Consistent boundary conditions for integrated RANS/LES simulations: Les inflow conditions

The increasing complexity of flow problems computed with numerical methods calls for the usage of hybrid approaches of Reynolds-averaged Navier Stokes (RANS) flow solvers and Large eddy Simulations (LES). Many flow solvers are developed using either RANS or LES. One possibility to combine these approaches is to let these separate flow solvers run simultaneously and exchange information at the interface. Considering a RANS domain upstream and an LES domain downstream, one of the arising problems is how to define transient LES inflow boundary conditions from the statistical RANS data at the outlet of the RANS domain. In this paper, an already existing approach of creating a data base from an auxiliary LES computation of a turbulent pipe flow prior to the actual LES computation is adapted for use in integrated RANS/LES computations. It is then furthermore refined in order to transmit amplitude and phase of a transient perturbation over the interface.