Scaling laws of electroconvective flow with finite vortex height near permselective membranes

Liu, Wei; Zhou, Yueting; Shi, Pengpeng

doi:10.1103/physreve.102.033102

Cited by 11 publications

(8 citation statements)

References 40 publications

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“…Recently, Lui et al presented results from scaling analysis and DNS of electroconvection in the absence of an externally imposed shear flow. These results support a linear scaling of both the dimensionless steady-state vortex height and overlimiting current with V . Similarly, studies have also shown that gravitational effects can play an important role in the onset of convective flow especially in systems with large Rayleigh numbers, where Rayleigh–Bernard convection can lead to an unstable overlimiting current and this effect becomes more pronounced as the characteristic length of the system increases. , …”

Section: Introductionsupporting

confidence: 76%

“…Meanwhile for 0.1 mM, the extent of convection keeps increasing linearly with voltage, and for voltages higher than 250 V T , the flow occurs even beyond the experimental viewing window. Previous studies have reported a linear scaling for nonsheared electroconvection for steady vortex height, but we find this scaling valid for chaotic electroconvection too. , Figure shows a comparison of the vortex size distribution for different c and highlights the marked effect of electrolyte concentration. For example, at c = 0.1 M, vortices remain small and localized near the permselective interface (Figure a, e).…”

Section: Resultsmentioning

confidence: 45%

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Structure and Dynamics of Electric-Field-Driven Convective Flows at the Interface between Liquid Electrolytes and Ion-Selective Membranes

et al. 2021

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At voltages above a certain critical value, V c ≈ 20 kT/e, a space charge layer forms near ion-selective interfaces in liquid electrolytes. Interactions between the space charge and an imposed electric field drives a hydrodynamic instability known as electroconvection. Through particle tracking velocimetry we experimentally study the structure and dynamics of the resultant electroconvective flow. Consistent with previous numerical simulations, we report that, following imposition of a sufficiently large voltage, electroconvection develops gradually as pairs of counter-rotating vortices, which nucleate at the interface between an ion-selective substrate and a liquid electrolyte. Depending on the imposed voltage and cell geometry, the vorticies grow to length scales of hundreds of micrometers. Electroconvective flows are also reported to be structured and multiscale, with the size ratio of the largest to the smallest observable vortices inversely proportional to the Debye screening length.

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Section: Introductionsupporting

confidence: 76%

Section: Resultsmentioning

confidence: 45%

Structure and Dynamics of Electric-Field-Driven Convective Flows at the Interface between Liquid Electrolytes and Ion-Selective Membranes

et al. 2021

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“…Using a first-order approximation 1/∂x ∼ 1/∂y ∼ 1/δ 0 , (∂ 2 c + /∂x∂y)/(∂c + /∂y) can be further simplified as∼1/δ 0 , where the depletion layer thickness δ 0 can be identified by a given vortex height d EC . Furthermore, the slip velocity can be estimated by u s ∼ φ 2 (1/δ 0 ) (Kwak et al 2017), which is proven to be valid for analysing the slip velocity of non-shear flows (Liu et al 2020b). However, for the shear shielding case, the slip velocity is dominated by the shear flow velocity.…”

Section: Critical Selection Of Shear Shelteringmentioning

confidence: 99%

“…2017), which is proven to be valid for analysing the slip velocity of non-shear flows (Liu et al. 2020 b ). However, for the shear shielding case, the slip velocity is dominated by the shear flow velocity.…”

Section: Theoretical Analysismentioning

confidence: 99%

“…However, linear overlimiting behaviour has been observed by experiments (Kwak et al 2013b;Kang & Kwak 2020) and simulations (Shi & Liu 2018). Liu et al (2020b) subsequently revealed the balance mechanism of convective flux and electrostatic flux and derived the linear law of ion transport efficiency, which can be used to explain the linear overlimiting behaviour.…”

Section: Introductionmentioning

confidence: 97%

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Critical selection of shear sheltering in electroconvective flow from chaotic to steady state

2022

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Ion and water are transported by electroconvection near permselective membranes, resulting in complex phenomena associated with the flow–fines interaction. Sheltering the flow chaos by the shear flow is a common strategy in plasma fluids and has recently been successfully applied to control ionic fluids. The paper herein reveals the critical selection of shear velocity regarding the fluid from a chaotic to a steady state through numerical and theoretical analyses. For the shear sheltering, the dimensionless Debye length ${\lambda _D}$ with varying channel height is introduced to achieve a comprehensive discussion of the factors and laws affecting the shear vortex state. Based on an analysis of the vortex driving mechanism, the scaling of the slip velocity ${u_s}\sim {(\lambda _D^{ - 1}\Delta {\phi ^4})^{1/3}}$ is recommended as the critical selection factor for the steady and chaotic state under a fixed shear flow velocity, which involves the dimensionless Debye length ${\lambda _D}$ and voltage difference $\Delta \phi $ . Furthermore, for ionic fluid control by shear flow, a critical shear velocity ${U_{HPC}}$ is proposed to distinguish the electroconvective flow from a chaotic state to a steady state. When the shear flow velocity ${U_{HP}} > {U_{HPC}}$ , the shear flow shelters chaos, and the scaling law is also recommended for the regulation of the critical shear flow velocity ${U_{HPC}}$ jointly by ${\lambda _D}$ and $\Delta \phi $ . The analysis is confirmed by direct numerical simulation and existing experimental data (J. Fluid Mech, vol. 813, 2017, pp. 799–823). This work provides a more comprehensive physical insight for shear sheltering and affects the design of electromembrane microfluidics.

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Application of computational fluid dynamics technique in electrodialysis/reverse electrodialysis processes

Gurreri

Ciofalo

Cipollina

et al. 2022

Current Trends and Future Developments on (Bio-) Membranes

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Scaling laws of electroconvective flow with finite vortex height near permselective membranes

Cited by 11 publications

References 40 publications

Structure and Dynamics of Electric-Field-Driven Convective Flows at the Interface between Liquid Electrolytes and Ion-Selective Membranes

Structure and Dynamics of Electric-Field-Driven Convective Flows at the Interface between Liquid Electrolytes and Ion-Selective Membranes

Critical selection of shear sheltering in electroconvective flow from chaotic to steady state

Application of computational fluid dynamics technique in electrodialysis/reverse electrodialysis processes

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