论文标题

在量子流体中漂移和杂质转运

Stokes drift and impurity transport in a quantum fluid

论文作者

Giuriato, Umberto, Krstulovic, Giorgio, Onorato, Miguel, Proment, Davide

论文摘要

Stokes漂移是一种经典的流体效应,其中行驶波将动量转移到流体的示踪剂上,从而导致在传入波的方向上的非零漂移速度。这种效果是允许颗粒(即杂质)通过流量传输的驱动机制。在经典的(粘性)流体中,这通常是由于存在粘性阻力而发生的。由于量子流体最终缺乏粘度,因此杂质仅由惯性效应和压力梯度驱动。我们介绍了量子流体中Stokes漂移类似的理论预测,用于使用多时间分析渐近扩张获得的经典杂质。我们发现,在领先顺序,漂移方向和振幅取决于波相对于初始杂质位置。在第二阶,平均在初始条件下占主导地位,我们的理论模型恢复了经典的Stokes漂移,但其系数取决于相对颗粒流体的密度比。对二维总距离的数值模拟与经典杂质相结合,证实了我们的发现。我们的预测是可以在实验上测试的,例如,使用光质晶体中获得的光流体。

Stokes drift is a classical fluid effect in which travelling waves transfer momentum to tracers of the fluid, resulting in a non-zero drift velocity in the direction of the incoming wave. This effect is the driving mechanism allowing particles, i.e. impurities, to be transported by the flow; in a classical (viscous) fluid this happens usually due to the presence of viscous drag forces. Because of the eventual absence of viscosity in quantum fluids, impurities are driven by inertial effects and pressure gradients only. We present theoretical predictions of a Stokes drift analogous in quantum fluids for classical impurities obtained using multi-time analytical asymptotic expansions. We find that, at the leading order, the drift direction and amplitude depend on the initial impurity position with respect to the wave phase; at the second order, dominant after averaging over initial conditions, our theoretical model recovers the classical Stokes drift but with a coefficient that depends on the relative particle-fluid density ratio. Numerical simulations of a two-dimensional Gross-Piteaveskii equation coupled with a classical impurity corroborate our findings. Our predictions are experimentally testable, for instance, using fluids of light obtained in photorefractive crystals.

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