18.3.5. Physical Model Parameters

Material Properties
`realeos liquid prop`
Type	Integer
Default Value	1
Description	This parameter controls whether liquid saturation properties are extracted using the Rackett equation, which is a function of temperature (realeos liquid prop = 1), or using the full equation of state, which is a function of both temperature and pressure (realeos liquid prop = 2) — the latter is more accurate. For details, see Real Gas Liquid Properties in the CFX-Solver Theory Guide.
Combustion Models
`coupled scalars`
Type	Logical
Default Value	f
Description	All combustion models that solve for the mixture fractions of the reactants and products (single or multiple step reaction models), are solved using a coupled multigrid linear solver. This means that all of the mixture fraction equations are solved simultaneously, with the mixture mass transfer source terms linearized in each equation. Under certain conditions, this coupling procedure can fail, leading to oscillatory convergence or divergence. In this case, you can disable the coupled solver and switch to a segregated approach to solving the mixture fraction equations. This is achieved by setting this parameter to `'f'`.
`use kolmogorov ts for extinction`
Type	Logical
Default Value	f
Description	This parameter is provided for backwards compatibility with the first release of the extinction model. It is not recommended for use (leave at default setting of `'f'`, which uses the turbulence time scale for the flame extinction model). When set to `'t'`, the Kolmogorov time scale is used in the extinction model (not recommended).
Turbulence Models
`apply ic fluctuations for les`
Type	Logical
Default Value	f
Description	If set to `'t'`, to force the application of velocity fluctuations when restarting an LES. This is most useful when using a RANS solution as this initial guess. For details, see LES Initialization.
General Grid Interface
`force intersection`
Type	Logical
Default Value	f
Description	On all GGI interfaces (fluid-fluid attachments, periodicity and frame change interfaces), the solver performs an intersection procedure to connect the two sides of the interface together. This procedure is CPU intensive, so the result of the intersection is stored in the outgoing results file, for future use (for example, upon restart of the simulation). You can force a re-intersection of the GGI interface if desired, upon restart, by setting this parameter to `'t'`. It is rare that this parameter should be needed, as it generally only results in wasted CPU time upon a restarted simulation.
`ggi vertex weighting value`
Type	Integer
Default Value	2
Description	Weighting applied to GGI vertices during partitioning. A larger value assigns a larger weight to vertices on GGI boundaries to account for the fact that the assembly effort is higher at GGI interfaces. For more information, see Node-based and Element-based Partitioning.
`mpf ggi force flow balance`
Type	Logical
Default Value	f
Description	Usually flow balance is not enforced at GGI interfaces for multiphase flows. By setting the value of this parameter to 't', the code will enforce flow balance. This can help with the convergence of many inhomogeneous multiphase flows that include such interfaces.
`stage energy closure option`
Type	Integer
Default Value	2
Description	With option = 2, conservation of rothalpy is enforced; with option = 1, conservation of rothalpy is not enforced.
`stage velocity factor option`
Type	Integer
Default Value	1
Description	This parameter is applicable only to the mixing plane with the `Constant Total Pressure` downstream velocity constraint option. The default value of `1` provides the standard treatment of the mixing plane. Use a value of `2` if the momentum conservation across the mixing plane (stage) interface is found to be unsatisfactory.
Mesh Displacement
`meshdisp phase angle convention`
Type	Integer
Default Value	1
Description	Expert Parameter `meshdisp phase angle convention` selects a convention for traveling wave direction: For a value of 0, no convention is enforced. For a value of 1 (default): For a rotating component: a forward traveling wave, which corresponds to a positive phase angle or IBPA, moves in the direction of machine rotation. For a stationary component (for example, a model of a stand-alone stator): a forward traveling wave moves in the direction of increasing sector tag number (increasing angle variable). A forward traveling wave that uses this convention is illustrated in Case 3: Blade Flutter. For a value of 2: For a rotating component: a forward traveling wave, which corresponds to a positive phase angle or IBPA, moves opposite to the direction of machine rotation. For a stationary component (for example, a model of a stand-alone stator): a forward traveling wave moves in the direction of increasing sector tag number (increasing angle variable). Note that this is the same as for a value of 1.
Miscellaneous
`asm momentum drift flux`
Type	Logical
Default Value	f
Description	This parameter adds the ASM drift fluxes into the momentum equation.
`mpf ptot option`
Type	Integer
Default Value	0
Description	When `mpf ptot option = 0` (the default), only the compressible phase is considered when computing the total pressure; the dispersed phase contributions are not added. When `mpf ptot option = 1`: For total pressure boundaries in cases where the continuous phase is compressible, the dispersed phase contributions are added to the total pressure. For porous interfaces, an incompressible fluid approximation is made for all phases. For stage interfaces, an incompressible fluid approximation is made for all phases. The approximations that are made when `mpf ptot option = 1` are accurate in each of the following limits: The dispersed phases are dilute by mass. The continuous compressible phase has a low Mach number. The continuous phase is dilute by mass fraction. Note that, for droplets in gas, the dilute droplet mass fraction limit can imply a very small droplet volume fraction.
`tbulk for htc`
Type	Real
Default Value	300 K
Description	When the Heat Transfer Coefficient (HTC) is computed for a temperature specified wall, by default a near-wall fluid temperature is used for a temperature scale. However, for consistency with traditional 1D analyses, you may want to enter a reference bulk temperature to compute the HTC. This parameter is that reference value. Thus the HTC computed when this parameter is provided is equal to the local heat flux calculated by the solver divided by the difference of the specified wall temperature and this specified bulk temperature.
`topology simplification`
Type	Logical
Default Value	t
Description	This parameter controls internal mesh topology simplification. It can improve performance for models with a large number of 2D primitives. While the simplification will not change the output regions (in CFD-Post), it may lead to small differences in solution results due to rounding errors, especially for single precision solutions. Note that topology simplification does not take effect for models involving System Coupling or radiation. Also note that topology simplification cannot be used if there are region changes introduced by re-reading CCL during a solver run (for example, using the Edit Run In Progress command).
`transient initialisation override`
Type	Logical
Default Value	f
Description	When set to `'t'`, enables solver default values to be used for initialization in a transient simulation.