Inlet
The Inlet node adds a set of boundary conditions that describe inlets in fluid-flow simulations.
Mixture Boundary Condition
Select a Mixture boundary condition for the inlet — Velocity (the default) or Pressure.
Velocity
For Velocity click the Normal inflow velocity (the default) or Velocity field buttons.
•
For Normal inflow velocity enter a value or expression for J0 (SI unit: m/s).
•
For Velocity field specify that the velocity at the boundary is equal to a given j0 (SI unit: m/s) and enter the components in the matrix:
Pressure
This condition specifies the normal stress which in most cases is approximately equal to the pressure. Enter the Pressure p0 (SI unit: Pa) at the boundary. The default is 0 Pa. Enter a relative pressure value in p0 (SI unit: Pa). Or if the reference pressure pref defined at the physics interface level is equal to 0 Pa, enter an absolute pressure in p0.
•
The Suppress backflow check box is selected by default. This option adjusts the inlet pressure, , locally in order to reduce the amount of fluid exiting the domain through the boundary. If suppress backflow is deselected, the inlet boundary can become an outlet depending on the pressure field in the rest of the domain.
•
Flow direction controls in which direction the fluid enters the domain.
-
For Normal flow (the default) it prescribes zero tangential velocity component.
-
For User defined define an Inflow velocity direction, dj (dimensionless). The magnitude of dj does not matter, only the direction. dj must point into the domain.
Dispersed Phase Boundary Condition
The default is Dispersed phase concentration. See Wall>Dispersed Phase Boundary Condition for the settings.
See Dispersed Phase Boundary Condition Equations for more information.
Turbulence Conditions
This section is available for Mixture Model, Turbulent Flow interfaces so that the inlet conditions for the turbulence variables can be specified.
No additional inlet conditions are required for the algebraic turbulence models: Algebraic yPlus and L-VEL.
For the Mixture Model, Spalart-Allmaras interface, a value or expression for the Undamped turbulent kinematic viscosity υ0 should be specified. The default value is 3*mm.nu.
For transport-equation turbulence models, apart from Spalart–Allmaras, the following settings are available under the Specify turbulence length scale and intensity option:
•
Turbulent intensity IT
•
Turbulent length scale LT
For the v2-f turbulence model, the additional choice between Isotropic turbulence and Specify turbulence anisotropy appears. For Specify turbulence anisotropy, a value for the turbulent relative fluctuations at the inlet, ζ0, may be specified. When Specify turbulence variables is selected, values or expressions for the dependent turbulence variables should be defined. Availability is based on the physics interface and the boundary condition chosen.
•
Turbulent kinetic energy k0
•
Turbulent dissipation rate ε0
•
Specific dissipation rate ω0
•
Turbulent relative fluctuations ζ0
•
Elliptic blending function α0
The turbulent length scale LT and turbulence intensity IT are related to the turbulence variables, see Theory for the Turbulent Flow Interfaces.
See Inlet in the Single-Phase Flow interfaces