Thermal Homogenization in Spherical Reservoir by EHD Conduction Phenomenon

2008 ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Electric Field ◽  
Body Force ◽  
Mixing Time ◽  
Dielectric Fluid ◽  
Dimensionless Numbers ◽  
Fluid Medium ◽  
Two Fluids ◽  
Resultant Velocity ◽  
Higher Temperature ◽  
Spherical Reservoir

Electrohydrodynamic (EHD) conduction phenomenon involves the interaction of electric field and flow field in a dielectric fluid medium via the process of dissociation and recombination of free charges. This paper numerically studies the effect of electric conduction phenomenon on the mixing mechanism of two fluids with identical physical properties but separated due to the non-homogeneity of the temperature field. The fluid is designated to be restored in a spherical reservoir and it is not spontaneously mixed since the reservoir is predicted to be located in non-gravity environment. The electrodes are embedded on the reservoir surface such that the resultant electric body force causes the fluid with higher temperature mixes with the colder fluid and vice versa. The electric field and electric body force distribution and the resultant velocity field are presented. The results are illustrated in the form of time evolution of temperature distribution inside the reservoir. The effects of primary dimensionless numbers on the mixing time are studied.

Thermal Homogenization in Spherical Reservoir by Electrohydrodynamic Conduction Phenomenon

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Temperature Distribution ◽  
Body Force ◽  
Mixing Time ◽  
Electric Conduction ◽  
Nonuniform Temperature ◽  
Dimensionless Numbers ◽  
Steady State Condition ◽  
Resultant Velocity ◽  
Final Steady State ◽  
Spherical Reservoir

Effect of electric conduction phenomenon on the mixing mechanism is studied numerically to thermally homogenize a dielectric liquid with an initial nonuniform temperature distribution. The fluid is stored in a spherical reservoir, and the electrodes are embedded on the reservoir surface such that the resultant local electric body forces mix the fluid. The electric field and electric body force distributions along with the resultant velocity field at the final steady-state condition are presented. The mixing mechanism is illustrated by the time evolution of temperature distribution inside the reservoir. The effects of primary dimensionless numbers on the mixing time are studied.

Nematic ordering of polarizable colloidal rods in an external electric field: theory and experiment

2015 ◽  
Vol 17 (34) ◽  
pp. 22423-22430 ◽  
Author(s):  
Thomas Troppenz ◽  
Anke Kuijk ◽  
Arnout Imhof ◽  
Alfons van Blaaderen ◽  
Marjolein Dijkstra ◽  
...  
Keyword(s):  
Field Theory ◽  
Confocal Microscopy ◽  
Electric Field ◽  
External Electric Field ◽  
Dielectric Fluid ◽  
Fluid Medium ◽  
Nematic Ordering ◽  
Theory And Experiment ◽  
Colloidal Rods

The orientation of dielectric colloidal rods dispersed in a dielectric fluid medium exposed to an external electric field: theory and confocal microscopy measurements.

Control of Dielectric Fluid Flow Distribution in Micro-Tubes With EHD Conduction Pumping: Numerical Study

2011 ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Fluid Flow ◽  
Electric Field ◽  
Conduction Mechanism ◽  
Numerical Study ◽  
Fluid Motion ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Dielectric Fluid ◽  
Total Flow ◽  
Flow Through

The control of fluid flow distribution in micro-scale tubes is numerically investigated. The flow distribution control is achieved via electric conduction mechanism. In electrohydrodynamic (EHD) conduction pumping, when an electric field is applied to a fluid, dissociation and recombination of electrolytic species produces heterocharge layers in the vicinity of electrodes. Attraction between electrodes and heterocharge layers induces a fluid motion and a net flow is generated if the electrodes are asymmetric. The numerical domain comprises a 2-D manifold attached to two bifurcated tubes with one of the tubes equipped with a bank of uniquely designed EHD-conduction electrodes. In the absence of electric field, the total flow supplied at the manifold’s inlet is equally distributed among the tubes. The EHD-conduction, however, operates as a mechanism to manipulate the flow distribution to allow the flow through one branch surpasses the counterpart of the other branch. Its performance is evaluated under various operating conditions.

Parametric Study of Dielectrophoretic Interactive Motion of Particles

2015 ◽  
Author(s):  
Mohammad Robiul Hossan ◽  
Matthew J. Benton ◽  
Prashanta Dutta ◽  
Robert Dillon
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Electric Field ◽  
Free Particle ◽  
Immersed Boundary ◽  
Label Free ◽  
Navier Stokes Equation ◽  
Immersed Interface Method ◽  
Immersed Interface ◽  
Fluid Medium

Dielectrophoresis (DEP) has become one of the most popular mechanisms for label free particle manipulations and transport in microfluidics. The efficacy of this mechanism is greatly dependent on the understanding and control of DEP interactive motion among particles. In this study, we performed a systematic investigation to understand the effect of particles size and electrical properties on DC DEP interactions among particles using in-house hybrid immersed boundary – immersed interface numerical method. Immersed boundary method is employed to predict flow field and immersed interface method is used to simulate electric field. The numerical model utilizes Maxwell’s stress tensor to obtain DEP forces, while solving transient Navier-Stokes equation it determines the hydrodynamic interaction between each of the particles and the fluid containing them. By varying the number of particles as well as the particles’ size, electrical properties and initial orientations, a number of possibilities were considered. Results indicate that the particles with similar electrical conductivities attract each other and tend to align themselves parallel to the external electric field regardless of sizes. If electrical conductivity of particles is lower than that of the fluid medium then the particle-particle interactions is caused by the negative DEP. If electrical conductivity of particles is higher than that of the fluid medium then the interactive motions of particle is attributed to the positive DEP. On the other hand, electrically dissimilar particles still attract each other but tend to align perpendicular to the electric field. Both negative and positive DEP contributes in interactions between electrically dissimilar particles. Numerical simulation also shows that the identical sized particles move at the same speed during interaction. In contrast, smaller particles moves faster than the larger particle during the interactions. This study explains the effect of size and electrical properties on DEP interactive motions of particles and can be utilized to design microfluidic devices for DEP particle manipulations.

scholarly journals Sedimentation of a surfactant-laden drop under the influence of an electric field

2018 ◽  
Vol 849 ◽  
pp. 277-311 ◽  
Author(s):  
Antarip Poddar ◽  
Shubhadeep Mandal ◽  
Aditya Bandopadhyay ◽  
Suman Chakraborty
Keyword(s):  
Surface Tension ◽  
Electric Field ◽  
Surfactant Concentration ◽  
Perturbation Technique ◽  
Internal Flow ◽  
Dielectric Fluid ◽  
Regular Perturbation ◽  
Spherical Drop ◽  
Leaky Dielectric ◽  
Marangoni Stress

The sedimentation of a surfactant-laden deformable viscous drop acted upon by an electric field is considered theoretically. The convection of surfactants in conjunction with the combined effect of electrohydrodynamic flow and sedimentation leads to a locally varying surface tension, which subsequently alters the drop dynamics via the interplay of Marangoni, Maxwell and hydrodynamic stresses. Assuming small capillary number and small electric Reynolds number, we employ a regular perturbation technique to solve the coupled system of governing equations. It is shown that when a leaky dielectric drop is sedimenting in another leaky dielectric fluid, the Marangoni stress can oppose the electrohydrodynamic motion severely, thereby causing corresponding changes in the internal flow pattern. Such effects further result in retardation of the drop settling velocity, which would have otherwise increased due to the influence of charge convection. For non-spherical drop shapes, the effect of Marangoni stress is overcome by the ‘tip-stretching’ effect on the flow field. As a result, the drop deformation gets intensified with an increase in sensitivity of the surface tension to the local surfactant concentration. Consequently, for an oblate type of deformation the elevated drag force causes a further reduction in velocity. For similar reasons, prolate drops experience less drag and settle faster than the surfactant-free case. In addition to this, with increased sensitivity of the interfacial tension to the surfactant concentration, the asymmetric deformation about the equator gets suppressed. These findings may turn out to be of fundamental significance towards designing electrohydrodynamically actuated droplet-based microfluidic systems that are intrinsically tunable by varying the surfactant concentration.

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