Homogenization of granular pipe flow

本提案旨在实现颗粒管流的均质化。这种流动的一个基本问题是，它们本质上是不稳定的，材料传输的特点是沿管道的固体分数(密度波)变化很大。这些波在管道内壁上引起潜在的破坏性压力瞬变，并提供了导致流动间歇行为的机制。尽管颗粒管流中密度波的动力学一直是人们深入研究的主题，但如何在管道中产生可控的、计量的质量流量和颗粒物质的均匀流动仍然是一个具有挑战性的问题。在本项目中，我们将设计规则来对抗流动间歇的原因，即密度波的触发机制。我们的颗粒管流均化策略包括在管道内壁添加适当设计的纹理，以防止通过沿管道均匀分布颗粒撞击而形成稳定的堵塞。通过离散元方法(DEM)基于颗粒的数值模拟，研究不同织构对不同类型颗粒材料流动的影响，以确定取决于颗粒形状和尺寸分布的最佳织构设计。首先，我们将重点研究垂直管道中重力驱动的流动的均化。随后，将DEM模拟与流体动力学模拟相结合，研究了不同纹理对水平管内流体驱动颗粒流均化的影响。

The present proposal aims at the homogenization of granular pipe flows. One fundamental problem in such flows is that they are intrinsically unstable, with the material transport being characterized by large variations in solid fraction (density waves) along the pipe. These waves induce potentially destructive pressure transients on the pipe’s inner-wall and provide the mechanism responsible for the intermittent behavior of the flow. Although the dynamics of density waves in granular pipe flows have been the subject of intense research, it is still a challenging problem to produce controlled, metered mass flux and homogeneous flow of granular materials in transport through a pipe. In the present project we will design rules for combating the cause of flow intermittency that is the triggering mechanism of density waves. Our strategy for homogenizing granular pipe flows consists of adding a suitably designed texture to the pipe’s inner-wall in order to prevent the formation of stable plugs by more homogeneously distributing particle impingements along the pipe. By means of particle-based numerical simulations using the Discrete Element Method (DEM), we will investigate the effect of different textures on the flow of granular materials of different types, in order to identify optimal texture designs depending on particle shape and size distribution. First, we will focus on the homogenization of gravity-driven flows through vertical pipes. Subsequently, the effect of the different textures on the homogenization of fluid-driven granular flows in horizontal pipes shall be investigated bycombining the DEM simulations with fluid dynamics simulations.