Eulerian Multiphase Flow Model Reference

Table 1. Eulerian Multiphase Model Reference
Theory	See Eulerian Multiphase.
Provided By	[physics continuum] > Models > Multiphase Model
Example Node Path	Continua > [physics continuum] > Models > Eulerian Multiphase (EMP)
Requires	A multiphase simulation with the following model activated: Material: Multiphase
Properties	Key properties are: Velocity Convection, Volume Fraction Convection. See Eulerian Multiphase Properties.
Activates	Physics Models	Gradients (Selected automatically) Viscous Regime
	Reference Values	Reference Pressure. See Setting Reference Values.
	Initial Conditions	Reference Pressure. See Setting Reference Values.
	Boundary Inputs	Phase-specific boundary types for Outlet and Wall boundaries. See Boundary Settings.
	Region Inputs	Phase Conditions: Energy Source Option Mass Source Option Momentum Source Option Turbulence Source Option (for Turbulent viscous regimes) Physics Conditions: Initial Condition Option See Region Settings.
	Solvers	Segregated EMP Flow Solver Volume Fraction Solver
	Report Options	Phase Mass Flow Force (EMP) Moment (EMP) See Reports.
	Field Functions	See Field Functions.

Eulerian Multiphase Properties

Unless you are thoroughly familiar with the theoretical aspects of this model and the Simcenter STAR-CCM+ discretization techniques, do not change the Expert settings. The values in that category have been optimized for accuracy and performance.

Velocity Convection

Selects the convection scheme for flow velocity.

Method

Corresponding Method Nodes

1st-Order

Selects the first-order upwind convection scheme.

None.

2nd-Order

Selects the second-order upwind convection scheme.

None.

MUSCL 3rd-order/CD

Selects the MUSCL 3rd-order/CD convection scheme. This scheme is a blend between a MUSCL 3rd-order upwind scheme and the 3rd-order central-differencing reconstruction scheme.

See Hybrid MUSCL 3rd-Order/CD.

Upwind Blending Factor

Specifies the proportion of upwind differencing, $ς_{u b f}$ related to Eqn. (891).

The default provides the most robustness for the scheme. Reducing it would, in principle, increase accuracy. However, unless you are thoroughly familiar with the theoretical aspects of bounded differencing, do not change this property. The default value reflects optimization for accuracy and performance. The default value is 1.0.

Volume Fraction Convection

Selects the convection scheme for volume fraction.

Method	Corresponding Method Nodes
1st-Order Selects the first-order upwind convection scheme.	None.
2nd-Order Selects the second-order upwind convection scheme. If you use this option, set the Volume Fraction Minimum expert property to have a value greater than the default setting of 0.0.	None.
HRIC This option is available only when the Large Scale Interface Detection Model is enabled. The HRIC scheme is used in VOF simulations to maintain a sharp interface between the participating fluid phases. See High-Resolution Interface Capturing (HRIC).	Angle Factor The angle factor $C_{θ}$ in the HRIC convection discretization scheme for interface tracking. If the free surface is not smooth and not following the grid lines, increase its value. CFL_l The lower Courant number limit in the HRIC convection discretization scheme. This value is ${C o}_{l}$ in Eqn. (2594). CFL_u The upper Courant number limit in the HRIC convection discretization scheme. This value is ${C o}_{u}$ in Eqn. (2594).
Adaptive Interface Sharpening (ADIS) This option is available only when the Large Scale Interface Detection Model is enabled. Selects the Adaptive Interface Sharpening (ADIS) scheme. This scheme adaptively blends an interface sharpening scheme (the High Resolution Interface Capture (HRIC) scheme) and a Total Variation Diminishing (TVD) scheme (the first order or second order scheme). See Adaptive Interface Sharpening (ADIS) Scheme for Volume Fraction.	Angle Factor See above. CFL_l See above. CFL_u See above. Use Second Order TVD When this option is deactivated, the first order scheme is used as the Total Variation Diminishing (TVD) scheme in blending. Number of Cell Layers for Smoothing Specifies the number of cells across which the blending function is smoothed from the Large Interface Marker Band. See $n_{s}$ in Eqn. (2316). The default value is 3 cells. Blending Constant Specifies the blending constant $B$ in Eqn. (2316). Increasing this value makes the transition sharper.

Minimum Volume Fraction

Sets a lower limit on the value of volume fraction in a cell for any phase. The default value is 0.0. If you have the Volume Fraction Convection set to 2nd-order, enter a value greater than zero. When instability issues arise, set to 1.0E-25.

Flow Boundary Diffusion

Activate the flow-boundary diffusion fluxes (or viscous fluxes for flow models)—see Eqn. (898). This property is activated by default.

Minimum Absolute Pressure

Minimum allowable absolute pressure (for compressible flows).

Secondary Gradients

Neglect or include the boundary secondary gradients for diffusion and/or the interior secondary gradients at mesh faces.

Method	Corresponding Physics Value Nodes
On Include both secondary gradients.	None.
Off The outlet behaves like a wall for the selected phase. This option is available on outlets.	None.
Interior Only Include the interior secondary gradients only.	None.
Boundaries Only Include the boundary secondary gradients only.	None.

Velocity Convection

Selects the convection scheme for flow velocity.

Method

Corresponding Method Nodes

1st-Order

Selects the first-order upwind convection scheme.

None.

2nd-Order

Selects the second-order upwind convection scheme.

None.

MUSCL 3rd-order/CD

Selects the MUSCL 3rd-order/CD convection scheme. This scheme is a blend between a MUSCL 3rd-order upwind scheme and the 3rd-order central-differencing reconstruction scheme.

See Hybrid MUSCL 3rd-Order/CD.

Upwind Blending Factor

Specifies the proportion of upwind differencing, $ς_{u b f}$ related to Eqn. (891).

The default provides the most robustness for the scheme. Reducing it would, in principle, increase accuracy. However, unless you are thoroughly familiar with the theoretical aspects of bounded differencing, do not change this property. The default value reflects optimization for accuracy and performance. The default value is 1.0.

Volume Fraction Convection

Selects the convection scheme for volume fraction.

Method	Corresponding Method Nodes
1st-Order Selects the first-order upwind convection scheme.	None.
2nd-Order Selects the second-order upwind convection scheme. If you use this option, set the Volume Fraction Minimum expert property to have a value greater than the default setting of 0.0.	None.
HRIC This option is available only when the Large Scale Interface Detection Model is enabled. The HRIC scheme is used in VOF simulations to maintain a sharp interface between the participating fluid phases. See High-Resolution Interface Capturing (HRIC).	Angle Factor The angle factor $C_{θ}$ in the HRIC convection discretization scheme for interface tracking. If the free surface is not smooth and not following the grid lines, increase its value. CFL_l The lower Courant number limit in the HRIC convection discretization scheme. This value is ${C o}_{l}$ in Eqn. (2594). CFL_u The upper Courant number limit in the HRIC convection discretization scheme. This value is ${C o}_{u}$ in Eqn. (2594).
Adaptive Interface Sharpening (ADIS) This option is available only when the Large Scale Interface Detection Model is enabled. Selects the Adaptive Interface Sharpening (ADIS) scheme. This scheme adaptively blends an interface sharpening scheme (the High Resolution Interface Capture (HRIC) scheme) and a Total Variation Diminishing (TVD) scheme (the first order or second order scheme). See Adaptive Interface Sharpening (ADIS) Scheme for Volume Fraction.	Angle Factor See above. CFL_l See above. CFL_u See above. Use Second Order TVD When this option is deactivated, the first order scheme is used as the Total Variation Diminishing (TVD) scheme in blending. Number of Cell Layers for Smoothing Specifies the number of cells across which the blending function is smoothed from the Large Interface Marker Band. See $n_{s}$ in Eqn. (2316). The default value is 3 cells. Blending Constant Specifies the blending constant $B$ in Eqn. (2316). Increasing this value makes the transition sharper.

Flow Boundary Diffusion

Activate the flow-boundary diffusion fluxes (or viscous fluxes for flow models)—see Eqn. (898). This property is activated by default.

Momentum Interpolation

Selects the momentum interpolation method for the pressure-velocity coupling term of the discretized momentum equation Eqn. (928). Momentum interpolation is required to ensure that checkerboarding and any other unphysical numerical oscillations are suppressed in a simulation.

Method	Corresponding Physics Value Nodes
Rhie-Chow Selects the Rhie-Chow approach. In order to calculate the mass flux, the cell velocity is interpolated to the faces. This interpolated velocity is corrected using a dissipation term which is calculated using the Rhie-Chow method to prevent checkerboarding. The interpolated velocity is then used to calculate the convective fluxes, which are used in the discretization of the momentum equation. The Rhie-Chow interpolation method does not account for flow coupling that results from the inter-phase forces in multiphase flow.	None.
Phase Coupled Selects the Phase Coupled approach which is an extension of the Rhie-Chow interpolation method, as it includes the flow coupling that results from the inter-phase forces. When there is strong coupling between phases, this improves convergence and accuracy of the results.	None.

Method

Corresponding Physics Value Nodes

Rhie-Chow

Selects the Rhie-Chow approach. In order to calculate the mass flux, the cell velocity is interpolated to the faces. This interpolated velocity is corrected using a dissipation term which is calculated using the Rhie-Chow method to prevent checkerboarding. The interpolated velocity is then used to calculate the convective fluxes, which are used in the discretization of the momentum equation.

The Rhie-Chow interpolation method does not account for flow coupling that results from the inter-phase forces in multiphase flow.

None.

Phase Coupled: Selects the Phase Coupled approach which is an extension of the Rhie-Chow interpolation method, as it includes the flow coupling that results from the inter-phase forces. When there is strong coupling between phases, this improves convergence and accuracy of the results.

None.

Boundary Settings

These options are specified in the properties of the phases under the Phase Conditions node for the boundary.

Wall and Outlet Boundaries

Type

The phase-specific boundary option.

Method	Corresponding Physics Value Nodes
Outlet Normal outlet behavior (default option for outlet boundaries).	None.
Phase Impermeable The outlet behaves like a wall for the selected phase. This option is available on outlets.	None.
Phase Permeable The wall behaves like an outlet for the phase. This option is available on wall boundaries.	Wall Permeability The proportion of mass flux that passes through the wall. The default is 1.0.
Wall Normal wall behavior (default option for wall boundaries).	None.

Region Settings

The following settings apply to each phase.

Energy Source Option

Lets you specify energy source options for each phase.

See Energy Source Option.

Mass Source Option

Method	Corresponding Physics Value Nodes
Mass Source Option When activated, user-specified mass sources are enabled.	Mass Source Mass Source Pressure Derivative Mass Source Volume Fraction Derivative See Mass Source Option.

Method

Corresponding Physics Value Nodes

Mass Source Option: When activated, user-specified mass sources are enabled.

Mass Source
Mass Source Pressure Derivative
Mass Source Volume Fraction Derivative

See Mass Source Option.

Momentum Source Option

Method	Corresponding Physics Value Nodes
None Specified Adds a specified momentum source to the momentum equation.	When the Specified method is selected: Momentum Source Momentum Source Velocity Derivative See Momentum Source Option.

Method

Corresponding Physics Value Nodes

None
Specified: Adds a specified momentum source to the momentum equation.

When the Specified method is selected:

Momentum Source
Momentum Source Velocity Derivative

See Momentum Source Option.

Turbulence Source Option

Available when a turbulence model is activated in the phase.

Method	Corresponding Physics Value Nodes
Turbulence Source Option None Specified	When the Specified method is selected: Specific Dissipation Rate Source Available for the K-Omega turbulence model. See K-Omega Regions Reference. Turbulent Kinetic Energy Source Available for both the K-Omega and K-Epsilon turbulence model. Turbulent Dissipation Rate Source Available for the K-Epsilon turbulence model. Turbulent Dissipation Rate Source Derivative Available for the K-Epsilon turbulence model. Turbulent Kinetic Energy Source Derivative Available for the K-Epsilon turbulence model. See K-Epsilon Regions Reference.

Method

Corresponding Physics Value Nodes

Turbulence Source Option

None
Specified

When the Specified method is selected:

Specific Dissipation Rate Source

Available for the K-Omega turbulence model.

See K-Omega Regions Reference.

Turbulent Kinetic Energy Source

Available for both the K-Omega and K-Epsilon turbulence model.

Turbulent Dissipation Rate Source

Available for the K-Epsilon turbulence model.

Turbulent Dissipation Rate Source Derivative

Available for the K-Epsilon turbulence model.

Turbulent Kinetic Energy Source Derivative

Available for the K-Epsilon turbulence model.

See K-Epsilon Regions Reference.

The following settings apply to fluid regions.

Initial Condition Option: Lets you customize initial conditions for an individual region.
See Setting Initial Conditions for a Particular Region.

Reports

Phase Mass Flow

Force (EMP): See Force (EMP) report for details.

Moment (EMP): See Moment (EMP) report for details.

Field Functions

These field function are available only when Temporary Storage Retained is activated for the Segregated EMP Flow solver.

Interface Sharpening Blending Function: The blending function that is used for blending the HRIC and TVD schemes. This is $f_{b l e n d i n g}$ in Eqn. (2316).
Ap-Ratio of [phase]: The ratio between diagonal and non diagonal terms of the $\bar{a}$ coefficient matrix in Eqn. (930). The ratio is defined as $A_{p} = \frac{\sum a_{o f f D i a g}}{a_{D i a g} + \sum a_{o f f D i a g}}$ , and the range is [0,1]. High Ap-Ratio of [phase] values indicate strong coupling between phases, in such case using the Phase Coupled momentum interpolation approach could improve convergence.