Visualization and PIV study of wing-tip vortices for three different tip configurations

The planform, profile, and cross-sectional views of the wing-tip region of a half-wing model with an aspect ratio of 3.2 and three different wing configurations, namely, square-cut, simple fairing, and Whitcomb?s full winglet wing-tip, were visualized at various angles of attack using smoke-wire visualization technique. Visualization pictures clearly show that the wing-tip vortices at different angles of attack and wing-tip configurations had distinct formation and structure characteristics. A comparison of simple fairing and Whitcomb?s winglet configurations shows that the wing-tip vortices of the Whitcomb?s winglet configuration were reduced in strength and displaced outboard and upward, at least in the near-wake region. This resulted in an increased lift-to-drag ratio for the Whitcomb?s winglet configuration. The changes in the wing-tip vortex characteristics and the improved aerodynamic performance of the winglet were confirmed by Particle Image Velocimetry (PIV) measurements of the cross-flow velocity of the wing-tip trailing regions and the force measurement of the model.     

MODAL DISCONTINUOUS GALERKIN METHOD FOR SHOCK WAVE STRUCTURES

The discontinuous Galerkin （DG） finite element method has been popular as a numerical technique for solving the conservation laws, In the present study, in order to investigate the shock wave structures in highly thermal nonequilibrium, an explicit modal cell-based DG scheme is developed for solving the conservation laws in conjunction with nonlinear coupled constitutive relations （NCCR）. Convergent iterative methods for solving alge- braic constitutive relations are also implemented in the DG scheme. It is shown that the new scheme works well for all Mach numbers, for example, Ma = 15.