• oundary conditions are extremely important. See also Chapter (), where the boundary conditions are described.
• The computational model can be either compressible, or incompressible.
• The typical criteria for using compressible model is the density is varying by , or the Mach number is larger than .
• Within this fan tutorial the fluid flow model is compressible.
• At the inlet the atmospheric total pressure and total temperature are prescribed
• At the outlet outletVent boundary condition is prescribed
• At the rigid walls velocity is zero.
• For rotational components the Multiple Reference Frame (MRF) is used.
• For steady-state computations the initial conditions have no influence to the results.
• For steady-state computations the initial conditions just help to make the case run.

The quantities to be set are following:

• static pressure p
• static temperature T
• velocity vector U
• turbulent kinetic energy k
• specific turbulence dissipation omega

The initial and boundary conditions for all variables are set in files located in directories named by numbers. Typically directory 0 is recommended to start a simulation from. Initial conditions are set in parameter internalField putting the values into the cell centers. At boundaries, initial conditions are set individually by parameter value.

It is useful to keep initial and boundary conditions in e.g. 0.org folder and copy it right before the start of simulation. The initial and boundary condition from 0.org directory are copied to 0:

# cp -r 0.org/* 0