June 1, 2023 at 5:37 pmc.brunoSubscriber
I am trying to compute the platelet lysis index (PLI) in my simulations by solving this transport equation:
where tau is the shear stress.
My simulations are steady state, so if I have understood correctly from Ansys Fluent User Guide, this is the type of equation I am solving in Fluent with the diffusion coefficient equal to zero:
I have prepared the UDF for my source term:
To obtain convergence in my simulations I had to change the under relaxation factor of my UDS to 0.50.
After runnign my simulation I use CFD post to compute the power of my scalar (PLI = scalar 0 ^(1/0.77)).
I am expecting a PLI distribution similar to this:
But the resuls that I get are like this:
I also tried on a simplier geometry and I think that the results are stil wrong in terms of values but the colormap is more similar to what I am supposed to obtain:
I was wondering if there is something wrong in my code for the source term or if this might be related to something else?
Thank you in advance!
June 2, 2023 at 12:48 pmRobAnsys Employee
What scalar diffusion did you set? How turbulent is the flow?
June 2, 2023 at 1:43 pm
June 2, 2023 at 1:48 pmRobAnsys Employee
I'd set the Diffusion coefficient as a very (e-14 or so) small number rather than zero. Zero's can cause problems if you divide!
How well refined is the mesh? What other settings did the paper(?) use or report?
June 12, 2023 at 5:34 pmc.brunoSubscriber
I have run a simulation with diffusion coefficient set to e-14 and indeed results look better. However, the values of my uds are still very small.
This is with the local scale:
This is with user defined scale:
Regarding my mesh, I have got 3'060'421 elements and this is how it looks like:
In terms of the settings of the paper, simulations are unsteady state and laminar flow, no-flux (for PLI ) conditions were applied at the walls and PLI= 0 at the inlet.
I was wondering if there is something wrong in my code or something I am missing when adapting my equation to the one that Fluent solves?
Thank you very much!
June 13, 2023 at 9:01 amRobAnsys Employee
Possibly, but that's not something I can really comment on.
The mesh isn't great. It looks refined enough on the cross channels but it's very coarse down the longer sections. Have a look at decomposition (break up the geometry) and then sweep/multizone.
- 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
- Suppress Fluent to open with GUI while performing in journal file
- Mesh Interfaces in ANSYS FLUENT
- Time Step Size and Courant Number
- error: Received signal SIGSEGV
© 2023 Copyright ANSYS, Inc. All rights reserved.