Fluid Mechanics Seminar: Anthony Wachs

There is still much to understand in the dynamics of particulate flows, even for mono-disperse spheres suspended in a Newtonian fluid. The major difficulty in terms of comprehension and modeling is the broad range of scales in the system: from the particle to the flow domain. Indeed, the large-scale dynamics are controlled by the small-scale interactions between the particles and the surrounding fluid, as well as between the particles themselves as they contact. In the framework of a multi-scale analysis, I review the models for finite-size particles at the different scales, i.e. the micro, meso and macro-scale models, and present the conceptual assumptions that are generally used to derive them. I briefly introduce the numerical methods implemented in our code PeliGRIFF to investigate particulate flow dynamics at the micro and meso scales, namely Fictitious Domain and two-way Euler Lagrange for fluid/solid momentum exchange and Discrete Element Method for solid/solid collisions, and present their main numerical and computational features. Then, I illustrate what can be achieved with this type of numerical tool on various flow configurations (including heat and mass transfer) ranging from Stokes to inertial regimes, but also discuss the current inherent limitations in terms of computations. Finally, I suggest how these simulations can contribute both to extend our understanding of the intricate transfer mechanisms taking place in these flows and to improve the design of the related industrial processes as, e.g., fluidized beds in catalytic cracking and biomass conversion.