DNS using Fluent

- March 31, 2019 at 1:05 am
  
  ehkh
  Subscriber
  
  Hi,
  
  I am planning to perform DNS using fluent for turbulent flow in a three dimensional triangular cavity, to do so I understand that I need to use very fine mesh and as a consequence a very large number of cells that could reach 10trillion cells for small geometry.
  
  My question is what's the minimum RAM, CPU and processor required to run the simulation.
  
  Thanks
- March 31, 2019 at 5:54 am
  
  DrAmine
  Ansys Employee
  
  A rule of thumb minimum of 2 Bytes per cell for double precision run.
- March 4, 2021 at 9:09 am
  
  wcj1n18
  Subscriber
  
  Hi, just looking into something similar. If we are looking to do DNS (which of course requires a very high level of precision), is the double precision on Fluent sufficient? I mean, if it rounds to a given number of decimal places, can this not accumulate to an inaccurate figure after a large number of timesteps? Or can it be assumed that double precision will be sufficient for almost all cases?n
- March 4, 2021 at 9:16 am
  
  Aitor
  Subscriber
  
  The error induced by the diffusion of the numerical scheme or the geometry of the mesh will be more important than the one induced by the computer arithmetic.n
- March 4, 2021 at 9:38 am
  
  Rob
  Forum Moderator
  
  As comments, your mesh resolution and time step will play a greater role in numerical issues than the solver precision. Good luck getting the compute hardware to run the cell count you need for DNS, KAUST might have enough cores.... https://www.ansys.com/about-ansys/news-center/07-18-17-ansys-saudi-aramco-kaust-shatter-supercomputing-record but it may be a bit ambitious for Ansys Student! n