RSM turbulence low speed simulation

flow_CH · December 4, 2019, 04:32

Hello. I hope you are all great.

I am simulating a channel in Fluent. When It simulates with k-epsilon, k-omega and other turbulence models, the cpu usage in 100% from starting of simulation to the end.

But in RSM turbulence model, the cpu usage perodically goes up and comes back down and again.... Therefore, it results in very low simulation speed for this model compared to other ones.
I know that RSM calculates 5 further equations but what is the reason of that cpu processing behaviour? Is it normal for this model?

Thanks

LuckyTran · December 4, 2019, 11:15

Are you running a large model cell countwise? Check if your RAM is bottlenecked. More equations means more variables have to be stored in RAM. If you RAM capacity is exceeded, you are dead. If your RAM speed is slow, the cpu can just be waiting on RAM.

flow_CH · December 4, 2019, 11:23

Quote:

Originally Posted by LuckyTran

Are you running a large model cell countwise? Check if your RAM is bottlenecked. More equations means more variables have to be stored in RAM. If you RAM capacity is exceeded, you are dead. If your RAM speed is slow, the cpu can just be waiting on RAM.

Thanks for your reply.
How can I check whether RAM's capacity is enough or not? I should check it during simulation?

LuckyTran · December 4, 2019, 11:58

Yes during the simulation. Check how many GB of your RAM is being used, and how many you have. If you are in windows, open the task manager. If RAM usage exceeds 80%, that could already be the problem.

December 4, 2019, 04:32	RSM turbulence low speed simulation	#1
flow_CH Senior Member FHydro Join Date: Jan 2013 Posts: 197 Rep Power: 13	Hello. I hope you are all great. I am simulating a channel in Fluent. When It simulates with k-epsilon, k-omega and other turbulence models, the cpu usage in 100% from starting of simulation to the end. But in RSM turbulence model, the cpu usage perodically goes up and comes back down and again.... Therefore, it results in very low simulation speed for this model compared to other ones. I know that RSM calculates 5 further equations but what is the reason of that cpu processing behaviour? Is it normal for this model? Thanks Last edited by flow_CH; December 4, 2019 at 08:55.

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December 4, 2019, 11:15		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,668 Rep Power: 65	Are you running a large model cell countwise? Check if your RAM is bottlenecked. More equations means more variables have to be stored in RAM. If you RAM capacity is exceeded, you are dead. If your RAM speed is slow, the cpu can just be waiting on RAM.

December 4, 2019, 11:58		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,668 Rep Power: 65	Yes during the simulation. Check how many GB of your RAM is being used, and how many you have. If you are in windows, open the task manager. If RAM usage exceeds 80%, that could already be the problem.