Illinois Institute of Technology’s Department of Mechanical, Materials, and Aerospace Engineering welcomes Alfredo Soldati, professor of fluid mechanics and director of the Institute of Fluid Mechanics and Heat Transfer at TU Wien, to present a lecture, titled “Anisotropic Particles in Turbulent Shear Flow,” on Wednesday, November 16, from 3:30–4:30 p.m. in Room 104 of the John T. Rettaliata Engineering Center. 

Abstract

Turbulent flows with suspended anisotropic particles of non-spherical shape are a common occurrence in many industrial (e.g. papermaking, pharmaceutical processing, soot emission) and natural processes (e.g. pollen species, icy clouds, and plankton and marine snow). But there are many different ways for particles to be anisotropic so that many investigations have focused on the simpler but rich problem of small ellipsoidal particles translating, orienting, and rotating turbulent flows (Voth & Soldati, Anisotropic particles in Turbulence, Annu. Rev. Fluid Mech., 2017). However, current awareness of the anthropogenic oceanic pollution with plastic microfibres that are elongated and non-axisymmetric, demands for better understanding of fibre interaction with turbulent flows. In this talk, we will briefly review the models used to describe the dynamics of small ellipsoidal particles in turbulence, and then we will add a further complexity consisting on allowing the elongated particles to be slightly curved. We will present a series of experiments focusing on the dynamics of non-axisymmetric—quasistraight to slightly curved—fibres. Experiments are done in the TU Wien Turbulent Water Channel at Re  = 180; 360, and 720, and fibre lengths range from about 1 up to 20 Kolmogorov length scales. Their aspect ratio ranges from 40 to 120. In these flow conditions particles are neutrally buoyant, inertia-less, and rigid. We will highlight the effect of curvature of slender fibres on spinning and tumbling rates and we will propose conceptual models and scalings laws.