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On the Importance of Accurate Simulation of Attached Boundary Layers in the Frame of Hybrid RANS/LES & WMLES

AMS Seminar Series

Speaker: Sébastien Deck & Nicolas Renard, ONERA

Presentation

Seminar Slide Deck (PDF-3.3MB)

Abstract

CFD is playing an ever-expanding role in aerospace and enhancing its capabilities to predict unsteady turbulent flows is considered as a major objective to the field. The oral presentation will revolve around the major question of the treatment of attached boundary layers in the frame of high Reynolds number applications. The first option consists in modelling boundary layers fully in RANS mode while separated regions are resolved in LES. To obtain a practical hybrid RANS/LES approach, a robust RANS shielding function is mandatory which has been difficult to achieve independently from the grid refinement and pressure gradient. To overcome this serious issue in applied aerodynamics, we present here a complete and automatic (i.e., without user input) solution to this problem, namely the ZDES mode 2 (2020) technique (Deck & Renard, J.Comp.Phys., 2020). The second option consists in resolving turbulence in the outer part of the boundary layer which is classically referred to as WMLES. The accurate simulation of boundary layers raises a host of technical issues (e.g., turbulence injection around complex geometries within compressible flow solvers). The weight of the turbulence model in hybrid RANS/LES context with or without a wall law will be discussed especially with regard to the prediction of skin friction.

Biography

Photo of Sébastien Deck
Sébastien Deck (Ph.D.) is currently Research Director at ONERA, the French Aerospace Lab, and is leading the Advanced Turbulence Modeling and Simulation research unit of the Aerodynamics, Aeroelasticity, Acoustics Department. His expertise in the prediction of dynamic loads around space launcher configurations has led him to develop advanced turbulence modelling approaches. He is the author of Zonal Detached Eddy Simulation (ZDES) and has been developing this multi-resolution approach with his group since the early 2000’s. His main topics of interest concern high Reynolds number wall turbulence and separating/reattaching flow dynamics at all Mach numbers.

Photo of Nicolas Renard
Nicolas Renard (Ph.D.) is currently Research Scientist at ONERA, the French Aerospace Lab, in the Advanced Turbulence Modeling and Simulation research unit of the Aerodynamics, Aeroelasticity, Acoustics Department. His main topics of interest concern hybrid RANS/LES modelling as well as the physics of wall turbulence at high-Reynolds numbers. His major field of expertise is the turbulent skin friction and especially its decomposition into physical mechanisms. He is contributing to the development of the different flavours of ZDES in close connection with Sébastien Deck and has a strong interest towards aeronautical applications.