Les Gustins Summer School

I have co-organized the summer school "Les Gustins" during the past 5 years. It is intended for physics and mathematics researchers (starting for Master degree) who want to discover new topics of physics in an informal atmosphere. We also organize each year a public session intended for non-specialist audience. The last edition (2024) has been supported by IESF (Ingenieurs de France) and Université Grenoble-Alpes. During each edition, I had the opportunity to give some introductory presentations on various topic related to fluid mechanics for a broad audience of physicist. You can find a resume of all the contributions and more informations on our website !

A macroscopic spin-1/2

During 'Les Gustins', I gave with S. Bernardet a presentation about half-integer spin. The latter is often encountered in quantum mechanics, but it is puzzling for the intuition as it does not invariant under a 360 degree rotation. In order to better understand it, we tried to build a macroscopic object with such behavior. After several attempts and the help of E. Dumas from the University of Chicago, we finally came up with the spinorial ball that is manipulated in the video. It shows that the origin of half-integer spin is not quantum but rather geometric and results from the existence of group homomorphism. You can find out more about this here.

Science of a coffee cup

Coffee is the most shared feature between all physicist, but a coffee cup is also a great playground for experiments. With Aleksi Bossart from Technorama Museum, we made a comprehensive review about all the physical phenomena that can be witnesses in a coffee cup. The latters includes (among others) optical caustics, acoustic degeneracy lifting, tea-leaf paradox or layers formation in latte (in video, inspired from this work). For each topic, a short movie and quantitative analysis with standard equipment is performed, and the results are compared with a minimal model. An experimental conference connected with this work should take place in Spring 2025. A preprint paper can be found here.

Schlieren experiment

For the open days of EPFL, I had the opportunity to setup an experimental realization of Schlieren experiment using a large (50 cm diameter) telescop mirror. This setup allows to access the tiny light deflections produced by inhomogeneities in the air, which occurs for instance when one looks at the blurred background above a hot fire.

The video shows for instance the air flow generated by my hand at temperature 37 C in the surrounding air at approximately 20 C. A poster with more explainations can be found here (in french).

Fluid motion near a moving ball

We studied recently the circular trajectory of a ball pulled by a rope at the water surface. In order to satisfactory explain our experimental results, we had to incorporate in our model the lift force generated by the fluid's motion around the ball. The experimental movie shows a stack of 15 consecutive images in the laboratory and in the comoving frame, which allows to materialize the streamlines. A clear asymetry is visible and is responsible for a lift force directed toward the center of the trajectory. You can find our more on this with our arxiv paper !

Shaping a liquid with vibrations

The shape of a large liquid interface under standard experimental condition is horizontal due to gravity. However, one can use vibrations to modify the interface's shape resulting in so-called vibro-equilibrium. In this video, we show the interface of viscous silicon oil submitted to high frequency (100 Hz) vibration. Thanks to the vibrations, we were able to trap air bubbles under the liquid at precise locations shaped as a smiley. The presence of the air bubble 'pushes' the liquid, which results in printing the smiley shape of bubbles at the liquid surface. You can find details about this effect in this arxiv publication.

...and more to come :)