动态失速涡的绝对／对流不稳定性分析

计算了等速上仰ＮＡＣＡ００１２翼型动态失速过程的流场结构，在准定常假设下对失速主涡形成的分离泡进行了绝对／对流不稳定性分析．随攻角增大，失速主涡流场经历了对流不稳定到绝对不稳定的变化．当绝对不稳定区增大到覆盖整个分离泡时，流场从整体稳定转变到整体不稳定，出现涡量二次尖峰状喷发，切断了主剪切层，主涡随之脱体，导致动态失速

Absolute and Convective Instability in Dynamic Stall Vortex

The accurate flow structure of NACA0012 airfoil undergoing a constant rate pitching up motion is calculated. Under the quasisteady hypothesis, the instability of the leading separated bubble formed by flow around NACA0012 airfoil is investigated. As the angleofattack increases, the flow profiles of certain area in the bubble change from convectively unstable to absolutely unstable. When the absolutely unstable area is big enough, the whole leading vortex becomes globally unstable. This global instability causes the second vorticity eruption which breaks the main shear layer and leads to the detachment of the main vortex from the body, i.e., the dynamic stall.