
The following recommendations appear under the Boundary Conditions tab (Figure 25.21.5):
For geometry that is axisymmetric or axisymmetric swirl (as set in the Solver panel), the centerline (xaxis) boundary type should be set to axis. See Section 7.16.
Define Boundary Conditions...
This boundary condition is intended for incompressible flows, and its use in compressible flows will lead to a nonphysical result because it allows stagnation conditions to float to any level (see Section 7.4). If you decide to select a different boundary type, go to the Boundary Conditions panel.
Define Boundary Conditions...
Outflow boundary conditions in FLUENT are used to model flow exits where the details of the flow velocity and pressure are not known prior to solution of the flow problem. One of the limitations when using outflow boundary conditions is that outflow boundary conditions are not compatible with pressure inlets. Therefore, it is recommended that you use velocity or mass flow inlets instead of pressure inlets when used in combination with outflow boundaries. See Section 7.10 for a list of limitations that exist with outflow boundaries.
Define Boundary Conditions...
Outflow boundaries cannot be used if you are modeling unsteady flows with varying density, even if the flow is incompressible. See Section 7.10 for more limitations that exist with outflow boundaries.
Define Boundary Conditions...
For cases that have density specified as the ideal gas law, and the operating pressure is greater than zero, the operating pressure will be added to the gauge pressure to yield the absolute pressure. For more information, see Sections 8.3.6 and 8.14.2.
Define Operating Conditions...
In compressible flows , isentropic relations for an ideal gas are applied to relate total pressure, static pressure, and velocity at a pressure inlet boundary. Your input of total pressure, , at the inlet and the static pressure, , in the adjacent fluid cell are related, as described in Equations 7.36 and 7.37 of Section 7.3.3. It is recommended that pressure boundary conditions are not set to zero for compressible flows that use the ideal gas law.
Define Boundary Conditions...
If your case setup has any of the turbulence models enabled, be sure to review the default parameters for the K and Epsilon Turbulence Specification Method in the outlet and inlet boundary conditions. FLUENT's default parameters for the Backflow Turb. Kinetic Energy and Backflow Turb. Dissipation Rate are 1. You can either adjust the values, or select a different Turbulence Specification Method. For general information turbulence parameters, see Section 7.2.2.
Define Boundary Conditions...
When the Shell Conduction option is enabled in the Wall boundary condition panel, FLUENT will compute heat conduction within the wall, in addition to conduction across the wall. therefore, you must specify a nonzero Wall Thickness in the Wall panel, because the shell conduction model is relevant only for walls with nonzero thickness. See Section 7.13.1 for information on shell conduction in thin walls.
Define Boundary Conditions...
When enabling the VOF model, the Volume Fraction in the inlet and outlet boundary conditions for each phase should be set either to 0 or 1. No intermediate values are permitted. For general information on boundary condition setup, see Section 23.9.8.
Define Boundary Conditions...
You cannot assign an outflow boundary conditions when using the mixture and Eulerian multiphase models. Note the limitations of this boundary condition in Section 7.10. FLUENT can model the effects of open channel flow using the VOF formulation. In such a case, outflow boundary conditions can be used at the outlet of open channel flows, to model flow exits where the details of the flow velocity and pressure are not known prior to solving the flow problem. See Section 23.3.9, under the heading Outflow Boundary, for more information.
Define Boundary Conditions...
In cases where the fluid zone motion type is specified as Moving Mesh or Moving Reference Frame, all wall zones should be set to Moving Wall in the Momentum tab of the Wall boundary conditions panel. The wall motion should be defined Relative to Adjacent Cell Zone. The exception to this is if the walls are stationary in the absolute frame. To define wall motion, see Section 7.13.1.
Define Boundary Conditions...
If selecting either Moving Mesh or Moving Reference Frame in the Fluid boundary condition panel, be sure to set nonzero values for the rotational and translational velocities. Refer to Section 7.17.1 for user inputs.
Define Boundary Conditions...
For massflowinlet and velocityinlet boundary conditions, the default values in FLUENT are and , respectively. Review the settings and adjust accordingly. See Sections 7.4.2 and 7.5.2 for default parameters of velocity inlets and mass flow inlets, respectively.
Define Boundary Conditions...