Inertial particles in homogeneous shear turbulence: experiments and direct numerical simulation

The interaction between turbulence and a dispersed phase has been studied for a long time, as it is central to a large number of natural phenomena and technical applications which range from raindrops formation in clouds or air bubbles transport in oceans to injection systems in combustion engines. The most salient feature of this interaction, i.e. the phenomenon of preferential accumulation, has been highlighted in a large number of both numerical and experimental studies, see e.g. the recent review in [1]. Because of the different inertia between the two phases, particles do not sample the fluid domain uniformly under the action of turbulent transfert. Instead, small heavy particles are observed to be ejected from high-vorticity zones and to accumulate in regions of high strain. Lighter-than-fluid particles display the opposite tendency to migrate towards high-vorticity regions. For both heavy and light particles, the non-uniformities which arise in the instantaneous concentration field are of interest per se, since they influence important processes such as the rate of interparticle collisions or bubble coalescence. Moreover, large local concentration peaks can be created through the mechanism of inertial clustering even at modest values of the bulk volume or mass fraction. In turn, this results in a significant feedback on the carrier field which may lead to profound modifications of the turbulence structure even at the largest scales, see e.g. [2] for the case of a bubble-laden turbulent boundary layer.