Numerical Simulations of Electric Field Driven Self-Assembly of Monolayers of Mixtures of Nanoparticles

2017 ◽  
Author(s):  
E. Amah ◽  
N. Musunuri ◽  
Ian S. Fischer ◽  
Pushpendra Singh
Keyword(s):  
Electric Field ◽  
Physical Properties ◽  
Numerical Simulations ◽  
Self Assembly ◽  
Composite Particle ◽  
Critical Value ◽  
Direct Numerical Simulations ◽  
Composite Particles ◽  
Liquid Interfaces ◽  
Induced Dipole

We numerically study the process of self-assembly of particle mixtures on fluid-liquid interfaces when an electric field is applied in the direction normal to the interface. The force law for the dependence of the electric field induced dipole-dipole and capillary forces on the distance between the particles and their physical properties obtained in an earlier study by performing direct numerical simulations is used for conducting simulations. The inter-particle forces cause mixtures of nanoparticles to self-assemble into molecular-like hierarchical arrangements consisting of composite particles which are organized in a pattern. However, there is a critical electric intensity value below which particles move under the influence of Brownian forces and do not self-assemble. Above the critical value, when the particles sizes differed by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles forming a ring around it. Approximately same sized particles, when their concentrations are approximately equal, form binary particles or chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate, but when their concentrations differ the particles whose concentration is larger form rings around the particles with smaller concentration.

Self-Assembly of Monolayers of Mixtures of Particles

2016 ◽  
Author(s):  
Edison C. Amah ◽  
Naga Musunuri ◽  
Ian S. Fischer ◽  
Pushpendra Singh ◽  
Md. Shahadat Hossain
Keyword(s):  
Electric Field ◽  
Field Intensity ◽  
Self Assembly ◽  
Electric Field Intensity ◽  
Composite Particle ◽  
The Self ◽  
The Other ◽  
Composite Particles ◽  
Liquid Interfaces ◽  
Number Of Particles

We have numerically studied the self-assembly process of particle mixtures on fluid-liquid interfaces when an electric field is applied in the direction normal to the interface. The electric and capillary forces on the particles causes them to self-assemble into molecular-like hierarchical arrangements consisting of composite particles arranged in a pattern. As in experiments, the structure of a composite particle depends on factors such as the relative sizes of the particles and their polarizibilities, and the electric field intensity. If the particles sizes differ by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles forming a ring around it. The number of particles in the ring and the spacing between the composite particles depends on their relative polarizibilities, the size of the smaller particles and the electric field intensity. Approximately same sized particles, on the other hand, form chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate.

Self-Assembly of Monolayers of Submicron Sized Particles on Thin Liquid Films

2013 ◽  
Author(s):  
Shriram Pillapakkam ◽  
N. A. Musunuri ◽  
P. Singh
Keyword(s):  
Electric Field ◽  
Self Assembly ◽  
Uv Light ◽  
Capillary Forces ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Liquid Interfaces ◽  
Uv Curable ◽  
Particle Monolayer ◽  
Uv Curable Resin

In this paper, we present a technique for freezing monolayers of micron and sub-micron sized particles onto the surface of a flexible thin film after the self-assembly of a particle monolayer on fluid-liquid interfaces has been improved by the process we have developed where an electric field is applied in the direction normal to the interface. Particles smaller than about 10 microns do not self-assemble under the action of lateral capillary forces alone since capillary forces amongst them are small compared to Brownian forces. We have overcome this problem by applying an electric field in the direction normal to the interface which gives rise to dipoledipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another liquid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film.

scholarly journals Turbulent drag reduction by anisotropic permeable substrates – analysis and direct numerical simulations

2019 ◽  
Vol 875 ◽  
pp. 124-172 ◽  
Author(s):  
G. Gómez-de-Segura ◽  
R. García-Mayoral
Keyword(s):  
Drag Reduction ◽  
Numerical Simulations ◽  
Critical Value ◽  
Direct Numerical Simulations ◽  
Mean Flow ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
Theoretical Predictions ◽  
The Mean ◽  
The Difference

We explore the ability of anisotropic permeable substrates to reduce turbulent skin friction, studying the influence that these substrates have on the overlying turbulence. For this, we perform direct numerical simulations of channel flows bounded by permeable substrates. The results confirm theoretical predictions, and the resulting drag curves are similar to those of riblets. For small permeabilities, the drag reduction is proportional to the difference between the streamwise and spanwise permeabilities. This linear regime breaks down for a critical value of the wall-normal permeability, beyond which the performance begins to degrade. We observe that the degradation is associated with the appearance of spanwise-coherent structures, attributed to a Kelvin–Helmholtz-like instability of the mean flow. This feature is common to a variety of obstructed flows, and linear stability analysis can be used to predict it. For large permeabilities, these structures become prevalent in the flow, outweighing the drag-reducing effect of slip and eventually leading to an increase of drag. For the substrate configurations considered, the largest drag reduction observed is ${\approx}$20–25 % at a friction Reynolds number $\unicode[STIX]{x1D6FF}^{+}=180$.

scholarly journals THIN SHELL WORMHOLE DUE TO DYADOSPHERE OF A CHARGED BLACK HOLE

2009 ◽  
Vol 24 (01) ◽  
pp. 53-61 ◽  
Author(s):  
F. RAHAMAN ◽  
M. KALAM ◽  
K. A. RAHMAN
Keyword(s):  
Black Hole ◽  
Electric Field ◽  
Physical Properties ◽  
Pair Production ◽  
Thin Shell ◽  
Gamma Ray ◽  
Critical Value ◽  
Gamma Ray Bursts ◽  
Charged Black Hole ◽  
Special Region

To explain Gamma Ray Bursts, Ruffini argued that the event horizon of a charged black hole is surrounded by a special region called, the Dyadosphere where electric field exceeds the critical value for e+e- pair production. In the present work, we construct a thin shell wormhole by performing a thought surgery between two dadospheres. Several physical properties of this thin shell wormhole have been analyzed.

scholarly journals Lyapunov dimension of elastic turbulence

2017 ◽  
Vol 822 ◽  
Author(s):  
Emmanuel Lance Christopher VI M. Plan ◽  
Anupam Gupta ◽  
Dario Vincenzi ◽  
John D. Gibbon
Keyword(s):  
Reynolds Number ◽  
Constitutive Model ◽  
Numerical Simulations ◽  
Mathematical Analysis ◽  
Critical Value ◽  
Weissenberg Number ◽  
Direct Numerical Simulations ◽  
Chaotic Behaviour ◽  
Two Dimensional ◽  
Lyapunov Dimension

Low-Reynolds-number polymer solutions exhibit a chaotic behaviour known as ‘elastic turbulence’ when the Weissenberg number exceeds a critical value. The two-dimensional Oldroyd-B model is the simplest constitutive model that reproduces this phenomenon. To make a practical estimate of the resolution scale of the dynamics, one requires the assumption that an attractor of the Oldroyd-B model exists; numerical simulations show that the quantities on which this assumption is based are bounded. We estimate the Lyapunov dimension of this assumed attractor as a function of the Weissenberg number by combining a mathematical analysis of the model with direct numerical simulations.

Redistribution and Removal of Particles From Drop Surfaces

2009 ◽  
Author(s):  
S. Nudurupati ◽  
M. Janjua ◽  
P. Singh ◽  
N. Aubry
Keyword(s):  
Dielectric Properties ◽  
Electric Field ◽  
Physical Properties ◽  
Electric Field Intensity ◽  
Drop Size ◽  
Dimensionless Parameter ◽  
Critical Value ◽  
Uniform Electric Field ◽  
Dielectrophoretic Force ◽  
Drop Radius

It was recently shown by us that particles distributed on the surface of a drop can be concentrated at the poles or equator of the drop by subjecting the latter to a uniform electric field. In this paper, we present experimental results for the dependence of the dielectrophoretic force on the parameters of the system such as the particles’ and drop’s radii and the dielectric properties of the fluids and particles, and define a dimensionless parameter regime for which the technique can work. Specifically, we show that if the drop radius is larger than a critical value, that depends on the physical properties of the drop and ambient fluids and the particles, it is not possible to concentrate particles and thus clean the drop of the particles it carries at its surface because the drop breaks or tip-streams at an electric field intensity smaller than that needed for concentrating particles. However, since the dielectrophoretic force varies inversely with the drop radius, the effectiveness of the concentration mechanism increases with decreasing drop size, and therefore the technique is guaranteed to work provided the drop radius is sufficiently small.

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