Time domain implementation of a spectral non-reflecting boundary condition for unsteady turbomachinery flows

We show the implementation of a spectral, non-reflecting boundary condition (NRBC) for time marching, unsteady simulations of flows in turbomachinery com- ponents. It is well known that reflections from artificial boundaries can impair the prediction of unsteady flow phenomena. In the context of turbomachinery flows, some frequency domain methods address this issue by means of spectral NRBC. Since these NRBC are non-local in space and time, their implementation in time domain solvers is not straightforward. We elaborate on these difficulties and on how we deal with them. Applications of the NRBC to a two-dimensional flutter configuration and to the prediction of rotor-stator interactions of a real fan configuration are shown. The most important feature of the presented method is the combination of increased robustness and good reflection properties