Characteristics of electrohydrodynamic roll structures in laminar planar Couette flow

Abstract

A bst r act .T he behaviour of an incompressible dielect ric liquid subject ed t o a laminar planar Couet t e ow wit h unipolar charge inject ion is invest igat ed numerically in two dimensions. T he comput at ions show new morphological charact erist ics of roll st ruct ures t hat arise in t his forced elect ro-convect ion problem. T he charge and velocity magnit ude dist ribut ions between t he two parallel elect rodes are discussed as a funct ion of t he t op wall velocity and t he EHD Rayleigh number, T for t he case of st rong charge inject ion. A wide enough paramet ric space is invest igat ed such t hat t he observed EHD roll st ruct ures progress t hrough t hree regimes. T hese regimes are de ned by t he presence of a single or double-roll free convect ive st ruct ure as observed elsewhere [1], a sheared or st ret ched roll st ruct ure, and nally by a regime where t he perpendicular velocity gradient is su cient t o prevent t he generat ion of a roll. T hese t hree regimes have been delineat ed as a funct ion of t he wall t o ionic drift velocity U W = E , and t he T number. In t he st ret ched regime, an increase in U W = E can reduce charge and moment um uct uat ions whilst in parallel de-st rat ify charge in t he region between t he two elect rodes. T he st ret ched roll regime is also charact erised by a subst ant ial in uence of U W = E on t he st eady development t ime, however in t he t radit ional non-st ret ched roll st ruct ure regime, no in uence of U W = E on t he development t ime is not ed.

Coulomb-driven electroconvection turbulence in two-dimensional cavity

“…Because there are multiple control parameters in EHD flow, some EHD chaotic flows could not be recognized as EHD turbulence even though the electric Rayleigh number was high. This is because the electric Reynolds number influenced by electric mobility may be low (Traoré & Pérez 2012;Huang et al 2021), or the EHD flow is forced by external shear, causing stochastic flow relaminarization (Kourmatzis & Shrimpton 2015).…”

“…This is because the electric Reynolds number influenced by electric mobility may be low (Traoré & Pérez 2012; Huang et al. 2021), or the EHD flow is forced by external shear, causing stochastic flow relaminarization (Kourmatzis & Shrimpton 2015).…”