Christophe Henry - Laboratoire Lagrange, Université Côte d'Azur, CNRS, OCA, Bd de l'Observatoire, Nice, France - Keywords: two-phase flows, turbulence, particle suspensions

Christophe Henry - Laboratoire Lagrange, Université Côte d'Azur, CNRS, OCA, Bd de l'Observatoire, Nice, France - Keywords: two-phase flows, turbulence, particle suspensions

Contribution title: Suspensions of non-spherical particles in turbulent flows

This research activity aims at deepening our understanding and developing new models related to the transport and deposition of non-spherical particles in wall-bounded turbulent flows.

The accumulation of suspended particles on surfaces affects a number of fields, ranging from industrial applications (fouling of pumps by micro-organisms or fouling of combustion engines by soot particles) to environmental issues (dynamics of pollutants or volcanic ashes in the atmosphere) with implications even in our every-day life (accumulation of limescale in pipes). This accumulation results from the coupling between the transport of suspended particles by the fluid and the adhesion between particles and surfaces. One of the key challenges related to this research is that it involves different fields (including fluid dynamics, interface chemistry and material sciences) which span a wide range of time- and spatial-scales.

Significant breakthrough in the dynamics of spherical particles in wall-bounded flows and their modeling has been made in the past decades [Henry et al., Adv Colloid Interfac, 2012]. When dealing with non-spherical particles, an additional component appears: the orientation of particles with respect to the fluid flow. This orientation has been shown to exhibit a rich dynamics in the case of rigid axisymmetric ellipsoids in turbulent flows [Voth & Soldati, Annu Rev Fluid Mech]. In particular, such anisotropic particles were shown to display tumbling motion, where their orientation with respect to the main fluid direction reverses. Yet, detailed investigations of the dynamics of particles with any shape are still needed to complete our understanding of the dynamics of complex-shaped particles in turbulent flows.

Within this scope, the specific aim of this research is to study the dynamics of deformable particles with any shape, as in fiber suspensions or chains of particles (as aggregates of diatom in the ocean). For that purpose, numerical experiments will be performed by developing and using new microscopic simulation tools: these fine simulations will incorporate Direct Numerical Simulations (DNS) of wall-bounded turbulent flows along with fine descriptions of deformable chains of particles. With respect to these objectives, three main challenges will be tackled:
(i). Characterize the dynamics of elongated, deformable and inertial chains in the near-wall region;
(ii). Develop models for chain-chain and chain-wall interactions and characterize their effects;
(iii). Characterize the effect of chain feedback on near-wall turbulence.

This research project will thus lead to the developing new simulation tools for the dynamics of non-spherical particles in turbulent flows while deepening our understanding of the corresponding phenomena. A key to the success of this research activity is the close collaboration with researchers both at the local level (M. Bossy at INRIA) and at the national level (J.P. Minier at EDF R&D;): it will create a new dynamic by combining industrial, engineering, physical and mathematical point of views.