Growth and separation of a start-up vortex from a two-dimensional shear layer
Growth and separation of a start-up vortex from a two-dimensional shear layer
复制标题
二维剪切层中启动涡流的生长和分离
DOI：
10.1063/1.4758793
复制
发表时间：
2012
影响因子：
4.6
通讯作者：
C. Tropea
中科院分区：
文献类型：
--
作者：
P. Sattari;D. Rival;R. Martinuzzi;C. Tropea
利用时间分辨粒子图像测速仪对二维启动射流产生的孤立线涡的演化过程进行了实验研究。目前这种形态的涡旋增长与任何外部施加的长度尺度或与可能潜在影响涡旋增长的其他涡旋结构或壁的相互作用无关。提出了一个基于从剪切层到涡旋的环流输送的早期涡旋发展模式，该模式与实验数据符合得很好。该模型利用剪切层特征速度和剪切层厚度为涡旋的发展提供了一种定标方案。由于剪切层曲率的减小，涡旋从供给剪切层中逐渐分离出来，从而限制了涡旋的发展。这一现象与剪切层倾向于沿流向保持的趋势和剪切层上涡旋的诱导速度之间的竞争有关。最后，引入了一个代表这种竞争的无量纲数，它能够描述涡旋从剪切层中逐渐分离的过程。
The evolution of an isolated line vortex generated by a starting two-dimensional jet is studied experimentally using time-resolved particle image velocimetry. The vortex growth in this current configuration is not linked to any externally imposed length scales or interactions with other vortical structures or walls that could potentially influence vortex growth. A model for the early-stage vortex growth, based on the transport of circulation from the shear layer into the vortex, is proposed and found to agree well with experimental data. The model provides a scaling scheme for vortex growth using shear-layer characteristic velocity and shear-layer thickness. The vortex growth is limited through a gradual separation of the vortex from the feeding shear layer, arising from decreased shear-layer curvature. This phenomenon is linked to a competition between the shear-layer tendency to remain in the streamwise direction and the induced velocity from the vortex on the shear layer. Finally, a dimensionless number representing this competition is introduced, which in turn is able to describe the gradual separation of the vortex from the shear layer.