[Pedro95]

Hello everyone,

First of all, sorry in advance if this is the wrong place for this thread, we would appreciate it if you could point us to the correct place.

Long story short, we want to upgrade our hardware, and would appreciate any advice/insight. What we have now is clearly insufficient.

We are looking to perform CFD calculations with OpenFoam of a large sea area (volume of around 1km x 1km x 200m) around a single offshore structure or ship (estimated size of around 100m – 200m, with small elements of around 0.3m).

We expect our cases to run in the range of 10 to 100 million cells, depending on the size of the structure. We think most cases will be at the lower end, so we want to size our hardware for it, but still be able to handle the larger ones even at the expense of much longer calculation times.

The aim of the simulation is to extract turbulence data from both the far wake and very close to the structure using DDES.

We are looking to upgrade our hardware for the task. We have found some rule of thumb estimates regarding RAM requirements (4Gb for each million cells) and CPU recommendations (around 2 cores per 1 million cells).

However, we would appreciate advice on how this should all fit together, what kind of aspects to prioritize or what are critical requirements to take into account.

We are currently considering computers that have the following specs:

**-*RAM no less than 256GB.



**-*2 x CPUs of around 16 cores each.


Some questions we have:

- It is our understanding that dividing cores between multiple CPUs is more efficient. Does OpenFoam handle multiple cores across several CPUs the same way it handles a single multicore CPU?

- What should we take into account when pairing CPUs and RAM units? We are aware of the importance of RAM bandwidth, but values do not seem to be readily available from CPU providers and*we are not sure how to estimate it.

- What is a good rule of thumb to estimate time it takes for a simulation against processing capability?

- What kind of graphics card would be necessary for visualizing a solution on paraview?

We would appreciate any advice regarding issues we might be missing or recommendations to select a specific computer model.

Many thanks in advance for your help! Any private messages regarding this issue are also more than welcome