Can the law of maximum entropy production describe the field-induced orientation of ellipsoids of rotation?

Abstract

Abstract Electrostatic approaches are successful in explaining the experimentally observed field-induced orientations of the axis with the highest Clausius-Mossotti factor. For conductive or nonconductive, prolate or oblate spheroids, this is always the longest axis when different frequency-dependent dispersions of their effective conductivity along the three principal axes are neglected. Here, it is shown that these orientations correspond to the ‘law of maximum entropy production’ (LMEP) by comparing the axes-ratio dependencies of the torques calculated with the electrostatic approach with the effective conductivity differences between a suspension with field-oriented and randomly oriented objects. At low volume fraction, the obtained conductivity differences, which enter the LMEP, predict almost exactly the torque curves when plotted over axis ratio of the objects. Since the field-induced orientation at constant field strength increases the effective conductivity, the suspension system obviously does not behave according to the Prigogine principle, which would demand the minimization of energy dissipation and entropy production through object orientation. However, the Prigogine principle requires the suspension system to be close to equilibrium in its linear range. These conditions must be rejected if the LMEP is to be applied. Apparently the LMEP provides a phenomenological criterion for axis orientation, even though it is not yet clear whether and how increased conductivity, power dissipation and entropy production can also be introduced as driving forces at the single object level. However, the results also indicate that the disregard of energy dissipation may not be a problem in the electrostatic description of field-induced object orientation.