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Instabilities, Waves and Turbulence

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Research in our group is focused on hydrodynamic instabilities, free-surface flows and turbulence. We conduct experiments on wind-generated waves, falling films, turbulence and waves in rotating fluids, and turbulent mixing of miscible fluids.

Permanent members:

P. Carles, P.-P. Cortet, A. Davaille, G. Gauthier, F. Giorgiutti, P. Gondret, J.-P. Hulin, J. Martin, F. Moisy, L. Pauchard, M. Rabaud, N. Rakotomalala, N. Ribe, D. Salin, L. Talon

Non Permanent members:

M. Brunet (PhD), M. Leang (PhD), S. Perrard (PostDoc)

Former Members:

S. Atis (PhD, 2013), J. Boisson (PostDoc, 2012), F. Boulogne (PhD, 2013), A. Campagne (PhD, 2015), E. Digiuseppe (PostDoc, 2012), B. Gallet (PostDoc, 2013), E. Herbert (PostDoc, 2013), C. Lamriben (PhD, 2012), T. Lemee (PhD, 2013), N. Machicoane (PostDoc, 2016), G.-J. Michon (Tech staff, 2012), A. Paquier (PhD, 2016), C. Ruyer-Quil (TA UPMC, 2013), B. Saintyves (PostDoc, 2013), A. Samanta (PhD, 2012), A. Sibrant (PostDoc, 2017), F. Touitou (PhD, 2012), R. Villey (PostDoc, 2016)

Kelvin wake or Mach cone?

M. Rabaud, F. Moisy

The angle of the wake behind a duck or a ship is always 39 degrees, independent of its velocity: this is the classical Kelvin wake. But is this really the case? A detailed analysis of a set of airborne images of ship wakes from Google Earth shows that the wake angle rather follows a law analogous to the Mach cone for supersonic airplanes. Why?

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F. Moisy, M. Rabaud Phys. Rev. E 89, 063004 (2014).

Lift Crisis

M. Rabaud

Collaboration: P. Bot, G. Thomas, A. Lombardi, C. Lebret (Naval Academy Research Institute, IRENAV Brest)

After the pioneering work of G. Eiffel (1912) the « Drag crisis » is now a well known phenomena of fluid mechanics for a bluff body moving at large velocity. During this crisis the drag force becomes, surprisingly, a decreasing function of the relative velocity. We have shown that at the drag crisis, non-up/down symmetrical bodies can also experience a strong "lift crisis", i.e. a sharp transition or even an inversion in their lift force.

Bot P., Rabaud M., Thomas G., Lombardi A. and and Lebret C., Phys. Rev. Lett 117, 234501 (2016) [PDF]

Liquid rope coiling

N. Ribe
Collaborations: M. Habibi and D. Bonn

If you like honey on your toast at breakfast, you are ready to perform a simple and beautiful fluid mechanics experiment. Plunge a spoon into the honey jar, and then hold it vertically several inches above the toast. The falling honey builds a whirling corkscrew-shaped structure - a phenomenon called "liquid rope coiling".

(Photo H. Hosseini)

N. Ribe, J. Fluid Mech. 812, R2 (2017).

Gravity induced mixing of two miscible fluids in vertical and tilted tubes

J. Znaien, F. Moisy, J.-P. Hulin
Collaborations: Y. Tanino, E.J. Hinch (DAMTP-Cambridge)

The buoyant mixing of two fluids of different densities in a tilted tube is investigated. The fluids are initially in an unstable configuration (the heavier fluid is above the lighter fluid), and show a rich variety of phenomena, including stable counterflows, intermittency and fully turbulent mixing.

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Y. Tanino, F. Moisy, J.-P. Hulin, J. Turbulence 16 (5), 484-502 (2015).

Inertial waves in a rotating fluid

N. Machicoane,P.-P. Cortet, F. Moisy

Collaboration : B. Voisin (LEGI, Grenoble).

Inertial waves are emitted from a sinusoidal disturbance in a homogeneous rotating fluid. The propagation of this wave is dispersive and anisotropic. Visualization of this phenomenon is achieved using a corotating Particle Image Velocimetry (PIV) system.

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N. Machicoane, P.-P. Cortet, B. Voisin, and F. Moisy, Phys. Fluids 27, 066602 (2015).

Swirling a glass of wine

F. Moisy, J. Bouvard

Collaboration: W. Herreman (LIMSI, Universite Paris-Sud)

It is common knowledge that prescribing an orbital motion to a glass of wine generates a rotating gravity wave that comes along with a swirling mean flow. This mean flow rotates in the direction of the wave and recirculates poloidaly (radially and vertically), thus permanently pushing new fluid to the surface where it aerates and releases the wine's aromas. Precisely the same kind of orbital shaking is used on a more professional level in bioreactors for the cultivation of biological cells. We present here new experiments to capture the physical mechanism of mean flow generation in an orbital shaken fluid.

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J. Bouvard, W. Herreman, F. Moisy, Phys. Rev. Fluids 2, 084801 (2017)

Rotating turbulence

N. Machicoane, A. Campagne, P.-P. Cortet, F. Moisy

Collaboration : B. Gallet (CEA Saclay).

The two-dimensional structuration of a turbulent flow in a rotating frame is a key mechanism for geophysical flows (ocean, atmosphere, rotating stars etc.) Using the rotating platform Gyroflow, we measure the anisotropic energy flux responsible for this two-dimensional structuration.

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Campagne A., Machicoane M., Gallet B., Cortet P.-P. and Moisy F., J. Fluid Mech 794, R5 (2016).

Machicoane M., Moisy F., and Cortet P.-P., Phys. Rev. Fluid 1, 073701 (2016).

Wind waves generation

A. Paquier, F. Moisy, M. Rabaud

How does wind create waves? This seemingly simple question has been the starting point of numerous theoretical, numerical, and experimental works of research. We approach this problem with a new experiment allowing to detect the very first deformations at the surface of a viscous fluid with an accuracy of a few microns.

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A. Paquier, F. Moisy, M. Rabaud Phys. Rev. Fluid 1, 234501 (2016).