scholarly journals Physics of Magnetopause Reconnection: A Study of the Combined Effects of Density Asymmetry, Velocity Shear, and Guide Field

2010 ◽  
Vol 2010 ◽  
pp. 1-17 ◽  
Author(s):  
Kentaro G. Tanaka ◽  
Masaki Fujimoto ◽  
Iku Shinohara
Keyword(s):  
Shear Flow ◽  
Flow Direction ◽  
Electron Flow ◽  
Velocity Shear ◽  
Field Effects ◽  
Guide Field ◽  
Sliding Motion ◽  
Particle Simulations ◽  
Flow Effects ◽  
Magnetopause Reconnection

Magnetopause reconnection would be characterized by the density jump across the current sheet, the flow shear across the boundary, and nonzero guide field. While effects of each of these elements have been studied, the effects arising from the combination of these are still unexplored. Two-dimensional full-particle simulations show that the combination of shear flow and/or guide field with density asymmetry induces the sliding motion of theX-line along the magnetopause. The direction of theX-line motion is controlled either by the ion flow at theX-line when the shear flow effects dominate or by the electron flow at theX-line when the guide field effects dominate. The shear flow effects and the guide field effects may counteract each other in determining the direction of theX-line motion and, in the close proximity of the subsolar region where the flow is slow, theX-line motion can be opposite to the flow direction.

scholarly journals Simulation of Flexible Fibre Particle Interaction with a Single Cylinder

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 191
Author(s):  
Naser Hamedi ◽  
Lars-Göran Westerberg
Keyword(s):  
Reynolds Number ◽  
Shear Flow ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Particle Interaction ◽  
Orientation Angle ◽  
Factors Affecting ◽  
Single Cylinder ◽  
Flow Past ◽  
Fibre Suspension

In the present study, the flow of a fibre suspension in a channel containing a cylinder was numerically studied for a very low Reynolds number. Further, the model was validated against previous studies by observing the flexible fibres in the shear flow. The model was employed to simulate the rigid, semi-flexible, and fully flexible fibre particle in the flow past a single cylinder. Two different fibre lengths with various flexibilities were applied in the simulations, while the initial orientation angle to the flow direction was changed between 45° ≤ θ ≤ 75°. It was shown that the influence of the fibre orientation was more significant for the larger orientation angle. The results highlighted the influence of several factors affecting the fibre particle in the flow past the cylinder.

The heat/mass transfer to a finite strip at small Péclet numbers

1978 ◽  
Vol 86 (1) ◽  
pp. 49-65 ◽  
Author(s):  
R. C. Ackerberg ◽  
R. D. Patel ◽  
S. K. Gupta
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Shear Flow ◽  
Sodium Hydroxide Solution ◽  
Flow Direction ◽  
Mathematical Problem ◽  
Limiting Current ◽  
Transfer Rates ◽  
Uniform Shear ◽  
Uniform Shear Flow

The problem of heat transfer (or mass transfer at low transfer rates) to a strip of finite length in a uniform shear flow is considered. For small values of the Péclet number (based on wall shear rate and strip length), diffusion in the flow direction cannot be neglected as in the classical Leveque solution. The mathematical problem is solved by the method of matched asymptotic expansions and expressions for the local and overall dimensionless heat-transfer rate from the strip are found. Experimental data on wall mass-transfer rates in a tube at small Péclet numbers have been obtained by the well-known limiting-current method using potassium ferrocyanide and potassium ferricyanide in sodium hydroxide solution. The Schmidt number is large, so that a uniform shear flow can be assumed near the wall. Experimental results are compared with our theoretical predictions and the work of others, and the agreement is found to be excellent.

scholarly journals The lift on a small sphere in a slow shear flow

1965 ◽  
Vol 22 (2) ◽  
pp. 385-400 ◽  
Author(s):  
P. G. Saffman
Keyword(s):  
Shear Flow ◽  
Velocity Profile ◽  
Kinematic Viscosity ◽  
Lift Force ◽  
Flow Direction ◽  
Functional Dependence ◽  
Small Sphere ◽  
Translation Velocity ◽  
Parabolic Velocity Profile ◽  
Direction Opposite

It is shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to the streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamlines moving in the direction opposite to V. Here, a denotes the radius of the sphere, κ the magnitude of the velocity gradient, and μ and v the viscosity and kinematic viscosity, respectively. The relevance of the result to the observations by Segrée & Silberberg (1962) of small spheres in Poiseuille flow is discussed briefly. Comments are also made about the problem of a sphere in a parabolic velocity profile and the functional dependence of the lift upon the parameters is obtained.

scholarly journals Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

2013 ◽  
Vol 31 (9) ◽  
pp. 1535-1541 ◽  
Author(s):  
K.-I. Nishikawa ◽  
P. Hardee ◽  
B. Zhang ◽  
I. Duţan ◽  
M. Medvedev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Magnetic Fields ◽  
Electric Field ◽  
Flow Direction ◽  
Transverse Magnetic ◽  
Velocity Shear ◽  
Helmholtz Instability ◽  
Magnetic Field Generation ◽  
Relativistic Jet

Abstract. We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin–Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5) is larger than for a relativistic jet case (γj = 15).

Numerical simulation of Reynolds number effects on velocity shear flow around a circular cylinder

2010 ◽  
Vol 26 (5) ◽  
pp. 685-702 ◽  
Author(s):  
Shuyang Cao ◽  
Shigehira Ozono ◽  
Yukio Tamura ◽  
Yaojun Ge ◽  
Hironori Kikugawa
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Velocity Shear ◽  
Reynolds Number Effects

Fibre Orientation Control Related to Papermaking

2006 ◽  
Author(s):  
A. Carlsson ◽  
F. Lundell ◽  
L. D. So¨derberg
Keyword(s):  
Shear Flow ◽  
Flow Field ◽  
Surface Structure ◽  
Fibre Orientation ◽  
Flow Direction ◽  
Glass Plate ◽  
Ccd Camera ◽  
Plate Surface ◽  
Steerable Filters ◽  
Fibre Suspension

The wall effect on the orientation of fibres suspended in a shear flow has been studied experimentally. A fibre suspension, driven by gravity down an inclined glass plate, constitutes the shear flow field. A CCD-camera was mounted underneath the flow in order to visualize the flow. The orientation of fibres in the plane perpendicular to the plate was determined, by using the concept of steerable filters. In a region close to the smooth plate surface the fibres oriented themselves perpendicular to the flow direction. This did not occur when the surface structure was modified with ridges.

Critical velocity shear flow for triggering L-H transition and its parametric dependence in the HL-2A tokamak

2020 ◽  
Vol 60 (9) ◽  
pp. 092002
Author(s):  
A.S. Liang ◽  
X.L. Zou ◽  
W.L. Zhong ◽  
A. Ekedahl ◽  
X.R. Duan ◽  
...  
Keyword(s):  
Shear Flow ◽  
Critical Velocity ◽  
Velocity Shear ◽  
Parametric Dependence

A mesoscopic numerical study of shear flow effects on asphaltene self-assembly behavior in organic solvents

2020 ◽  
Vol 22 (36) ◽  
pp. 20758-20770
Author(s):  
Mohammad Ahmadi ◽  
Hassan Hassanzadeh ◽  
Jalal Abedi
Keyword(s):  
Shear Flow ◽  
Organic Solvents ◽  
Self Assembly ◽  
Brownian Dynamics ◽  
Numerical Study ◽  
The Self ◽  
Dynamics Simulation ◽  
Brownian Dynamics Simulation ◽  
Assembly Behavior ◽  
Flow Effects

We employ the Brownian dynamics simulation to examine the shear flow effects on the self-assembly behavior of asphaltenes.

Flow induced crystallization of LDPE nanocomposites: A rheological and morphological characterization

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Fiorenza Azzurri ◽  
Paola Stagnaro ◽  
Lucia Conzatti ◽  
Dario Cavallo ◽  
Luca Repetto ◽  
...  
Keyword(s):  
Shear Flow ◽  
Flow Direction ◽  
Crystallization Rate ◽  
Morphological Characterization ◽  
External Flow ◽  
Nucleation Density ◽  
Induced Crystallization ◽  
Flow Induced Crystallization ◽  
Nucleating Effect

AbstractThe flow induced crystallization behaviour of a LDPE:PE-g-MA:D72T 90:9:1 nanocomposite has been investigated by in-situ Rheo-SALS technique and data have been compared with those obtained from a reference LDPE:PE-g-MA 90:9 sample. Rheo SALS results, confirming thermal analysis findings, indicate that under mild shear flow fields the organoclay exhibits a negligible nucleating effect. Both nucleation density and, as a consequence, crystallization rate, are not appreciably affected by the application of external flow field for both the examined systems, revealing that no evident synergic effects between the organoclay and the shear flow are present. On the other hand, Rheo SALS analysis indicates that the nanocomposite submitted to flow exhibits a higher level of crystal orientation. TEM morphological analyses support this observation suggesting that the orientation of the nanofiller along the flow direction templates the growth of oriented crystals.

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