Hi,
I would like to inquire if there is a specific meaning or physical concept behind the “Boundary Conditions in Flow Direction” in FlowDict module.
I noticed that the “Boundary Conditions in Flow Direction” can be set to "Periodic" in FlowDict. However, for the simulation model, the voxel size in the flow direction (e.g., the Z-direction) should be constrained and should not be periodically repeated. Otherwise, the thickness of the simulation model may change.
I am wondering if this setting affects the thickness of the model.

Best regards,
Danny

Hi Danny,

the Boundary Conditions in Flow Direction define how the flow enters and leaves your structure depending on the chosen flow directions.

The Periodic boundary condition repeats the structure periodically before the inflow and after the outflow plane. In the example shown below this option does not work since there is no connected flow path. This option works best for periodic structures and structures with high porosity. We recommend using periodic boundary condition when possible, as the computational memory requirements are comparatively low leading to shorter runtimes.


The Symmetric boundary condition mirrors the structure at the inflow and outflow plane. This option works well for low porosity structures because the pores remain connected due to the mirroring.


The Velocity inlet, Pressure outlet boundary conditions apply a constant flow velocity in the inlet and a constant pressure drop in the outlet.


All the options described above do not change the thickness of your model. The option Add implicit region adds voxel before the inflow plane and after the outflow plane. This option changes the thickness of the structure and influences the final simulation result.


I hope this clarifies your question.
Please let me know if anything is unclear or if you have any further questions.

Kind regards,
Jonas