TY - JOUR
T1 - Characteristics of electrohydrodynamic roll structures in laminar planar Couette flow
AU - Kourmatzis, Agisilaos
AU - Shrimpton, John S.
PY - 2016/2/3
Y1 - 2016/2/3
N2 - The behaviour of an incompressible dielectric liquid subjected to a laminar planar Couette flow with unipolar charge injection is investigated numerically in two dimensions. The computations show new morphological characteristics of roll structures that arise in this forced electro-convection problem. The charge and velocity magnitude distributions between the two parallel electrodes are discussed as a function of the top wall velocity and the EHD Rayleigh number, T for the case of strong charge injection. A wide enough parametric space is investigated such that the observed EHD roll structures progress through three regimes. These regimes are defined by the presence of a single or double-roll free convective structure as observed elsewhere (Vazquez et al 2008 J. Phys. D 41 175303), a sheared or stretched roll structure, and finally by a regime where the perpendicular velocity gradient is sufficient to prevent the generation of a roll. These three regimes have been delineated as a function of the wall to ionic drift velocity UW/κE, and the T number. In the stretched regime, an increase in UW/κE can reduce charge and momentum fluctuations whilst in parallel de-stratify charge in the region between the two electrodes. The stretched roll regime is also characterised by a substantial influence of UW/κE on the steady development time, however in the traditional non-stretched roll structure regime, no influence of UW/κE on the development time is noted.
AB - The behaviour of an incompressible dielectric liquid subjected to a laminar planar Couette flow with unipolar charge injection is investigated numerically in two dimensions. The computations show new morphological characteristics of roll structures that arise in this forced electro-convection problem. The charge and velocity magnitude distributions between the two parallel electrodes are discussed as a function of the top wall velocity and the EHD Rayleigh number, T for the case of strong charge injection. A wide enough parametric space is investigated such that the observed EHD roll structures progress through three regimes. These regimes are defined by the presence of a single or double-roll free convective structure as observed elsewhere (Vazquez et al 2008 J. Phys. D 41 175303), a sheared or stretched roll structure, and finally by a regime where the perpendicular velocity gradient is sufficient to prevent the generation of a roll. These three regimes have been delineated as a function of the wall to ionic drift velocity UW/κE, and the T number. In the stretched regime, an increase in UW/κE can reduce charge and momentum fluctuations whilst in parallel de-stratify charge in the region between the two electrodes. The stretched roll regime is also characterised by a substantial influence of UW/κE on the steady development time, however in the traditional non-stretched roll structure regime, no influence of UW/κE on the development time is noted.
UR - http://www.scopus.com/inward/record.url?scp=84954559637&partnerID=8YFLogxK
U2 - 10.1088/0022-3727/49/4/045503
DO - 10.1088/0022-3727/49/4/045503
M3 - Article
AN - SCOPUS:84954559637
SN - 0022-3727
VL - 49
SP - 1
EP - 13
JO - Journal of Physics D: Applied Physics
JF - Journal of Physics D: Applied Physics
IS - 4
M1 - 045503
ER -