Shear-induced Casimir forces in liquid layers

J. M. Ortiz de Zárate; T. R. Kirkpatrick; J. V. Sengers

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arXiv · 1804.06125

Shear-induced Casimir forces in liquid layers

J. M. Ortiz de Zárate·T. R. Kirkpatrick·J. V. Sengers

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Abstract

In stationary nonequilibrium states a coupling between hydrodynamic modes causes thermal fluctuations to become long ranged inducing nonequilibrium Casimir forces or pressures. Here we consider nonequilibrium Casimir pressures induced in liquids by a velocity gradient. Specifically, we have obtained explicit expressions for the magnitude of the shear-induced pressure enhancement in a liquid layer between two horizontal plates that complete and correct results previously presented in the literature. In contrast to nonequiibrium Casimir pressures induced by a temperature gradient, kinetic theory shows that nonequilibrium contributions from short-range fluctuations are no longer negligible. In addition, it is noted that computer simulations of model fluids in shear observe effects from molecular correlations at nanoscales that have a different physical origin. The idea that such computer simulations probe shear-induced pressures resulting from coupling of long-wavelength hydrodynamic modes is erroneous.

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J. M. Ortiz de Zárate, T. R. Kirkpatrick, J. V. Sengers. 2018-04-17. Shear-induced Casimir forces in liquid layers. https://arxiv.org/abs/1804.06125

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