Outflow Conditions for Integrated Large Eddy Simulation/Reynolds-Averaged Navier–Stokes Simulations

The numerical flow prediction of highly complex flow systems, such as the aerothermal flow through an entire aircraft gas turbine engine, requires the application of multiple specialized flow solvers, which have to run simultaneously in order to capture unsteady multicomponent effects. The different mathematical approaches of different flow solvers, especially large eddy simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) flow solvers, pose challenges in the definition of boundary conditions at the interfaces. Here, a method based on a virtual body force is proposed to impose Reynolds-averaged velocity fields near the outlet of an LES flow domain in order to take downstream flow effects computed by a RANS flow solver into account. This method shows good results in the test case of a swirl flow, where the influence of a flow contraction downstream of the LES domain is represented entirely by the Reynolds-averaged velocity field at the outlet of the LES domain.