Numerical Investigation of Unsteady Transonic Shock/Boundary-Layer Interaction for Aeronautical Applications

Abstract

The presented research work deals with numerical simulation of 2-D and 3-D unsteady transonic flows typical for aircraft aerofoils and wings. The analysis focuses on periodic shock motion caused by the unsteady shock/boundary-layer interaction and the subsequent alternating boundary layer separation, occurring on stationary geometries and under constant free-stream conditions (shock-buffet). This mechanism can play an important role in the aeroelastic excitation of large-span wings of modern aircraft. Shock-buffet is investigated using three different 2-D aerofoils, two symmetrical (NACA 64A010 and 0012) and one supercritical (NLR 7301), and a generic 3-D wing-nacelle-pylon configuration. In the investigation the DLR-Tau code, a time-accurate hybrid RANS/DES flow solver, is used and the simulation results serve to: (a) gain insight into the underlying physics of shock-buffet excitation mechanisms, (b) assess the sensitivity of shock buffet to variation of flow parameters, (c) analyse the role of profile geometry, (d) study the influence of modelling parameters (turbulence modelling, temporal resolution).

From the analysis of numerical results a comprehensive analytical theory of shock-buffet is introduced, based on convective and acoustic mechanisms, and validated against the results of CFD simulations. At the end, an appropriate procedure for finding the shock-buffet onset boundary by the means of numerical simulations is proposed.