| Popis: |
In the current study the vorticity confinement approach was applied to tip vortices shed by edges of stationary wings in order to predict induced drag by far-field integration in Trefftz plane. The vorticity confinement parameter was evaluated first by application to convection of vortices in uniform flow and then to tip vortices shed by finite-aspect ratio rectangular wing in subsonic flight. Dependence of vorticity confinement parameter on the flight Mach number and the angle of attack was evaluated. The aerodynamic drag results with application of vorticity confinement are much more close to analytic lifting line theory compared to integration over surface of wing. While the viscous profile drag is more accurately evaluated by surface integration, the induced drag needs to be evaluated in the far field by applying vorticity confinement to prevent its numerical diffusion by upwind schemes. To apply vorticity confinement to viscous and turbulent flows, it is shown that vorticity confinement does not affect the physical rate of dissipation of vortices in viscous/turbulent flows at time scales corresponding to convection of vortices from the wing to Trefftz plane of integration. To account for turbulent effects on tip vortices, vorticity confinement was applied in combination with Spalart-Allmaras, k-e, and six Reynolds stresses models of turbulence. |
