Other Boundary Conditions
Empty, Wedge
OpenFOAM does not have two-dimensional or axisymmetric mesh. A three-dimensional mesh with one layer in the height direction and Empty boundary conditions on the top and bottom faces becomes a two-dimensional problem. A wedge-oriented three-dimensional mesh with one layer in the rotation direction and Wedge boundary conditions on both sides becomes an axisymmetric problem.
Symmetry
Use for boundary surfaces with symmetry conditions.
Interface
A condition that describes the relationship between two boundary surfaces. It is used when there are two boundary surfaces at the same location. It is used on boundary surfaces that have no thickness inside the computational domain and through which flow passes, or on cell zone boundaries. The mesh of the two paired boundary surfaces do not need to match.
There are three types of interfaces: Internal Interface, Rotational Periodic, and Translational Periodic.
Use openfoam’s cyclicAMI condition.
Cyclic
interface, but the two paired mesh must match completely.
Porous Jump
Porous Jump is a condition that causes a pressure change in a cyclic plane inside the computational domain.
The inputs are as follows
- Darcy Coefficient, $D$
- Inertia Coefficient, $I$
- Porous media thickness, $L$
- Coupled boundary
Positive values of the Darcy Coefficient and Inertial Coefficient result in a pressure drop and negative values result in a pressure increase.
The pressure change is calculated by the following equation where $mu$ is the viscosity, $rho$ is the density, and $U$ is the velocity.
$\Delta p = -\left(D \mu U + \frac{1}{2} I \rho U^2 \right)L$
- $\mu$ : viscosity
- $\rho$ : density
- $U$ : velocity
The boundary conditions used by openfoam are porousBafflePressure for pressure and cyclic for everything else.
Fan
Fan is a condition that velocity-pressure curve is used for pressure and velocity calculation. It can be used for the cyclic plane inside the computational domain.
The velocity-pressure curve file can be a text file in csv format with the velocity in the first column and the pressure in the second column.
The boundary conditions used by openfoam are fan for pressure and cyclic for everything else.