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So far, electrohydrodynamic (EHD) pumps based on the injection or the field-enhanced dissociation (the Wien effect) at the surface of metal electrodes have been studied. This paper proposes and studies both numerically and experimentally a fundamentally new pump scheme, namely, the EHD pump operating due to the Wien effect in a conical hole located in the solid insulation barrier. An experimental setup of the pump has been created, and performance (pressure vs flow rate) characteristics have been measured that satisfactorily agree with the results of computer simulation. With the size of the hole being a fraction of a millimeter, the proposed system performance is comparable to that of the previously studied EHD pumps. [ABSTRACT FROM AUTHOR]

The structure of electrohydrodynamic (EHD) flows in a variable electric field has been investigated based on computer simulation of EHD flows in a needle–plane electrode system. The characteristic frequency interval of a feed sine-wave voltage with an amplitude of 5 kV has been considered. Changes in the charge and velocity structures of EHD flows are described, and the characteristic features of the flows versus feed voltage frequency are presented. The periodicity of such EHD flows is demonstrated. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) flows emerge in dielectric liquids under the action of the Coulomb force and underlie energy-efficient techniques for heat and mass transfer. The key issue in the phenomena is the way how the net charge is created. One of the most promising, yet poorly studied charge formation mechanisms is the field-enhanced dissociation (or the Wien effect). So the paper studies an EHD flow caused solely by the effect by virtue of both experiment and computer simulation. To preclude the competing mechanism of charge formation--the injection--a new EHD system of a special design was examined. Its main feature is the use of solid insulation to create the region of the strong electric field far from the electrode metal surfaces. The experimental study used the particle image velocimetry technique to observe velocity distributions, whereas the computations were based on the complete set of electrohydrodynamic equations employing the commercial software package COMSOL Multiphysics. Spatial distributions of key quantities (including the ion concentrations, the total space charge density, and the velocity) and the acting forces were obtained in the computer simulation and were analyzed. The experimental flow structure was observed for a number of voltages up to 30 kV. The comparison of the numerical and experimental results yielded a good quantitative agreement for strong electric fields though some overshoot was observed for weak ones. The results allow concluding on the applicability of the Onsager theory of the field-enhanced dissociation in the context of EHD flows. [ABSTRACT FROM AUTHOR]

The paper presents the technique for computing current?time characteristics of the transient regime, taking place after the pulsed application or change of high voltage, and dynamical current?voltage ones obtained with the voltage sawtooth modulation. The basis of the simulation is the complete set of electrohydrodynamic equations with both the convective and the migration mechanisms of charge transport being taken into account jointly. The numerical calculations were performed using commercial software package COMSOL Multiphysics based on the finite element method. The simulation was carried out for the needle?plane electrode system. The unsteady-state current passage processes, including electrohydrodynamic flow formation, were calculated. The interrelation between the latter and the total current passing through the electrical circuit were investigated. The shape and features of the current?voltage characteristics obtained with the voltage sawtooth modulation were shown to be dependent on the mechanism of charge formation. The qualitative comparison between the simulated dynamical current? voltage characteristics and the original experimental data has shown a good agreement. [ABSTRACT FROM AUTHOR]

Complex investigation of the structure of electrohydrodynamic (EHD) flows in a needle-plane electrode system is carried out on the basis of analysis of experimental data and the results of computer simulation. An algorithm of iterative simulation of the volume charge distribution in a fluid is developed. Simulation is carried out using the ANSYS system. The fields of velocities and pressures, as well as electric characteristics of EHD flows, are calculated. Analysis of the results reveals a number of features of EHD flows in the electrode system under investigation. Peculiarities of the band structure are determined, and the characteristic size of the low-pressure zone near the active electrode, as well as the sizes of the acceleration and deceleration zones of the fluid in the electrode gap, is determined. [ABSTRACT FROM AUTHOR]

Computer-aided simulation of the electrohydrodynamic flow pattern in an asymmetric system of electrodes (configured as “narrow depression under plane” or “blade above plane”) is carried out. The objective of the simulation is to reveal a correspondence between the kinematic flow pattern and the distribution of driving (Coulomb) forces. The kinematic pattern of the flow simulated is compared with the results of experimental data processing. Good agreement between the simulation results and experimental data is found. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The study investigates the process of the electrical current passage in a system with non-uniform electric field under assured absence of injection. The cell has a special design, with the region of the strong electric field located far from metal electrode surfaces and the non-linearity of the current-voltage characteristics ensured solely by the field-enhanced dissociation. The characteristics were measured experimentally and studied numerically for dielectric liquids with different values of low-voltage conductivity; the results were compared. The computations were carried out on the basis of the complete set of electrohydrodynamic equations using commercial software package COMSOL Multiphysics. [ABSTRACT FROM AUTHOR]