The full impulse response of two-dimensional jet/wake flows and implications for confinement
The full impulse response of two-dimensional jet/wake flows and implications for confinement
复制标题
二维射流/尾流的完整脉冲响应及其对约束的影响
DOI：
10.1017/s0022112007007975
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发表时间：
2007
影响因子：
3.7
通讯作者：
M. Juniper
中科院分区：
文献类型：
--
作者：
M. Juniper
在这一理论研究中，对无约束和有约束的无粘喷流/尾流进行了线性时空分析，以确定它们是绝对不稳定的还是对流不稳定的。脉冲响应是在整个外部流体中评估的，而不仅仅是在冲量点，在广泛的密度比范围内。这证实了主导鞍点可以有效地迁移到发散本征函数的平面。这表明，在一定的密度比和剪切数下，即使在冲量的上游和冲量点处直接衰减，响应也可以在具有交叉流分量的某些方向上增长。这种流动在无约束时是对流不稳定的，但在有约束时则变得绝对不稳定。禁闭的其他影响已经在以前的一篇论文中进行了描述。总而言之，这些文章对喷油器的设计具有重要的意义，喷油器通常在高雷诺数和大密度比下使用受限剪切流来在燃烧室中产生强烈的混合。
In this theoretical study, a linear spatio-temporal analysis is performed on unconfined and confined inviscid jet/wake flows in order to determine whether they are absolutely or convectively unstable. The impulse response is evaluated in the entire outer fluid, rather than just at the point of impulse, over a wide range of density ratios. This confirms that the dominant saddle point can validly migrate into the plane of diverging eigenfunctions. This reveals that, at certain density ratios and shear numbers, the response can grow upstream in some directions with a cross-stream component, even though it decays directly upstream of, and at, the point of impulse. This type of flow is convectively unstable when unconfined, but becomes absolutely unstable when confined. Other effects of confinement are described in a previous paper. Together, these articles have important implications for the design of fuel injectors, which often employ confined shear flows at high Reynolds number and large density ratios to generate strong mixing in combustion chambers.