking that they were just sat there completely redundant. Is this understanding incorrect?

LuckyTran · July 8, 2021, 04:17

Let Star-CCM do the partitioning for you. It's wayyy better at it than your amateur skills

If you run on on 40 cores on your supercomputer and you don't see the speed up that you expect, then there is another issue.

wcj1n18 · July 8, 2021, 05:41

Yes, it was a problem in my batch script and there is no need for partitioning when simulating in parallel. Thanks.

July 5, 2021, 10:37	Pipe Flow with Multiple Regions for Computer Cluster	#1
wcj1n18 Member Will Crawford-Jones Join Date: Jan 2021 Posts: 43 Rep Power: 5	Hello, I need to do a simulation with a large number of cells and hence want to use the university's supercomputer. As a practice run I want to simulate pipe flow with it split, cross-sectionally, into multiple (80) regions, each region being assigned to a different core on the supercomputer. I understand that I would then have to partition by region. How do I split one region (simply a cuboid) into multiple regions? Another approach I have tried is using the 'split' feature in solidworks. When imported to Star-ccm+ these are automatically separated into 80 parts. Each of these can then easily be assigned to separate regions. The problem then is that each of these sub-regions have walls between them, which I do not want. I also tried deleting the unwanted surfaces prior to creating the regions, however, once I try to mesh this I encounter an error ("Failed meshing part 1 of 80, An edge attached to part surface "..." is free"). This is because each sub-region that is being meshed is not 'sealed', because I have deleted one of the faces. I understand that I could perhaps solve this in the "Repair Surface" feature but don't know how to do this. I think the first approach makes the most sense, i.e., split a region into multiple regions, but how do I do this? Thanks Will Last edited by wcj1n18; July 6, 2021 at 05:35.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
how to set periodic boundary conditions	Ganesh	FLUENT	15	November 18, 2020 06:09
High speed compressible flow through pipe	Munni	Main CFD Forum	6	December 7, 2015 11:33
setup problems - LES pipe flow with cyclic BC (1) and direct mapped inlet (2)	florian_krause	OpenFOAM	22	June 13, 2013 21:25
Pipe Flow	Saima	CFX	1	January 10, 2011 16:41
outlet boudary condition for a flow in the pipe	Atit	CFX	2	November 9, 2004 17:43

July 6, 2021, 06:21		#2
ashokac7 Senior Member Ashok Chaudhari Join Date: Aug 2016 Location: Pune, India Posts: 260 Rep Power: 10	Why are you splitting region into multiple? We don't need to do that for large mesh either. Software takes care of parallelization. We just need to assign a number of cores we want to use for simulation.

July 6, 2021, 07:31		#3
wcj1n18 Member Will Crawford-Jones Join Date: Jan 2021 Posts: 43 Rep Power: 5	I was of the understanding that this is what partitioning was, i.e. the sub-domain that each core deals with. When I've tested across 40 cores in the computer cluster it doesn't seem any quicker than if I just use a few cores, so I was thinking that they were just sat there completely redundant. Is this understanding incorrect?

July 8, 2021, 04:17		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	Let Star-CCM do the partitioning for you. It's wayyy better at it than your amateur skills If you run on on 40 cores on your supercomputer and you don't see the speed up that you expect, then there is another issue.

July 8, 2021, 05:41		#5
wcj1n18 Member Will Crawford-Jones Join Date: Jan 2021 Posts: 43 Rep Power: 5	Yes, it was a problem in my batch script and there is no need for partitioning when simulating in parallel. Thanks.