The mechanical behavior of fiber-like objects dispersed in a turbulent flow represents a complex and fascinating problem from both the fundamental and applied viewpoint. In particular, the dynamics of finite-size fibers (i.e., having length substantially larger than the dissipative lengthscale) has started to be understood only quite recently. We will review our major findings on both rigid and flexible, finite-size fibers, which have been obtained by means of direct numerical simulations (DNS) of homogeneous isotropic turbulence where a two-way coupling between the carrier and dispersed phase is ensured via an immersed boundary method. Remarkably, these findings paved the way for the successful development of a novel experimental method, which has been named "Fiber Tracking Velocimetry" (FTV), able to measure at a prescribed lengthscale some relevant two-point statistics (i.e., PDFs of transverse velocity increments and corresponding structure functions), naturally overcoming the well-known issues due to relative dispersion when using pairs of tracers. Moreover, we will explore the non-dilute regime at relatively large concentrations, where the backreaction of the dispersed phase to the carrier flow is not negligible, by analyzing the mechanisms of turbulence modulation dramatically altering (with respect to the single-phase case) both the macroscopic properties and the scale-by-scale energy budget of the carrier flow.
About the Speaker
Dr. Stefano Olivieri is currently a Postdoctoral Scholar in the Complex Fluids and Flows Unit at the Okinawa Institute of Science and Technology (OIST), Japan. He received his B.Sc./M.Sc. in Mechanical/Aeronautical Engineering and his Ph.D. in Fluid Dynamics and Environmental Engineering from the University of Genoa, Italy. His research interests concern particle-laden flows, fluid-structure interaction and bio-inspired aerodynamics, investigating such problems primarily by means of high-fidelity, direct numerical simulations. Specific topics include the dynamics of filament-like objects in fully-developed turbulence, the development of passive aeroelastic energy harvesters, and the impact of turbulence on the self-sustained flapping motion of flexible plates and flags.