Transit time difference and equal or non-equal transit time theory for airfoils with lift  

作　　者：Chenyuan BAI Ziniu WU 

机构地区：[1]Ministry of Education Key Laboratory of Fluid Mechanics,Beihang University,Beijing 100083,China [2]Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China

出　　处：《Chinese Journal of Aeronautics》2022年第2期8-11,共4页中国航空学报（英文版）

基　　金：supported partly by the National Key Project of China(No.GJXM92579);the National Science and Technology Major Project of China(No.2017-II-003-0015);the National Natural Science Foundation of China(No.11721202)。

摘　　要：The transit time difference of fluid particles moving along the upper and lower surfaces of a lift-producing airfoil is studied here both theoretically and numerically.We show that,under thin airfoil assumption and for potential flow,the transit time difference is equal to the circulation divided by the square of the inflow velocity and the lift coefficient is equal to half of the number of chords travelled by the airfoil during the transit time difference.An analysis of transit time difference for very thick airfoil(c.f.very large angle of attack)suggests the transit time may change sign beyond thin airfoil assumption,a conclusion supported by an example of flow with an attached vortex.Thus,fluid particles may transit the upper surface with less,equal and more time than those transiting the lower surface for lift producing airfoils,depending on the configuration of flow structure and geometry.

关 键 词：AIRFOIL Equal transit time theory LIFT Non-equal transit time theory Transit time 

分 类 号：V211.41[航空宇航科学与技术—航空宇航推进理论与工程]