Eur. Phys. J. B 26, 515-520 (2002)
https://doi.org/10.1140/epjb/e20020121

Electric Nusselt number characterization of electroconvection in nematic liquid crystals

¹ Department of Physics, Kent State University, Kent, OH 44242 USA
² LEMTA, INPL - UHP - CNRS, 2 avenue de la Forêt de Haye, 54504 Vandœuvre Cedex, France

Corresponding author: ^a emmanuel.plaut@ensem.inpl-nancy.fr

Received: 21 January 2001
Revised: 1 February 2002
Published online: 15 April 2002

Abstract

We develop a characterization method of electroconvection structures in a planar nematic liquid crystal layer by a study of the electric current transport. Because the applied potential difference has a sinusoidal time dependence, we define two electric Nusselt numbers corresponding to the in-phase and out-of-phase components of the current. These Nusselt numbers are predicted theoretically using a weakly nonlinear analysis of the standard model. Our measurements of the electric current confirm that both numbers vary linearly with the distance from onset until the occurence of secondary transitions. A systematic comparison between our theoretical and experimental results, using no adjusted parameters, demonstrates moderate agreement, but discrepancies remain. Electric transport measurements during electroconvection represent a quantitative test of the standard model completely independent from optical probes. Thus, the technique described here can be a useful complement to traditional structural measurements.