Publications by Pier Giuseppe Ledda

Instability and trajectories of buoyancy-driven annular disks: A numerical study

François Gallaire, Pier Giuseppe Ledda, Giovanni Vagnoli

We investigate the stability of the steady vertical path and the emerging trajectories of a buoyancy -driven annular disk as the diameter of its central hole is varied. The steady and axisymmetric wake associated with the steady vertical path of the disk, ...

Amer Physical Soc2024

Permeability sets the linear path instability of buoyancy-driven disks

François Gallaire, Pier Giuseppe Ledda, Giuseppe Antonio Zampogna, Giovanni Vagnoli

The prediction of trajectories of buoyancy-driven objects immersed in a viscous fluid is a key problem in fluid dynamics. Simple-shaped objects, such as disks, present a great variety of trajectories, ranging from zig-zag to tumbling and chaotic motions. Y ...

Cambridge University Press2023

Homogenization theory captures macroscopic flow discontinuities across Janus membranes

François Gallaire, Pier Giuseppe Ledda, Giuseppe Antonio Zampogna, Kevin Wittkowski

Janus membranes, thin permeable structures with chemical and geometrical asymmetric properties, show great potential in industrial separation processes. Yet the link between the micro- and macro-scale behaviours of these membranes needs to be established r ...

Cambridge University Press2023

From coating flow patterns to porous body wake dynamics via multiscale models

Pier Giuseppe Ledda

Multiscale phenomena are involved in countless problems in fluid mechanics. Coating flows are known to exhibit a broad variety of patterns, such as wine tears in a glass and dripping of fresh paint applied on a wall. Coating flows are typically modeled und ...

EPFL2022

Transport across thin membranes: Effective solute flux jump

François Gallaire, Pier Giuseppe Ledda, Giuseppe Antonio Zampogna

A model to describe the transport across membranes of chemical species dissolved in an incompressible flow is developed via homogenization. The asymptotic matching between the microscopic and macroscopic solute concentration fields leads to a solute flux j ...

AIP Publishing2022

Gravity-driven coatings on curved substrates: a differential geometry approach

François Gallaire, Pier Giuseppe Ledda

Drainage and spreading processes in thin liquid films have received considerable attention in the past decades. Yet, our understanding of three-dimensional cases remains sparse, with only a few studies focusing on flat and axisymmetric substrates. Here, we ...

Cambridge University Press2022

On the effect of a penetrating recirculation region on the bifurcations of the flow past a permeable sphere

François Gallaire, Pier Giuseppe Ledda, Giuseppe Antonio Zampogna, Matteo Ciuti

We study the flow past a permeable sphere modeled using homogenization theory. The flow through the porous medium is described by the Darcy law, in which the permeability quantifies the resistance for the fluid to pass through the microstructure. A slip co ...

AIP Publishing2021

Instability of a thin viscous film flowing under an inclined substrate: the emergence and stability of rivulets – CORRIGENDUM

Gioele Mariano Nicolò Balestra, François Gallaire, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

Cambridge University Press2021

Hydrodynamic-driven morphogenesis of karst draperies: spatio-temporal analysis of the two-dimensional impulse response – CORRIGENDUM

Gioele Mariano Nicolò Balestra, François Gallaire, Matthieu Wyart, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

Cambridge University Press2021

Instability of a thin viscous film flowing under an inclined substrate: steady patterns – CORRIGENDUM

Gioele Mariano Nicolò Balestra, François Gallaire, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

Cambridge University Press2021

Homogenization-based design of microstructured membranes: wake flows past permeable shells

François Gallaire, Edouard Boujo, Pier Giuseppe Ledda, Giuseppe Antonio Zampogna

A formal framework to characterize and control/optimize the flow past permeable membranes by means of a homogenization approach is proposed and applied to the wake flow past a permeable cylindrical shell. From a macroscopic viewpoint, a Navier-like effecti ...

Cambridge University Press2021

Drops on the Underside of a Slightly Inclined Wet Substrate Move Too Fast to Grow

François Gallaire, Pierre-Thomas Paul Brun, Pier Giuseppe Ledda

Pendant drops suspended on the underside of a wet substrate are known to accumulate fluid from the surrounding thin liquid film, a process that often results in dripping. The growth of such drops is hastened by their ability to translate over an otherwise ...

AMER PHYSICAL SOC2021

Hydrodynamic-driven morphogenesis of karst draperies: spatio-temporal analysis of the two-dimensional impulse response

François Gallaire, Matthieu Wyart, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

We study the role of hydrodynamic instabilities in the morphogenesis of some typical karst draperies structures encountered in limestone caves. The problem is tackled using the long wave approximation for the fluid film that flows under an inclined substra ...

Cambridge University Press2021

Prediction of Self-Assembled Dewetted Nanostructures for Photonics Applications via a Continuum-Mechanics Framework

François Gallaire, Fabien Sorin, Louis Marie Philippe Martin-Monier, Pier Giuseppe Ledda, Pierre-Luc Eloi Piveteau

When a liquid film lies on a nonwettable substrate, the configuration is unstable, and the film spontaneously ruptures to form droplets. This phenomenon, known as dewetting, commonly leads to undesirable morphological changes. Nevertheless, recent works, c ...

American Physical Society (APS)2021

Instability of a thin viscous film flowing under an inclined substrate: the emergence and stability of rivulets

Gioele Mariano Nicolò Balestra, François Gallaire, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

We study the pattern formation of a thin film flowing under an inclined planar substrate. The phenomenon is studied in the context of the Rayleigh-Taylor instability using the lubrication equation. Inspired by experimental observations, we numerically stud ...

Cambridge University Press2020

Instability of a thin viscous film flowing under an inclined substrate: steady patterns

Gioele Mariano Nicolò Balestra, François Gallaire, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

The flow of a thin film coating the underside of an inclined substrate is studied. We measure experimentally spatial growth rates and compare them to the linear stability analysis of a flat film modelled by the lubrication equation. When forced by a statio ...

Cambridge University Press2020

Dripping down the rivulet

Gioele Mariano Nicolò Balestra, François Gallaire, Gaëtan Pierre Clément Lerisson, Pier Giuseppe Ledda

This paper is associated with a video winner of a 2018 American Physical Society's Division of Fluid Dynamics (DFD) Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. ...

2019

Flow dynamics of a dandelion pappus: A linear stability approach

François Gallaire, Francesco Viola, Lorenzo Siconolfi, Pier Giuseppe Ledda

The study and control of flow instabilities is a key problem in aerodynamics. Aircrafts are designed not only to generate the lift force needed to balance their weight but, more importantly, to be stable and reasonably steady when in cruise conditions. Sim ...

2019

Suppression of von Karman vortex streets past porous rectangular cylinders

François Gallaire, Francesco Viola, Lorenzo Siconolfi, Pier Giuseppe Ledda

Although the stability properties of the wake past impervious bluff bodies have been widely examined in the literature, similar analyses regarding the flow around and through porous ones are still lacking. In this work, the effect of the porosity and perme ...

2018