Abstract We study drop impact on a deep pool of the same fluid, with an emphasis air layer trapped under droplets from its formation to rupture. The penetration velocity at very short time scale prior rupture is shown, using energy argument and experimental verification, be one-half velocity. then deduce dependence position liquid viscosity show that volume resulting bubbles can related both those impacting solid surfaces rigid spheres surfaces.

While the dynamics of complete wetting has been widely studied for liquids, way a gas spreads on solid is by far less known. We report here events following rise millimeter-size air bubble towards textured material immersed in water and covered thin plastron air. Bubbles contact either directly at end rise, or after few rebounds, which affects initial shape resulting contact. Then, material, owing to surface tension later buoyance, tends flatten further bubble. The corresponding are shown...

Green algae of the $Volvocine$ lineage, spanning from unicellular $Chlamydomonas$ to vastly larger $Volvox$, are models for study evolution multicellularity, flagellar dynamics, and developmental processes. Phototactic steering in these organisms occurs without a central nervous system, driven solely by response individual cells. All such spin about body-fixed axis as they swim; directional photosensors on each cell thus receive periodic signals when that is not aligned with light. The...

Sponges, the basalmost members of animal kingdom, exhibit a range complex architectures in which microfluidic channels connect multitudes spherical chambers lined with choanocytes, flagellated filter-feeding cells. Choanocyte can possess scores or even hundreds such cells, drive flows entering through porous walls and exiting into sponge channels. One mysteries choanocyte chamber is its shape, as it seems inappropriate for inducing directional transport since many flagella beat opposition to...

One of the characteristic features many marine dinoflagellates is their bioluminescence, which lights up nighttime breaking waves or seawater sliced by a ship's prow. While internal biochemistry light production these microorganisms well established, manner fluid shear mechanical forces trigger bioluminescence still poorly understood. We report controlled measurements relation between stress and at single-cell level, using high-speed imaging micropipette-held cells dinoflagellate...

Abstract Sponges, the basalmost members of animal kingdom, exhibit a range complex architectures in which microfluidic channels connect multitudes spherical chambers lined with choanocytes, flagellated filter-feeding cells. Choanocyte can possess scores or even hundreds such cells, drive flows entering through porous walls and exiting into sponge channels. One mysteries choanocyte chamber is its shape, as it seems inappropriate for inducing directional transport since many flagella beat...

A plate placed above a porous substrate through which air is blown can levitate if the airflow strong enough. We first model flow needed for taking off, and then examine how an asymmetric texture etched on surface induces directional motion of hovercraft. discuss design impacts propelling efficiency, it be used to manipulate these frictionless objects both in translation rotation.

A superhydrophobic capillary tube immersed in water and brought contact with the bath surface will be invaded by air, owing to its aerophilicity. We discuss this phenomenon where ingredients of classical rise are inverted, which leads noticeable dynamical features. (1) The main regime air invasion is linear time, due viscous resistance water. (2) Menisci tubes millimetre-size radii strongly oscillate before reaching their equilibrium depth, a consequence inertia. On whole, descent provides...

Water is extremely mobile on non-wetting surfaces, which it glides at high velocities. We discuss how a few indentations placed the surface markedly slow down drops forced to hit and jump above these hurdles. The corresponding “friction” characterized shown be inertial in nature, we interpret as result of successive soft shocks against obstacles.

Droplets moving along fibers have a mobility limited by viscous dissipation. Here, we discuss the opposite situation of bubbles on threads immersed in water. Contrasting with drops, is generally fixed visco-inertial skin friction, which allows them to move at much larger velocity than reported dual situation. We conclude establishing how friction becomes purely when increasing bath viscosity.

Sponges, the basalmost members of animal kingdom, exhibit a range complex architectures in which microfluidic channels connect multitudes spherical chambers lined with choanocytes, flagellated filter-feeding cells. Choanocyte can possess scores or even hundreds such cells, drive flows entering through porous walls and exiting into sponge channels. One mysteries choanocyte chamber is its shape, as it seems inappropriate for inducing directional transport since many flagella beat opposition to...

A plate floating on a cushion of air blown through porous substrate is set in motion when herringbone-shaped grooves redirect the airflow preferred direction, allowing contactless manipulation objects.

Green algae of the Volvocine lineage, spanning from unicellular Chlamydomonas to vastly larger Volvox , are models for study evolution multicellularity, flagellar dynamics, and developmental processes. Phototactic steering in these organisms occurs without a central nervous system, driven solely by response individual cells. All such spin about body-fixed axis as they swim; directional photosensors on each cell thus receive periodic signals when that is not aligned with light. The flagella...

One of the characteristic features many marine dinoflagellates is their bioluminescence, which lights up nighttime breaking waves or seawater sliced by a ship’s prow. While internal biochemistry light production these microorganisms well established, manner fluid shear mechanical forces trigger bioluminescence still poorly understood. We report controlled measurements relation between stress and at single-cell level, using high-speed imaging micropipette-held cells dinoflagellate Pyrocystis...