scholarly journals Direct Numerical Simulation of Particles in Spatially Varying Electric Fields †

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 52 ◽  
Author(s):  
Edison Amah ◽  
Muhammad Janjua ◽  
Pushpendra Singh
Keyword(s):  
Particle Size ◽  
Electric Fields ◽  
Numerical Scheme ◽  
Particle System ◽  
Particle Interaction ◽  
Body Motion ◽  
Numerical Code ◽  
Electric Force ◽  
Combined System ◽  
Splitting Technique

A numerical scheme is developed to simulate the motion of dielectric particles in the uniform and nonuniform electric fields of microfluidic devices. The motion of particles is simulated using a distributed Lagrange multiplier method (DLM) and the electric force acting on the particles is calculated by integrating the Maxwell stress tensor (MST) over the particle surfaces. One of the key features of the DLM method used is that the fluid-particle system is treated implicitly by using a combined weak formulation, where the forces and moments between the particles and fluid cancel, as they are internal to the combined system. The MST is obtained from the electric potential, which, in turn, is obtained by solving the electrostatic problem. In our numerical scheme, the domain is discretized using a finite element scheme and the Marchuk-Yanenko operator-splitting technique is used to decouple the difficulties associated with the incompressibility constraint, the nonlinear convection term, the rigid-body motion constraint and the electric force term. The numerical code is used to study the motion of particles in a dielectrophoretic cage which can be used to trap and hold particles at its center. If the particles moves away from the center of the cage, a resorting force acts on them towards the center. The MST results show that the ratio of the particle-particle interaction and dielectrophoretic forces decreases with increasing particle size. Therefore, larger particles move primarily under the action of the dielectrophoretic (DEP) force, especially in the high electric field gradient regions. Consequently, when the spacing between the electrodes is comparable to the particle size, instead of collecting on the same electrode by forming chains, they collect at different electrodes.

Direct Numerical Simulations (DNS) of Particles in Spatially Varying Electric Fields

2014 ◽  
Author(s):  
Edison C. Amah ◽  
Pushpendra Singh ◽  
Mohammad Janjua
Keyword(s):  
Electric Fields ◽  
Numerical Scheme ◽  
Particle System ◽  
Particle Diameter ◽  
Solid Particles ◽  
Body Motion ◽  
Point Dipole ◽  
Electric Force ◽  
Combined System ◽  
Splitting Technique

A numerical scheme is developed to simulate the motion of dielectric particles in uniform and nonuniform electric fields of a micro fluidic device. The particles are moved using a direct simulation scheme in which the fundamental equations of motion of fluid and solid particles are solved without the use of models. The motion of particles is tracked using a distributed Lagrange multiplier method (DLM) and the electric force acting on the particles is calculated by integrating the Maxwell stress tensor (MST) over the particle surfaces. One of the key features of the DLM method is that the fluid-particle system is treated implicitly by using a combined weak formulation where the forces and moments between the particles and fluid cancel, as they are internal to the combined system. The MST is obtained from the electric potential, which, in turn, is obtained by solving the electrostatic problem. In our numerical scheme the Marchuk-Yanenko operator-splitting technique is used to decouple the difficulties associated with the incompressibility constraint, the nonlinear convection term, the rigid-body motion constraint and the electric force term. A comparison of the DNS results with those from the point-dipole approximation shows that the accuracy of the latter diminishes when the distance between the particles becomes comparable to the particle diameter; the domain size is comparable to the diameter; and also when the dielectric mismatch between the fluid and particles is relatively large.

Direct Numerical Simulation (DNS) of Suspensions in Spatially Varying Electric Fields

2007 ◽  
Author(s):  
M. Janjua ◽  
S. Nudurupati ◽  
P. Singh ◽  
I. Fischer ◽  
Nadine Aubry
Keyword(s):  
Rigid Body ◽  
Electric Fields ◽  
Lagrange Multiplier ◽  
Numerical Scheme ◽  
Rigid Body Motion ◽  
Solid Particles ◽  
Lagrange Multiplier Method ◽  
Body Motion ◽  
Multiplier Method ◽  
Point Dipole

We have developed a numerical scheme to simulate the motion of dielectric particles in uniform and nonuniform electric fields. The particles are moved using a direct simulation scheme in which the fundamental equations of motion of fluid and solid particles are solved without the use of models. The motion of particles is tracked using a distributed Lagrange multiplier method (DLM) and the electric force acting on the particles is calculated by integrating the Maxwell stress tensor (MST) over the particle surfaces. One of the key features of the DLM method is that the fluid-particle system is treated implicitly by using a combined weak formulation where the forces and moments between the particles and fluid cancel, as they are internal to the combined system. The flow inside the particles is forced to be a rigid-body motion using the distributed Lagrange multiplier method. The MST is obtained from the electric potential, which, in turn, is obtained by solving the electrostatic problem. In our numerical scheme the Marchuk-Yanenko operator-splitting technique is used to decouple the difficulties associated with the incompressibility constraint, the nonlinear convection term, and the rigid-body motion constraint. A comparison of the DNS results with those from the point-dipole approximation shows that the accuracy of the latter diminishes when the distance between the particles becomes comparable to the particle diameter, the domain size is comparable to the diameter, and also when the dielectric mismatch between the fluid and particles is relatively large.

Direct Simulation of Electrorheological Suspensions

2001 ◽  
Author(s):  
Aijun Wang ◽  
Pushpendra Singh ◽  
Nadine Aubry
Keyword(s):  
Electric Field ◽  
Stokes Equations ◽  
Hydrodynamic Force ◽  
Particle System ◽  
Electrostatic Force ◽  
Body Motion ◽  
Three Dimensions ◽  
Spherical Particles ◽  
Point Dipole ◽  
Direct Simulation

Abstract A new distributed multiplier/fictitious (DLM) domain method is developed for direct simulation of electrorheological (ER) suspensions subjected to spatially uniform electrical fields. The method is implemented both in two and three dimensions. The fluid-particle system is treated implicitly using the combined weak formulation described in [1,2]. The governing Navier-Stokes equations for the fluid are solved everywhere, including the interior of the particles. The flow inside the particles is forced to be a rigid body motion by a distribution of Lagrange multipliers. The electrostatic force acting on the polarized spherical particles is modeled based on the point-dipole approximation. Using our code we have studied the time evolution of particle-scale structures of ER suspensions in channels subjected to the pressure driven flow. In our study, the flow direction is perpendicular to that of the electric field. Simulations show that when the hydrodynamic force is zero, or very small compared to the electrostatic force, the particles form chains that are aligned approximately parallel to the direction of electric field. But, when the magnitude of hydrodynamic force is comparable to that of the electrostatic force the particle chains orient at an angle with the direction of the electric field. The angle between the particle chain and the direction of the electric field depends on the relative strengths of the hydrodynamic and electrostatic forces.

Comparative Study on Micronsized and Nanosized Carica papaya Seed Modified Pullulan as Biocoagulant in Wastewater Treatment

2021 ◽  
Vol 317 ◽  
pp. 276-282
Author(s):  
Deong Jing Lie ◽  
Mazatusziha Ahmad ◽  
Nur Sabrina Azhar
Keyword(s):  
Particle Size ◽  
Wastewater Treatment ◽  
Carica Papaya ◽  
Municipal Wastewater ◽  
Particle Interaction ◽  
Test Method ◽  
Treated Wastewater ◽  
Limited Information ◽  
Natural Polymers ◽  
Jar Test

Plant-based coagulants have been used as an alternative material to replace chemical coagulant in wastewater treatment. So far, limited information was found on the incorporation of plant-based biocoagulant to natural polymers and the effect of particle size upon wastewater treatment application. Thus, this study was conducted to explore the effectiveness of micronsized and nanosized Carica Papaya (CP) seed modified pullulan as biocoagulant. Biocoagulant were prepared at different composition of CP to pullulan, with the CP content range from 1% to 9%. The biocoagulant were characterized via Particle Size Analyzer (PSA), Fourier Transform Infrared Spectroscopy (FTIR) and morphological analysis via Field Emission Scanning Electron Microscopy (FESEM). It was used to treat municipal wastewater. The treated wastewater quality was analyzed by jar test method with dosage of biocoagulant used was 0.6g/L. Result showed that the 10% (D10), 50% (D50) and 90% (D90) distribution of micronsized CP had particle size of 0.3675 µm, 0.8433 µm and 1.9537 µm respectively. The nanosized CP was 0.4473nm (D10), 2.3758nm (D50) and 2.9938nm (D90). Characterization of biocoagulant via FTIR revealed the appearance of O-H, C=O, C-H and C-O-C bond which contribute to particle interaction for turbidity reduction of wastewater. Jar test analysis found that at 3% micronsized CP and 7% nanosized CP were able to reduce turbidity up to 59.65% and 65.27% respectively. Both size of biocoagulant slightly changed the pH of treated wastewater to neutral, increased in dissolved oxygen (DO) and reduced in total suspended solid (TSS). Overall, nanosized CP was found more effective as compared to micronsized CP.

Structure Formation of Sulfur-Based Composite: The Model

2014 ◽  
Vol 1040 ◽  
pp. 592-595 ◽  
Author(s):  
Denis G. Kiselev ◽  
Evgeniy Valerjevich Korolev ◽  
Vladimir Smirnov
Keyword(s):  
Boundary Layer ◽  
Particle System ◽  
Particle Interaction ◽  
Numerical Algorithms ◽  
Binary Interaction ◽  
Environment Interaction ◽  
Simultaneous Application ◽  
Numerical Studies ◽  
Key Factor ◽  
The Law

In material science the simultaneous application of theoretical examination, experimental and numerical studies are often required. This is especially true for modern composite materials with extra inter-boundary nanoscale layers. Thickness of layers is usually about tens of nanometers, while diameters of particles of filler are about several hundreds of nanometers. Thus, during the theoretical study and numerical experiments the size and properties of inter-boundary layer must be taken into account. The proper choice of the model is the key factor for the adequate results of simulation. In the present work we have derived such a model. The system under investigation – disperse-filled composite material with inter-boundary layers of different properties – is represented by particle system; these classes of models can be characterized by high generality. Initial equation for the law of motion is sequentially extended with terms which account for different phenomena – conservative binary interaction, non-conservative interaction with environment, interaction with planar boundaries and non-conservative particle-particle interaction via inter-boundary layer. The reduction of the law of motion to the system of ordinary differential equations had opened the possibility for utilization of the vast majority of numerical algorithms for the prediction of the structural properties of nanomodified sulfur-based composite.

Classification Inversion Algorithm of Circular Cylinder Particle Size Distribution Based on the Light Extinction Date

2011 ◽  
Vol 105-107 ◽  
pp. 2113-2116
Author(s):  
Hong Tang ◽  
Wen Bin Zheng
Keyword(s):  
Particle Size ◽  
Circular Cylinder ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle System ◽  
Distribution Functions ◽  
Light Extinction ◽  
Particle Sizing ◽  
Inversion Algorithm ◽  
Cylinder Particle

Particulate flow is commonly encountered in industries as well as in many other chemical and mechanical engineering applications. The accurate measurement of particle size distribution is of the utmost importance since it decides the physical and chemical characteristic of the particles. The light extinction method can be used for in-line monitoring of particle systems thus providing real time measurements of both particle size distribution and particle concentration. In light extinction particle sizing, a classification inversion algorithm is proposed for the circular cylinder particles. The measured circular cylinder particle system is inversed with different particle distribution functions and classified according to the inversion errors in the dependent model. The simulation experiments illustrate that it is feasible to use the inversion errors of object functions to inverse the circular cylinder particle size distribution in the light extinction particle sizing technique. This classing inversion algorithm can avoid the defects that the type of the size distribution must be assumed beforehand for the light extinction method.

scholarly journals ELECTRIC FORCE LINES OF THE DOUBLE REISSNER–NORDSTROM EXACT SOLUTION

2008 ◽  
Vol 17 (08) ◽  
pp. 1159-1177 ◽  
Author(s):  
ARMANDO PAOLINO ◽  
MARCO PIZZI
Keyword(s):  
Exact Solution ◽  
Black Hole ◽  
Electric Fields ◽  
Maxwell Equation ◽  
Naked Singularity ◽  
Extreme Case ◽  
The Other ◽  
Electric Force ◽  
Coordinate Systems ◽  
Equal Sign

Recently Alekseev and Belinski have presented a new exact solution to the Einstein–Maxwell equation which describes two Reissner–Nordstrom (RN) sources in reciprocal equilibrium (no struts or strings); one source is a naked singularity, the other is a black hole: this is the only possible configuration for two separable objects, apart from the well-known extreme case (mi = ei). In the present paper, after a brief summary of this solution, we study in some detail the coordinate systems used and the main features of the gravitational and electric fields. In particular, we graph the plots of the electric force lines in three qualitatively different situations: equal-sign charges, opposite charges and the case of a naked singularity near a neutral black hole.

Direct Simulation of Electrorheological Suspensions Subjected to Spatially Nonuniform Electric Field

2002 ◽  
Author(s):  
J. Kadaksham ◽  
P. Singh ◽  
N. Aubry
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Lagrange Multiplier ◽  
Dipole Approximation ◽  
Nonuniform Electric Field ◽  
Lagrange Multiplier Method ◽  
Body Motion ◽  
Multiplier Method ◽  
Point Dipole ◽  
Time Step

A numerical method based on the distributed Lagrange Multiplier method (DLM) [2,8] is developed for direct simulations of electrorheological (ER) liquids subjected to spatially varying electric fields. The flow inside particle boundaries is constrained to be rigid body motion by the distributed Lagrange multiplier method. The point-dipole approximation [6] is used to model the electrostatic forces acting on the polarized particles. The code is verified by performing a convergence study that shows that the results are independent of mesh and time step sizes. In a spatially nonuniform electric field the particles move to the regions where the magnitude of electric field is locally maximum when the particle permittivity is greater than that of the liquid. On the other hand, when the particle permittivity is smaller than that of the liquid the particles move to the regions of local minimum of electric field.

A Remediation Scheme to Global Warming: Engineering Biodegradable Aerosols With Maximum Scattering Potential

2006 ◽  
Author(s):  
Daniel Attinger ◽  
Brendan Green
Keyword(s):  
Particle Size ◽  
Global Warming ◽  
Exploratory Study ◽  
Mie Scattering ◽  
Index Of Refraction ◽  
Numerical Code ◽  
Biodegradable Nanoparticles ◽  
Tiny Amount ◽  
Wide Range ◽  
Scattering Potential

This exploratory study evaluates the following moderation scheme against global warming: deploying nanoparticles in the atmosphere in order to scatter a tiny amount of sunlight (1% or 2W/m2) up to space. Such a strategy could be a last-resort method to counteract unbearable effects of global warming. For particles made of a wide range of known materials, the scattering ability is defined to quantify how efficient the particle is at scattering sunlight. This scattering ability is a function of the particle radius and index of refraction, and is calculated by an in-house numerical code solving the Mie scattering equations. The code is validated against scattering calculations for SO2 particles published by Schwartz[1]. Our calculations show that an optimum particle size exists, which would minimize the amounts to be deployed in the atmosphere. Also, we evaluate the deployment of biodegradable nanoparticles, which would counteract global warming and minimize dangers related to their redeposition.

Electrically Assisted Aerosol Reactors using Ring Electrodes

1998 ◽  
Vol 520 ◽  
Author(s):  
H. Briesen ◽  
A. Fuhrmann ◽  
S. E. Pratsinis
Keyword(s):  
Particle Size ◽  
Electric Fields ◽  
Optical Fibers ◽  
Total Production ◽  
Electrical Fields ◽  
Synthesis Of Nanoparticles ◽  
Practical Applications ◽  
Electrically Assisted ◽  
Aerosol Reactors ◽  
Electrostatic Dispersion

ABSTRACTNanostructured materials have distinctly different properties than the bulk because the number of atoms or molecules on their surface is comparable to that inside the particles creating a number of new materials and applications. Despite this potential for nanoparticles, very few practical applications have been developed because of the current high cost of these materials ($100/lb). On the other hand, flame aerosol reactors are routinely used for inexpensive production (∼$1/lb) of submicron sized commodities such as carbon blacks, pigmentary titania, fumed silica and preforms for optical fibers in telecommunications. Flame technology can be used also for synthesis of nanoparticles with precisely controlled characteristics. In these reactors, gas mixing is used to widely control the primary particle size and crystallinity of product powders while electric fields can be used to narrowly control the primary, and aggregate particle size and crystallinity. Here the application of axial electrical fields on a silica producing flame using hexamethyldisiloxane (HMDS) as precursor is presented. Experiments varying the precursor delivery rate corresponding to total production rates of 10, 20 and 30 g/h are presented. Electric fields decreased the particle size by electrostatic dispersion and repulsion of charged particles and by the reduced particle residence time inside the flame.

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