Flow Turbulence Combust (2014) 93:63–92 DOI 10.1007/s10494-014-9534-8 Synthetic Turbulence Generators for RANS-LES Interfaces in Zonal Simulations of Aerodynamic and Aeroacoustic Problems Michael L. Shur · Philippe R. Spalart · Michael K. Strelets · Andrey K. Travin Received: 16 August 2013 / Accepted: 25 February 2014 / Published online: 6 May 2014 © Springer Science+Business Media Dordrecht 2014 Abstract The paper presents the detailed formulation and validation results of simple and robust procedures for the generation of synthetic turbulence aimed at providing artificial turbulent content at the RANS-to-LES interface within a zonal Wall Modelled LES of attached and mildly separated wall-bounded flows. There are two versions of the proce- dure. The aerodynamic version amounts to a minor modification of a synthetic turbulence generator developed by the authors previously, but the acoustically adapted version is new and includes an internal damping layer, where the pressure field is computed by “weight- ing” of the instantaneous pressure fields from LES and RANS. This is motivated by the need to avoid creating spurious noise as part of the turbulence generation. In terms of pure aerodynamics, the validation includes canonical shear flows (developed channel flow, zero pressure gradient boundary layer, and plane mixing layer), as well as a more complex flow over the wall-mounted hump with non-fixed separation and reattachment, with emphasis on a rapid conversion from modeled to resolved Reynolds stresses. The aeroacoustic applica- tions include the flow past a trailing edge and over a two-element airfoil configuration. In all cases the methodology ensures a very acceptable accuracy for the mean flow, turbulent statistics and, also, the near- and far-field noise. Keywords Zonal RANS-LES · Turbulent content at RANS-LES interface · Attached and mildly separated flows · Aeroacoustics M. L. Shur · M. K. Strelets () · A. K. Travin Saint-Petersburg State Polytechnic University, Saint-Petersburg, Russia e-mail: strelets@mail.rcom.ru M. L. Shur · M. K. Strelets · A. K. Travin New Technologies and Services, LLC, Saint-Petersburg, Russia P. R. Spalart Boeing Commercial Airplanes, Seattle, USA