Liquid-gas interface motion
Track a resolved free surface while controlling interface smearing, local velocities and transient stability.
MULTIPHASE, VOF & FREE-SURFACE CFD
Resolve moving interfaces without losing control of timestep, mesh or physical interpretation.
Abecator supports transient multiphase CFD for waves, sloshing and liquid-gas free surfaces where interface resolution, Courant number, numerical diffusion and boundary treatment strongly affect the result.
ENGINEERING PROBLEMS
Transient flow problems driven by a moving phase interface.
Free-surface CFD requires a balance between physical fidelity and numerical control. Mesh, timestep and boundary conditions are often as important as the multiphase model itself.
Wave generation & propagation
Define wave conditions, propagation region, damping strategy and monitoring so reflected energy does not contaminate the result.
Tank and container dynamics
Study transient free-surface motion, impact regions, fluid redistribution and sensitivity to excitation or fill level.
Moving bodies & fluid interaction
Where required, review moving/deforming/overset strategies and how the motion couples to the transient multiphase field.
TYPICAL CFD SCOPE
Design the transient methodology before pressing Run.
VOF cases can consume large computational budgets while still producing a numerically weak answer. The setup needs an explicit interface-resolution and timestep plan.
01
Define interface physics
Phases, density/viscosity ratios, gravity, surface tension relevance, initial fill/interface and expected motion scale.
02
Design interface mesh
Refinement targets the free-surface zone, wave length/height, narrow gaps and impact regions rather than refining the whole domain.
03
Set timestep strategy
Courant number, interface advection and physical timescale are used together to define a defensible transient step.
04
Control boundaries & reflections
Wave inlets/outlets, damping zones, pressure boundaries and domain length are checked against the phenomenon being simulated.
WHAT GETS CHECKED
Common reasons VOF results become unreliable.
The simulation may remain numerically stable while the interface is too diffused, reflected waves dominate or the timestep suppresses the real transient response.
A✓
Interface resolution
Cell size relative to wave/interface features is checked so the free surface is physically meaningful.
B✓
Courant number & timestep
Local transient transport is checked rather than relying on one global timestep rule.
C✓
Numerical diffusion
Interface compression/advection behaviour and mesh alignment are reviewed if the free surface becomes overly smeared.
D✓
Boundary reflection
Outlet and damping treatment are checked so reflected waves are not mistaken for physical response.
POSSIBLE DELIVERABLES
Transient evidence with a clear numerical basis.
Support can focus on a failing case, a new VOF methodology or interpretation of a complex transient response.
VOF setup methodology
Recommended mesh, timestep, boundaries, interface treatment, monitoring and sensitivity plan.
Transient troubleshooting
Identify whether instability, diffusion, reflections, poor conservation or motion coupling is driving the problem.
Free-surface interpretation
Wave elevation, phase distribution, impact regions, flow structures and time-history interpretation relevant to the project.
Independent model review
Challenge mesh, timestep, boundaries and whether the transient evidence is strong enough for the engineering conclusion.
SOFTWARE & METHODS
Transient CFD with deliberate numerical control.
Typical workflows may involve STAR-CCM+, OpenFOAM, VOF, adaptive/local refinement, wave damping, moving/overset meshes and engineering time-history analysis.
Courant / Time-Step Calculator → STAR-CCM+ AMR Guide → Overset Mesh Guide →
HAVE A VOF OR FREE-SURFACE CFD PROBLEM?
Start with the phases, motion timescale and quantity the transient model must predict.
Use the project inquiry to describe the current setup, interface behaviour and what is unstable, uncertain or too expensive.
MULTIPHASE RESOURCES
Time resolution and interface resolution have to be designed together.
Use Courant number as a starting constraint, then diagnose timestep sensitivity, interface diffusion and boundary reflections in the solved flow.