Turbulence and Multiphase Flows

The Komolgorov theory for three-dimensional isotropic and homogeneous turbulent flows relies on dimensional analysis and the observations of turbulent flows showing an energy transfer from the larger to smaller structures of the flow. Observations showed that the energy injected in the larger scales of the turbulent flow is dissipated at the smaller scales. The question is how the energy gets from the large to the small scales. The father of the modern concept of the “energy cascade” is Richardson (1922). His observations led him to propose a multistage process of energy cascade in which the large structures pass their energy onto slightly smaller structures, which in turn pass their energy to even smaller structures, and so on. Although well established, these results do not describe the full myriad of turbulent flows encountered in practice, and the search for a more complete or unified theoretical approach describing all turbulent flows remains elusive. Whether we consider the terrestrial atmosphere, ocean, mantle, or clouds emitted during sneezes or coughs, turbulence is combined with a complex range of other effects such as rotation, stratification, topography, multiple fluid phases, etc. Understanding their dynamics is surely not just about recreating replicates of these flows, but studying and thus understanding a hierarchy of different but related systems (Hide, 1983). Only then will we be able to truly understand the physical picture governing such flows, and thus possibly predict them. In that spirit, various works on homogeneous turbulent flows in rotation and multiphase flows are grouped in this section.