The characteristic type non-reflecting boundary condition (NRBC) is implemented at inflow and outflow boundaries in a pressure based solver on unstructured meshes. The NRBC eliminates artificial reflection from the boundaries of the numerical domain and allows for physically correct behavior of waves propagating out of the domain. The numerical implementation of NRBC is based on the characteristics theory of the Euler and Navier-Stokes equations. The relaxation term included into the incoming wave equations is written in terms of the wave amplitudes to be uniformly applicable at the flow inlets and outlets. The method is applied in transient and steady state formulations. Comparison of numerical results with known analytical solutions for wave propagation in plane, cylindrical and spherical coordinates confirms non-reflecting behavior of this boundary condition formulation.
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