Ph.D in the Emergent Complexity in Physical Systems Laboratory (ECPS)
“Turbulent patterns in wall-bounded shear flows: invariant solutions and their bifurcations”
When wall-bounded shear flows become turbulent, the flow may self-organize into characteristic spatially periodic patterns of unknown origin. To understand how regular patterns emerge in a turbulent flow, a nonlinear theory is needed. In my Ph.D thesis, we construct and analyze exact invariant solutions of the 3D nonlinear fluid flow equations that capture the non-trivial spatial structure of patterns in turbulent flow. This approach requires high-performance computational tools, that have been developed as part of my thesis and are now publicly available within a widely used state-of-the-art open source software.
Using the developed numerical methods, turbulent patterns in two types of wall-bounded shear flows have been studied: oblique turbulent-laminar stripes in plane Couette flow and a multitude of convection patterns arising in inclined layer convection when the angle of inclination is varied. The existence and properties of exact invariant solutions underlying these patterns leads to a better understanding of the complex spatio-temporal dynamics in spatially extended turbulent flows.
Now I am working as a software engineer at PSI Software AG in Berlin on forecasting renewable energies and their influence on our electrical grid.
PhD in the Geo-Energy Laboratory (GEL)
“Hydraulic stimulation of pre-existing discontinuities in tight rocks”
Deep geothermal energy represents a promising source of renewable energy that might play a key role in the World’s future energy balance. It is a constant resource, largely available across continents that can be used to supply heat and possibly electricity. Despite its great potential, there are still some issues that prevent its diffusion and employment. Perhaps, one of the most important is induced seismicity that tremendously affects public safety as well as its opinion on this type of green energy. In my PhD thesis supervised by Prof. B. Lecampion, we proposed theoretical models and specific numerical algorithms that can help understanding the role of fluid injection and propagation at depth on the transition between a-seismic and seismic deformations.
Currently, I am working at Swiss Seismological Service (SED) at ETH Zürich as postdoc associate. My research activity is mainly about numerical modelling of induced seismicity using empirical, hybrid and physic-based models.
I am also involved in an international project called “Innovation for De-Risking Enhanced Geothermal Energy Projects (DEEP)” where I am responsible for the development of new generation of induced seismicity forecasting models based on Deep Learning techniques.
PhD in the Laboratory of Fluid Mechanics and Instabilities (LFMI)
“Pattern formation in thin liquid films: from coating-flow instabilities to microfluidic droplets”
Nature and industrial applications abound with thin viscous flows, ranging from the lava flow on volcanoes to the lubricating layer around confined droplets in microchannels. We all have already observed that thin-film flows often form well-defined patterns, as the tears in a glass of wine, or the crystalline-like pattern of pendent droplets under the kitchen lid.
The aim of this thesis is to investigate the mechanisms underpinning the pattern formation in thin-film flows for different configurations. A theoretical model is developed and complemented with advanced stability analyses, numerical simulations and experiments.
We show that the gravity-driven instability of a liquid film under curved or inclined substrates is at the origin of the fascinating karst formations encountered in limestone caves. Furthermore, we find and rationalize a stable regime of these film flows that can be harnessed to produce hemispherical elastic shells in a very robust and versatile manner.
We also provide a detailed characterization of the thin-film profiles around confined droplets, key for a better prediction of their dynamics in microfluidic devices.
In spite of the broad range of scales considered, we show that all the treated problems and the pattern selections can be described by similar lubrication equations.
Gioele is now co-responsible of the iPrint Institute and Assistant Professor at the HES-SO University of Applied Sciences and Arts of Western Switzerland in Fribourg (HEIA-FR), where he teaches fluid mechanics classes. His research is focused on the development of new digital printing and manufacturing techniques and processes.
PhD in the Laboratory for Multiscale Mechanics Modeling (LAMMM)
The mechanics of crack-tip dislocation emission and twinning
This thesis proposes two new theories for describing the mechanics of crack tip dislocation emission and twinning. Dislocation emission from a crack tip is a necessary mechanism for crack tip blunting and toughening, and at the same time one of the classical problems in mechanics of materials. A material is intrinsically ductile under Mode I loading when the critical stress intensity factor for dislocation emission KIe is lower than the critical stress intensity factor KIC for cleavage. KIe is usually evaluated using the approximate Rice theory. Atomistic simulations have shown that this theory is reasonable but not highly accurate. The discrepancy arises because Mode I emission is accompanied by the formation of a surface step that is not considered in the Rice theory. In this work we propose a new theory for Mode I emission based on the idea that (i) the stress resisting step formation at the crack tip creates “lattice trapping” against dislocation emission such that (ii) emission is due to a mechanical instability at the crack tip. Furthermore, a theory for crack-tip twinning has been proposed accounting for (i) the absence of the step formation, and (ii) the fact that nucleation does not occur directly at the tip. Both theories are quantitatively validated against atomistic simulations across a wide set of fcc materials.
Phd in the Laboratory for Hydraulic Machines (LMH)
“Collapse phenomena of deformed cavitation bubbles”
After completing my PhD in the laboratory for hydraulic machines (LMH) under the supervision of Mohamed Farhat, I obtained an SNSF Early Postdoc Mobility fellowship to work at the University of Colorado Boulder, USA. This experience allowed me to apply the knowledge that I had gained during my PhD on the fluid dynamics of cavitation bubbles to studies of ultrasound contrast agent microbubbles in biomedical applications.
I have since returned to Switzerland as an assistant professor of multiphase fluid dynamics at ETH Zurich, where I am building a lab to continue with experimental research activities involving fast fluid dynamics at small scales.