Stability, bifurcation properties, and the spatiotemporal behavior of different nonlinear combination structures of spiral vortices in the counterrotating Taylor-Couette system are investigated by full numerical simulations and by coupled amplitude-equation approximations. Stable cross-spiral structures with continuously varying content of left- and right-spiral modes are found. They provide a stability transferring connection between the initially stable, axially counterpropagating wave states of pure spirals and the axially standing waves of so-called ribbons that become stable slightly farther away from the onset of vortex flow.
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http://dx.doi.org/10.1103/PhysRevLett.96.044506 | DOI Listing |
Micromachines (Basel)
January 2025
School of Mechanical and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, China.
Inertial microfluidics, as an efficient method for the manipulation of micro-/nanoparticles, has garnered significant attention due to its advantages of high throughput, structural simplicity, no need for external fields, and sheathless operation. Common structures include straight channels, contraction-expansion array (CEA) channels, spiral channels, and serpentine channels. In this study, we developed a CEA channel embedded with hook-shaped microstructures to modify the characteristics of vortices.
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November 2024
Division of Mechanical Engineering and Design, School of Engineering, London South Bank University, London, SE1 0AA, UK.
Spiral, one of the most well-known functional patterns in nature that can be observed in structures such as the proboscis of lepidoptera and snail shells or as vortices forming in flowing fluids, has long served as a source of inspiration for humans in the creation of numerous spiral-based designs. Double-spiral is a design derived from spirals, which has been previously presented and utilized as a compliant joint. Advantageous properties of double-spirals, such as easily adjustable design, multiple degrees of freedom, reversible extensibility, and tunable deformability make them promising candidates for the development of mechanically intelligent structures that exhibit unique behavior and reach desired functions, such as soft grippers, continuum manipulators, energy-dissipative structures, and foldable metamaterials.
View Article and Find Full Text PDFIn this paper, the circular Bessel Gaussian beams (CBGBs) carrying power-cotangent-phase vortices are firstly introduced, whose propagation dynamics are explored theoretically and experimentally. The number of spiral lobes, rotation direction, rotation angle, and shape of the new type of beam can be flexibly modulated by controlling multiple parameters of power-cotangent-phase vortices. Accordingly, the effect of multiple beam parameters on abruptly autofocusing ability is quantified and compared by using the K-value curve that is described by ratio Im/I, where Im and I correspond to the maximum intensities at different propagation distance and the initial plane, respectively.
View Article and Find Full Text PDFOptical vortices, which are beams with helical wavefronts and spiral phase mismatches, have garnered considerable attention in various fields. In this study, we theoretically proposed and experimentally implemented a simple method for generating first-order optical vortices. To generate first-order vortex beams using the polarization field in the momentum space of photonic crystal slabs, topological half charges are required.
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