The evolution of a strongly magnetized electron system is identical to that of an ideal two-dimensional ~2-D! fluid; an electron column is equivalent to a fluid vortex. We have studied the stability of 2-D vortex patterns with electron columns confined in a Malmberg–Penning trap. The following cases are presented: the stability of N vortices arranged in a ring; the stability of N vortices arran...

We demonstrate that a concentric ring coupler can be employed for nonlinear switching of the angular momentum of light carried by an optical vortex. We find different types of stationary vortex states in the nonlinear coupler and study coupling of both power and momentum of an optical vortex launched into one of the rings, demonstrating that the switching takes place well below the collapse thr...

We use direct numerical simulations to study control of jets in crossflow by axial pulsing. Our main idea is that pulsing generates vortex rings; the effect of pulsing on jets in crossflow can therefore be explained by studying the behavior of vortex rings in crossflow. A method is proposed that allows optimal values of pulsation frequency, modulation and energy to be estimated a priori. This i...

It is known that the stable and unstable manifolds of dynamical systems theory provide a powerful tool for understanding Lagrangian aspects of time-periodic flows. In this work we consider two time-periodic vortex ring flows. The first is a vortex ring with an elliptical core. The manifolds provide information about entrainment and detrainment of irrotational fluid into and out of the volume tr...

A vortex ring is a torus-shaped fluidic vortex. During its formation, the fluid experiences a rich variety of intriguing geometrical intermediates from spherical to toroidal. Here we show that these constantly changing intermediates can be 'frozen' at controlled time points into particles with various unusual and unprecedented shapes. These novel vortex ring-derived particles, are mass-produced...

We have studied oscillation of a pendulum in water using spherical bobs. By measuring the loss in potential energy, we estimate the drag coefficient on the sphere and compare to data from liquid-helium experiments. The drag coefficients compare very favorably illustrating the true scaling behavior of this phenomenon. We also studied the decay of amplitude of the pendulum over time. As observed ...

Vertical transects of Doppler vertical velocity data, obtained from an airborne profiling millimeter-wave cloud radar, are composited for a large number of cumulus clouds (Cu) at various stages of their life cycle, to examine typical circulations patterns. The Cu clouds range in depth between ;500 and 6000 m and are generally nonprecipitating. They were sampled on board the University of Wyomin...

Background During rapid filling of the left ventricle, a vortex ring forms downstream from the mitral valve. Previous experiments in water tanks have shown that vortex ring formation is an optimized method for fluid transport. The rotation of the vortex ring leads to mixing of the inflowing blood and blood that was already in the ventricle (Figure 1). In water tanks, the amount of mixing decrea...

For moderate Reynolds numbers, a sphere striking a wall in the normal direction leads to the trailing recirculating wake threading over the sphere and developing into a complex vortex ring system as it interacts with the wall. The primary vortex ring, which consists of vorticity from the wake, persists and convects slowly outwards away from the sphere due to the motion induced from its image. T...

We discuss an experimental technique developed to visualize quantized vortices in helium II. We illuminate micron-sized solid particles of hydrogen suspended in the fluid, and mark quantized vortex cores within the volume observed by a camera. While, under some circumstances, the particles modify vortex dynamics by the action of viscous drag and by pinning vortex intersections, we do capture ba...