Acoustical and optical vortices have attracted large interest due to their ability in capturing and manipulating particles with the use of the radiation pressure. Here we show that acoustical vortices can also induce axial vortical flow reminiscent of cyclones whose topology can be controlled by adjusting the properties of the acoustical beam. In confined geometry, the phase singularity enables generating attractive streaming with a flow directed toward the transducer. This opens perspectives for contact-less vortical flow control.
The Universal Aspect Ratio of Vortices in Rotating Stratified Flows: Theory and Simulation
我们推导出旋转分层流体中稳定且缓慢演变的涡旋的涡旋纵横比$α$（垂直半厚度与水平长度尺度）的关系，作为涡旋$N_c$内和涡旋外背景流体中Brunt-Vaisala频率的函数$\bar{N}$、科里奥利参数$f$和涡旋的罗斯比数$Ro$：$α^2 = Ro(1+Ro) f^2/(N_c^2-\bar{N}^2)$。这个关系式对气旋和反气旋在旋转或地转状态下都是有效的;它适用于Boussinesq流体或理想气体中的涡旋，并且背景密度梯度不需要是均匀的。我们的$α$关系式对旋转分层流中的平衡涡有许多结果。例如，气旋必须具有$N_c^2 > \bar{N}^2$ ;在准地转涡旋中，弱反气旋（具有$|Ro| < 1$）必须具有$N_c^2 < \bar{N}^2; and strong anticyclones must have $ N_c ^2> \bar{N}^2 $. We verify our relation for $ α $ with numerical simulations of the three-dimensional Boussinesq equations for a wide variety of vortices, including: vortices that are initially in (dissipationless) equilibrium a…
Final states of two-dimensional turbulence above large-scale topography: stationary vortex solutions and barotropic stability
The Hong Kong University of Science and Technology（香港科技大学）；Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology（香港及澳门海洋研究中心）
