scholarly journals Vortex patterns in a mesoscopic superconducting rod with a magnetic dot

2010 ◽  
Vol 81 (10) ◽  
Author(s):  
Mauro M. Doria ◽  
Antonio R. de C. Romaguera ◽  
F. M. Peeters
Keyword(s):  
Vortex Patterns ◽  
Magnetic Dot

Formation of Vortex Street in Laminar Boundary Layer

1980 ◽  
Vol 47 (2) ◽  
pp. 227-233 ◽  
Author(s):  
M. Kiya ◽  
M. Arie
Keyword(s):  
Boundary Layer ◽  
Shear Flow ◽  
Laminar Boundary Layer ◽  
Solid Wall ◽  
Vortex Sheet ◽  
Vortex Street ◽  
Bluff Bodies ◽  
Uniform Shear ◽  
Uniform Shear Flow ◽  
Vortex Patterns

Main features of the formation of vortex street from free shear layers emanating from two-dimensional bluff bodies placed in uniform shear flow which is a model of a laminar boundary layer along a solid wall. This problem is concerned with the mechanism governing transition induced by small bluff bodies suspended in a laminar boundary layer. Calculations show that the background vorticity of shear flow promotes the rolling up of the vortex sheet of the same sign whereas it decelerates that of the vortex sheet of the opposite sign. The steady configuration of the conventional Karman vortex street is not possible in shear flow. Theoretical vortex patterns are experimentally examined by a flow-visualization technique.

Energy spectra of a single-electron magnetic dot using the massless Dirac–Weyl equation

2010 ◽  
Vol 22 (35) ◽  
pp. 355501 ◽  
Author(s):  
C M Lee ◽  
Richard C H Lee ◽  
W Y Ruan ◽  
M Y Chou
Keyword(s):  
Single Electron ◽  
Energy Spectra ◽  
Weyl Equation ◽  
Magnetic Dot

scholarly journals Multi-Jet Annulus/Core-Flow Mixing—Experiments and Calculations

1992 ◽  
Author(s):  
S. J. Baker ◽  
J. J. McGuirk
Keyword(s):  
Jet Impingement ◽  
Cfd Validation ◽  
Mean Velocity ◽  
Core Tube ◽  
Core Diameter ◽  
Eddy Viscosity Model ◽  
Flow Mixing ◽  
Stable Conditions ◽  
Jet Trajectory ◽  
Vortex Patterns

LDV measurements are reported of the flow-field associated with a single row of radially injected jets penetrating a core-tube flow. Emphasis is placed on the influence of small feed-annulus height on jet entry conditions and resulting trajectories and mixing patterns. Conditions of unstable jet behaviour, with strong vortex patterns in the jet holes, were observed for small annulus heights and high annulus velocities. Most measurements were however taken under stable conditions to allow the data to be used in a CFD validation exercise. Significant differences in the strength of backflow generated at jet impingement and in the turbulence field in the immediate hole vicinity were observed for different annulus height/core diameter ratios. These were accompanied by jet trajectory and annulus flow structure changes. Measurements of all 3 mean velocity components and associated normal stresses enabled the data to be utilised to assess a 3D CFD calculation incorporating a k-ε turbulence closure. The strength of forward and back flow generated at impingement was accurately predicted when the QUICK discretisation scheme was used. However, the size of upstream vortex was overpredicted. As expected using an eddy viscosity model the turbulence field at jet impingement and in the hole vicinity was not correctly reproduced. The turbulence generation in the flow approaching the hole was greatly overestimated by the turbulence model used.

scholarly journals Resonant Mixing in Glass Bowl Microbioreactor Investigated by Microparticle Image Velocimetry

Micromachines ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 284 ◽  
Author(s):  
Sven Meinen ◽  
Lasse Jannis Frey ◽  
Rainer Krull ◽  
Andreas Dietzel
Keyword(s):  
Surface Waves ◽  
Growth Conditions ◽  
Capillary Surface ◽  
Mixing Conditions ◽  
Glass Slides ◽  
Image Velocimetry ◽  
Resonance Frequencies ◽  
Microparticle Image Velocimetry ◽  
Growing Conditions ◽  
Vortex Patterns

Microbioreactors are gaining increased interest in biopharmaceutical research. Due to their decreasing size, the parallelization of multiple reactors allows for simultaneous experiments. This enables the generation of high amounts of valuable data with minimal consumption of precious pharmaceutical substances. However, in bioreactors of all scales, fast mixing represents a crucial condition. Efficient transportation of nutrients to the cells ensures good growing conditions, homogeneous environmental conditions for all cultivated cells, and therefore reproducible and valid data. For these reasons, a new type of batch microbioreactor was developed in which any moving mixer component is rendered obsolete through the utilization of capillary surface waves for homogenization. The bioreactor was fabricated in photosensitive glass and its fluid volume of up to 8 µL was provided within a bowl-shaped volume. External mechanical actuators excited capillary surface waves and stereo microparticle image velocimetry (µPIV) was used to analyze resulting convection at different excitation conditions in varied reactor geometries. Typical vortex patterns were observed at certain resonance frequencies where best mixing conditions occurred. Based on the results, a simplified 1D model which predicts resonance frequencies was evaluated. Cultivation of Escherichia coli BL21 under various mixing conditions showed that mixing in resonance increased the biomass growth rate, led to high biomass concentrations, and provided favorable growth conditions. Since glass slides containing multiple bowl reactors can be excited as a whole, massive parallelization is foreseen.

Uniform Magnetic Dot Fabrication by Nanoindentation Lithography

2011 ◽  
Vol 50 (4) ◽  
pp. 046505
Author(s):  
Nobuaki Kikuchi ◽  
Tomohiko Hashimoto ◽  
Satoshi Okamoto ◽  
Ze Shen ◽  
Osamu Kitakami
Keyword(s):  
Magnetic Dot

Vortex synchronization in the cylinder wake due to harmonic and non-harmonic perturbations

2016 ◽  
Vol 804 ◽  
pp. 248-277 ◽  
Author(s):  
Efstathios Konstantinidis ◽  
Demetri Bouris
Keyword(s):  
Relative Velocity ◽  
Numerical Study ◽  
Vortex Formation ◽  
Phase Portraits ◽  
Cylinder Wake ◽  
Frequency Space ◽  
Flow Past A Cylinder ◽  
Harmonic Perturbation ◽  
Perturbation Frequency ◽  
Vortex Patterns

This paper reports a numerical study of two-dimensional periodically perturbed flow past a cylinder. Both harmonic and non-harmonic perturbation waveforms of the inflow velocity are considered for a maximum instantaneous Reynolds number of 180. Phase portraits of the lift force are employed to identify the dynamical state of the cylinder wake and determine the range of kinematical parameters for which primary synchronization occurs, that is the regime where vortex formation is phase-locked to the subharmonic of the perturbation frequency. The effect of different perturbation waveforms on the synchronization range and on patterns of vortex formation is examined in detail over the normalized amplitude–frequency space. It is shown that systematic shifts of the synchronization range, towards either higher or lower frequencies, can be attained by imposing different perturbation waveforms. As a consequence, in certain regions of the parameter space it is possible to obtain multiple periodic and/or quasi-periodic wake states for waveforms of exactly the same amplitude and frequency. For the range of parameters where synchronization occurs, different vortex patterns are attained in the wake involving the shedding of solitary and binary vortices, or mixtures thereof, which can be controlled by the perturbation waveform. The phenomenology of these patterns, which result from modification of the basic Kármán mode in the unperturbed wake, is discussed and explained in terms of the generation of circulation that is induced by perturbations in the relative velocity. Vortex patterns from cylinders oscillating either in line with or transverse to a free stream are recast in the framework of the relative velocity.

Numerical investigation of hydrodynamic characteristics of fish-like undulation using the adaptive dynamic-grid method

2021 ◽  
pp. 2150299
Author(s):  
Zeyu Guo ◽  
Gucheng Zhu ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Frictional Force ◽  
Control Method ◽  
Turbulent Viscosity ◽  
Flow Characteristics ◽  
Grid Method ◽  
Wave Number ◽  
Hydrodynamic Characteristics ◽  
Substantial Impact ◽  
Vortex Patterns ◽  
Undulatory Swimming

To investigate the hydrodynamics of undulatory swimming, a key issue in numerical analysis is to determine the correlation between undulatory locomotion and the flow characteristics. In this study, a novel dynamic-grid generation method, the adaptive control method, is implemented to deal with the moving and morphing boundaries in an unsteady flow field at all Reynolds numbers. This method, based on structured grids, can ensure the orthogonality and absolute controllability of the grids and is performed to precisely simulate the wake and the boundary layer. The NACA0010 wing is employed as a two-dimensional (2D) body model of a fish in the simulations. To maintain the calculation stability, the increase stage of the amplitude is defined as a smooth transitional stage. Analysis of hydrodynamic coefficients reveals that undulation results in a significant increase of frictional force in laminar flow [Formula: see text]. However, the undulation also results in a reduction of the frictional force when the fish swims in turbulent flow [Formula: see text]. The vorticity distribution and the [Formula: see text]-criterion are both used to accurately capture the shedding vortexes in the wake. Furthermore, these vortex pairs have a substantial impact on the turbulence and the wake, in which the turbulent kinetic energy and the turbulent viscosity ratio both decrease at [Formula: see text]. The wake of an undulatory fish presents different vortex patterns with various kinematic parameters. When the phase velocity is greater than the incoming velocity and the wave number is sufficiently large, thrust is yielded, accompanying the distinct reverse Karman Street in the wake.

Nanometer-sized polyradical particles: Organic magnetic dot array formed on a silicon microfabricated substrate

2006 ◽  
Vol 45 (3) ◽  
pp. 521-530 ◽  
Author(s):  
Manabu Tanaka ◽  
Shingo Imai ◽  
Takashi Tanii ◽  
Yoshiteru Numao ◽  
Naonobu Shimamoto ◽  
...  
Keyword(s):  
Magnetic Dot
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