Homogenization of granular pipe flow

本建议的目的是均匀化的颗粒管流。这种流动中的一个基本问题是，它们本质上是不稳定的，材料输送的特征在于固体分数（密度波）沿管道沿着的大变化。这些波在管道内壁上引起潜在的破坏性压力瞬变，并提供了造成流动间歇行为的机制。尽管颗粒管流中密度波的动力学特性一直是人们研究的热点，但如何在管道中产生可控的、可计量的质量流量和均匀的颗粒流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密度波的触发机制，即流动不稳定性的原因。我们的策略包括添加一个适当设计的纹理管道的内壁，以防止形成稳定的塞子更均匀地分布颗粒沿沿着管道的冲击。通过使用离散元方法（DEM）的基于颗粒的数值模拟，我们将研究不同类型的颗粒材料的流动上的不同纹理的效果，以确定最佳的纹理设计取决于颗粒的形状和尺寸分布。首先，我们将集中在重力驱动的垂直管道流的均匀化。随后，将DEM模拟与流体动力学模拟相结合，研究不同纹理对水平管道中流体驱动颗粒流均匀化的影响。

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.