【摘要】 风洞实验观察到高超声速椭圆锥短轴处的转捩位置与其两侧相差很多,这是因为短轴处存在流向涡,基本流与其两侧明显不同,所以短轴处的稳定性与两侧有本质的区别,进而导致转捩位置与两侧不同。本文在短轴处进行二维全局稳定性分析,研究此处的稳定性。使用Arnoldi方法进行计算,并与其它方法结果进行了对比验证。找到了不稳定的外模态,研究了不稳定模态的增长率随频率、波数和流向位置的变化。发现了不稳定模态的产生机理,即由基本流剪切的无粘拐点不稳定性造成。阐明了不存在内模态的原因在于没有符合内模态特性的Fjortoft拐点。更多还原

【Abstract】 In wind tunnel experiment,transition location near minor-axis of hypersonic elliptic cone is quite different from that on each side.This is due to the streamwise vortices near minor-axis, which lead to significant difference of basic flow from that on each side.Consequently,instability near minor-axis has essential difference from that on each side,resulting in different transition locations.In this paper,Bi-Global instability analysis is carried out to investigate the instability near minor-axis.Arnoldi method is employed,and the numerical results are validated by comparing with those calculated through other methods.Unstable outer modes are found,and the variation of their growth is studied against frequency,wavenumber,and streamwise location.The physical mechanism of unstable modes is found that they are caused by inviscid inflection instability of shearing basic flow.Unstable inner mode does not exist,because there is no Fjortoft inflection point corresponding to inner mode characteristic.更多还原