Inertial Particles In Homogeneous Shear Turbulence: Experiments and Direct Numerical Simulation.

In this paper we are concerned with the analysis of the interaction between heavy point-like particles and a homogeneous shear flow. Such flow is characterized by a linear mean velocity profile and thus it retains one of the most relevant feature of common turbulent flows such as boundary layers or jets, without involving the additional complications associated with the presence of solid boundaries or spatial inhomogeneities. The structure and the statistical properties of the particle field in these conditions will be analyzed via of a number of different tools, such as the Vorono? analysis and the assessment of the Angular Distribution Function (ADF), which generalizes the classical Radial Distribution Function to anisotropic conditions. To perform this kind of analysis, we will use a combination of experimental and numerical investigations. The use of numerics allows to gather a much richer information than that accessible by experiments, where the measurement of particle positions and velocites is typically limited to two dimensions and where only a reduced range of parameters can be explored. Direct numerical simulations, on the contrary, allow to assess the influence of all relevant particle parameters, such as particle relaxation time or gravity, in a systematic way. However, because of the inherent limitations used in modelling the particle behavior, where simplified descriptions of the dynamics are adopted, the interpretation of the results requires some caution and a preliminary validation by means of appropriate experimental data is highly advisable.