The VOF model is supported with the GPU Solver as a beta feature with the following capabilities:
Implicit compressive scheme for VOF equation.
Segregated (SIMPLE and SIMPLEC) and coupled pressure-based solvers. The coupled pressure-based solved is only available for steady flow analysis.
First order and bounded second order temporal discretization schemes are available. As with the CPU solver VOF model, the bounded second order scheme is recommended.
Body Force Weighted and Modified Body Force Weighted pressure schemes.
Nonconformal Interfaces, moving reference frames, and sliding mesh.
Surface tension (Continuum Surface Force model) including wall adhesion.
Compressible liquid for phase material.
Velocity limiting for stability control.
RANS and URANS turbulence models.
Multiphase species transport model. See limitations below.
Usage of non-newtonian-power-law and carreau viscosity models.
Expressions
time-dependent gravity vector
mixture level boundary conditions
Boundary conditions
velocity-inlet/pressure-inlet/pressure-outlet/wall/shadow-wall/symmetry/periodic
pressure and volume fraction from neighboring cells for pressure outlets
mass flow inlet
Report definitions
surface reports of mass and volume flow rates on both mixture and phase levels.
volume reports of volume and mass on both mixture and phase levels. The volume report can include averaging or integrals of any field variables, but please see limitation below if phase density or molecular viscosity are used.
flux reports of mass flow rates on both mixture and phase levels
report definitions using phasic species mass fraction
other report definition types behave as for single phase calculations
The VOF model with the GPU Solver has the following limitations:
Energy model in multiphase is not yet available.
The GPU VOF solver does not currently use the same node-based numerics which are leveraged by the CPU-based VOF solver. This may sometimes lead to solution differences when comparing to equivalent CPU-based solutions on the same mesh. Node-based numerics can be more accurate, particularly for some surface tension-dominated flows, and will be implemented in the future.
When using the coupled solver with pseudo-transient, the automatic pseudo-timescale calculation does not yet include VOF-specific timescale estimates. If the VOF-specific contributions to the timescale are important to solver robustness, please inspect the Automatic timescale computed by the CPU solver (by activating Verbosity on the Run Calculation panel) and use a typical timescale from the CPU output as a User Specified timescale for the GPU run.
The generic solver limitations mention that the handling of reference pressure differs between CPU and GPU solvers for flow passages which do not have any pressure boundaries. This difference is cosmetic in the sense that the velocity field and pressure gradients are unaffected. But the pressure levels may have an offset between them, making it challenging to compare the pressure fields (and pressure-dependent quantities such as forces) between CPU and GPU simulations. The difference becomes more pronounced for transient runs involving VOF, because the pressure offset can change over time.
Adaptive time stepping is not yet supported.
User-input option only for operating density method.
In the multiphase species transport model, the Volumetric Reactions and Diffusion Energy Source are not yet supported.
When using phase density and molecular viscosity in the following volume report definitions, the integral/average is performed on the mixture quantity rather than the phase quantity:
volume integral
volume average
mass integral
mass average
Report definitions using phasic species molar fraction, mass concentration and molar concentration are not yet supported.