RESUMEN
The control of matter motion at liquid-gas interfaces opens an opportunity to create two-dimensional materials with remotely tunable properties. In analogy with optical lattices used in ultra-cold atom physics, such materials can be created by a wave field capable of dynamically guiding matter into periodic spatial structures. Here we show experimentally that such structures can be realized at the macroscopic scale on a liquid surface by using rotating waves. The wave angular momentum is transferred to floating micro-particles, guiding them along closed trajectories. These orbits form stable spatially periodic patterns, the unit cells of a two-dimensional wave-based material. Such dynamic patterns, a mirror image of the concept of metamaterials, are scalable and biocompatible. They can be used in assembly applications, conversion of wave energy into mean two-dimensional flows and for organising motion of active swimmers.
RESUMEN
A novel experiment to investigate fluid dynamics in quasi-two-dimensional flows has been built. A soap film is suspended horizontally in an annular channel with a rotating outer boundary, providing mean flow shear, and a vortex array is forced electromagnetically. The experiment will investigate sheared flow stability and the effect of mean flow shear on local vorticity and coherent structures. Particle image velocimetry measurements demonstrate the production of mean flow shear and induced vortices.
RESUMEN
Improved confinement has been achieved in the MST through control of the poloidal electric field, but it is now known that the improvement has been limited by bursts of an edge-resonant instability. Through refined poloidal electric field control, plus control of the toroidal electric field, we have suppressed these bursts. This has led to a total beta of 15% and a reversed-field-pinch-record estimated energy confinement time of 10 ms, a tenfold increase over the standard value which for the first time substantially exceeds the confinement scaling that has characterized most reversed-field-pinch plasmas.
RESUMEN
The fluctuation-induced dynamo