Mach number effects on buffeting flow on a half wing-body configuration

Abstract

Purpose The purpose of this paper is to discuss a numerical study of the flow over a wing representative of a large civil aircraft at cruise condition. For each Mach number considered, the numerical simulations indicate that critical angle of attack exists where the separated region increases in size and begins to oscillate. This phenomenon, known as transonic shock buffet, is reproduced by the unsteady simulation and much information can be extracted analysing location, amplitude and frequency content of the unsteadiness. Design/methodology/approach Reynolds-averaged Navier-Stokes simulations are conducted on a half wing-body configuration, at different Mach numbers and angles of attack. Different turbulence models are considered, and both steady-state results and time-accurate simulations are discussed. Findings The high number of cases presented in this study allows the creation of a database which, to the authors’ knowledge, has not been documented in literature before. The results indicate that, while high-fidelity approaches can improve the quality of the results, the URANS approach is capable of describing the main features of the buffet phenomenon. Research limitations/implications The presence of a turbulence model, despite allowing the description of the main unsteady phenomenon, might be insufficient to fully characterise the unsteadiness present in a transonic flow over a half wing-body configuration. Therefore, researchers are encouraged to verify by means of experimental investigation or high-fidelity approach the results issued from a Reynolds-averaged Navier-Stokes equations. Practical implications The results presented clearly indicate that, despite what proposed in recent research papers, transonic buffet can be described by means of time-accurate Reynolds-averaged Navier-Stokes equations. Such an approach is popular in the aeronautical industry because of its reduced costs, and could be used for wing design. Originality/value In this paper, the authors used a classical approach to tackle the known problem of transonic buffet in three-dimensional configurations. The large number of results presented can be used as a database for future numerical simulations and experiments, and allow to describe the flow-physics of the buffet unsteadiness on a half wing-body configuration.