Decoupling between inertial and gravitational effects in the dynamics of particles in turbulence*

Volcanic ash transport, atmospheric pollution and dust transport are examples of turbulent flows ladened with particles. However, the coupling between several non-dimensional numbers (Rouse, Stokes and Reynolds) provides an entanglement between effects. Decoupling between inertial and gravitational effects in the dynamics of heavy spherical particles in turbulence are experimentally investigated. Several particle-to-fluid density ratios and particle diameters (i.e. different Stokes numbers) are explored in microgravity. When the density of the particle differs from that of the fluid, inertial effects modify the way particles interact with turbulence, e.g., preferential concentration. Being in microgravity conditions allows to experimentally investigate these effects, mitigating possible competition with effects due to gravity (e.g. settling). The experiment is mounted in the Dryden Drop Tower located in Portland State University which provides 2.1 seconds of micro-gravity. Particle tracking velocimetry is performed to access the statistics of the particles. The correlation times between the particles and the flow as well as the Lagrangian statistics will be presented.