Simulation of dynamic Interaction of non spherical particles in a turbulent boundary Layer – PLAYER

CFD codes (Fluent) and/or thetis) are used to obtain the drag and the lift forces in order to deduce the hydrodynamic coeffcients acting on non spherical particles.

The present work verifies the ability of commercial CFD to determinate the hydrodynamics forces on non-spherical particles. Results seems to be better as Reynolds number increases. Nonetheless, the results obtained at low Reynolds require more explanation and have to be checked.The present study emphazises the difficulties to make a clear choice of the correlations that have to be used. Further works have to be made .For Re>250 the transition to laminar-unsteady regime for any particle orientation is observed.

Further studies are necessary to understand why the bad results at low Reynolds number. The mesh used has to be analysed.

International workshop, Lecce, June7-9, 2012 «Non ideal particles and aggregates in turbulence«.
oral presentation : « Ability of commercial CFD code to compute the hydrodynamics forces acting on non spherical particles«.
Jorge Andrès Sierra

This project aims at understanding and modelling the behaviour of non spherical inertial particles transported by turbulent flows. The modelling of dispersed phase flows as classically developed relies on the assumption that the particles are spherical. The main objective of the present project is to include the non sphericity of particles in the modelling in order to investigate macroscopic numerical simulations of particulate flows with industrial CFD tools. This study will be devoted to the dispersion mechanisms (interaction between turbulence and particles), and the collisions and rebounds on the walls, which are the main physical phenomena governing the dynamics of the dispersed phase. In this way, it is proposed to benefit from the complementary competences of each partner (LEMTA, IMFT, I2M) to solve the scientific difficulty associated to the non sphericity of the particles with a particular attention: working out of the Stokes regime (low particle Reynolds numbers), for which many research works exist in the literature. However, carrying out such simulations at a macroscopic scale requires defining exactly the hydrodynamic forces and the couple exerted on the particles. Similarly, the rebounds of non spherical particles on the walls will be a key aspect that will be also considered. Indeed, a macroscopic simulation requires the introduction of boundary conditions for the dispersed phase. Few existing models are devoted to this behaviour near the wall. In this way, the three partners put their complementary competences into common to significantly increase the understanding of the physical phenomena, the representativity of the models and the efficiency of the numerical methods. The present work is naturally split in several complementary tasks and will began by numerical simulations led at the particle scale (microscopic scale, I2M) so as to access to exact data which will be shared between the partners. They will be introduced in the simulations at a mesoscopic scale for which the collective effect of an ensemble of particles will be studied by a direct numerical simulation DNS of the fluid flow coupled to a Lagrangian DPS modelling. The dispersion as well as the rebounds of the particles on the walls will be then studied under a stochastic modelling point of view (LEMTA, IMFT). To reach the objective of performing numerical simulations at a macroscopic scale, simulations will be run with dedicated CFD tools of each partner. All the cleverness of the results will in this way been put into stress.