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Electrohydrodynamic pumps, as a representative type of nonmechanical pump, have received significant research attention due to their inherent advantages of having no moving parts and low power consumption. In particular, the planar charge injection pump has exhibited superior fluid driving performance, making it highly promising for applications in microscale flow driving and chip cooling. A sandwich structure pump with multiple pairs of planar interdigitated electrodes is numerically studied in this paper. The interaction of the flow, thermal, and electric fields is analyzed using the lattice Boltzmann method under different pump configurations, governing parameters, and convection mechanisms. The results reveal that the geometric configurations of the planar interdigitated electrodes have direct effects on the pumping performance and heat transfer rate. Specifically, an optimal configuration is achieved when the width of the collector is twice that of the emitter under two-pair electrode simulation conditions. More interestingly, competition between electric and thermal effects is observed, and the optimal threshold for heat transfer is found at an electric Rayleigh number of T = 300 for the considered cases. Finally, the interaction of the electric and thermal fields induces periodic oscillations. The single-vortex mechanism exhibits the longest oscillation period and inhibits heat transfer, while the multi-vortex mechanism has the shortest oscillation period and enhances heat transfer. [ABSTRACT FROM AUTHOR]

The transition process from laminar to chaotic flow in electro-thermal convection of a dielectric liquid is numerically investigated using a unified lattice Boltzmann method. The liquid is confined in a closed square cavity, and free charges are introduced into the system through a strong unipolar injection mechanism. Three cases with different Rayleigh numbers are considered. With the increase of electric Rayleigh number, various complicated dynamical behaviors are observed and three diverse transition routes to chaos are identified, namely, the quasi-periodic sequence involving four incommensurable frequencies, the intermittency sequence, and the alternating periodic-chaotic sequence. Numerical results are illustrated using time histories, Fourier frequency spectra, and phase portraits. The chaotic behavior is quantitatively analyzed through the calculation of fractal dimension and Lyapunov exponent. Typical flow patterns for both steady-state regime and periodic regime are also presented and discussed. [ABSTRACT FROM AUTHOR]

In this study, the strong unipolar charge injection induced by a uniform electric field was found to have a suppressing effect on Rayleigh-Bénard secondary instability, regardless of the charge injection direction. The liquid was modeled as a perfect dielectric, and the charge injection was assumed to be autonomous and homogeneous. Direct numerical simulations were performed using a newly developed unified lattice Boltzmann model for electrothermohydrodynamics (ETHD). The electric field was applied only when the flow is in a stable oscillation state of the secondary instability. Two different cases representing charge injection from above and below were considered. The results show that periodic temperature fluctuations can be fully suppressed by a sufficiently strong electric field and that the charge injection direction has a significant impact on the flow patterns. For even stronger electric field strength, the system turns into periodic oscillatory flow again and the fundamental frequency is two orders of magnitude higher than the original ones. Besides, the effects of charge injection direction on the flow intensity and heat transfer rate of ETHD are also investigated. [ABSTRACT FROM AUTHOR]