Learning Forum

[heisenmech]

Hello everyone,

I've been recently struggling with Fluent's high memory usage when running on my workstation which has 16 physical cores -and Xeon (R) CPU @2.30 GHz with 96 GB RAM. I had been using Fluent 2020 R1 without any issue until recently I noticed that the PC became extremely slow.

When I checked the task manager, I noticed that Fluent was using 99% of the memory with not very high CPU usage, which is strange because it should normally use most of the CPU. I used to launch Fluent with 28 solver processes with very similar cases, CPU usage were high and RAM usage was roughly around 70%.

I tried running with less processes, but no luck unfortunately.

Even when I stop the solver from iterating but keep the session open, RAM usage is still about 85%.

Please the screenshots attached.

Anyone else experiencing such issue? or what potentially is going wrong?

Many thanks,

Oguzhan

[Karthik Remella]

Hello,nWhat type of simulation are you running? Also, what is your overall mesh count? It is possible that the RAM is high because of your overall mesh count.nKarthiknn

[heisenmech]

Hello Karthik,nIt's an LES with around 27 million nodes -structured hexa. I remember running a simulation with very similar case but had no problem with RAM. As I mentioned CPU usage was high but RAM usage was pretty moderate. nWhat I have also noticed is that if you look at the first screenshot, CPU is not distributed equally between fi_mpi which I think is a bit strange,too.nThanks.n

[Rob]

Are you running either the Pressure Based Coupled or Density based solver? Do you have any dynamic adaption?n

[heisenmech]

Hi Rob,nIt's pressure based. Yes, I am running with Dynamic Stress. That's actually a good point. Maybe, that's why it constantly uses huge amount of RAM.n

[Rob]

If you're running adaption check the cell count: you may have more cells than you think. Also look into load balancing as you'll have loaded some cores more than others. n

[heisenmech]

Sorry, I think I misinterpreted your comment on dynamic adaption. There is no dynamic mesh adaption in my case. I just checked the partitioning and load balancing tab where dynamic mesh is grayed out. The only option available there is Mesh Adaption which is set to 5 by default.nI also double-checked the total cell count which matches perfectly with ICEM.nnSome other subsections under Partitioning and Balancing as follows;nnOptions --> No of Partition = 16 (16 cores are being used at the moment) , n --> Reporting verbosity = 1, Reordering Methods = Architecture AwarenOptimization --> Smooth = 3nWeighting --> Faces per Cell - User Specified = 2 Additional Cell WeightnDynamic Load Balancing --> Mesh Adaption = 5nn