IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 1, JANUARY/FEBRUARY 2015 669 Numerical Investigation of Electrohydrodynamic Plumes for Locally Enhanced Cooling in Dielectric Liquids Jian Wu, Member, IEEE, Philippe Traoré, Christophe Louste, Lucian Dascalescu, Fellow, IEEE, Fang-Bao Tian, and Alberto T. Pérez Abstract—In this paper, we numerically explored the potential application of electrohydrodynamic (EHD) plumes in cooling local regions with high temperature. The EHD plume is induced by ion injection from a sharp metallic blade immersed in a dielectric liquid. A 2-D simulation which took into account all relevant physical variables for EHD plumes in a nonisothermal liquid was performed. It is found that both the local and average Nusselt numbers dramatically increase with the increase of the electric Rayleigh number (T ) and the injection strength parameter (C). However, for the same T and C, the heat transfer augmentation effect is stronger for small Rayleigh numbers (Ra), which can be understood by comparing the relative importance between Coulomb force and buoyancy force. Index Terms—Charge injection, dielectric liquid, electrohy- drodynamic (EHD) plumes, finite-volume method, heat transfer enhancement, numerical simulation. I. I NTRODUCTION W HEN a sharp metallic blade (e.g., point, needle, knife, and so on) immersed in a liquid of very low conductiv- ity and subjected an external electric field, ion injection occurs because of the electrochemical reaction at the interface between the electrode and the liquid [1], [2]. The Coulomb force acting on injected free ions tends to destabilize the system and to induce convective motions. The induced motion appears in a jetlike form and is generally referred to as the electrohydrody- Manuscript received September 4, 2013; revised December 10, 2013; accepted May 26, 2014. Date of publication June 4, 2014; date of current ver- sion January 16, 2015. Paper 2013-EPC-668.R1, presented at 2013 IEEE Indus- try Applications Society Annual Meeting, Orlando, FL, USA, October 6–11, and approved for publication in the IEEE TRANSACTIONS ON I NDUSTRY APPLICATIONS by the Electrostatic Processes Committee of the IEEE In- dustry Applications Society. This work was supported in part by the French Government program “Investissements d’Avenir” (LABEX INTERACTIFS, reference ANR-11-LABX-0017-01, to J. Wu), in part by the Spanish Ministerio de Ciencia y Tecnología (MCYT) under Research Project FIS2011-25161, and in part by the Junta de Andalucía under Research Projects P10-FQM-5735 and P09-FQM-4584 (to A. T. Pérez). J. Wu, P. Traoré, C. Louste, and L. Dascalescu are with the Départe- ment Fluide-Thermique-Combustion, Institut PPrime, 86962 Futuroscope Chasseneuil, France (e-mail: jian.wu@univ-poitiers.fr; philippe.traore@ univ-poitiers.fr; christophe.louste@lea.univ-poitiers.fr; lucian.dascalescu@ univ-poitiers.fr). F.-B. Tian is with the School of Engineering and Information Technology, University of New South Wales, Canberra, ACT 2610, Australia (e-mail: f.tian@adfa.edu.au). A. T. Pérez is with the Departamento de Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, 41012 Seville, Spain (e-mail: alberto@us.es). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIA.2014.2328775 namic (EHD) plume [3], [4]. It is interesting to point out that EHD plumes share some analogies with thermal plumes due to a heat source [5], [6] and impinging jets [7], [8]. EHD plumes have already been widely observed in some early experiments with different shapes of blade [3], [4], [9]. Flow visualization is always a challenge in studies with EHD plumes (or any other type of EHD flows). In recent years, the particle image velocimetry technique has been used to show the flow structure of EHD plumes in a blade–plane configuration [10], [11]. Besides the flow structure, experimental works also reported that such EHD plumes could reach a velocity of 1 ms −1 [11], [12], which revealed potential applications of EHD plumes in enhancement of heat and mass transfer [13]. Some recent experimental results with the point–plane con- figuration demonstrated that convective heat transfer in dielec- tric liquids can be efficiently enhanced by ion injection from sharp metallic points [14]–[17]. The augmentation effect and some essential advantages of EHD-based apparatuses, like low power consumption and noise, fast response, and no moving part, imply that charge-injection-induced EHD plumes can be a promising way for active heat transfer control, especially in the microgravity environment [18], [19]. Direct numerical simulation is an efficient tool for stud- ies with EHD flows since some important information which is not accessible experimentally (e.g., charge density and electric field) can be directly read from numerical results. Great efforts have been made to accurately simulate electro- convective phenomena induced by unipolar charge injection in both plate–plate [20]–[24] and blade–plane configurations [25]–[31]. At the present stage, numerical studies with EHD plumes mainly focus on the modeling of electrodes with dif- ferent shapes and incorporating different injection laws to link the injected charge density at the emitter to the local electric field at the electrode. In [29], a numerical study with the 2-D EHD plume induced by charge injection from a single point was performed. Three different flow regimes (stable, regularly periodic, and chaotic) were observed by increasing the driving electric Rayleigh number. All three regimes have been confirmed by later experimental observations [8]. In [30], an attempt has been made to compare numerical solutions and experimental results of the blade–plate configuration. A fair good agreement was found for the longitudinal velocity profile. Recently, EHD plumes in a hyperbolic blade–plane configura- tion were simulated [31]. In this paper, autonomous and nonau- tonomous injection laws were considered and compared. Some 0093-9994 © 2014 IEEE. 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