Electroosmosis of Viscoelastic Fluids: Role of Wall Depletion Layer

Langmuir ◽  
2017 ◽  
Vol 33 (43) ◽  
pp. 12046-12055 ◽  
Author(s):  
Siddhartha Mukherjee ◽  
Sankha Shuvra Das ◽  
Jayabrata Dhar ◽  
Suman Chakraborty ◽  
Sunando DasGupta
Keyword(s):  
Viscoelastic Fluids ◽  
Depletion Layer ◽  
Wall Depletion

Depletion layer formation in suspensions of elastic capsules in Newtonian and viscoelastic fluids

2012 ◽  
Vol 24 (6) ◽  
pp. 061902 ◽  
Author(s):  
Pratik Pranay ◽  
Rafael G. Henríquez-Rivera ◽  
Michael D. Graham
Keyword(s):  
Viscoelastic Fluids ◽  
Depletion Layer ◽  
Layer Formation ◽  
Elastic Capsules

Alternating Current Electro-Osmotic Flow of the Maxwell Fluids Through a Circular Micro-Pipe

2012 ◽  
Vol 29 (2) ◽  
pp. 233-240 ◽  
Author(s):  
L.-X. Sun ◽  
Y.-J. Jian ◽  
L. Chang ◽  
H.-Y. Zhang ◽  
Q.-S. Liu
Keyword(s):  
Layer Thickness ◽  
Viscosity Ratio ◽  
Viscoelastic Fluids ◽  
Maxwell Fluid ◽  
Deborah Number ◽  
Depletion Layer ◽  
Velocity Amplitude ◽  
Velocity Magnitude ◽  
Linear Viscoelastic ◽  
Poisson Boltzmann Equation

AbstractAnalytical solutions are presented for time periodic EOF flow of linear viscoelastic fluids through a cylindrical micro-pipe. The linear viscoelastic fluids used here are described by the general Maxwell model. The solution involves analytically solving the linearized Poisson-Boltzmann equation, together with the Cauchy momentum equation and the general Maxwell constitutive equation considering the depletion effect produced by the interaction between macro-molecules of the Maxwell fluid and the channel surface. The overall flow is divided into depletion layer and bulk flow outside of depletion layer. The velocity expressions of these two layers were obtained, respectively. By numerical computations, the influences of the periodic EOF electric oscillating Reynolds number Re, Deborah number De, depletion layer thickness δ and the viscosity ratio γ of Maxwell to Newtonian fluids on velocity profile are presented. For a prescribed De, the increasing Re will cause large changes of the EOF velocity with decreasing velocity magnitude. For a given Re, large De gives large EOF velocity magnitude. Increasing γ will lead to larger velocity amplitude for a given lower Re. However, at higher Re, the velocity amplitude decreases with the viscosity ratio γ, especially within the depletion layer. In addition, large depletion layer thickness gives small EOF velocity magnitude for fixed Re and De. Finally, the influence of De on energy dissipation is studied. These results provide a detail insight of the flow characteristic of this flow configuration.

scholarly journals Plasma depletion layer: the role of the slow mode waves

2004 ◽  
Vol 22 (12) ◽  
pp. 4259-4272 ◽  
Author(s):  
Y. L. Wang ◽  
J. Raeder ◽  
C. T. Russell
Keyword(s):  
Solar Wind ◽  
Depletion Layer ◽  
Slow Mode ◽  
Local Flow ◽  
Flux Tubes ◽  
Mode Group ◽  
A New Technique ◽  
Plasma Depletion

Abstract. The plasma depletion layer (PDL) is a layer on the sunward side of the magnetopause with lower plasma density and higher magnetic field compared to their corresponding values in the upstream magnetosheath. The depletion layer usually occurs during northward (IMF) conditions with low magnetic shear across the magnetopause. We have previously validated the Raeder global model by comparing the computed formation of a magnetosheath density depletion with in-situ observations. We also have performed a detailed force analysis and found the varying roles that different MHD forces play along the path of a plasma parcel flowing around the magnetopause. That study resulted in a new description of the behavior of magnetosheath magnetic flux tubes which better explains the plasma depletion along a flux tube. The slow mode waves have been observed in the magnetosheath and have been used to explain the formation of the PDL in some of the important PDL models. In this study, we extend our former work by investigating the possible role of the slow mode waves for the formation of the PDL, using global MHD model simulations. We propose a new technique to test where a possible slow mode front may occur in the magnetosheath by comparing the slow mode group velocity with the local flow velocity. We find that the slow mode fronts can exist in certain regions in the magnetosheath under certain solar wind conditions. The existence and location of such fronts clearly depend on the IMF. We do not see from our global simulation results either the sharpening of the slow mode front into a slow mode shock or noticeable changes of the flow and field in the magnetosheath across the slow mode front, which implies that the slow mode front is not likely responsible for the formation of the PDL, at least for the stable solar wind conditions used in these simulations. Also, we do not see the two-layered slow mode structures shown in some observations and proposed in certain PDL models. Instead, we see only a one-layered spatial PDL structure under the stable solar wind conditions used in this study.

scholarly journals Flagellar swimming in viscoelastic fluids: role of fluid elastic stress revealed by simulations based on experimental data

2017 ◽  
Vol 14 (135) ◽  
pp. 20170289 ◽  
Author(s):  
Chuanbin Li ◽  
Boyang Qin ◽  
Arvind Gopinath ◽  
Paulo E. Arratia ◽  
Becca Thomases ◽  
...  
Keyword(s):  
Experimental Data ◽  
Elastic Stress ◽  
Viscoelastic Fluids ◽  
Flow Dynamics ◽  
Fluid Type ◽  
Biological Functions ◽  
Fluid Medium ◽  
Fluid Elasticity ◽  
Fluid Theory

Many important biological functions depend on microorganisms' ability to move in viscoelastic fluids such as mucus and wet soil. The effects of fluid elasticity on motility remain poorly understood, partly because the swimmer strokes depend on the properties of the fluid medium, which obfuscates the mechanisms responsible for observed behavioural changes. In this study, we use experimental data on the gaits of Chlamydomonas reinhardtii swimming in Newtonian and viscoelastic fluids as inputs to numerical simulations that decouple the swimmer gait and fluid type in order to isolate the effect of fluid elasticity on swimming. In viscoelastic fluids, cells employing the Newtonian gait swim faster but generate larger stresses and use more power, and as a result the viscoelastic gait is more efficient. Furthermore, we show that fundamental principles of swimming based on viscous fluid theory miss important flow dynamics: fluid elasticity provides an elastic memory effect that increases both the forward and backward speeds, and (unlike purely viscous fluids) larger fluid stress accumulates around flagella moving tangent to the swimming direction, compared with the normal direction.

scholarly journals The role of surface depletion layer effects on the enhancement of the UV emission in ZnO induced by a nanostructured Al surface coating

2020 ◽  
Vol 504 ◽  
pp. 144409 ◽  
Author(s):  
Saskia Fiedler ◽  
Laurent O. Lee Cheong Lem ◽  
Cuong Ton-That ◽  
Matthew R. Phillips
Keyword(s):  
Surface Coating ◽  
Depletion Layer ◽  
Uv Emission ◽  
Surface Depletion

scholarly journals Investigating the Role of Surface Depletion in Governing Electron Transfer Events in Colloidal Plasmonic Nanocrystals

2021 ◽  
Author(s):  
Bharat Tandon ◽  
Sofia A. Shubert-Zuleta ◽  
Delia J. Milliron
Keyword(s):  
Electron Transfer ◽  
Metal Oxide ◽  
Electron Density ◽  
Doping Concentration ◽  
Volume Fraction ◽  
Depletion Layer ◽  
Chemical Doping ◽  
Sn Doping ◽  
Maximum Change

Doped metal oxide nanocrystals (NCs) attract immense attention because of their ability to exhibit a localized surface plasmon resonance (LSPR) that can be tuned extensively across the infrared region of the electromagnetic spectrum. LSPR tunability triggered through compositional and morphological changes during the synthesis (size, shape and doping percentage) is becoming well-established while the principles underlying dynamic, post-synthetic modulation of LSPR are not as well understood. Recent reports have suggested that the presence of a depletion layer on the NC surface may be instrumental in governing the LSPR modulation of doped metal oxide NCs. Here, we employ post-synthetic electron transfer to colloidal Sn-doped In2O3 NCs with varying size and Sn doping concentration to investigate the role of the depletion layer in LSPR modulation. By measuring the maximum change in LSPR frequency after NC reduction, we determine that a large initial volume fraction of the depletion layer in NCs results in a broad modulation of the LSPR energy and intensity. Utilizing a mathematical Drude fitting model, we track the changes in the electron density and the depletion layer volume fraction throughout the chemical doping process, offering fundamental insight into the intrinsic NC response resulting from such electron transfer events. We observe that the maximum change in electron density that can be induced through chemical doping is independent of Sn concentration, and subsequently, the maximum total electron density in the presence of excess reductant is independent of the NC diameter and is dependent only on the as-synthesized Sn doping concentration. This study establishes the central role that surface depletion plays in the electronic changes occurring in the NCs during post-synthetic doping and the results will be instrumental in advancing the understanding of optical and electrical properties of different colloidal plasmonic NCs.

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