The pre -breakdown characteristics of weakly ionized media in the high non-uniform electric field using calculations with refined grid cells

Abstract The theoretical model of a pre-breakdown ions formation in a liquid dielectric and their flows, caused by high non-uniform electric field is represented. The 3D system of the macroscopic pre-breakdown electrohydrodynamic equations is written. Influence of the electric field on the molecule dissociation rate is taken into account. The system includes the Poison equation for electric field potential, the equation of ions formation and the Navier-Stokes equations with electric force. In addition, results of modelling using refined mesh are presented.

Download Full-text

Study of the Effect of Electrophoresis on Transport of Biomolecules in Microreactors

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 1 ◽

10.1115/icnmm2011-58165 ◽

2011 ◽

Author(s):

Sina Jomeh ◽

Mina Hoorfar

Keyword(s):

Electric Field ◽

Charge Density ◽

Space Charge ◽

Stokes Equations ◽

Surface Concentration ◽

Space Charge Density ◽

Uniform Electric Field ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Chemical Reaction Kinetics

The effect of electrophoresis (i.e., applying uniform electric field to use the natural charge of particles) on the transport of a sample (like biomolecules) in active microreactors is numerically investigated. Navier-Stokes equations are solved along with the equations of electrostatics, species mass transport in the buffer and chemical reaction kinetics at reactive surfaces. Unlike previous studies, in which the effect of the charge of the sample bulk on the electric field has been neglected (i.e., the assumption of electroneutrality), here space charge density is assumed to be nonzero. As a result, the governing equations become fully coupled. The efficiency of the microreactor device is analyzed for two different geometries commonly used in biomolecule separation (i.e., open channel and microcylinders). It is shown that the electroneutrality assumption can drastically influence the final adsorbed concentration depending on the device configuration. Average adsorbed surface concentration is compared for each case as a measure of the performance of the device. The plots depicting the influence of the electric field and nonzero space charge density on the bulk concentration profile and the velocity field are also presented and discussed.

Download Full-text

Numerical Investigation of the Coulter Principle in a Microfluidic Device

Volume 2, Fora: Cavitation and Multiphase Flow; Fluid Measurements and Instrumentation; Microfluidics; Multiphase Flows: Work in Progress ◽

10.1115/fedsm2013-16011 ◽

2013 ◽

Author(s):

Muheng Zhang ◽

Yongsheng Lian

Keyword(s):

Electric Field ◽

Stokes Equations ◽

Equations Of Motion ◽

Navier Stokes ◽

Working Mechanism ◽

Navier Stokes Equations ◽

Sheath Flow ◽

Coulter Counters ◽

Pass Through ◽

Cell Motion

Coulter counters are analytical microfluidic instrument used to measure the size and concentration of biological cells or colloid particles suspended in electrolyte. The underlying working mechanism of Coulter counters is the Coulter principle which relies on the fact that when low-conductive cells pass through an electric field these cells cause disturbances in the measurement (current or voltage). Useful information about these cells can be obtained by analyzing these disturbances if an accurate correlation between the measured disturbances and cell characteristics. In this paper we use computational fluid dynamics method to investigate this correlation. The flow field is described by solving the Navier-Stokes equations, the electric field is represented by a Laplace’s equation in which the conductivity is calculated from the Navier-Stokes equations, and the cell motion is calculated by solving the equations of motion. The accuracy of the code is validated by comparing with analytical solutions. The study is based on a coplanar Coulter counter with three inlets that consist of two sheath flow inlet and one conductive flow inlet. The effects of diffusivity, cell size, sheath flow rate, and cell geometry are discussed in details. The impacts of electrode size, gap between electrodes and electrode location on the measured distribution are also studied.

Download Full-text

The Effect of Electrostatic Forces on the Distribution of Drops in a Channel

Volume 2: Symposia and General Papers, Parts A and B ◽

10.1115/fedsm2002-31237 ◽

2002 ◽

Author(s):

Arturo Ferna´ndez ◽

Jiacai Lu ◽

Asghar Esmaeeli ◽

Gre´tar Tryggvason

Keyword(s):

Electric Field ◽

Electric Fields ◽

Hydrodynamic Interaction ◽

Stokes Equations ◽

Navier Stokes ◽

Governing Equations ◽

Navier Stokes Equations ◽

Dielectric Fluids ◽

Wide Range ◽

Leaky Dielectric Model

Direct numerical simulations are used to examine the effect of electric fields on the behavior of suspension of drops in dielectric fluids. The effect of electric field is modeled using the “leaky dielectric” model, coupled with the full Navier-Stokes equations. The governing equations are solved using a front-tracking/finite volume technique. The interaction of the drops is strongly dependant on the conductivity and the permittivity ratio, but fibration, where drops line up into long columns, takes place over a wide range of these parameters. The hydrodynamic interaction due to fluid circulation induced by the electric field has a strong influence on the drop distribution and the rate of fibration.

Download Full-text

Effect of Electrostatic Field on Film Rupture

Journal of Fluids Engineering ◽

10.1115/1.2823519 ◽

1999 ◽

Vol 121 (3) ◽

pp. 651-655 ◽

Cited By ~ 8

Author(s):

Rama Subba Reddy Gorla ◽

Larry W. Byrd

Keyword(s):

Electric Field ◽

Electrostatic Field ◽

Body Force ◽

Stokes Equations ◽

Finite Amplitude ◽

Navier Stokes ◽

Film Rupture ◽

Navier Stokes Equations ◽

Long Wavelength ◽

The Stability

Nonlinear thin film rupture has been analyzed by investigating the stability of films under the influence of a nonuniform electrostatic field to finite amplitude disturbances. The dynamics of the liquid film is formulated using the Navier-Stokes equations including a body force term due to van der Waals attractions. The effect of the electric field is included in the analysis only in the boundary condition at the liquid vapor interface. The governing equation was solved by finite difference method as part of an initial value problem for spatial periodic boundary conditions. The electric field stabilizes the film and increases the time to rupture when a long wavelength perturbation is introduced.

Download Full-text

Remarks on the asymptotic behaviour of solutions to the compressible Navier–Stokes equations in the half-line

Proceedings of the Royal Society of Edinburgh Section A Mathematics ◽

10.1017/s030821050200032x ◽

2002 ◽

Vol 132 (03) ◽

pp. 627

Keyword(s):

Asymptotic Behaviour ◽

Stokes Equations ◽

Half Line ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Asymptotic Behaviour Of Solutions

Download Full-text

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.4.2020.05.0579 ◽

2020 ◽

Vol 14 (4) ◽

pp. 7369-7378

Author(s):

Ky-Quang Pham ◽

Xuan-Truong Le ◽

Cong-Truong Dinh

Keyword(s):

Stokes Equations ◽

Three Dimensional ◽

Axial Compressor ◽

Aerodynamic Performance ◽

Numerical Results ◽

Single Stage ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Operating Stability ◽

Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

Download Full-text