Synthesis on the unsteady transonic flow around a circular-arc aerofoil (TC8bis)

Abstract

In the context of the ETMA research program, a special emphasis has been devoted in the prediction of unsteady high-speed flows involving solid walls and interesting the aeronautical applications. The inherently unsteady flow around an aerofoil in the transonic regime is examined. The present category of flows develop an inherently unsteady shockinduced separation, followed by the onset of periodic vortex shedding downstream. This is the consequence of the amplification of a von Karman instability downstream the separation point. Furthermore, a second kind of instability may occur in the separated shear layer: This is a shear-layer (Kelvin-Helmholtz) instability, which occurs under the amplification of Tollmien-Schlichting waves. These two possible modes are a typical pattern in many turbulent wakes characterized by a simultaneous development of coherent structures and of a random, fine-scale turbulence background [1]. Under the action of the mentioned mechanisms the present category of turbulence flows, examined in the test-case TC8bis of the ETMA program, need an adapted methodology in order to predict their unsteady dynamic characteristics, which represent a major interest in the domain of aeronautical applications. In this part of the study, essentially the prediction of the effect due to the unsteady shock-induced separation and of the von Karman flow pattern is achieved, according to the physical experiment of Seegmiller, Marvin & Levy [2]. The predictions are carried out by INRIA (partner 1), in cooperation with IMFT (partner 15) and NTUA (partner 10).