C O N S I S T E N T A N D I N C O N S I S T E N T S T A B I L I Z A T I O N

To display this section, click the Show button () and select Stabilization. This section contains the settings for stabilization of the momentum transport (the fluid flow) in the Momentum transport area and stabilization of the equation for the dispersed phase in the Gas phase transport area.

Isotropic diffusion (Shock capturing, O(h2) requires a scale for the effective gas density. An appropriate scale is then the maximum value of the gas volume fraction.

D I S C R E T I Z A T I O N

To display this section, click the Show button () and select Discretization. Select a

Discretization of fluids—P2+P1 (the default) or P3+P2.

The Turbulent Bubbly Flow Interface

The Turbulent Bubbly Flow interface (), found under the Multiphase Flow>Bubbly Flow branch () in the Model Wizard, has the equations, boundary conditions, and volume forces for modeling turbulent two-phase flow a mixtures of liquids and gas bubbles, solving for the fluid velocities, the pressure, the averaged volume fraction occupied by each of the two phases, as well as the turbulent viscosity.

The main feature is the Fluid Properties feature, which adds the equations for turbulent bubbly flow and provides an interface for defining the fluid materials for the liquid and the gas and the slip velocity model to use.

When this interface is added, these default nodes are also added to the Model Builder— Turbulent Bubbly Flow, Fluid Properties, Wall (the default boundary type, applying Wall

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functions and No gas flux boundary conditions for the liquid and the gas, respectively), and Initial Values.

Right-click the Turbulent Bubbly Flow node to add other features that implement, for example, boundary conditions and volume forces.

•Flow in an Airlift Loop Reactor: Model Library path

CFD_Module>Multiphase_Tutorials>airlift_loop_reactor

Model

I N T E R F A C E I D E N T I F I E R

The interface identifier is a text string that can be used to reference the respective physics interface if appropriate. Such situations could occur when coupling this interface to another physics interface, or when trying to identify and use variables defined by this physics interface, which is used to reach the fields and variables in expressions, for example. It can be changed to any unique string in the Identifier field.

The default identifier (for the first interface in the model) is bf.

D O M A I N S E L E C T I O N

The default setting is to include All domains in the model to define the bubbly flow liquid and gas velocities, pressure, and the averaged volume fraction along with the equations that describe those fields. To choose specific domains, select Manual from the

Selection list.

P H Y S I C A L M O D E L

Specify if the gas concentration is low and whether to solve for the interfacial area or not.

Low Gas Concentration

Select the Low gas concentration check box if the gas volume fractions are low ( g less than a few percent). It is then in general valid to replace the continuity equation in Equation 8-3 with Equation 8-4. This option is selected by default.

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Turbulence Model Type

By default a k- turbulence model is used in the Turbulent Bubbly Flow interface.

This interface changes to a Laminar Bubbly Flow interface when the

Turbulence model type selected is None. See The Laminar Bubbly Flow Tip Interface for details.

Solve For Interfacial Area

To add a transport equation for the bubble density in order to determine the interfacial area, select the Solve for interfacial area check box.

R E F E R E N C E P R E S S U R E

Enter the Reference pressure (pref) in the field. The default value is 101325 Pa (1 atmosphere).

D E P E N D E N T V A R I A B L E S

The dependent variables (field variables) are for the Velocity field, liquid phase; Pressure,

Effective gas density; and Number density, gas phase. The names can be changed but the names of fields and dependent variables must be unique within a model.

The name for the dependent variables for turbulence can also be changed in the

Turbulent dissipation rate, Turbulent kinetic energy, and Reciprocal wall distance fields.

C O N S I S T E N T A N D I N C O N S I S T E N T S T A B I L I Z A T I O N

To display this section, click the Show button () and select Stabilization. This section contains the settings for stabilization of the momentum transport (the fluid flow) in the Momentum transport area, stabilization of the equation for the dispersed phase in the Gas phase transport area, and stabilization for the turbulence variables in the

Turbulence equations area.

Isotropic diffusion (Shock capturing, O(h2) requires a scale for the effective gas density. An appropriate scale is then the maximum value of the gas volume fraction.

When using a turbulence model, streamline and crosswind diffusion are

by default applied to the turbulence equations.

Note

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