Boundary conditions are required to 'close' the simulation problem. Careful attention should be applied to their selection so as to create a well-posed system of equations, which can be solved numerically.
The set of available Boundary conditions comprise of basic, turbulent and thermophysical types.
Wall-functions in OpenFOAM are modelled as boundary conditions, applied to the viscosity for momentum, and thermal diffusivity for energy.
Wall-functions
Thermal wall-functions for incompressible flow
Thermal wall-functions for compressible flow
The choice as to the most appropriate set of boundary conditions is dictated by the type of flow problem. In many cases, multiple possible selections exist; the following tables offer suggestions for subsonic flow.
subsonic inlet (flow specified):
Variable | Symbol | Type |
---|---|---|
pressure | p | zeroGradient |
velocity | U | fixedValue |
transported property | - | fixedValue |
derived property | - | calculated or zeroGradient |
subsonic outlet:
Variable | Symbol | Type |
---|---|---|
pressure | p | fixedValue |
velocity | U | inletOutlet or pressureInletOutletVelocity |
transported property | - | inletOutlet |
derived property | - | calculated or zeroGradient |
wall (impermeable, non-slip):
Variable | Symbol | Type |
---|---|---|
pressure | p | zeroGradient |
velocity | U | fixedValue |
transported property | - | fixedValue |
derived property | - | calculated or zeroGradient |