Velocity Fluctuations in Sedimenting Brownian Particles.
Velocity Fluctuations in Sedimenting Brownian Particles.
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沉积布朗粒子的速度波动。
DOI：
10.1103/physrevlett.118.198001
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发表时间：
2017
影响因子：
8.6
通讯作者：
T. Narayanan
中科院分区：
文献类型：
--
作者：
J. Möller;T. Narayanan
我们报道了在宏观沉降锋面开始之前，电荷稳定的布朗粒子在沉积悬浮液中的动力学的逐渐转变。利用多散斑超小角度X射线光子相关谱(USA-XPCS)，我们发现在沉积的早期阶段，明确的平流运动主导了胶体动力学。随着时间的推移，这些平流流的衰减和扩散运动成为动力学中的主要贡献。探索这些波动在较小Peclet数(<；1)下的时间发展，为确定沉积过程中速度波动的瞬变性质提供了一个新的视角，并展示了多散斑USA-XPCS的新的实验能力。
We report a gradual transition of dynamics in sedimenting suspensions of charge stabilized Brownian particles prior to the onset of the macroscopic sedimentation front. Using multispeckle ultrasmall-angle x-ray photon correlation spectroscopy (USA-XPCS), we show that well-defined advective motions dominate the colloid dynamics during the early stages of sedimentation. With elapsing time, these advective currents decay and diffusive motions become the dominating contribution in the dynamics. Probing the temporal development of these fluctuations at smaller Peclet numbers (<1) provides a new perspective for the mechanism determining the transient nature of velocity fluctuations in sedimentation and demonstrates new experimental capabilities enabled by multispeckle USA-XPCS.