超临界层流机翼边界层及气动特性分析

Analysis of the Boundary Layer and Aerodynamic Characteristics of a Supercritical Laminar Wing

高空长航时无人机设计巡航状态的雷诺数较小,黏性边界层对气动特性的影响较大。详细分析了雷诺数对机翼边界层和气动力的影响,用数值方法对超临界层流机翼三维层流-转捩-湍流混合边界层特性进行了研究,分析比较了高空小雷诺数和中空大雷诺数情况下机翼三维边界层的特性,尤其是边界层转捩点位置、表面摩阻和气动特性的雷诺数效应。研究表明雷诺数对于高空无人机机翼边界层厚度、摩擦阻力和升阻比影响较大;对层流机翼的转捩点位置和升力系数影响较小;自然层流机翼技术可以应用于高空无人机设计。

Reynolds number of high altitude long endurance (HALE) UAV in cruise state is small, thus the viscous effects on boundary layer and aerodynamic performance are serious. In this paper, the effects of Reynolds number on the boundary layer and aerodynamic characteristics of a supercritical laminar wing are presented. The laminar-transition-turbulent characteristics of three-dimensional boundary layers of the wing are investigated by using a numerical method. The effects of Reynolds number on boundary layer characteristics, and especially on the transition location and skin friction drag, are compared under high altitude lower Reynolds number and middle altitude high Reynolds number situations to analyze the effects in detail. The investigation shows that Reynolds number seriously affects the thickness of boundary layer, the skin friction drag and the ratio of lift to drag of HALE UAV, but has only a little effect on the boundary layer transition and lift coefficient. Thus the laminar wing technology can be used in HALE UAV design.