September 22, 2023 at 9:57 amJoan RicoSubscriberGood morning,I am running ANSYS Fluent CFD simulations on an HPC cluster.I am trying to simulate particle dispersion around a urban area, with a domain size of 10x10km, and 8M cells.This week I was ready to launch my final simulation in the cluster, but I have found an unexpected issue.For all the testing that I have been doing, I have been running my simulation on 4 nodes with 20 tasks per node.
Now, in order to obtain faster results for the real simulation, I wanted to increase the number of nodes to 8-12, but I just realised that when I increase this number, my simulation diverges and crashes after a few minutes.I first thought that it could be a problem with the mesh of my simulation, but then I do not understand why the simulation with 4(x20) runs without problems (currently running for 10h, see attached residuals evolution). On the other hand, I have tried launching exactly the same simulation (copy-paste) with 5, 6, 7, 8, 10, 12 and 16(x20) nodes, and they all crash after ~ 200 iterations (see also attached a typical profile). Does this make sense? Am I missing something?I tried finding some information online about such an issue but I didn't manage to finde any explanation.Do you think it could be a parallelization issue? In that case, do you have any advice for me? Should I use more or less tasks per node when increasing my number of nodes?Thank you very much in advance.Details of my simulation: Transient, LES, double precision, PISO P-V coupling, Second Order Upwind mom, Second order pressure.
September 25, 2023 at 2:38 pmSRPAnsys EmployeeHi,Fluent automatically decomposes your computational area into smaller subdomains as the number of nodes increases to disperse the computational strain. Inefficient communication between nodes might produce instability or divergence if the domain decomposition is not appropriate.Troubleshooting problems with parallel CFD simulations may be difficult, and it frequently entails a mix of modifying simulation parameters, optimising domain decomposition, and taking hardware limits into account. When growing the number of nodes, it is critical to methodically test alternative configurations and monitor performance to determine the underlying cause of divergence and failures.Thank you.
September 27, 2023 at 1:50 pmJoan RicoSubscriber
Thanks a lot for your answer!
- You must be logged in to reply to this topic.
Boost Ansys Fluent Simulations with AWS
Computational Fluid Dynamics (CFD) helps engineers design products in which the flow of fluid components is a significant challenge. These different use cases often require large complex models to solve on a traditional workstation. Click here to join this event to learn how to leverage Ansys Fluids on the cloud, thanks to Ansys Gateway powered by AWS.
Earth Rescue – An Ansys Online Series
The climate crisis is here. But so is the human ingenuity to fight it. Earth Rescue reveals what visionary companies are doing today to engineer radical new ideas in the fight against climate change. Click here to watch the first episode.
Subscribe to the Ansys Blog to get great new content about the power of simulation delivered right to your email on a weekly basis. With content from Ansys experts, partners and customers you will learn about product development advances, thought leadership and trends and tips to better use Ansys tools. Sign up here.
- Floating point exception in Fluent
- What are the differences between CFX and Fluent?
- Heat transfer coefficient
- Difference between K-epsilon and K-omega Turbulence Model
- Getting graph and tabular data from result in workbench mechanical
- The solver failed with a non-zero exit code of : 2
- Time Step Size and Courant Number
- Mesh Interfaces in ANSYS FLUENT
- Suppress Fluent to open with GUI while performing in journal file
- error: Received signal SIGSEGV
© 2023 Copyright ANSYS, Inc. All rights reserved.