Homogenization of granular pipe flow

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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.