CFD TOPIC HUB · MULTIPHASE & VOF
Multiphase and VOF CFD: resolve the interface and its timescale together.
Use this hub for free-surface and VOF simulations where interface transport, initialization, mesh resolution, timestep and boundary behavior determine whether the solution is physical.
Start from the decision the CFD model has to support.
A stable interface is not enough. The mesh and timestep must resolve the motion and the boundary conditions must let the phase system evolve without artificial reflection, diffusion or mass error.
Use these checks before adding model complexity.
- Design spatial and temporal resolution together around the interface motion.
- Use Courant number as a screening metric, not as the only timestep criterion.
- Check phase conservation, initialization and boundary behavior before tuning interface numerics.
Already have a CFD model that behaves incorrectly?
Start from the symptom and follow the Technical Case diagnostic sequence before tuning unrelated solver controls.
Browse Technical Cases →Build the modelling decision from the underlying physics.
Use the guides for definitions, assumptions, workflow design and evidence requirements.
Courant Number, CFL & Time Step
Connect cell size, transport speed and timestep
Open resource →ENGINEERING GUIDECFD Time-Step Independence Study
Prove the engineering signal is temporally resolved
Open resource →ENGINEERING GUIDECFD Verification vs Validation
Build credibility beyond a visually plausible interface
Open resource →Diagnose the failure mode when the solved model disagrees.
Technical Cases are organized around symptoms, likely causes, diagnostic order and controlled fixes.
VOF Interface Is Unstable or Smeared
Diagnose timestep, mesh, initialization and boundaries
Open resource →TECHNICAL CASECFD Time-Step Sensitivity
Challenge transient-resolution dependence
Open resource →TECHNICAL CASEMass Imbalance in CFD
Check complete conservation and accumulation
Open resource →Challenge the CFD with transparent engineering checks.
Independent calculations help reveal whether the problem is in the physics, inputs, numerical resolution or interpretation.
Continue with the same engineering context.
Move into structured training when you need the complete methodology, or engineering support when the answer depends on the actual project.
Connect adjacent modelling decisions.
Complex CFD problems often cross more than one topic cluster. Continue into the governing issue rather than searching by software menu alone.
Go deeper on the performance quantity or failure mode that controls the engineering decision.
This focused pair adds one engineering guide and one symptom-led Technical Case to the Multiphase & VOF cluster.
VOF Mesh & Time-Step Guidelines
Choose interface mesh and timestep together using local transport, Courant number, physical timescales, phase conservation and sensitivity evidence.
Read guide →TECHNICAL CASEVOF Phase Volume or Mass Is Not Conserved
Close the phase inventory using boundary fluxes and sources before testing timestep, interface transport, clipping and report definitions.
Open diagnostic case →