Three-Dimensional Transition Features in the Transonic Viscous Flow Around a Wing by Direct Simulation

Abstract

This study investigates the role of compressibility on the amplification of instability and on the establishment of three-dimensional motion in the viscous transonic flow around a wing of constant section, NACA0012, at zero incidence. The study is performed at the Reynolds number 10,000 and in Mach number range 0.2 to 0.98. Firstly, a 2D study is carried out, by using the two-dimensional version of the code developed, in order to identify the classes of instabilities that can be developed as inherently unsteady characteristics. Secondly, a detailed three-dimensional study is performed by focussing on the most predominant instability pattern which implies a shock-vortex interaction. Experimental studies of Dyment et al (1980), Rodriguez (1984) indicate the existence of inherently unsteady phenomena in transonic flows around bodies in transition to turbulence. Especially, phenomena due to shock wave-coherent structures interaction are reported. Due to the increased capabilities of supercomputers nowadays and to the efficient parallelization of the solvers developed in the present study, the investigation of this class of complex phenomena is possible by direct numerical simulation in three dimensions. Therefore, the objectives of the present study are to analyse the mechanisms of onset of threedimensionnality in the transonic regime, for which there are very few studies by this approach, to our knowledge. The Reynolds number range for the 3D study is 3000 and 5000. Moreover, this study focuses on the triple role played by the compressibility effects to enhance, to sustain and to inhibit the developed instabilities.