March 31, 2020 at 8:22 pmansysuserSubscriber
In the Fluent manual, section 18.3.4, there is a discussion of different schemes for interpolating near the interface of two phases in the VOF model. For example, the geometric reconstruction, donor-acceptor, etc. But there is no mention of how to choose one or the other and I do not see anywhere in the dialog boxes where these options are listed.
How can I choose one of these schemes in Fluent?
March 31, 2020 at 9:46 pm
March 31, 2020 at 10:09 pmansysuserSubscriber
I see. Thank you.
That does help, except in my drop down list I only have Compressive and Modified HRIC. I was hoping to use Geo-Reconstruct because it looks like it will help with the phases mixing too much. Do I need some other setting enabled before the Geo-Reconstruct is available? Please let me know.
The problem I am having is that the phases (liquid water and incompressible air) are mixing way beyond what is physical. Here is an example of the contour of the water phase fraction 1 second after an air bubble rises to the top of a closed container. The container is 1cm wide with 0.1mm mesh sizing. In reality, no such massive phase gradient would exist like this. I am wondering if Coupled Level set would be a better way to go. Any suggestions would be helpful.
March 31, 2020 at 10:14 pmKarthik RAdministrator
These options depend on your analysis type as well as your pressure-velocity coupling. If I remember correctly, steady VoF with coupled solver will not show you Geo-Reconstruct. However, a transient analysis with SIMPLE coupling should show you the Geo-Reconstruct option.
March 31, 2020 at 10:23 pm
March 31, 2020 at 10:35 pmKarthik RAdministrator
Which version of Fluent are you using?
March 31, 2020 at 10:48 pmansysuserSubscriber
I am using the version that came with Workbench 2019 R3
March 31, 2020 at 10:54 pm
April 1, 2020 at 2:29 am
April 2, 2020 at 12:07 amansysuserSubscriber
Thanks, Kremella. Yes, I was able to change to Geo-Recon by selecting explicit. However, the solution is now not correct.
Thanks, kkanade. I am not sure what those plots are supposed to be, but I do see there is a difference!
For my problem, the issue is that I am getting way too much phase mixing to be physical. See the contour plot above.
At the start of the simulation, I have a water zone and an air zone (with patching) that have a vertical boundary between them. Then the solution starts. Here is the difference at time step 8. Note the implicit solution evolves into a very nice motion that looks physically correct, except the extreme amount of phase mixing. The explicit formulation gets these strange ripples. Any suggestion would be much appreciated. (Note I had to drop the time step size to keep convergent. All other settings are the same except the Geom-Recon for the explicit formulation.)
April 2, 2020 at 3:06 am
April 2, 2020 at 6:19 amansysuserSubscriber
Thank you kkanade.
I just discovered that when I loaded the case and data files into the new Fluent module to try the explicit method, the wall contact angle was reset to the default value of 90 degrees. I am unsure why this happened, as all other settings remained unchanged. As such, I will run with the correct contact angle and come back to start another post if needed.
Thanks again, I appreciate everyone's efforts.
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