Three-Dimensional Laminar-Separation Bubble on a Cambered Thin Wing at Low Reynolds Numbers

摘要

Three-dimensional laminar-separation bubbles on a cambered thin wing with an aspect ratio of 6 at a Reynolds number of 60,000 have been investigated by solving the Reynolds-averaged Navier-Stokes equations. The k-ω shear-stress transport y-Re_θ turbulence-transition model is used to account for the effect of transition on the laminar separation-bubble development The aerodynamic forces are compared with the experimental data available for validation. The laminar-separation bubble is shown to evolve in its shape and dimension in both chord and span directions with increasing incidence due to its interaction with the wing-tip flow and the trailing-edge separation. The strongest three-dimensional effects are found at a moderate incidence of 6 deg and at higher incidences beyond 10 deg. Within the incidence range, the two-dimensional airfoil results are not reproduced at any of the span locations, including the symmetry plane, in the three-dimensional wing case. Generally, the chord wise development of the three-dimensional laminar-separation-bubble at the symmetry plane is delayed as compared with the two-dimensional laminar-separation bubble. Another noticeable point is the association of a sudden increase in lift-curve slope due to abrupt expansion of the laminar-separation bubble at a certain incidence. This phenomenon is observed in both the two- and three-dimensional cases, but at different incidences.