[griller81]

Hello folks,

I am an Aerospace Engineer from Melbourne, Australia, and I am working for a start-up company doing aircraft external aerodynamics. I am relatively new to CFD (used to doing a lot of hand calc-based stuff), and all of the nuances around the selection of hardware, however, I am working hard to transition my career into this line of work.

I am looking to build a workstation that I can use as my day-to-day rig for doing tasks ranging from design work in CATIA, Matlab, Excel, OpenVSP, etc., as well run CFD simulations in OpenFOAM and/or ANSYS Fluent.

I have a ~3yo i7-9750H based laptop at the moment, but it is getting pretty long in the tooth, so I am thinking of building a PC using current-gen components such as i9-14700k or the AMD 9 9000 Series ones when they come out shortly. I am however open to Xeon, threadripper, epyc etc., but I don't have much knowledge about the pros and cons of those for all of the non-CFD-related stuff I also do...

I have filled out the questionnaire below. Any advice would be greatly appreciated!

Which software do you intend to use?
ANSYS Fluent, OpenFOAM, Dassault 3D Experience, Blender
Are you limited by license constraints? I.e. does your software license only allow you to run on N threads?
No
What type of simulations do you want to run? And what's the maximum cell count?
subsonic external fluid flow, 1 - 10 million cells.
If there is a budget, how high is it?
$5000AUD for the PC (excludes screen, peripherals as I already have those)
What kind of setting are you in? Hobbyist? Student? Academic research? Engineer?
Engineer
Where can you source your new computer? Buying a complete package from a large OEM? Assemble it yourself from parts? Are used parts an option?
I would be comfortable building it myself from parts. I am open to used parts
Which part of the world are you from?
Melbourne, Australia
Anything else that people should know to help you better?
I am looking to get a fairly decent graphics card as part of this package (4080/4090...?) to help with the CATIA and Blender side of things.

[flotus1]

Looks like this needs a mix of everything. The CFD solver part would benefit from multi-core performnce, and memory bandwidth. While many of the other tasks rely heavily on single-threaded performance.

With a sizable portion of the budget taken up by the graphics card, I guess the AMD Ryzen 7 7800X3D is a good fit. Paired with some good RAM, like 2x32GB DDR5-6000 CL30.
I haven't paid too much attention to the Ryzen 9000 launch. From what I picked up, it is mostly an update in terms of power efficiency. The 7800X3D will still be faster for many tasks, and it is widely available now.
Unless solving the CFD simulations as fast as possible is top priority, this is my recommendation.

[griller81]

Originally Posted by flotus1

Looks like this needs a mix of everything. The CFD solver part would benefit from multi-core performnce, and memory bandwidth. While many of the other tasks rely heavily on single-threaded performance.

With a sizable portion of the budget taken up by the graphics card, I guess the AMD Ryzen 7 7800X3D is a good fit. Paired with some good RAM, like 2x32GB DDR5-6000 CL30.
I haven't paid too much attention to the Ryzen 9000 launch. From what I picked up, it is mostly an update in terms of power efficiency. The 7800X3D will still be faster for many tasks, and it is widely available now.
Unless solving the CFD simulations as fast as possible is top priority, this is my recommendation.

Hi Alex, thanks very much for your reply.

I agree that the graphics card has taken up a large portion of the budget, so if I downgraded that to a 4070 (~$850-1000 vs $3k AUD for a 4090), what would you recommend?

Is there a reason to prefer AMD over Intel? Is this related to the issues they've had with the microcode on the 13/14th gen CPUs?

[flotus1]

To be honest, I have not followed the entire news cycle on Intels 13th/14th gen CPU issues. So that wasn't the main reason here.
More importantly, the additional L3 cache of the X3D CPUs helps quite a bit with CFD solvers.
From a pure performance perspective, a 14th gen I7 is in the same ballpark. For that, some faster memory would help.

[griller81]

Originally Posted by flotus1

To be honest, I have not followed the entire news cycle on Intels 13th/14th gen CPU issues. So that wasn't the main reason here.
More importantly, the additional L3 cache of the X3D CPUs helps quite a bit with CFD solvers.
From a pure performance perspective, a 14th gen I7 is in the same ballpark. For that, some faster memory would help.

Understood.

So, what would you recommend if I reduce my GPU from a 4090 to a 4070 and free up ~$2k AUD? Stick with the 7800X3D and double the RAM? Any other options?

[flotus1]

It gets complicated...

Let me (over-)simplify: you have a wide variety of things the workstation should be good at. We can categorize the applications into two camps.
1) The CFD solver phase. This would benefit from having more cores, and the memory bandwidth to back them up
2) Pretty much everything else. These are lightly-threaded applications, that mostly need fast cores. but usually not many of them.

We can't have both, at least not within any reasonable budget.
Used server CPUs would be great for 1, but a significant downgrade for 2.
Latest-gen desktop CPUs excel at 2, but run into bandwidth limitations for 1.
Increased memory transfer rates from DDR5, and larger last level caches, made desktop CPUs a bit more appealing for 1.

So in the end, it is a question of priorities for you. The HEDT segment is pretty much dead. So it's either the fastest possible desktop CPU, or used server CPUs. There is no real middle ground here, that would not be way over budget.