Electrically driven toroidal Moffatt vortices: experimental observations

Perri, Anthony E.; Sankaran, A. N.; Kashir, Babak; Staszel, Christopher; Schick, Rudolf J.; Mashayek, Farzad; Yarin, Alexander L.

doi:10.1017/jfm.2020.472

Cited by 4 publications

(21 citation statements)

References 23 publications

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“…This result is qualitatively consistent with the experimental observation of Perri et al. (2020), who also reported a transient flow experiencing bifurcation. Furthermore, we found that increasing the charge diffusion effect can increase the size of vortices in this EHD flow.…”

Section: Discussionsupporting

confidence: 93%

“…In Perri et al. (2020), the authors observed transient EHD flows, suggestive of flow bifurcation to another state. In our numerical simulations, we can also observe an unsteady flow when increasing in the blade–plate EHD flow.…”

Section: Resultsmentioning

confidence: 95%

“…In this work, we will characterise the intrinsic flow characteristics and properties of the Moffatt-like eddies in the blade–plate EHD flow, supplementing the previous works of Perri et al. (2020, 2021) in a needle–plate configuration. More specifically, we will conduct direct numerical simulations (DNS) and global stability analyses of two-dimensional EHD flows between a high-voltage hyperbolic blade electrode and a grounded plate electrode.…”

Section: Introductionmentioning

confidence: 87%

“…Note that these equations are in principle the same as those used by Perri et al. (2020), except that the geometries are different in the two works, and we additionally consider the charge diffusion effect () in (2.2 c ). More specifically, the first two equations are the continuity equation and Navier–Stokes equations with additional Coulomb force terms.…”

Section: Problem Formulationmentioning

confidence: 99%

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Moffatt eddies in electrohydrodynamics flows: numerical simulations and analyses

Sun

Zhang

2022

J. Fluid Mech.

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We study numerically a sequence of eddies in two-dimensional electrohydrodynamics (EHD) flows of a dielectric liquid, driven by an electric potential difference between a hyperbolic blade electrode and a flat plate electrode (or the blade–plate configuration). The electrically driven flow impinges on the plate to generate vortices, which resemble Moffatt eddies (Moffatt, J. Fluid Mech., vol. 18, 1964, pp. 1–18). Such a phenomenon in EHD was first reported in the experimental work of Perri et al. (J. Fluid Mech., vol. 900, 2020, A12). We conduct direct numerical simulations of the EHD flow with three Moffatt-type eddies in a large computational domain at moderate electric Rayleigh numbers ( $T$ , quantifying the strength of the electric field). The ratios of size and intensity of the adjacent eddies are examined, and they can be compared favourably to the theoretical prediction of Moffatt; interestingly, the quantitative comparison is remarkably accurate for the two eddies in the far field. Our investigation also shows that a larger $T$ strengthens the vortex intensity, and a stronger charge diffusion effect enlarges the vortex size. A sufficiently large $T$ can further result in an oscillating flow, consistent with the experimental observation. In addition, a global stability analysis of the steady blade–plate EHD flow is conducted. The global mode is characterised in detail at different values of $T$ . When $T$ is large, the confinement effect of the geometry in the centre region may lead to an increased oscillation frequency. This work contributes to the quantitative characterisation of the Moffatt-type eddies in EHD flows.

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Section: Discussionsupporting

confidence: 93%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 87%

Section: Problem Formulationmentioning

confidence: 99%

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Moffatt eddies in electrohydrodynamics flows: numerical simulations and analyses

Sun

Zhang

2022

J. Fluid Mech.

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“…聚苯乙烯微球 [20] 。Chrikov 等对另一种维恩-昂萨格效应泵流动以及针-板结构电荷注入-传导机制电对流进行了 PIV 流场测量，直径 1-10 微米的硼硅酸盐空心球作为示踪粒子 [82,83] 。法国普瓦捷大学 Louste 等人较为系统地开展了介电液体电流动 PIV 测量工作，讨论了示踪粒子材料和浓度对测量结果的影响 [84,85] 。他们早期研究由电荷注入引起的流动 [86] ，近年来开始关注电导机制引起的流动 [87] 以及电荷注入-传导的过渡过程 [43] 。图 14 展示了一个封闭墙体内，9 对非对称平嵌电极(一对电极宽度分别为 1.3mm 和 3.8mm) [88,89] 。电导泵 PIV 测量工作还较少，且都是在封闭腔体内进行，没有外部流动。另外，PIV 测量结果显示简单的平板嵌入电极电导泵在低电压下的流场结构也很混乱 [86,87] ，说明电导泵内复杂流动特征和机理还有待深入研究。其他更复杂电极结构电导泵 PIV 测量还未有开展。 measured by PIV in a confined cavity [87] 微尺度电导泵(电极间距为几十微米到几百微…”

Section: 示了电极结构设计对电导泵性能有重要影响。unclassified