摘要
同轴射流广泛应用于航空航天领域,目前基于线性机制的理论模型对预测射流波包和噪声普遍存在局限性,非线性效应已成为研究热点。本文通过在线性抛物化稳定性方程(PSE)右端项中加入外部激励项,研究了亚声速同轴射流中非线性对波包演化的作用。当前工作主要聚焦于考察同轴射流中的波包特性,因为其存在两个剪切不稳定模态。基于同轴射流的基本流,采用求解线性PSE构建了线性波包,进一步通过求解伴随PSE方程得到了总体扰动能量对外部激励的敏感性。结果表明敏感性区域和流动较大响应区域均对应于内外临界层附近,且二者对外部激励均十分敏感,在下游区域可以看出,内外两个失稳模态之间存在一定程度的相互作用。最后,采用伴随优化的方法获得了关于外模态的最优激励,且施加最优激励之后波包得以更快速的增长。
Coaxial jets are widely applied in Aeronautics and Astronautics.However great limitation generally exists for predicting wavepackets and noise by theoretical models based on linear mechanisms,and the effect of nonlinearity has become a research hotspot recently.The effects of nonlinearity on wavepackets in subsonic coaxial jets with different velocity ratios are studied by adding external harmonic forcing to linear Parabolized Stability Equations(PSE).The present work focuses on investigating wavepacket model of coaxial jets due to the fact that there are two distinct shear layer modes.With the mean flow of coaxial jets,the linear model of wavepackets based on PSE is constructed,while the sensitivity of total disturbance energy with respect to external forcing is obtained by solving the adjoint PSE(APSE).The results show that the sensitivity and flow response reach their maximum around the inner and outer critical layers,both of them turn out to be sensitive to external forcing,while the mutual influence between two instability modes can be identified in the downstream region.Finally,the optimal forcing for the outer mode is obtained using an APSE based optimization methodology,giving rise to more rapid growth of wavepackets.
作者
张星辰
徐光春
万振华
孙德军
ZHANG Xingchen;XU Guangchun;WAN Zhenhua;SUN Dejun(Department of Modern Mechanics,University of Science and Technology of China,Hefei 230027,China;State Key Laboratory of Aerodynamics,China Aerodynamics Research and Development Center,Mianyang 621000,China)
出处
《空气动力学学报》
CSCD
北大核心
2020年第2期326-338,共13页
Acta Aerodynamica Sinica
基金
国家自然科学基金(11772323,91952103,11621202)
气动噪声控制重点实验室开放课题(ANCL20190102)
空气动力学国家重点实验室开放课题(SKLA20180205)。
关键词
同轴射流
波包
伴随
coaxial jets
wavepackets
adjoint
