Flow Patterns and Aerodynamic Performance of Unswept and Swept-Back Wings

摘要

The effects of sweep-back angle (LAMBDA), Reynolds number (Re), and angle of attack (alpha) on the boundary-layer flow structures and aerodynamic performance of a finite swept-back wing were experimentally investigated. The Reynolds number and sweep-back angle used in this test is 30,000 < Re < 130,000 and 0 deg <= LAMBDA <= 45 deg. The wing model was made of stainless steel, and the wing airfoil is NACA 0012. The chord length is 6 cm, and the semiwing span is 30 cm; and therefore, the semiwing aspect ratio is 5. The boundary-layer flow structures were visualized using the surface oil-flow technique. Seven boundary-layer flow modes were categorized by changing Re and alpha. A six-component balance is used to determine aerodynamic loadings. The aerodynamic performance is closely related to the boundary-layer flow modes. The stall angle of attack ((alpha)_(stall)) is deferred from 9 deg to 10 deg (for an unswept wing), to 30 deg to 35 deg (for a swept-back wings of LAMBDA > 30 deg). The deferment of (alpha)_(stall) is induced from the increased rotation energy and turbulent intensity generated from the secondary flow. Furthermore, the increased rotation energy and turbulent intensity resisted the reverse pressure generated at high alpha.