Hello everyone,

I am running a transient CFD simulation of a propeller in SIMULIA / 3DEXPERIENCE Flow Solver (R2026x) using a sliding mesh rotating zone, and I am consistently encountering the following error:

Rotating zone has partial contact with its surrounding regions. Check the mesh at the interface.

Problem setup
 

• Geometry:
   
  • Propeller inside a cylindrical rotating fluid zone
  • Cylinder embedded inside a stationary outer bounding box
• Topology:
   
  • One Rotating Zone Fluid (full cylinder volume)
  • One Stationary Zone Fluid (entire bounding box minus cylinder)
  • One Fluid-Fluid Interface between rotating and stationary regions
     
• Physics:
   
  • Transient
  • Sliding Mesh (not MRF)
  • Turbulence: SST k-ω
     
• Boundaries:
   
  • Propeller → Wall, no-slip, non-inertial
  • Outer bounding box → Default Wall, slip
  • Pressure outlet → 0 Pa gauge
• Mesh:
  • Hex-dominant mesh
  • Good skewness and angles
  • Aspect ratio is high near boundary layers but solver accepts it
  • Only a few cells flagged for “special treatment”
     

What I observe

• Simulation starts and sometimes advances 1 time increment
• Then stops with:
   
  • Partial contact error on the rotating zone
     
• Info messages show:
   
  • “unintended non-axisymmetric surfaces”
  • remaining faces assigned to Default Wall Boundary clones
     
• This happens even though:
   
  • The rotating zone is a single closed cylinder
  • The fluid interface is defined
  • There are no gaps in geometry
     
• If I switch to MRF, the case runs without errors

Questions

1. What exactly causes “partial contact with surrounding regions” in sliding-mesh cases?
2. Does this error mean that some rotating-zone boundary faces are not included in the Fluid Interface, and if so, how can I reliably detect and fix them?
3. Is it mandatory that 100% of the rotating zone boundary be paired through the Fluid Interface (no default wall faces at all)?
4. Are high-aspect-ratio boundary-layer cells near the interface known to trigger this error?
5. Is there a recommended best practice workflow (MRF → Sliding Mesh) to avoid this issue?

Any guidance or diagnostic tips would be greatly appreciated.

Thank you in advance.