粘性压力驱动流剪切的流动沉积物床的流变学
Rheology of mobile sediment beds sheared by viscous, pressure-driven flows
摘要：
我们提出了一个详细的比较剪切沉积物床的流变行为的压力驱动，直通道配置的基础上产生的数据，通过完全耦合，颗粒分辨直接数值模拟和实验测量reviously出版的Aussillous { \it等人}。(J.流体机械：第736卷，2013年，pp. 594-615）。高分辨率的模拟数据允许计算悬浮液在流向和垂直方向上的应力平衡以及流体和颗粒相之间的应力交换，这是推断流变学所需的信息，但迄今为止在实验中无法获得。应用这一知识的实验和数值数据，我们得到的纵向稳定，深度分辨的相关流变量的配置文件。流变量，如剪切粘度和法向粘度和有效摩擦系数的缩放行为进行检查和比较，来自流变实验和广泛使用的流变相关性的数据。我们表明，流变性能，以前已经推断出的环形Couette型剪切流中性浮力颗粒仍然持有我们的设置的沉积物输运在Poietille流和密集的制度，我们发现很好的协议与经验关系从中得出。将总应力从颗粒接触和流体动力学细分为多个部分，表明临界颗粒体积分数为0.3，以将致密区与稀区分开。在稀释状态下，即，在输沙层，多孔介质屏蔽了长程水动力相互作用，有效粘性服从爱因斯坦关系。
英文摘要：
We present a detailed comparison of the rheological behaviour of sheared sediment beds in a pressure-driven, straight channel configuration based on data that was generated by means of fully coupled, grain-resolved direct numerical simulations and experimental measurements reviously published by Aussillous {\it et al.} (J. Fluid Mech., vol. 736, 2013, pp. 594-615). The highly-resolved simulation data allows to compute the stress balance of the suspension in the streamwise and vertical directions and the stress exchange between the fluid and particle phase, which is information needed to infer the rheology, but has so far been unreachable in experiments. Applying this knowledge to the experimental and numerical data, we obtain the statistically-stationary, depth-resolved profiles of the relevant rheological quantities. The scaling behavior of rheological quantities such as the shear and normal viscosities and the effective friction coefficient are examined and compared to data coming from rheometry experiments and from widely-used rheological correlations. We show that rheological properties that have previously been inferred for annular Couette-type shear flows with neutrally buoyant particles still hold for our setup of sediment transport in a Poiseuille flow and in the dense regime we found good agreement with empirical relationships derived therefrom. Subdividing the total stress into parts from particle contact and hydrodynamics suggests a critical particle volume fraction of 0.3 to separate the dense from the dilute regime. In the dilute regime, i.e., the sediment transport layer, long-range hydrodynamic interactions are screened by the porous media and the effective viscosity obeys the Einstein relation.
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