Spatial anisotropy of velocity fluctuations on small length scales in a Taylor-Couette cell

1993 ◽  
Vol 48 (1) ◽  
pp. 322-327 ◽  
Author(s):  
Knut Jørgen Måløy ◽  
Walter Goldburg
Keyword(s):  
Small Length ◽  
Length Scales ◽  
Velocity Fluctuations ◽  
Spatial Anisotropy ◽  
Couette Cell ◽  
Taylor Couette

Impact of osmotic pressure on the stability of Taylor vortices

2022 ◽  
Vol 933 ◽  
Author(s):  
Rouae Ben Dhia ◽  
Nils Tilton ◽  
Denis Martinand
Keyword(s):  
Osmotic Pressure ◽  
Critical Conditions ◽  
Hydrodynamic Instabilities ◽  
Taylor Vortices ◽  
Dynamic Filtration ◽  
Analytical Criterion ◽  
Permeable Cylinders ◽  
Couette Cell ◽  
Taylor Couette ◽  
The Stability

We use linear stability analysis and direct numerical simulations to investigate the coupling between centrifugal instabilities, solute transport and osmotic pressure in a Taylor–Couette configuration that models rotating dynamic filtration devices. The geometry consists of a Taylor–Couette cell with a superimposed radial throughflow of solvent across two semi-permeable cylinders. Both cylinders totally reject the solute, inducing the build-up of a concentration boundary layer. The solute retroacts on the velocity field via the osmotic pressure associated with the concentration differences across the semi-permeable cylinders. Our results show that the presence of osmotic pressure strongly alters the dynamics of the centrifugal instabilities and substantially reduces the critical conditions above which Taylor vortices are observed. It is also found that this enhancement of the hydrodynamic instabilities eventually plateaus as the osmotic pressure is further increased. We propose a mechanism to explain how osmosis and instabilities cooperate and develop an analytical criterion to bound the parameter range for which osmosis fosters the hydrodynamic instabilities.

Ionic strength and polyelectrolyte molecular weight effects on floc formation and growth in Taylor–Couette flows

Soft Matter ◽  
2021 ◽  
Author(s):  
Athena E. Metaxas ◽  
Vishal Panwar ◽  
Ruth L. Olson ◽  
Cari S. Dutcher
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
Solution Ionic Strength ◽  
Radial Injection ◽  
Couette Cell ◽  
Taylor Couette

A Taylor–Couette cell capable of radial injection was used to study the effects of varying solution ionic strength and polyelectrolyte molecular weight on the polyelectrolyte-driven flocculation of bentonite suspensions.

scholarly journals Spin-charge separation at small length scales in the 2D t-J Model

1995 ◽  
Vol 99 (3-4) ◽  
pp. 509-511
Author(s):  
Roser Valent� ◽  
Claudius Gros
Keyword(s):  
Charge Separation ◽  
Small Length ◽  
Length Scales

scholarly journals Transmission x-ray microscopy at low temperatures: Irregular supercurrent flow at small length scales

2018 ◽  
Vol 97 (13) ◽  
Author(s):  
J. Simmendinger ◽  
S. Ruoss ◽  
C. Stahl ◽  
M. Weigand ◽  
J. Gräfe ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Small Length ◽  
Length Scales ◽  
X Ray

Vibration Characteristics of Multiwalled Carbon Nanotubes Embedded in Elastic Media by a Nonlocal Elastic Shell Model

2007 ◽  
Vol 74 (6) ◽  
pp. 1087-1094 ◽  
Author(s):  
Renfu Li ◽  
George A. Kardomateas
Keyword(s):  
Carbon Nanotubes ◽  
Shell Model ◽  
Multiwalled Carbon Nanotubes ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Elastic Media ◽  
Small Length ◽  
Multiwalled Carbon ◽  
Resonant Frequencies ◽  
Length Scales

In this paper, the vibrational behavior of the multiwalled carbon nanotubes (MWCNTs) embedded in elastic media is investigated by a nonlocal shell model. The nonlocal shell model is formulated by considering the small length scales effects, the interaction of van der Waals forces between two adjacent tubes and the reaction from the surrounding media, and a set of governing equations of motion for the MWCNTs are accordingly derived. In contrast to the beam models in the literature, which would only predict the resonant frequencies of bending vibrational modes by taking the MWCNT as a whole beam, the current shell model can find the resonant frequencies of three modes being classified as radial, axial, and circumferential for each nanotube of a MWCNT. Big influences from the small length scales and the van der Waals’ forces are observed. Among these, noteworthy is the reduction in the radial frequencies due to the van der Waals’ force interaction between two adjacent nanotubes. The numerical results also show that when the spring constant k0 of the surrounding elastic medium reaches a certain value, the lowest resonant frequency of the double walled carbon nanotube drops dramatically.

Flow Dynamics Characteristics in Micro and Nano Length Scale Devices With the Lattice-Boltzmann Method: The Air Bearing Problem

2008 ◽  
Author(s):  
Alvaro J. Ramirez ◽  
Amador M. Guzman ◽  
Rodrigo A. Escobar
Keyword(s):  
Poiseuille Flow ◽  
Lattice Boltzmann ◽  
Numerical Results ◽  
Flow Dynamics ◽  
Length Scale ◽  
Air Bearing ◽  
Small Length ◽  
Length Scales ◽  
Boltzmann Method ◽  
Acceptable Agreement

The Lattice-Boltzmann Method (LBM) has been used for investigating flow behavior and characteristics in mini, micro and nano channels with the objective of describing the transition among different length scales. In particular, we have used the LBM to describe the air bearing lubrication problem at very small scales. For doing this, first we simulate and characterize the Poiseuille flow through different length scale and compare the LBM numerical results to existing experimental and numerical results. We put special attention on the application of the slip boundary condition on the channel wall for very small length scales. Our numerical results for the Poiseuille flow show an acceptable agreement with the Fukui & Kaneko numerical solution for continuous and slip-velocity regimes. For both, the rarified flow regime and the free molecular flow regime our solutions do not show an acceptable agreement with the Fukui & Kaneko Model. Then, we focus on the Couette flow characterization at very small length scales. The pressure distribution on both walls for different Knudsen numbers is obtained and compared to existing numerical results. Last, we concentrate in the air bearing problem. We have looked at the best simulation parameters for successfully describing this device flow dynamics, and particularly, for determining the pressure distribution and the net force with a good accuracy.

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