September 11, 2022 at 5:53 pmmanelaero2020Subscriber
Hi everybody ;
I am simulating airflow in a pipeline with fluent. When I use coupled scheme for velocity-pressure, there is a considerable reverse flow ( order of 90%) at the outlets, and the computation diverges. Still, the problem disappears when I use simplec scheme.
Have you an idea why coupled scheme causes this instability? is this scheme not suitable for flow in pipelines?
Thank you a lot
September 12, 2022 at 8:39 amRobAnsys Employee
Without seeing the mesh and set up it's difficult to diagnose. I use both PBCS and SIMPLE in most models and haven't observed problems linked to the scheme that couldn't be explained by something else: most models I see are on support so there's usually something wrong.
September 12, 2022 at 7:24 pmmanelaero2020Subscriber
Thank you Rob.
The computation converged with no problem when I used simplec scheme. I have imposed mass flow inlet BC and pressure outlet for outlets. With the coupled scheme, computation converges when I block artificially reverse flow. I don't have mesh actually to show you, sorry. As a solution to the problem, I have refined mesh near outlets and extended outlets but it doesn't work. The mesh is tetrahedral with inflation layers. The initialization is standard, computation is steady, flow is incompressible, and a turbulence model is K-Omega SST . All spatial schemes are second order.
September 13, 2022 at 8:31 amRobAnsys Employee
I need to see some pictures. Blocking reverse flow isn't usually recommended, and I wouldn't expect much difference between PBCS and SIMPLEC. Did you use the same initialisation values in both cases? Is the flow compressible?
September 25, 2022 at 9:18 ammanelaero2020Subscriber
Sorry for the late reply :), I don't have mesh actually to show you some pictures.
The flow is incompressible, I have used ' standard initialization' for both cases ( SIMPLEC AND COUPLED schemes)
Maybe mesh or geometry is the reason because I have used coupled scheme for other problems of airflow in pipes
and solution has converged ( without preventing reverse flow option)
Have a nice day
September 26, 2022 at 11:17 amRobAnsys Employee
It could be several reasons, the solver settings tend not to be the cause: it's usually geometry, mesh or bc's. Without more information there's not a lot we can suggest.
- You must be logged in to reply to this topic.
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.
- Suppress Fluent to open with GUI while performing in journal file
- Floating point exception in Fluent
- What are the differences between CFX and Fluent?
- Heat transfer coefficient
- Getting graph and tabular data from result in workbench mechanical
- The solver failed with a non-zero exit code of : 2
- Difference between K-epsilon and K-omega Turbulence Model
- Time Step Size and Courant Number
- Mesh Interfaces in ANSYS FLUENT
- error in cfd post
© 2023 Copyright ANSYS, Inc. All rights reserved.