Frédéric Moisy
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Flexible floaters align with the direction of wave propagation Open
We investigate the slow, second order motion of thin flexible floating strips drifting in surface gravity waves. We introduce a diffractionless model (Froude-Krylov approximation) that neglects viscosity, surface tension, and radiation eff…
Preferential orientation of small floaters drifting in water waves Open
Elongated floaters drifting in propagating water waves slowly rotate towards a preferential orientation with respect to the direction of incidence. In this paper we study this phenomenon in the small floater limit $k L_x F_c$ arises from t…
Preferential orientation of small floaters drifting in water waves Open
Elongated floaters drifting in propagating water waves slowly rotate towards a preferential orientation with respect to the direction of incidence. In this article, we study this phenomenon in the small-floater limit $k L_x < 1 $, with $k$…
Wind-wave growth over a viscous liquid Open
Experimental and theoretical studies on wind-wave generation have focused\nprimarily on the air-water interface, where viscous effects are small. Here we\ncharacterize the influence of the liquid viscosity on the growth of\nmechanically ge…
Ostwald-like ripening in the two-dimensional clustering of passive particles induced by swimming bacteria Open
Clustering passive particles by active agents is a promising route for fabrication of colloidal structures. Here, we report the dynamic clustering of micrometric beads in a suspension of motile bacteria. We characterize the coarsening dyna…
Ostwald-like ripening in the two-dimensional clustering of passive particles induced by swimming bacteria Open
Clustering passive particles by active agents is a promising route for fabrication of colloidal structures. Here, we report the dynamic clustering of micrometric beads in a suspension of motile bacteria. We characterize the coarsening dyna…
Direct measurement of the aerotactic response in a bacterial suspension Open
Aerotaxis is the ability of motile cells to navigate toward oxygen. A key question is the dependence of the aerotactic velocity with the local oxygen concentration c. Here we combine simultaneous bacteria tracking and local oxygen concentr…
Direct measurement of the aerotactic response in a bacterial suspension Open
Aerotaxis is the ability of motile cells to navigate towards oxygen. A key question is the dependence of the aerotactic velocity with the local oxygen concentration c . Here we combine simultaneous bacteria tracking and local oxygen concen…
Kelvin-Helmholtz instability and formation of viscous solitons on highly viscous liquids Open
Viscous solitons are strongly non-linear surface deformations generated by\nblowing wind over a liquid beyond a critical viscosity. Their shape and\ndynamics result from a balance between wind drag, surface tension and viscous\ndissipation…
Shear instability and formation of viscous solitons on highly viscous liquids Open
Viscous solitons are strongly non-linear surface deformations generated by blowing wind over a liquid beyond a critical viscosity. Their shape and dynamics result from a balance between wind drag, surface tension and viscous dissipation in…
View article: Effect of a weak current on wind-generated waves in the wrinkle regime
Effect of a weak current on wind-generated waves in the wrinkle regime Open
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The Kelvin–Helmholtz instability, a useful model for wind-wave generation? Open
The Kelvin–Helmholtz instability, one of the most classical instabilities in fluid mechanics, was initially introduced to describe the generation of waves by wind. This instability is relevant to several natural and engineering flow config…
Motility and aerotaxis in $Sinorhizobium\ meliloti$, a soil bacterium Open
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View article: Motility and phototaxis of <i>Gonium</i> , the simplest differentiated colonial alga
Motility and phototaxis of <i>Gonium</i> , the simplest differentiated colonial alga Open
Green algae of the Volvocine lineage, spanning from unicellular Chlamydomonas to vastly larger Volvox, are models for the study of the evolution of multicellularity, flagellar dynamics, and developmental processes. Phototactic steering in …
View article: Effect of a weak current on wind-generated waves in the wrinkle regime
Effect of a weak current on wind-generated waves in the wrinkle regime Open
We investigate numerically the influence of a weak current on wind-generated\nsurface deformations for wind velocity below the onset of regular waves. In\nthat regime, the liquid surface is populated by small disorganised deformations\nelo…
View article: Motility and Phototaxis of <i>Gonium</i> , the Simplest Differentiated Colonial Alga
Motility and Phototaxis of <i>Gonium</i> , the Simplest Differentiated Colonial Alga Open
Green algae of the Volvocine lineage, spanning from unicellular Chlamydomonas to vastly larger Volvox , are models for the study of the evolution of multicellularity, flagellar dynamics, and developmental processes. Phototactic steering in…
Turbulent windprint on a liquid surface Open
We investigate the effect of a light turbulent wind on a liquid surface, below the onset of wave generation. In that regime, the liquid surface is populated by small disorganised deformations elongated in the streamwise direction. Formally…
Counter-rotation in an orbitally shaken glass of beer Open
Swirling a glass of wine induces a rotating gravity wave along with a mean flow rotating in the direction of the applied swirl. Surprisingly, when the liquid is covered by a floating cohesive material, for instance a thin layer of foam in …
Wake of inertial waves of a horizontal cylinder in horizontal translation Open
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Mean mass transport in an orbitally shaken cylindrical container Open
A cylindrical container partially filled with a liquid in orbital shaking\nmotion, i.e. in circular translation with fixed orientation with respect to an\ninertial frame of reference, generates, along with a rotating sloshing wave, a\nmean…
Two-dimensionalization of the flow driven by a slowly rotating impeller in a rapidly rotating fluid Open
We characterize the two-dimensionalization process in the turbulent flow\nproduced by an impeller rotating at a rate $\\omega$ in a fluid rotating at a\nrate $\\Omega$ around the same axis for Rossby number $Ro=\\omega/\\Omega$ down to\n$1…
Turbulent drag in a rotating frame Open
What is the turbulent drag force experienced by an object moving in a rotating fluid? This open and fundamental question can be addressed by measuring the torque needed to drive an impeller at a constant angular velocity ${\it\omega}$ in a…