具前緣突節翼形之氣動力性能模擬計算

Abstract

本文主要使用計算流體力學模擬探討突節外形的參數對翼前緣具突節之翼形的性能影響。以NACA0012做為主體翼形。本文針對不同的振幅、波長、翼展長度、突節個數進行計算解析，以了解各項參數變化時，對翼形性能之影響。使用週期性邊界探討波長與振幅的對於空氣動力性能的影響，以及在有限翼展下，分析波長、翼展長度、突節個數對於性能的影響統整不同展弦比下空氣動力性能的影響。計算結果顯示，無限翼展長度下；最大升力係數隨波長增加而增加。有限翼展長度下；固定展弦比，失速攻角、失速時升力係數、最大升力係數由流場可視化顯示，翼前緣波形突節翼形產生渦流增加動能向邊界層輸入能量，使氣流持續附著在升力面上保持層流狀態避免紊流產生，渦流動力供應維持或增加升力用以阻止失速，阻止氣流過早分離。

This study employs computational fluid dynamics (CFD) to investigate the effects of protuberances of varying geometric parameters on the performance of an airfoil with leading edge protuberances. The NACA 0012 airfoil is adopted as the baseline airfoil, and the geometric parameters are amplitude, wavelength, spanwise length, and number of protuberances.The results show that for an infinite wing, maximum lift coefficient increase with an increase in protuberance wavelength. For a finite wing, fixed aspect ratio, stall angle of attack, and stall lift coefficient all increase with the wavelength. As illustrated by flow visualizations, the leading edge protuberances generate vortices which impart kinetic energy to the boundary layer, such that the air remains attached to the suction surface of the wing, thereby maintaining laminar flow and avoiding turbulence. The kinetic energy from these vortices maintains or increases lift, and may be used to prevent stall by delaying separation.