ABSTRACT
Physics governing the locomotion of microorganisms and other microsystems is dominated by viscous damping. An effective swimming strategy involves the non-reciprocal and periodic deformations of the considered body. Here, we show that a magnetocapillary-driven self-assembly, composed of three soft ferromagnetic beads, is able to swim along a liquid-air interface when powered by an external magnetic field. More importantly, we demonstrate that trajectories can be fully controlled, opening ways to explore low Reynolds number swimming. This magnetocapillary system spontaneously forms by self-assembly, allowing miniaturization and other possible applications such as cargo transport or solvent flows.
ABSTRACT
We present an experimental study on gravity capillary wave turbulence in water. By using space-time resolved Fourier transform profilometry, the behavior of the wave energy density |η(k,ω)|(2) in the 3D (k,ω) space is inspected for various forcing frequency bandwidths and forcing amplitudes. Depending on the bandwidth, the gravity spectral slope is found to be either forcing dependent, as classically observed in laboratory experiments, or forcing independent. In the latter case, the wave spectrum is consistent with the Zakharov-Filonenko cascade predicted within wave turbulence theory.
ABSTRACT
In the framework of Rayleigh's description, we have investigated the eigenfrequencies of the capillary waves of a nonwetting droplet under forced oscillations (pointlike force). The theoretical model using the spherical harmonics Y(l,m)(theta, phi) as a part of the solution of the Laplace equation, is in good agreement with the experimental results. This model can be generalized for all kinds of excitations with a sitting or a levitating droplet due to the decomposition of the excitation on the spherical harmonics basis. From this study, a different theoretical way of interpreting droplet bouncing is presented motivating a wide range of industrial applications.
