快速上仰翼型的非定常前缘分离研究

AN INVESTIGATION OF UNSTEADY LEADING EDGE SEPARATION OF RAPIDLY PITCHED AIRFOILS

近几年,国外对翼型快速上仰运动进行了许多实验和理论研究,最大迎角可达60°以上,目的是探索如何利用由此产生的非常大的非定常气动力(如战斗机的超机动飞行)。研究的重点放在“动力失速问题”上,这时,称之为“动力失速涡”的“前缘涡”早已形成并向下游推移。但是,至今动力失速的确切原因和过程仍未被很好地了解。

The unsteady laminar flow separation phynomenon near the leading edge of an rapidly pitched airfoil at a constant rate is investigated computationally. The diffential-integral method, which is used to compute zonally unsteady flow field in this paper, can handle any flow region surrounding the airfoil, involving reversed separation lines. The emphasis is on studying flow behavior and features in the vicinity of the separation point, according to computed results. Three airfoil shapes, NACA 0012, NACA 0015 and unsymmetric SIKORSKY SC-1095 are studied. Finally, some relationship between shape factors and the leading edge separation is established, and a practical criterion is proposed.