The Euler-Euler Model, Laminar Flow (ee) interface (
), found under the
Multiphase Flow>Euler-Euler Model branch (
) when adding a physics interface, can be used to simulate the flow of two continuous and fully interpenetrating incompressible phases (see
Ref. 1 under the
Theory for the Euler-Euler Model Interfaces). The physics interface can model flow at low and moderate Reynolds numbers. Typical applications are fluidized beds (solid particles in gas), sedimentation (solid particles in liquid), or transport of liquid droplets or bubbles in a liquid.
When this physics interface is added, the following default physics nodes are also added in the Model Builder —
Phase Properties,
Wall, and
Initial Values. Then, from the
Physics toolbar, add other nodes that implement, for example, boundary conditions and volume forces. You can also right-click
Euler-Euler Model, Laminar Flow to select physics features from the context menu.
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern
<name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the
name string must be unique. Only letters, numbers, and underscores (_) are permitted in the
Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is
ee.
When Solid particles is selected, the
Solid Pressure section is available in the
Phase Properties node. Also see
Dispersed Phase in the theory section.
When Solid particles is selected, the
Solid Pressure section is available in the
Phase Properties node. Also see
Dispersed Phase in the theory section.
There are generally two ways to include the pressure in fluid flow computations: either to use the absolute pressure pA = p + pref, or the gauge pressure
p. When
pref is nonzero, the physics interface solves for the gauge pressure whereas material properties are evaluated using the absolute pressure. The reference pressure level is also used to define the density of incompressible fluids.
Turbulent flow can be simulated by changing the Turbulence model type to
RANS, k-ε (Reynolds-Averaged Navier–Stokes,
k-
ε).
To display this section, click the Show More Options button (
) and select
Advanced Physics Options in the
Show More Options dialog box. Normally these settings do not need to be changed.
The Residue volume fraction, continuous phase,
c,res, and
Residue volume fraction, dispersed phase,
d,res, set the smallest values used to avoid division by zero when evaluating terms that involve 1
/c and 1
/d. Observe that this value does not prevent
c or
d from becoming smaller than
c,res and
d,res, respectively.
Select the Use pseudo time stepping for stationary equation form check box to add pseudo time derivatives to the equation when the
Stationary equation form is used. When selected, also choose a
CFL number expression —
Automatic (the default) or
Manual.
Automatic sets the local CFL number (from the Courant–Friedrichs–Lewy condition) to the built-in variable
CFLCMP which in turn triggers a PID regulator for the CFL number. For
Manual enter a
Local CFL number CFLloc (dimensionless).
The Euler-Euler Model, Laminar Flow interface supports three options for the basis functions: P1+P1 (the default option),
P2+P1, and
P3+P2. They all represent Lagrangian basis functions of different orders: