Learning Forum

[TB22040019A51]

Hi Rocky Team,

I noticed that the Ansys Rocky 2026 R1 Release Highlights officially announced support for 2-way coupling between Rocky Unresolved and Fluent VOF multiphase model. This is a great enhancement for applications involving free-surface flows with particle interaction (e.g., aerated mixing tanks, slurry handling).

However, after reviewing the Rocky 2026 R1 Tutorial Guide and Verification Manual, I could not find any dedicated case or step-by-step workflow specifically demonstrating the VOF-DEM 2-way coupling setup. The existing 2-way coupling tutorials (Case 14 and Case 16) are based on the Eulerian multiphase approach, which differs significantly from the VOF framework in terms of phase definition and interface tracking.

My current understanding of the setup is:

1. In Fluent: Enable VOF multiphase model (e.g., primary phase = liquid, secondary phase = gas for free-surface tracking), plus a particle phase reserved for Rocky DEM coupling.
2. In Rocky: Enable 2-way coupling with Fluent, import the Fluent case/data file, and let Rocky handle the particle dynamics (collision, shape effects, buoyancy).
3. The coupling exchanges momentum source terms at each timestep, similar to the Eulerian 2-way coupling, but under the VOF single-velocity-field framework.

My questions are:

1. Is there any supplementary document, beta guide, or internal case study available for VOF-DEM 2-way coupling, even if not yet in the official tutorial?
2. Are there specific limitations or restrictions for this coupling (e.g., number of VOF phases, compressible phase support, GPU solver compatibility)?
3. Is there a roadmap for releasing an official VOF-DEM coupling tutorial in future updates?

Any guidance or documentation would be highly appreciated. I am happy to provide more details about my specific application if needed.

[Rob]

Check the CFD Coupling manual, 6.1 for some information. That should cover limitations etc. Note, I can't comment on future plans nor documentation. Partially as I don't know, but mainly as staff can't share anything that's not public. 

For now, if you follow the single phase tutorials but additionally check which phase is called in Rocky (if any) you should be OK. From the Fluent side, VOF tracks a free surface alongside holding cell fluid data so Rocky may just see cell density and viscosity for the phase interaction (plus all the usual flow data).