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Tristan Gilet

Education and Current Position

1999-2005 : Civil Engineer in Physics at the University of Liège, graduated in june 2005 with the highest honors and the congratulations from the jury.

2002-2004 : Civil Engineer in Aeronautics at SUPAERO (E.N.S.A.E. - Ecole Nationale Supérieure de l'Aéronautique et de l'Espace - Toulouse) within the framework of the TIME (Top Industrial Managers for Europe) project, graduated in june 2005.

2003-2004 : DEA in Fluid Dynamics at SUPAERO , graduated in june 2005 with high honors.

2005-present : PhD thesis in Physics (Fluid Dynamics) at the University of Liège, financially supported by FRIA.

Address

GRASP, Institut de Physique B5a, local 3/5
Sart-Tilman, Université de Liège,
B-4000 Liège, Belgium

Phone: +32(0)4.366.48.31
Fax: +32(0)4.366.29.90
E-mail: Tristan.Gilet@ulg.ac.be

Research Interests

	Partial coalescence of a droplet When a water droplet is laid down on a water/oil interface, it can experience a partial coalescence. The droplet does not completely empty. Capillary waves propagate on the droplet surface and converge at the top. This mechanism can delay the vertical collapse, and a pinch-off occurs: a new daughter droplet is formed. As many as 6 successive partial coalescences can be observed. So droplets are really similar to russian dolls ! The conditions for partial coalescence occurrence have been largely investigated.
	Droplets on vibrated interfaces Droplets are sometimes able to levitate for many minutes upon an air-liquid interface set in vibration at about 75Hz. The thin air film between the droplet and the liquid bath is constantly renewed. When the vibration amplitude is high enough, the droplet surf on the capillary wave that it generates at each rebounding: the droplet begins to walk quickly on the surface. The interface deformation made by each droplet can influence the behavior of neighbor droplets: attractions and repulsions take place, giving rise to structured lattices !
	Surfactant and droplet coalescence When surfactant molecules are added, the droplet coalescence becomes really wild. It even generates artistic forms. Let's see the Liquid Sculpture website !
	Water droplets on superhydrophobic surfaces Duck feathers are one of the best hydrophobic surfaces. Instead of spreading, water droplets remain spherical and stay on this micro-corrugated surface like a fakir stays on its nailed board. The contact surface between the droplet and the feather is so small that the droplet immediately takes off when a tiny force is applied on it. That's why ducks can go out of their bath perfectly dried ! Droplets rebound on this kind of surface has been investigated ... in microgravity !
	Lifetime of soapy bubbles Everybody has already seen big soapy bubbles staying for a long time at the surface of his bath. But why these bubbles collapse after about 2 minutes ? And why the lifetime of bubbles is greater when the size is increased ? An attempt to model this phenomenon has been made.

Sleep apnea and flows in collapsible tubes The pharynx is the real junction between the digestive system and the respiratory system. It has to be highly deformable to ensure deglutition. While breathing in, the whole airway experience a depression driven by the lungs. This depression is large enough to crush the pharynx (Think about a vacuum-cleaner !). During the day, a lot of muscles surrounding the pharynx act to avoid this collapse. But during the night, these muscles can fall asleep and the pharynx collapse. No more breath is possible until the muscles are awaken. By understanding the flow properties in collapsible tubes, one can control the exact overpressure needed to keep the airways open.

Coherent structures in turbulent flows This project was made at the Von Karman Institute . A Large-Eddy simulation of a round jet impinging on a heated plate has been performed with the commercial software FLUENT. The coherent structures dynamics has been investigated by using the so-called Q-factor criterion. Instantaneous visualizations, films, 1-point correlations, time-signal analyses, ... were some of the tools applied to get information about the coherent structure evolution and their impact on the flow. The noticeable importance of the coherent part of the flow in turbulent fluctuations enhancement has been shown.

Publications

• Critical parameters for the partial coalescence of a droplet.
  T. Gilet, K. Mulleners, J.P. Lecomte, N. Vandewalle & S. Dorbolo
  Phys. Rev. E (submitted)
• Dancing droplets onto liquid surfaces.
  N. Vandewalle, D. Terwagne, K. Mulleners, T. Gilet & S. Dorbolo
  Phys. of Fluids - Gallery of Fluid Motion 2006

Conferences

• Cascades of coalescences for droplets near liquid interfaces.
  APS division of fluid dynamics (Chicago - nov.2005)
  
• Bouncing droplets on a vibrated liquid/gaz interface.
  APS division of fluid dynamics (Tampa-FL - nov.2006)
  
• A deeper analysis of the partial coalescence of a droplet onto a planar interface.
  APS division of fluid dynamics (Tampa-FL - nov.2006)
  

Other interests

1989-present : Music ! My second life...
I've learned piano improvization for many years (jazz, variety and even classic impro). I've been playing in many groups - the last one: Fool Tchazz Quartet. I love jazz !!! Listen to Chick Corea, Bobby Mc Ferrin, the New-York Voices, Michel Petrucciani, Claude Nougaro and Maurane (among others) ! I have been studying music writing for four years...

1994-1998 : A little theater...

1996-1999 : Active member of OXFAM (fair trade).

1998-2002 : Concerts in retirement homes.

2003-present : Flying (Private Pilot Licence obtained in march 2004).

July 2003 : Participation to the 6th Student Parabolic Flight Campaign. Our experiment: techniques of artistic painting in 0-G !!!

Running, alpinism, walking, ...

Photos