Reconstruction of Turbulent Fluctuations Using a Hybrid RANS/LES Approach

A hybrid RANS/LES approach is presented and assessed considering several flows, which can be interpreted as the most general case of the NLDE approach as defined by Morris et al. [P. J. Morris, L. N. Long, A. Bangalore, and A. Wang, J. Comput. Phys.133, 56 (1997)]. A decomposition into three parts of the exact solution of the Navier–Stokes equations is considered: mean flow, resolved fluctuations, and unresolved (subgrid) fluctuations. The mean flow is computed using a classical RANS method, while resolved fluctuations are derived from a LES method. This approach is succesfully assessed on the stationary and the pulsed plane channel flow configurations. The case of the flow around a low-pressure turbine blade is discussed in a second step. The hybrid method is also demonstrated to be robust with respect to several sources of error and provides good results in the case of a coarsened grid simulation, a reduced computational domain simulation, and nonconsistent mean flow fields.