Full Rotational Dynamics of Plastic Microfibers in Turbulence.

The motion, settling, and dispersion of microplastics in the ocean are determined by their rotational dynamics. We present experiments on elongated, large aspect ratio, and mildly curved plastic fibers slightly longer than the Kolmogorov length scale. Exploiting their uniquely identifiable three-dimensional orientation, we perform original optical Lagrangian investigations and provide a set of homogeneous data on their rotation rates around their longitudinal axis: spinning rate, and transversal axes: tumbling rates, which we explain in the context of the general features of turbulence.

The TU Wien Turbulent Water Channel: Flow control loop and three-dimensional reconstruction of anisotropic particle dynamics.

A horizontal water channel facility was built to study particle dynamics in a turbulent flow. The channel is sufficiently long to produce fully developed turbulence at the test section, and the width-to-height ratio is sufficiently large to avoid the sidewall effect for a large proportion of the cross-section. The system was designed to study the dynamics of complex-shaped particles in wall-bounded turbulence, the characteristics of which can be finely controlled.

Modelling the direct virus exposure risk associated with respiratory events.

The outbreak of the COVID-19 pandemic highlighted the importance of accurately modelling the pathogen transmission via droplets and aerosols emitted while speaking, coughing and sneezing. In this work, we present an effective model for assessing the direct contagion risk associated with these pathogen-laden droplets. In particular, using the most recent studies on multi-phase flow physics, we develop an effective yet simple framework capable of predicting the infection risk associated with different respiratory activities in different ambient conditions.

Short-range exposure to airborne virus transmission and current guidelines.

After the Spanish flu pandemic, it was apparent that airborne transmission was crucial to spreading virus contagion, and research responded by producing several fundamental works like the experiments of Duguid [J. P. Duguid, 44, 6 (1946)] and the model of Wells [W.

Turbulent Drag Reduction by a Near Wall Surface Tension Active Interface.

In this work we study the turbulence modulation in a viscosity-stratified two-phase flow using Direct Numerical Simulation (DNS) of turbulence and the Phase Field Method (PFM) to simulate the interfacial phenomena. Specifically we consider the case of two immiscible fluid layers driven in a closed rectangular channel by an imposed mean pressure gradient. The present problem, which may mimic the behaviour of an oil flowing under a thin layer of different oil, thickness ratio / = 9, is described by three main flow parameters: the shear Reynolds number (which quantifies the importance of inertia compared to viscous effects), the Weber number (which quantifies surface tension effects) and the viscosity ratio = / between the two fluids.

Turbulent breakage of ductile aggregates.

In this paper we study breakage rate statistics of small colloidal aggregates in nonhomogeneous anisotropic turbulence. We use pseudospectral direct numerical simulation of turbulent channel flow and Lagrangian tracking to follow the motion of the aggregates, modeled as sub-Kolmogorov massless particles. We focus specifically on the effects produced by ductile rupture: This rupture is initially activated when fluctuating hydrodynamic stresses exceed a critical value, σ>σ(cr), and is brought to completion when the energy absorbed by the aggregate meets the critical breakage value.

Upscale energy transfer and flow topology in free-surface turbulence.

Free-surface turbulence, albeit constrained onto a two-dimensional space, exhibits features that barely resemble predictions of simplified two-dimensional modeling. We demonstrate that, in a three-dimensional open channel flow, surface turbulence is characterized by upscale energy transfer, which controls the long-term evolution of the larger scales. We are able to associate downscale and upscale energy transfer at the surface with the two-dimensional divergence of velocity.

Time persistence of floating-particle clusters in free-surface turbulence.

We study the dispersion of light particles floating on a flat shear-free surface of an open channel in which the flow is turbulent. This configuration mimics the motion of buoyant matter (e.g.

Protocols to compare infusion distribution of wound catheters.

Multi-holed wound catheters are increasingly used in clinical practice to administer analgesic/anaesthetic locally to the painful region. The distribution of flow infused during controlled (continuous or intermittent) administration of medication is believed to be an important issue for successful pain relief. Nevertheless, this information is not available from the literature.

Water quality control in the river Arno.

In this work, we analyzed pollution in the river Arno using a non-steady advection-dispersion-reaction equation (ADRE) calibrated on experimental data. We examined the influence different pollution control strategies have on dissolved oxygen (DO). We considered (i) flow rate variation; (ii) local oxygenation at critical points; (iii) dynamic modification of wastewater load.