Wake Evolution of High-Lift Configuration from Roll-Up to Vortex Decay

Abstract

The development of aircraft’s wake in high-lift configuration is studied from the rollup until vortex decay. An aircraft model and the surrounding flow field obtained from high-fidelity Reynolds-averaged Navier-Stokes simulation are swept through a ground-fixed computational domain to initialize the wake. After the wake initialization, the large-eddy simulation (LES) of the vortical wake is performed until vortex decay. In this paper we consider an aircraft model in high-lift configuration where flaps and slats are deployed. In a few wingspan lengths downstream, the complex vorticity structures of the aircraft wake focus on co-rotating vortex pairs originated from wing- and flap-tips. Each co-rotating vortex pair merges at t∗= 0.25 and a common counter-rotating vortex pair is formed at around t∗= 1.0 entraining the turbulent wake into the vortex system. The rolled-up vortex has axial velocity in the vortex core whose magnitude is a half of the maximum tangential velocity. Behaviors of the formed vortex pair are similar to those of a typical vortex pair defined by a vortex model such as the Lamb-Oseen model. The descent speed of the vortices is slightly faster than that of the reference descent speed, i.e., w = 1.1w0. In addition it is confirmed that the ambient turbulence accelerates vortex linking and decay as in the case of a typical vortex pair. The overall behavior of wake vortices is not affected by the difference of mesh resolution considered here, except for vortex core radius.