Vortex dipole interactions in a stratified fluid

1994 ◽  
pp. 138-174
Author(s):  
Sergey I. Voropayev ◽  
Yakov D. Afanasyev
Keyword(s):  
Stratified Fluid ◽  
Dipole Interactions ◽  
Vortex Dipole

Two-dimensional vortex-dipole interactions in a stratified fluid

1992 ◽  
Vol 236 ◽  
pp. 665-689 ◽  
Author(s):  
S. I. Voropayev ◽  
Ya. D. Afanasyev
Keyword(s):  
Experimental Investigation ◽  
Vertical Wall ◽  
Stratified Fluid ◽  
Two Dimensional ◽  
Initial State ◽  
Vorticity Distribution ◽  
Vortex Dipoles ◽  
Dipole Interactions ◽  
Vortex Dipole ◽  
State Of Rest

Planar motion produced when a viscous fluid is forced from an initial state of rest is studied. We consider a vortex dipole produced by the action of a point force (Cantwell 1986), and a vortex quadrupole produced by the action of two equal forces of opposite direction. We also present results from an experimental investigation into the dynamics of the interactions between vortex dipoles as well as between vortex dipoles and a vertical wall in a stratified fluid. Theoretical consideration reveals that the dynamics of two-dimensional vortex-dipole interactions are determined by two main governing parameters: the dipolar intensity of the vorticity distribution (momentum) and the quadrupolar intensity of the vorticity distribution of the flow. We document details of different basic types of interactions and present a physical interpretation of the results obtained in terms of vortex multipoles: dipoles, quadrupoles and their combinations.

Tuning the Magnetic Vortex State in Magnetite Nanodiscs for Remote Control of Biological Signalling

2019 ◽  
Author(s):  
Danijela Gregurec ◽  
Alexander W. Senko ◽  
Andrey Chuvilin ◽  
Pooja Reddy ◽  
Ashwin Sankararaman ◽  
...  
Keyword(s):  
Remote Control ◽  
Ion Channels ◽  
Ground State ◽  
Magnetic Particles ◽  
Colloidal Stability ◽  
Vortex State ◽  
Magnetic Vortex ◽  
Electron Holography ◽  
Dipole Interactions ◽  
Magnetite Particles

In this work, we demonstrate the application of anisotropic magnetite nanodiscs (MNDs) as transducers of torque to mechanosensory cells under weak, slowly varying magnetic fields (MFs). These MNDs possess a ground state vortex configuration of magnetic spins which affords greater colloidal stability due to eliminated dipole-dipole interactions characteristic of isotropic magnetic particles of similar size. We first predict vortex magnetization using micromagnetic stimulations in sub-micron anisotropic magnetite particles and then use electron holography to experimentally investigate the magnetization of MNDs 98–226 nm in diameter. When MNDs are coupled to MFs, they transition between vortex and in-plane magnetization allowing for the exertion of the torque on the pN scale, which is sufficient to activate mechanosensitive ion channels in cell membranes.<br>

LABORATORY STUDIES OF THE OF EDDY FORMATION IN ROTATING AND NON-ROTATING FLUID DUE TO SPATIALLY NON-UNIFORM WIND FORCING

2017 ◽  
Author(s):  
Dmitry Elkin ◽  
Dmitry Elkin ◽  
Andrey Zatsepin ◽  
Andrey Zatsepin
Keyword(s):  
Water Area ◽  
The Black Sea ◽  
Rotating Fluid ◽  
Rotating Platform ◽  
Cyclonic Vorticity ◽  
Dipole Structure ◽  
Air Jet ◽  
Vortex Dipole ◽  
Eddy Formation ◽  
Observation Results

Laboratory investigation of eddy formation mechanism due to spatially non-uniform wind impact was fulfilled. Experiment was provided in a cylindrical and a square form tank filled with homogeneous or stratified fluid and displaced on a rotating platform. In the absence of the platform rotation, an impact of the single air jet lead to the formation of a symmetric vortex dipole structure that occupied the whole water area in the tank. In the presence of the platform rotation, a compact anticyclonic eddy was formed in a part of the dipole with anticyclonic vorticity, while in a part with cyclonic vorticity no any compact eddy was observed. The laboratory results were successfully compared with the field observation results fulfilled in the at the Black Sea coastal zone near Gelendzhik.

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