- •Why CFD is Important for Modeling
- •How the CFD Module Helps Improve Your Modeling
- •Model Builder Options for Physics Feature Node Settings Windows
- •Where Do I Access the Documentation and Model Library?
- •Typographical Conventions
- •Quick Start Guide
- •Defining the Physics
- •Meshing
- •Modeling Strategy
- •Geometrical Complexities
- •Material Properties
- •The Choice of Solver and Solver Settings
- •Coupling to Other Physics Interfaces
- •Adding a Chemical Species Transport Interface
- •Equation
- •Discretization
- •Transport Feature
- •Migration in Electric Field
- •Reactions
- •Reactions
- •Initial Values
- •Initial Values
- •Boundary Conditions for the Transport of Concentrated Species Interface
- •Mass Fraction
- •Mass Fraction
- •Flux
- •Inflow
- •Inflow
- •No Flux
- •Outflow
- •Flux Discontinuity
- •Flux Discontinuity
- •Symmetry
- •Open Boundary
- •Physical Model
- •Transport Properties
- •Model Inputs
- •Fluid Properties
- •Diffusion
- •Migration in Electric Field
- •Diffusion
- •Model Inputs
- •Density
- •Diffusion
- •Porous Matrix Properties
- •Porous Matrix Properties
- •Initial Values
- •Initial Values
- •Domain Features for the Reacting Flow, Concentrated Species Interface
- •Boundary Conditions for the Reacting Flow, Concentrated Species Interface
- •Reacting Boundary
- •Inward Flux
- •Physical Model
- •Transport Properties
- •Fluid Properties
- •Migration in Electric Field
- •Porous Matrix Properties
- •Initial Values
- •Domain Features for the Reacting Flow, Diluted Species Interface
- •Boundary Conditions for the Reacting Flow, Diluted Species Interface
- •Pair and Point Conditions for the Reacting Flow, Diluted Species Interface
- •Multicomponent Mass Transport
- •Multicomponent Diffusion: Mixture-Average Approximation
- •Multispecies Diffusion: Fick’s Law Approximation
- •Multicomponent Thermal Diffusion
- •References for the Transport of Concentrated Species Interface
- •Domain Equations
- •Combined Boundary Conditions
- •Effective Mass Transport Parameters in Porous Media
- •Selecting the Right Interface
- •The Single-Phase Flow Interface Options
- •Laminar Flow
- •Coupling to Other Physics Interfaces
- •The Laminar Flow Interface
- •Discretization
- •The Creeping Flow Interface
- •Discretization
- •Fluid Properties
- •Fluid Properties
- •Mixing Length Limit
- •Volume Force
- •Volume Force
- •Initial Values
- •Initial Values
- •The Turbulent Flow, Spalart-Allmaras Interface
- •The Rotating Machinery, Laminar Flow Interface
- •Rotating Domain
- •Rotating Domain
- •Initial Values
- •Initial Values
- •Rotating Wall
- •Wall
- •Boundary Condition
- •Interior Wall
- •Boundary Condition
- •Normal Stress
- •Inlet
- •Boundary Condition
- •Velocity
- •Pressure, No Viscous Stress
- •Outlet
- •Boundary Condition
- •Pressure
- •Laminar Outflow
- •No Viscous Stress
- •Vacuum Pump
- •Symmetry
- •Open Boundary
- •Boundary Stress
- •Boundary Condition
- •Periodic Flow Condition
- •Flow Continuity
- •Pressure Point Constraint
- •Non-Newtonian Flow—The Power Law and the Carreau Model
- •Theory for the Pressure, No Viscous Stress Boundary Condition
- •Theory for the Laminar Inflow Condition
- •Theory for the Laminar Outflow Condition
- •Theory for the Slip Velocity Wall Boundary Condition
- •Theory for the Vacuum Pump Outlet Condition
- •Theory for the No Viscous Stress Condition
- •Theory for the Mass Flow Inlet Condition
- •Turbulence Modeling
- •Eddy Viscosity
- •Wall Functions
- •Initial Values
- •Wall Distance
- •Inlet Values for the Turbulence Length Scale and Intensity
- •Initial Values
- •The Spalart-Allmaras Turbulence Model
- •Inlet Values for the Turbulence Length Scale and Intensity
- •Pseudo Time Stepping for Turbulent Flow Models
- •References for the Single-Phase Flow, Turbulent Flow Interfaces
- •Selecting the Right Interface
- •Coupling to Other Physics Interfaces
- •Discretization
- •Fluid-Film Properties
- •Initial Values
- •Initial Values
- •Inlet
- •Outlet
- •Wall
- •Symmetry
- •Discretization
- •Initial Values
- •Initial Values
- •Fluid-Film Properties
- •Border
- •Inlet
- •Outlet
- •Conditions for Film Damping
- •The Reynolds Equation
- •Structural Loads
- •Gas Outflow Conditions
- •Rarefaction and Slip Effects
- •Geometry Orientations
- •References for the Thin-Film Flow Interfaces
- •Selecting the Right Interface
- •The Multiphase Flow Interface Options
- •The Relationship Between the Interfaces
- •Bubbly Flow
- •Coupling to Other Physics Interfaces
- •The Laminar Two-Phase Flow, Level Set Interface
- •Discretization
- •The Laminar Two-Phase Flow, Phase Field Interface
- •Domain Level Settings for the Level Set and Phase Field Interfaces
- •Fluid Properties
- •Mixing Length Limit
- •Initial Values
- •Initial Values
- •Volume Force
- •Volume Force
- •Gravity
- •Boundary Conditions for the Level Set and Phase Field Interfaces
- •Wall
- •Boundary Condition
- •Initial Interface
- •The Turbulent Flow, Two-Phase Flow, Level Set Interface
- •The Turbulent Two-Phase Flow, Phase Field Interface
- •Wall Distance Interface and the Distance Equation
- •Level Set and Phase Field Equations
- •Conservative and Non-Conservative Formulations
- •Phase Initialization
- •Numerical Stabilization
- •References for the Level Set and Phase Field Interfaces
- •Stabilization
- •Discretization
- •Level Set Model
- •Initial Values
- •Initial Values
- •Boundary Conditions for the Level Set Function
- •Inlet
- •Initial Interface
- •No Flow
- •Outlet
- •Symmetry
- •Discretization
- •Initial Values
- •Initial Values
- •Phase Field Model
- •Boundary Conditions for the Phase Field Function
- •Initial Interface
- •Inlet
- •Wetted Wall
- •Wetted Wall
- •Outlet
- •The Level Set Method
- •Conservative and Non-Conservative Form
- •Initializing the Level Set Function
- •Variables For Geometric Properties of the Interface
- •Reference for the Level Set Interface
- •About the Phase Field Method
- •The Equations for the Phase Field Method
- •Conservative and Non-Conservative Forms
- •Additional Sources of Free Energy
- •Variables and Expressions
- •Reference For the Phase Field Interface
- •The Laminar Bubbly Flow Interface
- •Reference Pressure
- •Discretization
- •The Turbulent Bubbly Flow Interface
- •Reference Pressure
- •Discretization
- •Fluid Properties
- •Slip Model
- •Initial Values
- •Initial Values
- •Volume Force
- •Volume Force
- •Gravity
- •Gravity
- •Mass Transfer
- •Mass Transfer
- •Boundary Conditions for the Bubbly Flow Interfaces
- •Wall
- •Liquid Boundary Condition
- •Gas Boundary Condition
- •Inlet
- •Liquid Boundary Condition
- •Gas Boundary Condition
- •Outlet
- •Liquid Boundary Condition
- •Gas Boundary Condition
- •Symmetry
- •Gas Boundary Conditions Equations
- •The Mixture Model, Laminar Flow Interface
- •Stabilization
- •Discretization
- •The Mixture Model, Turbulent Flow Interface
- •Stabilization
- •Mixture Properties
- •Mass Transfer
- •Mass Transfer
- •Initial Values
- •Initial Values
- •Volume Force
- •Volume Force
- •Gravity
- •Gravity
- •Boundary Conditions for the Mixture Model Interfaces
- •Wall
- •Mixture Boundary Condition
- •Dispersed Phase Boundary Condition
- •Inlet
- •Mixture Boundary Condition
- •Dispersed Phase Boundary Condition
- •Outlet
- •Mixture Boundary Condition
- •Symmetry
- •The Bubbly Flow Equations
- •Turbulence Modeling in Bubbly Flow Applications
- •References for the Bubbly Flow Interfaces
- •The Mixture Model Equations
- •Dispersed Phase Boundary Conditions Equations
- •Turbulence Modeling in Mixture Models
- •Slip Velocity Models
- •References for the Mixture Model Interfaces
- •Dispersed Phase
- •Discretization
- •Domain Conditions for the Euler-Euler Model, Laminar Flow Interface
- •Phase Properties
- •Solid Viscosity Model
- •Drag Model
- •Solid Pressure Model
- •Initial Values
- •Boundary, Point, and Pair Conditions for the Euler-Euler Model, Laminar Flow Interface
- •Wall
- •Dispersed Phase Boundary Condition
- •Inlet
- •Two-Phase Inlet Type
- •Continuous Phase
- •Dispersed Phase
- •Outlet
- •Mixture Boundary Condition
- •The Euler-Euler Model Equations
- •References for the Euler-Euler Model, Laminar Flow Interface
- •Selecting the Right Interface
- •The Porous Media Flow Interface Options
- •Coupling to Other Physics Interfaces
- •Discretization
- •Fluid and Matrix Properties
- •Mass Source
- •Mass Source
- •Initial Values
- •Initial Values
- •Boundary Conditions for the Darcy’s Law Interface
- •Pressure
- •Pressure
- •Mass Flux
- •Mass Flux
- •Inflow Boundary
- •Inflow Boundary
- •Symmetry
- •No Flow
- •Discretization
- •Fluid and Matrix Properties
- •Volume Force
- •Volume Force
- •Forchheimer Drag
- •Forchheimer Drag
- •Initial Values
- •Initial Values
- •Mass Source
- •Boundary Conditions for the Brinkman Equations Interface
- •Discretization
- •Fluid Properties
- •Porous Matrix Properties
- •Porous Matrix Properties
- •Forchheimer Drag
- •Forchheimer Drag
- •Volume Force
- •Volume Force
- •Initial Values
- •Initial Values
- •Boundary Conditions for the Free and Porous Media Flow Interface
- •Microfluidic Wall Conditions
- •Boundary Condition
- •Discretization
- •Domain, Boundary, and Pair Conditions for the Two-Phase Darcy’s Law Interface
- •Fluid and Matrix Properties
- •Initial Values
- •Initial Values
- •No Flux
- •Pressure and Saturation
- •Pressure and Saturation
- •Mass Flux
- •Inflow Boundary
- •Inflow Boundary
- •Outflow
- •Pressure
- •Darcy’s Law—Equation Formulation
- •About the Brinkman Equations
- •Brinkman Equations Theory
- •References for the Brinkman Equations Interface
- •Reference for the Free and Porous Media Flow Interface
- •Darcy’s Law—Equation Formulation
- •The High Mach Number Flow, Laminar Flow Interface
- •Surface-to-Surface Radiation
- •Discretization
- •Initial Values
- •Initial Values
- •Shared Interface Features
- •Fluid
- •Dynamic Viscosity
- •Inlet
- •Outlet
- •Consistent Inlet and Outlet Conditions
- •Pseudo Time Stepping for High Mach Number Flow Models
- •References for the High Mach Number Flow Interfaces
- •Selecting the Right Interface
- •The Non-Isothermal Flow Interface Options
- •Coupling to Other Physics Interfaces
- •The Non-Isothermal Flow, Laminar Flow Interface
- •Discretization
- •The Conjugate Heat Transfer, Laminar Flow Interface
- •The Turbulent Flow, Spalart-Allmaras Interface
- •Fluid
- •Dynamic Viscosity
- •Wall
- •Boundary Condition
- •Initial Values
- •Pressure Work
- •Viscous Heating
- •Dynamic Viscosity
- •Turbulent Non-Isothermal Flow Theory
- •References for the Non-Isothermal Flow and Conjugate Heat Transfer Interfaces
- •Selecting the Right Interface
- •The Heat Transfer Interface Options
- •Conjugate Heat Transfer, Laminar Flow
- •Conjugate Heat Transfer, Turbulent Flow
- •Coupling to Other Physics Interfaces
- •Accessing the Heat Transfer Interfaces via the Model Wizard
- •Discretization
- •Heat Transfer in Solids
- •Translational Motion
- •Translational Motion
- •Pressure Work
- •Heat Transfer in Fluids
- •Viscous Heating
- •Dynamic Viscosity
- •Heat Source
- •Heat Source
- •Initial Values
- •Initial Values
- •Boundary Conditions for the Heat Transfer Interfaces
- •Temperature
- •Temperature
- •Thermal Insulation
- •Outflow
- •Symmetry
- •Heat Flux
- •Heat Flux
- •Inflow Heat Flux
- •Inflow Heat Flux
- •Open Boundary
- •Periodic Heat Condition
- •Surface-to-Ambient Radiation
- •Boundary Heat Source
- •Boundary Heat Source
- •Heat Continuity
- •Pair Thin Thermally Resistive Layer
- •Pair Thin Thermally Resistive Layer
- •Thin Thermally Resistive Layer
- •Thin Thermally Resistive Layer
- •Line Heat Source
- •Line Heat Source
- •Point Heat Source
- •Convective Cooling
- •Out-of-Plane Convective Cooling
- •Upside Heat Flux
- •Out-of-Plane Radiation
- •Upside Parameters
- •Out-of-Plane Heat Flux
- •Domain Selection
- •Upside Inward Heat Flux
- •Change Thickness
- •Change Thickness
- •Porous Matrix
- •Heat Transfer in Fluids
- •Thermal Dispersion
- •Dispersivities
- •Heat Source
- •Equation Formulation
- •Activating Out-of-Plane Heat Transfer and Thickness
For each of the two fluids, you specify the density and viscosity. You can easily use non-Newtonian models for any of the two fluids, based on the power law, the Carreau model or using an arbitrary user defined expression.
Two-Phase Flow, Phase Field
The Laminar Two-Phase Flow, Phase Field Interface (
) and The Turbulent Two-Phase Flow, Phase Field Interface (
) found under the Two-Phase Flow, Phase Field branch (
), also model two fluids separated by a fluid interface. You can switch between the Two-Phase Flow, Level Set interface and the Two-Phase Flow, Phase Field interface using a drop-down list available in both interfaces. This may be useful if you are not sure which provides the best solution. A library of common surface tension coefficients between some common substances is available in this interface.
Similar to other fluid flow interfaces, compressible flow is possible to model in this interface at speeds of less than 0.3 Mach in the Two-Phase Flow, Phase Field interface. You can also model incompressible flow and simplify the equations to be solved. Stokes’ law is an option.
For each of the two fluids, you specify the density and viscosity. You can easily use non-Newtonian models for any of the two fluids, based on the power law, the Carreau model or using an arbitrary user defined expression.
Coupling to Other Physics Interfaces
Often, you may be simulating applications that couple fluid-flow to another type of phenomenon described in another physics interface. Although this is not often another type of flow, it can still involve interfaces supported in the CFD Module and COMSOL Multiphysics base package. This is especially in case of applications that include chemical reactions and mass transport, as covered in Chemical Species Transport Branch, or energy transport, found in Heat Transfer Branch.
More extensive descriptions of heat transfer, such as involving radiation, can be found in the Heat Transfer Module, while tools for modeling chemical reactions and mass transport are in the Chemical Reaction Engineering Module.
T H E M E C H A N I S M S F O R M O D E L I N G M U L T I P H A S E F L O W | 189
T h e L a m i n a r F l o w , T w o - P h a s e , L e v e l S e t a n d P h a s e F i e l d I n t e r f a c e s
The following sections list all the physics interfaces and the features associated with them under the Multiphase Flow branch (
). The descriptions follow a structured order as defined by the order in the branch. Because many of the interfaces are integrated with each other, some features described also cross reference to other interfaces.
• Selecting the Right Interface
See Also
This section includes these topics:
•The Laminar Two-Phase Flow, Level Set Interface
•The Laminar Two-Phase Flow, Phase Field Interface
•Domain Level Settings for the Level Set and Phase Field Interfaces
•Fluid Properties
•Volume Force
•Gravity
•Initial Values
•Boundary Conditions for the Level Set and Phase Field Interfaces
•Wall
•Initial Interface
|
• Mathematics, Moving Interface Branch |
See Also |
• The Turbulent Flow, Two-Phase, Level Set and Phase Field Interfaces |
|
190 | C H A P T E R 6 : M U L T I P H A S E F L O W B R A N C H