2-D and 3-D Electroconvection, Experiments and Models.

1994 ◽  
Vol 367 ◽  
Author(s):  
V. Fleury ◽  
J.-N. Chazalviel
Keyword(s):  
Supporting Electrolyte ◽  
Three Dimensional ◽  
Electrochemical Process ◽  
Vortex Rings ◽  
Electrochemical Growth ◽  
Coulombic Force ◽  
Original Presentation ◽  
Concentrated Solution ◽  
Convective Vortices ◽  
Positive Space

In recent years, a lot of work has been devoted to electrochemical growth without supporting electrolyte1. A model, proposed by one of us2, predicts the existence of a positive space charge and of a large electric field in the active zones of the deposit. This leads to the existence of a coulombic force on the liquid. We show that this coulombic force triggers convective vortices in Hele-Shaw cells3,4, while it triggers vortex rings in three-dimensional cells5.We then couple the electrochemical process to the convective flow and show that, while the border between the depleted and concentrated zones has the shape of an arch in Hele-Shaw cells, it has a toroidal shape in 3-D. When many vortex rings are present, the border between the depleted and the concentrated solution is in the form of domes. We give experimental evidence of the vortex rings. (The original presentation was accompanied by a video movie which can be obtained upon request).

scholarly journals Exploration of collagen cavitation based on peptide electrolysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rui Zhai ◽  
Hui Chen ◽  
Zhihua Shan
Keyword(s):  
Structural Changes ◽  
Preparation Method ◽  
Supporting Electrolyte ◽  
Three Dimensional ◽  
Anode Region ◽  
New Approach ◽  
New Material ◽  
Animal Skin ◽  
Exchange Membrane ◽  
Material Preparation

AbstractElectrochemical modification of animal skin is a new material preparation method and new direction of research exploration. In this study, under the action of the electric field using NaCl as the supporting electrolyte, the effect of electrolysis on Glycyl-glycine(GlyGl), gelatin(Gel) and Three-dimensional rawhide collagen(3DC) were determined. The amino group of GlyGl is quickly eliminated within the anode region by electrolysis isolated by an anion exchange membrane. Using the same method, it was found that the molecular weight of Gel and the isoelectric point of the Gel decreased, and the viscosity and transparency of the Gel solution obviously changed. The electrolytic dissolution and structural changes of 3DC were further investigated. The results of TOC and TN showed that the organic matter in 3DC was dissolved by electrolysis, and the tissue cavitation was obvious. A new approach for the preparation of collagen-based multi-pore biomaterials by electrochemical method was explored.

scholarly journals Single and multiple vortex rings in three-dimensional Bose-Einstein condensates: Existence, stability, and dynamics

2017 ◽  
Vol 95 (4) ◽  
Author(s):  
Wenlong Wang ◽  
R. N. Bisset ◽  
C. Ticknor ◽  
R. Carretero-González ◽  
D. J. Frantzeskakis ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Vortex Rings ◽  
Bose Einstein

Vortex rings impinging on walls: axisymmetric and three-dimensional simulations

1993 ◽  
Vol 256 ◽  
pp. 615-646 ◽  
Author(s):  
Paolo Orlandi ◽  
Roberto Verzicco
Keyword(s):  
Numerical Simulations ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Vortex Rings ◽  
Compression Phase ◽  
Vortex Pairing ◽  
The Impact ◽  
Good Agreement ◽  
Three Dimensional Simulations

Accurate numerical simulations of vortex rings impinging on flat boundaries revealed the same features observed in experiments. The results for the impact with a free-slip wall compared very well with previous numerical simulations that used spectral methods, and were also in qualitative agreement with experiments. The present simulation is mainly devoted to studying the more realistic case of rings interacting with a no-slip wall, experimentally studied by Walker et al. (1987). All the Reynolds numbers studied showed a very good agreement between experiments and simulations, and, at Rev > 1000 the ejection of a new ring from the wall was seen. Axisymmetric simulations demonstrated that vortex pairing is the physical mechanism producing the ejection of the new ring. Three-dimensional simulations were also performed to investigate the effects of azimuthal instabilities. These simulations have confirmed that high-wavenumber instabilities originate in the compression phase of the secondary ring within the primary one. The large instability of the secondary ring has been explained by analysis of the rate-of-strain tensor and vorticity alignment. The differences between passive scalars and the vorticity field have been also investigated.

Curvature-induced deformations of the vortex rings generated at the exit of a rectangular duct

2019 ◽  
Vol 864 ◽  
pp. 141-180 ◽  
Author(s):  
Abbas Ghasemi ◽  
Burak Ahmet Tuna ◽  
Xianguo Li
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Single Mode ◽  
The Self ◽  
Vortex Rings ◽  
Potential Core ◽  
Vortex Pairing ◽  
Time Space ◽  
Axis Switching

Rectangular air jets of aspect ratio $2$ are studied at $Re=UD_{h}/\unicode[STIX]{x1D708}=17\,750$ using particle image velocimetry and hot-wire anemometry as they develop naturally or under acoustic forcing. The velocity spectra and the spatial theory of linear stability characterize the fundamental ($f_{n}$) and subharmonic ($f_{n}/2$) modes corresponding to the Kelvin–Helmholtz roll-up and vortex pairing, respectively. The rectangular cross-section of the jet deforms into elliptic/circular shapes downstream due to axis switching. Despite the apparent rotation of the vortex rings or the jet cross-section, the axis-switching phenomenon occurs due to reshaping into rounder geometries. By enhancing the vortex pairing, excitation at $f_{n}/2$ shortens the potential core, increases the jet spread rate and eliminates the overshoot typically observed in the centreline velocity fluctuations. Unlike circular jets, the skewness and kurtosis of the rectangular jets demonstrate elevated anisotropy/intermittency levels before the end of the potential core. The axis-switching location is found to be variable by the acoustic control of the relative expansion/contraction rates of the shear layers in the top (longer edge), side (shorter edge) and diagonal views. The self-induced vortex deformations are demonstrated by the spatio-temporal evolution of the phase-locked three-dimensional ring structures. The curvature-induced velocities are found to reshape the vortex ring by imposing nonlinear azimuthal perturbations occurring at shorter wavelengths with time/space evolution. Eventually, the multiple high-curvature/high-velocity regions merge into a single mode distribution. In the plane of the top view, the self-induced velocity distribution evolves symmetrically while the tilted ring results in the asymmetry of the azimuthal perturbations in the side view as the side closer to the acoustic source rolls up in more upstream locations.

scholarly journals Fabrication of nano/microstructures for SERS substrates using an electrochemical method

2020 ◽  
Vol 11 ◽  
pp. 1568-1576
Author(s):  
Jingran Zhang ◽  
Tianqi Jia ◽  
Xiaoping Li ◽  
Junjie Yang ◽  
Zhengkai Li ◽  
...  
Keyword(s):  
Electrochemical Method ◽  
Treatment Time ◽  
Low Cost ◽  
Three Dimensional ◽  
Electrochemical Process ◽  
Sers Substrate ◽  
Raman Intensity ◽  
Experimental Conditions ◽  
Sers Substrates ◽  
Au Film

Based on an electrochemical method, three-dimensional arrayed nanopore structures are machined onto a Mg surface. The structured Mg surface is coated with a thin gold (Au) film, which is used as a surface-enhanced Raman scattering (SERS) substrate. A rhodamine 6G (R6G) probe molecule is used as the detection agent for the SERS measurement. Different sizes of arrayed micro/nanostructures are fabricated by different treatment time using the electrochemical process. The topographies of these micro/nanostructures and the thickness of the Au film have an influence on the Raman intensity of the Mg substrate. Furthermore, when the thickness of Au film coating is held constant, the Raman intensity on the structured Mg substrates is about five times higher after a treatment time of 1 min when compared with other treatment times. The SERS enhancement factor ranges from 106 to 1.75 × 107 under these experimental conditions. Additionally, a 10−6 mol·L−1 solution of lysozyme was successfully detected using the Mg–Au nanopore substrates. Our low-cost method is reproducible, homogeneous, and suitable for the fabrication of SERS substrates.

scholarly journals Bifurcation and stability of single and multiple vortex rings in three-dimensional Bose-Einstein condensates

2015 ◽  
Vol 92 (4) ◽  
Author(s):  
R. N. Bisset ◽  
Wenlong Wang ◽  
C. Ticknor ◽  
R. Carretero-González ◽  
D. J. Frantzeskakis ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Vortex Rings ◽  
Bose Einstein ◽  
Bifurcation And Stability
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