Velocity of an interface driven by an entropic force under shear flow

Yutaro Kado; Shin-ichi Sasa

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arXiv · 2608.20878

Velocity of an interface driven by an entropic force under shear flow

Yutaro Kado·Shin-ichi Sasa

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Abstract

Thermal fluctuations can drive an interface when bulk fluctuation amplitudes differ between two phases. We study how shear flow modifies this mechanism using a stochastic non-conserved order- parameter model. For a planar interface parallel to the imposed shear, we derive its propagation velocity in the weak-noise and small-bias regime. The driving force comprises a shear-modified entropic contribution determined by bulk fluctuation spectra and a non-equilibrium contribution arising from the breaking of time-reversal symmetry. At low shear rates, the entropic term provides the dominant contribution to the velocity of an interface near the zero-velocity plane of the shear flow, and the shear-induced change in the velocity scales as the 4/3 power of the shear rate. At high shear rates, two-dimensional simulations show that the measured velocity is largely accounted for by the modified bulk entropic contribution.

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Yutaro Kado, Shin-ichi Sasa. 2026-08-21. Velocity of an interface driven by an entropic force under shear flow. https://arxiv.org/abs/2608.20878

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