Looking for some help to buy hardware

Bazinga · December 5, 2014, 10:12

Dear community,

I have a budget of about 12.000 US$ and need to buy a computer for CFD Simulations but I have very little knowledge about hardware and a some questions.

The softwares that we are using are ANSYS CFX and OpenFOAM and the problems we are working with at the moment are about 10mio. cells max for RANS simulations and 1mio cells max for LES simulation, but it might increase in the near future when we buy the new machine. If you need more information, please let me know.

Should we use CPU or GPU with the given budget and softwares?

Does it make more sense to buy one computer or two computers? Is ANSYS and OpenFOAM capable to use two computers for one simulation? I was told that it might be more efficient to buy two computers for ~6k each instead of one computer for the whole budget because the components for one computer would be much more expensive and the ratio of effiency to cost would drop.

Do you have any recommendations for a setup of a computer that would fit my needs?

I am open for any kind of comments, thoughts or answers.

If some important information is missing, please let me know and I will provide the information.

Thanks in advance

huey1080 · December 12, 2014, 11:28

Hi Bazinga,

This represents only my experience with Fluent but for now, GPU are not crucial to run simulations. They are mainly useful for multigrid simulations with turbulent mono-phase flow. If I were you, I would rather go with a multi-core CPU and let some space for the GPU for later calculations.
10 million cells will surely require something like 20 cores so there is always the debate between i7 (for speed) and Xeon (for cores) but in CFD, I prefer more cores because there is a limit on the number of cells that 1 core can take so I will go with a Xeon, preferably 2 at 10 or 12 cores on the same card.
And for the ram, same rule of thumb would advise on 2Gb of RAM per million of cells for a basic simulation (turbulent and compressible) so with the system you are looking at a minimum of 24gb so 12gb on each CPU but that is a minimum. For LES, I would put 32 minimum on each CPU.

December 5, 2014, 10:12	Looking for some help to buy hardware	#1
Bazinga Senior Member Join Date: Jun 2012 Location: Germany, Bochum Posts: 230 Rep Power: 16	Dear community, I have a budget of about 12.000 US$ and need to buy a computer for CFD Simulations but I have very little knowledge about hardware and a some questions. The softwares that we are using are ANSYS CFX and OpenFOAM and the problems we are working with at the moment are about 10mio. cells max for RANS simulations and 1mio cells max for LES simulation, but it might increase in the near future when we buy the new machine. If you need more information, please let me know. Should we use CPU or GPU with the given budget and softwares? Does it make more sense to buy one computer or two computers? Is ANSYS and OpenFOAM capable to use two computers for one simulation? I was told that it might be more efficient to buy two computers for ~6k each instead of one computer for the whole budget because the components for one computer would be much more expensive and the ratio of effiency to cost would drop. Do you have any recommendations for a setup of a computer that would fit my needs? I am open for any kind of comments, thoughts or answers. If some important information is missing, please let me know and I will provide the information. Thanks in advance

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December 12, 2014, 11:28		#2
huey1080 New Member Quentin Lux Join Date: Feb 2012 Location: Quebec Posts: 23 Rep Power: 14	Hi Bazinga, This represents only my experience with Fluent but for now, GPU are not crucial to run simulations. They are mainly useful for multigrid simulations with turbulent mono-phase flow. If I were you, I would rather go with a multi-core CPU and let some space for the GPU for later calculations. 10 million cells will surely require something like 20 cores so there is always the debate between i7 (for speed) and Xeon (for cores) but in CFD, I prefer more cores because there is a limit on the number of cells that 1 core can take so I will go with a Xeon, preferably 2 at 10 or 12 cores on the same card. And for the ram, same rule of thumb would advise on 2Gb of RAM per million of cells for a basic simulation (turbulent and compressible) so with the system you are looking at a minimum of 24gb so 12gb on each CPU but that is a minimum. For LES, I would put 32 minimum on each CPU.