Short-Scale Instabilities in Trailing Wake Vortices in a Stratified Fluid
Short-Scale Instabilities in Trailing Wake Vortices in a Stratified Fluid
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分层流体中尾流涡的短尺度不稳定性
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
R. Robins
中科院分区：
文献类型：
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作者：
D. Delisi;R. Robins
报告使用实验室实验和三维数字代码对非湍流和非剪切密度分层流体中翼尖尾迹涡流的演变进行测量。众所周知，正如我们的实验室和数值结果所证实的那样，非分层流体中这些涡流的主要不稳定性是克劳不稳定性，其特征初始波长约为 8.6b 0 ，其中 b 0 是涡流之间的初始分离距离。然而，在分层流体中，我们的实验室观察和数值模拟显示出在 b 0 -2b 0 附近的较短波长的不稳定性。这种不稳定性出现在漩涡垂直迁移几乎达到最大程度的演化过程中。观察到的不稳定性在幅度和波长上都随着时间的推移而增加。当涡旋弗劳德数约为 1 时，不稳定性首先在 2 左右的无量纲时间 T 处变得可见，并在 T 约为 4 时达到最大值
Measurements of the evolution of wingtip trailing wake vortices in nonturbulent and unsheared density-stratified fluids are reported, using both laboratory experiments and a three-dimensional numerical code. As is widely known, and as our laboratory and numerical results confirm, the primary instability for these vortices in an unstratified fluid is the Crow instability, which has a characteristic initial wavelength of around 8.6b 0 , where b 0 is the initial separation distance between the vortices. In stratified fluids, however, our laboratory observations and numerical simulations show an instability with a shorter wavelength of around b 0 -2b 0 . This instability appears at a time in the evolution when the vertical migration of the vortices has reached nearly its maximum extent. The observed instability grows both in amplitude and wavelength with time. When the vortex Froude number is around one, the instability first becomes visible at a nondimensional time T of around 2 and reaches a maximum at T of around 4