Fluid-particle interactions: from the simple pendulum to collective effects in turbulence
Résumé
This PhD thesis covers many features of fluid-particle interactions,
ranging from a simple pendulum submerged in a flow to the presence of
superclusters of water droplets in a wind tunnel. The thesis is divided
in two parts : a first one considering single particle interactions and
a second one considering collective effects. Concerning the first part
we will focus in the dynamics of towed systems in a laminar and a
turbulent sorrounding flow and the instabilities they can develop. For
the turbulent case, we have also copared the dynamics of a towed sphere
with the freely advected situation. Concerning the collective effects,
three different flows have been studied: a water tunnel, a von Kármán
flow and wind tunnel. A broad range of Reynold numbers (based on Taylor
microscale), Kolmogorov dissipation scales and particles diameters and
densities has been covered. Using Voronoï diagrams, we have quantified
preferential concentration as a function of the Stokes number and the
Reynolds number, and then the presence and properties of clusters.