Learning Forum

[2mudrt52]

Hi,

I’m running ANSYS Fluent 2025 R2 with Fluent Meshing → Watertight Geometry Workflow only (university license). I’m simulating VOF free-surface (air/water, open-channel) flow through a plastic collection net (fishing net basically)+flow around floating solid to measure the drag. I need to model a thin net panel inside the fluid domain as a Porous Jump (pressure loss only), but the panel is internal (does not touch outer boundaries).

 

Problem: I struggle to create a robust porous-jump setup without the case failing. To assign porous jump, I tried:

 

• splitting the fluid domain into 2 volumes and using the split plane as internal,
• imprinting/splitting the net patch on the internal plane,
• applying share topology / joining, etc.

 

 

But I often get “pairs not joined” on the internal interface, zones disappear/merge after meshing, and porous-jump ends up as a wall or cannot be assigned cleanly.

 

Question: What is the recommended, fail-safe workflow in Watertight Geometry to create an internal surface for a net and assign it as Porous Jump for VOF open-channel cases?

Specifically: should this be done as a baffle (wall + shadow), an internal face zone, or by splitting into two cell zones and making a mesh interface—what’s the most robust method in Fluent 2025 R2 which later also doesn't cause solver issues ?

 

Thanks!

[SamW]

Hello,

I know this is a bit of an older question, but in case you're still looking into it, or for others coming across this question, please look into the porous-jump boundary condition. The Porous Jump boundary condition is available for homogeneous multiphase models, such as the VOF (Volume of Fluid) model.

 

You can modify an interior-type boundary to model a porous jump. To do this, you should create two adjacent fluid zones which have shared topology. A named surface between the two where you want to apply it will make it easier to assign the porous-jump condition. Once you have the mesh created and the case open in solver mode, you can right-click on the boundary in the model tree and change the type to porous-jump. This is outlined in section 8.4.22.1.1 in the link above.