FreeBird User Manual¶
About FreeBird¶
FreeBird is an iRIC solver for 3D open-channel and river flow simulation. It uses a σ-coordinate finite difference method to compute complex flow fields with free surfaces.
OpenMP parallelization is supported for faster computation, enabling practical run times even on large 3D grids.
Features Covered in This Manual¶
Obstacle Cell¶
A solid cell that blocks all vertical layers from the riverbed to the water surface. Use this for structures that completely obstruct the flow, such as bridge piers and revetment foundations.
The Obstacle Top Elevation setting from previous versions has been removed. For partial-height structures, use Structure BC instead.
Structure BC¶
A boundary condition that blocks all σ-layers below a specified crest elevation. Use this for partial-height hydraulic structures such as weirs, sills, and abutments.
| Feature | Details |
|---|---|
| Selection method | Polygon cell selection in plan view |
| Key parameter | Structure Top Elevation (crest elevation) |
| Overflow | Flow passes above the crest elevation |
Structure Culvert¶
A boundary condition that defines a culvert opening through the wall of a Structure BC body. Available in i-direction and j-direction variants.
Quick Start¶
1. Create a grid in iRIC
2. Full-block structures → Set Obstacle Cell in Cell Attributes
3. Partial-height structures → Set Structure BC in Boundary Conditions
4. Structures with culvert → Add Structure Culvert BC
5. Run the simulation