7.4 Non-Reflecting Boundary Conditions

The standard pressure boundary condition, imposed on the boundaries of artificially truncated domain, results in the reflection of the outgoing waves. As a consequence, the interior domain will contain spurious wave reflections. Many applications require precise control of the wave reflections from the domain boundaries to obtain accurate flow solutions. Non-reflecting boundary conditions provide a special treatment to the domain boundaries to control these spurious wave reflections.

In ANSYS FLUENT, two types of non-reflecting boundary conditions (NRBC) are available:

• turbo-specific NRBC

• general NRBC

Turbo-specific NRBCs, as the name indicates, are oriented toward turbomachinery types of geometry and are applicable only in steady-state calculations. On the other hand, the general NRBC, can be used in both steady and unsteady calculations, and have no geometric restrictions. Both methods are available in the density-based solver and when the compressible ideal-gas law is used.

NRBCs are not available in the pressure-based solver.