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Ideal Computer Specs for 3D turbulent, transient, multiphase simulations?

    • Patrick Kirby
      Subscriber

      Hello,

      I am unsure if this is the best spot to ask this question, but I am curious about the recomended computer specs for solving this type of problem. This type of probelm is a 3d, turbulent, transient, multiphase simulation (Euler-Euler). These simulations take me a good deal of time. I make use of an adaptive time step and can later implement the non iterative time step adavancement, but other than cleanly defining the problem, I can't think of other methods to optimize/speed-up my solution. I can't say I'm much of a hardware guy, I more so enjoy the use of the software. The computer I currently use has 6 cores and 12 logical processors, my geometry is broken into about 700,000 cells. Related literature describes the use of 40-540 processors, making me think that I am greatly laking in computational power.

      There really aren't any symmetries that I can take advantage of and I could decrease the mesh density, but that historically decreases the accuracy of the simulation. I suppose my basic question is...am I underpowered and are there any recs for the best manner to resolve this?

       

      Thanks

    • Rob
      Ansys Employee

      Read the supported hardware stuff on https://www.ansys.com/it-solutions/platform-support to make sure you're not trying to use a chip set we don't support. Note, anything we haven't tested is not supported but that doesn't mean it won't work: my work laptop is technically unsupported hardware! 

      First off, don't use virtual cores, and I think the manual recommends turning off hyperthreading. You may also benefit from running on 5 of the 6 cores depending on bus/memory/interconnect stuff: I break computers rather than knowing all of the right terms. 

      Now, with 700k cells you'll see a linear speed up out to 10-20 cores ish, it's hard to be precise because multiphase isn't as simple as load balancing is cells plus some model influence. That's one solver plus an HPC pack (I think that gives you 12 cores at present, but check with the Ansys licence documentation). 

      So, you may be a little underpowered, but not excessively. Anyways, you'll always want a bit more compute power so it's down to whether it's slow enough to spend money! 

       

       

       

       

    • Patrick Kirby
      Subscriber

      Thanks Rob, very helpful as always. It seems we have 12 licenses overall. I am trying to run my simulations on multiple computers at the same time, so I fear I may be slowing myself down. I turned off the hyperthreading on the ThinkPad. 

      Will the simulations automatically seek the HPC pack, or is there something that I have to set in Fluent?

      Another idea that I was looking into was the usage of the computers GPU, which does appear to be supported by ANSYS, though I'm not so sure about fluent. When I looked over the tutorials relating to "offloading" they make mention that only offloading certain kernels will improve computational time. Would the kernels associated with the RSM turbulence model be fair game for offloading?

      Thanks and apologies for any lack of clarity, I've run simulations many times and have a decent understanding of some theory, but the hardware component I've always left to others. In this case I'm trying to run a series of simulations which seem to take a good deal of time and therefore am looking to optimize the workflow.

    • Rob
      Ansys Employee

      I always leave hardware to others! 

      Fluent should pick up the HPC/parallel licence automatically, so assuming it's all set up properly you just put in the core count & it'll launch. If it doesn't please check the errors on here: nearly all install problems have been asked before. 

      The gpu acceleration should work on RSM but the benefit may be marginal. It's more noticeable on the some of the radiation equations. The new gpu solver will give a significant speed up, but you need the right sort of gpu. 

       

    • Patrick Kirby
      Subscriber

      An additional related question to computation time. My work/school has a terrible internet connection, I lost connectivity 4 times over the past week (halting my simulations). Could I just put a license on my machine and not worry about the connection issues, or is there some other manner to mitigate the times in which the connection is lost?

    • Rob
      Ansys Employee

      You can, but that would need a separate licence for your machine. That's not free, but also isn't something I can cover in any depth on here: it's one for your licence holder to discuss with the Ansys account team. 

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