Direct Numerical Simulation of Particulate Flows with Collisions

The comprehension of fluid/solid interactions in moderately to highly concentrated particulate flows is still limited even if the fluid is Newtonian and particles are assumed to be ideal spheres (or circular cylinders in 2D modelling). M ost of the complexity relies on the various scales in the process: from the particle to the flow domain, and the corresponding momentu m transfers. As the solid fraction exceeds a certain critical value (which lies in the range 5 to 8%), the probability of collisions b etween particles grows non-negligible and a proper treatment of all multi-body collisions is required in the modelling of the system. Here, we present an original numerical approach to address particulate flows with collisions based on the coupling of a Discrete Eleme nts method for the solid part and a standard Finite Elements solver for the fluid part. Coupling is achieved by a Distributed Lagrange Multiplier/Fictitious Domain method. Our numerical strategy highlights some promising ^M capabilities to survey a large number of particulate flow problems without any restriction on the size, the shape (which is constraine d to be at least convex) or the polydispersity of the suspension as well as the rheological properties of the suspending fluid. Result s on the 2D sedimentation of isometric polygonal particles in a Newtonian fluid as well as new 3D results give a flavour of what can b e expected from this type of approach.