Introduction
An OpenFOAM case is a structured description of a physical problem and the numerical method used to solve it.
Understanding that structure allows you to explain the simulation, modify it deliberately, and diagnose errors more effectively.
Learning objective
Locate the principal case settings and explain how they define the physical and numerical model.
Key idea
A simulation is defined by the combination of geometry, fluid properties, boundary conditions, physical models, and numerical settings.
Understand the idea
A typical OpenFOAM case contains three main directories:
- 0: initial field values and boundary conditions.
- constant: mesh information and physical or model configuration.
- system: execution controls, numerical schemes, and solution settings.
The exact files depend on the OpenFOAM version and the case.
For the MRF setup, identify the rotating cell zone and the settings defining its origin, axis, and speed.
Also inspect the boundary conditions. The inlet and outlet determine how the system exchanges fluid with its surroundings. Wall conditions must consistently represent which physical surfaces rotate and which remain stationary.
Check units as carefully as numerical values. For example, pressure-related fields may represent different quantities depending on the solver.
Engineering example
Trace the inlet from the mesh boundary definition to the field files.
Confirm that its name matches and explain what each boundary condition imposes. Then repeat the exercise for the outlet and rotor walls.
This connects configuration entries to physical surfaces rather than treating the files as isolated settings.
Practical task
Create a table with these columns:
Parameter | Value | Units | File location | Physical meaning
Include the fluid properties, rotation settings, inlet conditions, outlet conditions, and turbulence model if one is used.
Checkpoint
Can an incorrectly configured case still run without reporting a software error?
Yes. A case can be syntactically valid while representing the wrong physical problem. Successful execution does not establish that its boundary conditions or model choices are appropriate.
References
- OpenFOAM User Guide
- The configuration files and README supplied with the starter.