Oceanic realistic application of a microplastic biofouling model to the river discharge case.

Marine biofouling is considered one of the major biophysical processes influencing the vertical dynamics of plastic debris in seawater. We numerically implement, for the first time, this mechanism within a fine-resolution, regional model of the Tyrrhenian Sea, in order to simulate the dispersion of microplastics (MPs) released at the mouth of a highly polluting river. Four polymers and three particle sizes are used to quantify algal concentration influence on the trajectories, fates, and accumulation spots of the tracked MPs, by comparing 2002 winter and summer runs encompassing or not biofouling.

Lagrangian Supersaturation Fluctuations at the Cloud Edge.

Evaporation of cloud droplets accelerates when turbulence mixes dry air into the cloud, affecting droplet-size distributions in atmospheric clouds, combustion sprays, and jets of exhaled droplets. The challenge is to model local correlations between droplet numbers, sizes, and supersaturation, which determine supersaturation fluctuations along droplet paths (Lagrangian fluctuations). We derived a statistical model that accounts for these correlations.

Potential of organic carbonates production for efficient carbon dioxide capture, transport and storage: Reaction performance with sodium hydroxide-ethanol mixtures.

Carbon dioxide storage is one of the main long-term strategies for reducing carbon dioxide emissions in the atmosphere. A clear example is Norway's Longship project. If these projects should succeed, the transport of huge volumes of carbon dioxide from the emissions source to the injection points may become a complex challenge.

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.

Buoyancy-Driven Flow through a Bed of Solid Particles Produces a New Form of Rayleigh-Taylor Turbulence.

Rayleigh-Taylor (RT) fluid turbulence through a bed of rigid, finite-size spheres is investigated by means of high-resolution direct numerical simulations, fully coupling the fluid and the solid phase via a state-of-the-art immersed boundary method. The porous character of the medium reveals a totally different physics for the mixing process when compared to the well-known phenomenology of classical RT mixing. For sufficiently small porosity, the growth rate of the mixing layer is linear in time (instead of quadratical) and the velocity fluctuations tend to saturate to a constant value (instead of linearly growing).

Continuous Growth of Droplet Size Variance due to Condensation in Turbulent Clouds.

We use a stochastic model and direct numerical simulation to study the impact of turbulence on cloud droplet growth by condensation. We show that the variance of the droplet size distribution increases in time as t^{1/2}, with growth rate proportional to the large-to-small turbulent scale separation and to the turbulence integral scales but independent of the mean turbulent dissipation. Direct numerical simulations confirm this result and produce realistically broad droplet size spectra over time intervals of 20 min, comparable with the time of rain formation.

Numerical study of laminar-turbulent transition in particle-laden channel flow.

We present direct numerical simulations of subcritical transition to turbulence in a particle-laden channel flow, with particles assumed rigid, spherical, and heavier than the fluid. The equations describing the fluid flow are solved with an Eulerian mesh, whereas those describing the particle dynamics are solved by Lagrangian tracking. Two-way coupling between fluid and particles is modeled with Stokes drag.

Dispersion of swimming algae in laminar and turbulent channel flows: consequences for photobioreactors.

Shear flow significantly affects the transport of swimming algae in suspension. For example, viscous and gravitational torques bias bottom-heavy cells to swim towards regions of downwelling fluid (gyrotaxis). It is necessary to understand how such biases affect algal dispersion in natural and industrial flows, especially in view of growing interest in algal photobioreactors.

[Prognostic stratification of survivors of lst myocardial infarction: evaluation of regional kinetics and ejection fraction by bidimensional echocardiography].

To determine the prognostic value of some echocardiographic indices of left ventricular function (ejection fraction, wall motion score index, left ventricular dimension) in the first year after acute myocardial infarction, we studied prospectively 162 consecutive patients (mean age: 61 +/- 11) who survived the hospital phase of a first acute myocardial infarction. Two-dimensional echocardiography was performed at hospital discharge (mean: 20 +/- 3 days after admission). For the analysis of wall motion, an 11 segment model of the left ventricle was used; from the scoring system of segmental ventricular function (1 = normal, 2 = hypokinetic, 3 = akinetic, 4 = dyskinetic, 5 = aneurysmal) we derived the wall motion score index (sum of assigned number to each segment/11).