Electrohydrodynamics Research Papers - Academia.edu (original) (raw)

Here we implemented a 3D comprehensive Eulerian-Lagrangian model in order to investigate the electrostatic spray transfer processes in the high-speed rotary bell sprayer. This efficient algorithm contains spray dynamics, airflow, paint... more

Here we implemented a 3D comprehensive Eulerian-Lagrangian model in order to investigate the electrostatic spray transfer processes in the high-speed rotary bell sprayer. This efficient algorithm contains spray dynamics, airflow, paint droplets tracking and an electrostatic effect to simulate atomization. The algorithm is implemented using the OpenFOAM package. A solver for the particle trajectory was used to illustrate the process of spray transport and also the interaction of the airflow and the particle that is solved by momentum coupling. Creating an initial condition of the particle approach has been proposed that is matched with practical applications. The fluid-dynamics is simulated by solving the unsteady 3D compressible Navier-Stokes equations. Unsteady flow is computed by using a Large eddy simulation (LES) turbulence approach, while the motion of the particles is simulated by tracking the droplet size distribution approach. The model correctly predicts that the bell cup spin forces the paint particles to fall off from the bell surface towards the high-velocity airflow. The present work illustrates a tentative benchmark and contains a systematic analysis of the recirculation zone length, the toroidal vortex, the overspray phenomena and the flowfield characteristics like mean velocity, pressure, turbulent kinetic energy and velocity fluctuation. The results indicate as dominant operating parameter the air-paint flow rate with voltage level deeply affecting the spray shape. A more uniform distribution of the coating is obtained by growing this high-velocity shaping airflow, although the values of the transfer efficiency (TE) are reduced. The distribution of the particle size is very sensitive to changes in the rotational speed. Experimental results obtained in this study put forward a clear link between the shaping air flow rate and the rotation frequency on the aerodynamics and also provide valuable insights to design modern ERBS. The paint spray distribution obtained in the present work is validated against coating experimental results with suitable accuracy.

The effect of the electrohydrodynamic system with various electrode layouts on a solar chimney pilot is investigated experimentally. A pilot setup was constructed which consisted of a chimney with 3 m height and 3 m collector diameter.... more

The effect of the electrohydrodynamic system with various electrode layouts on a solar chimney pilot is investigated experimentally. A pilot setup was constructed which consisted of a chimney with 3 m height and 3 m collector diameter. The purpose of this research was to enhance the solar chimney performance with the electrohydrodynamic system for the parallel, radial, and symmetric layouts. By using of corona wind, the outlet fluid temperature is increased, and the outlet absorber is decreased. For the three layouts , the most growth in the outlet fluid temperature is 14 °C, which is observed in the parallel layout. Also, in the parallel array, the most outlet absorber temperature drop is 7 °C. The results show that parallel layout with six electrodes and 3 cm spacing between the electrodes has the best performance. Also, various hours of the day are studied and the best time for turning on the electrohydrodynamic system is 1:00 p.m. The electrohydrodynamic system makes an increase in the fluid velocity from 1.7 to 2.3 m s À1 , and this growth improves the performance about 28%.

The use of ionic wind propulsion for aircraft has been discussed in the literature. Here the authors discuss ionic wind propulsion as a transport possibility in space which is conceivable although, presently theoretical. With the current... more

The use of ionic wind propulsion for aircraft has been discussed in the literature. Here the authors discuss ionic wind propulsion as a transport possibility in space which is conceivable although, presently theoretical. With the current advancements in technology, such a propulsion system not only seems much more feasible outside of Earth, it also offers a promising means of transport in the future for human exploration and habitation on the moon or within the inner-planets.

The net drag result of the ionic current in a conductive fluid, such as electrohydrodynamic (EHD) effect and electrospray (Taylor cone effect), has been investigated as a space and energy saving technology for enforced heat and mass... more

The net drag result of the ionic current in a conductive fluid, such as electrohydrodynamic (EHD) effect and electrospray (Taylor cone effect), has been investigated as a space and energy saving technology for enforced heat and mass management. Electrostatically enforced evaporation, convection, and phase-change thermal transfer are briefly discussed and experimentally evaluated. The emphasis of the investigation was on the maximal efficiency of the consumed power. The significance of EHD phenomena for energy saving is demonstrated with examples of temperature stabilization for solid-state lighting and the dewatering of pulp in the paper industry.

We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a horizontal surface in the presence of an electric field applied parallel to the surface. The model includes the effect of bounding solid... more

We investigate the electrostatic stabilization of a viscous thin film wetting the underside of a horizontal surface in the presence of an electric field applied parallel to the surface. The model includes the effect of bounding solid dielectric regions above and below the liquid-air system that are typically found in experiments. The competition between gravitational forces, surface tension and the nonlocal effect of the applied electric field is captured analytically in the form of a nonlinear evolution equation. A semi-spectral solution strategy is employed to resolve the dynamics of the resulting partial differential equation. Furthermore, we conduct direct numerical simulations (DNS) of the Navier-Stokes equations using the volume-of-fluid methodology and assess the accuracy of the obtained solutions in the long-wave (thin film) regime when varying the electric field strength from zero up to the point when complete stabilization occurs. We employ DNS to examine the limitations of the asymptotically derived behavior as the liquid layer thickness increases, and find excellent agreement even beyond the regime of strict applicability of the asymptotic solution. Finally, the asymptotic and computational approaches are utilized to identify robust and efficient active control mechanisms allowing the manipulation of the fluid interface in light of engineering applications at small scales, such as mixing.

This paper presents a numerical performance evaluation of the electrostatic rotary bell sprayer (ERBS) with a particular focus on droplet charge, electric field, and ambient conditions through the implementation of a high-voltage... more

This paper presents a numerical performance evaluation of the electrostatic rotary bell sprayer (ERBS) with a particular focus on droplet
charge, electric field, and ambient conditions through the implementation of a high-voltage control-ring field pattern effect into the fully turbulent airflow and by including the atomized droplets discrete phase. The simulation shows that the inclusion of droplet charging and electric
field coupling, with different parametric values, significantly impacts the atomized droplet distribution over the spray plume and the deposition rate. This analysis was conducted using a three-dimensional (3D) Eulerian–Lagrangian model to describe the two-phase spraying flow
by extending the base OpenFOAM package. The procedure includes an unsteady compressible Navier–Stokes solver combined with a large
Eddy simulation approach to model turbulence effects on the air flowfield. This is coupled to the spray dynamics by including droplet trajectory tracking, wall film dynamics, and electric field charge. The approach is further extended to include the evaporation phenomenon and
the transport of its products. Compared to a conventional ERBS, herein, we provide an in-depth analysis of the fluid dynamic characteristics
around the ERBS with a control-ring field pattern for vorticity, velocity, and electrical fields. The results indicate that the control-ring operation improves the performance and transfer efficiency of the ERBS, and it also helps to harmonize the direction of the charged paint droplets.
For the first time, finding a balance between the effect of the inside bell cup surface and control-ring voltage and charged droplet has been
conducted.

Single event electrospraying (SEE) is a method for the on-demand deposition of picoliter volumes of liquid. To investigate the influence of the size of the meniscus on the volume deposited per SEE, glass capillaries were used with and... more

Single event electrospraying (SEE) is a method for the on-demand deposition of picoliter volumes of liquid. To investigate the influence of the size of the meniscus on the volume deposited per SEE, glass capillaries were used with and without an anti-wetting coating comprising a self-assembled 1H,1H,2H,2H-perfluorodecyltrichlorosilane-based monolayer to control the meniscus size. The deposited volume was determined experimentally and we developed a model that incorporates electrostatics and electrodynamics on the one hand, and hydrostatics, fluid dynamics, and surface tension effects on the other hand. The volumes deposited from both a capillary with unmodified nozzle front (large meniscus) and from a capillary with a modified nozzle front (small meniscus) can be predicted by the theoretical model.

The electro-spinning process and morphology of electro spun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: a) solution properties, b) processing conditions, c) ambient conditions.... more

The electro-spinning process and morphology of electro spun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: a) solution properties, b) processing conditions, c) ambient conditions. In this paper, we report the results of a comprehensive investigation of the effects of changing the conductivity of poly ethylene oxide (PEO) water solution on electro-spinning process and fiber morphology. The effects of the conductivity of PEO solution on jet current and jet path are discussed. Furthermore, fiber diameter and fiber uniformity are investigated by using scanning electron microscopy (SEM) techniques. It was found that the fiber diameter decreases with increasing solution conductivity at first, reaches a minimum value and it increases again.

Abstract: With the present article, the authors summarize over 15 years of work dedicated to studying the effects of the electrical and the gravitational force fields on two-phase and single-phase thermofluid dynamics. Results obtained on... more

Abstract: With the present article, the authors summarize over 15 years of work dedicated to studying the effects of the electrical and the gravitational force fields on two-phase and single-phase thermofluid dynamics. Results obtained on several microgravity platforms are presented and the role played by the electric field in the different heat transfer processes is analyzed. In particular, the regimes of nucleate boiling and film boiling are treated. Also, the parameters controlling the liquid–vapor interface instability and the main consequences regarding the critical heat flux (CHF) are outlined. In the final section, the promising technique of ion injection for efficient heat transfer enhancement in single-phase liquids is described, together with the main results obtained under different flow regimes and geometries. The following dielectrics were compared: R113, Vertrel XF, and FC-72 for the pool boiling research; again FC-72 and HFE-7100 for the single-phase convection heat transfer experiments.

Fe-ZSM-5 catalysts, prepared by different methods, have been characterized by TPR and XRD and tested in the NO-SCR by NH3. The sublimation method leads to the most active catalysts. Nevertheless the preparation starting from Fe(acac)3,... more

Fe-ZSM-5 catalysts, prepared by different methods, have been characterized by TPR and XRD and tested in the NO-SCR by NH3. The sublimation method leads to the most active catalysts. Nevertheless the preparation starting from Fe(acac)3, which is a preparation easy to implement from an industrial point of view, seems to be a very attractive alternative way.On the most active catalyst,

In this paper, we have presented a 2D Lagrangian two-phase numerical model to study the deformation of a droplet suspended in a quiescent fluid subjected to the combined effects of viscous, surface tension and electric field forces. The... more

In this paper, we have presented a 2D Lagrangian two-phase numerical model to study the deformation of a droplet suspended in a quiescent fluid subjected to the combined effects of viscous, surface tension and electric field forces. The electrostatics phenomena are coupled to hydrodynamics through the solution of a set of Maxwell equations. The relevant Maxwell equations and associated interface conditions are simplified relying on the assumptions of the so-called leaky dielectric model. All governing equations and the pertinent jump and boundary conditions are discretized in space using the incompressible Smoothed Particle Hydrodynamics method with improved interface and boundary treatments. Upon imposing constant electrical potentials to upper and lower horizontal boundaries, the droplet starts acquiring either prolate or oblate shape, and shows rather different flow patterns within itself and in its vicinity depending on the ratios of the electrical permittivities and conductivities of the constituent phases. The effects of the strength of the applied electric field, permittivity, surface tension, and the initial droplet radius on the droplet deformation parameter have been investigated in detail. Numerical results are validated by two highly credential analytical results which have been frequently cited in the literature. The numerically and analytically calculated droplet deformation parameters show good agreement for small oblate and prolate deformations. However, for some higher values of the droplet deformation parameter, numerical results overestimate the droplet deformation parameter. This situation was also reported in literature and is due to the assumption made in both theories, which is that the droplet deformation is rather small, and hence the droplet remains almost circular. Moreover, the flow circulations and their corresponding velocities in the inner and outer fluids are in agreement with theories.

A parametric study of a single needle-to-grid EHD air pump, intended for semiconductor cooling applications, is being presented in this paper. The effect of the distance between the emitter and collector electrodes, as well as the radius... more

A parametric study of a single needle-to-grid EHD air pump, intended for semiconductor cooling applications, is being presented in this paper. The effect of the distance between the emitter and collector electrodes, as well as the radius of the collector's grid wires, is being examined. To that end, several experimental EHD pump prototypes have been fabricated and their performance has been investigated. The experiments demonstrate that this simple and low-cost design is capable of producing usable results, depending on the space and voltage restrictions of the application, for emitter to collector distances greater than 15 mm.

—Electrohydrodynamic motion and deformation of a sedimenting drop in the presence of a uniform alternating electric field is investigated experimentally. Application of an electric field causes a drop to deform to an ellipsoidal shape. As... more

—Electrohydrodynamic motion and deformation of a sedimenting drop in the presence of a uniform alternating electric field is investigated experimentally. Application of an electric field causes a drop to deform to an ellipsoidal shape. As a result of this deformation, the terminal velocity of the drop is affected. In this study, a detailed experimental investigation of the effect of a horizontally directed uniform alternating electric field on the sed-imentation velocity and deformation characteristics of deionized water drop and silicone oil drop falling in castor oil medium is presented. Both water and silicone oil drops are found to deform to a prolate shape on application of electric field, which retards the drop motion in the vertical direction. There is a marked decrease in drop velocity with increase in strength of the alternating electric field.

The electrospinning process and morphology of electrospun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: 1) solution properties; 2) processing conditions; and 3) ambient... more

The electrospinning process and morphology of electrospun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: 1) solution properties; 2) processing conditions; and 3) ambient conditions. In this paper, we report the results of a comprehensive investigation of the effects of changing the conductivity of polyethylene oxide (PEO)/water solution on the electrospinning process and fiber morphology. The effects of the conductivity of PEO solution on the jet current and jet path are discussed. Furthermore, the fiber diameter and fiber uniformity are investigated by using scanning electron microscopy techniques.

During the AC electrokinetic manipulation of particles in suspension on microelectrode structures, strong frequency-dependent fluid flow is observed. The fluid movement is predominant at frequencies below the reciprocal charge relaxation... more

During the AC electrokinetic manipulation of particles in suspension on microelectrode structures, strong frequency-dependent fluid flow is observed. The fluid movement is predominant at frequencies below the reciprocal charge relaxation time, with a reproducible pattern occurring close to and across the electrode surface. This paper reports measurements of the fluid velocity as a function of frequency and position across the electrode. Evidence is presented indicating that the flow occurs due to electroosmotic stress arising from the interaction of the electric field and the electrical double layer on the electrodes. The electrode polarization plays a significant role in controlling the frequency dependence of the flow.

Electrohydrodynamic thrusters (EHDTs) are propulsion mechanisms able to ionize air and create thrust without the need for moving parts or propellant and provide many benefits, including efficiency and maintainability, over the different... more

Electrohydrodynamic thrusters (EHDTs) are propulsion mechanisms able to ionize air and create thrust without the need for moving parts or propellant and provide many benefits, including efficiency and maintainability, over the different methods of propulsion in existence today. This research was the first to experimentally investigate whether the angle of the negative electrode with respect to the normal or the distance between two positive electrodes had an effect on thrust produced by a triangular EHDT at a constant voltage.
Five different levels of the two independent variables were tested five times each, and the results were analyzed for statistical significance through the use of a Kruskal-Wallis nonparametric test.
The research was able to support that the control for both angle of the ground electrode, 0° with relation to the normal, and corona wire distance, 0 cm between wires, resulted in the highest thrust produced at a constant voltage. This research was able to provide new findings to contribute to the developing field of EHDTs, contributing to the continued improvement of this technology with the goal of making it a viable propulsion method for a variety of applications.

The selective catalytic reduction (SCR) of NO (2000 ppm) by NH3(2000 ppm) in the presence of oxygen (3%) was carried out on Cu(x)-FAU (x=theoretical exchange degree) catalysts prepared by ion exchange or impregnation and calcined at 773... more

The selective catalytic reduction (SCR) of NO (2000 ppm) by NH3(2000 ppm) in the presence of oxygen (3%) was carried out on Cu(x)-FAU (x=theoretical exchange degree) catalysts prepared by ion exchange or impregnation and calcined at 773 K. The samples were characterized by UV–visible and IR spectroscopy, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), and temperature-programmed desorption (TPD) of NH3. Ion-exchanged