Here we report a simple microfluidics phenomenon which allows the efficient mass production of micron size gas bubbles with perfectly monodisperse and controllable diameter. It resorts on self-excited breakup (which locks at certain frequency) short microligament coflowing in focused liquid stream. In this work, describe physics obtain closed expressions for bubble diameter as function properties, geometry, flow parameters, from large set experimental results.

Making use of experimental and theoretical considerations, in this Letter we deduce a criterion to determine the critical velocity for which drop impacting smooth dry surface either spreads over substrate or disintegrates into smaller droplets. The derived equation, expresses splash threshold as function material properties two fluids involved, radius, mean free path molecules composing surrounding gaseous atmosphere, has been thoroughly validated experimentally at normal atmospheric...

Cylindrical liquid jets are inherently unstable and eventually break into drops due to the Rayleigh-Plateau instability, characterized by growth of disturbances that either convective or absolute in nature. Convective instabilities grow amplitude as they swept along flow, while at a fixed spatial location. Liquid nearly always convectively unstable. Here we show two-phase can breakup an instability depends on capillary number outer liquid, provided Weber inner is >O(1). We verify our...

We provide a comprehensive and systematic description of the diverse microbubble generation methods recently developed to satisfy emerging technological, pharmaceutical, medical demands. first introduce theoretical framework unifying physics bubble formation in wide variety existing types generators. These devices are then classified according way bubbling process is controlled: outer liquid flows (e.g., coflows, cross flows, flow-focusing flows), acoustic forcing, electric fields. also...

At the beginning of last century Worthington and Cole discovered that high-speed jets ejected after impact an axisymmetric solid on a liquid surface are intimately related to formation collapse air cavity created in wake impactor. In this paper, we combine detailed boundary-integral simulations with analytical modelling describe such circular disk water. We extend our earlier model Gekle et al . ( Phys. Rev. Lett. , vol. 102, 2009 034502), valid for describing only jet base dynamics, whole...

A new regime of operation PDMS-based flow-focusing microfluidic devices is presented. We show that monodisperse microbubbles with diameters below one-tenth the channel width (here w = 50 μm) can be produced in low viscosity liquids thanks to a strong pressure gradient entrance region channel. In this bubbles are generated at tip long and stable gas ligament whose diameter, which varied by tuning appropriately liquid flow rates, substantially smaller than width. Through procedure volume...

We experimentally determine the phase diagram for impacting ethanol droplets on a smooth, sapphire surface in parameter space of Weber number $\mathit{We}$ versus temperature $T$ . observe two transitions, namely one towards splashing (disintegration droplet) with increasing , and Leidenfrost state (no contact between droplet plate due to lasting vapour film) Consequently, there are four regimes: no (deposition regime), (contact–splash neither nor (bounce finally contact, but (film–splash...

Here we provide a self-consistent analytical solution describing the unsteady flow in slender thin film which is expelled radially outwards when drop hits dry solid wall. Thanks to fact that fluxes of mass and momentum entering into toroidal rim bordering expanding liquid sheet are calculated analytically, show here our theoretical results closely follow measured time-varying position with independence wetting properties substrate. The particularization equations dynamics at instant reaches...

Here we provide a theoretical framework describing the generation of fast jet ejected vertically out liquid when bubble, resting on liquid–gas interface, bursts. The self-consistent physical mechanism presented here explains emergence as consequence collapse gas cavity driven by low capillary pressures that appear suddenly around its base cap, thin film separating bubble from ambient gas, pinches. resulting pressure gradient deforms which, at moment ejection, adopts shape truncated cone....

We reveal for the first time by experiments that within a narrow parameter regime, two cavitation bubbles with identical energy generated in antiphase develop supersonic jet. High-resolution numerical simulation shows mechanism jet amplification based on toroidal shock wave and bubble necking interaction. The microjet reaches velocities excess of $1000\text{ }\text{ }\mathrm{m}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$. demonstrate potential flow theory established Worthington jets accurately...

Analytical considerations and potential-flow numerical simulations of the pinch-off bubbles at high Reynolds numbers reveal that bubble minimum radius, rn, decreases as tau proportional to r2n sqrt[1lnr2n], where is time break up, when local shape near singularity symmetric. However, if gas convective terms in momentum equation become order those liquid, no longer symmetric evolution neck changes a rn tau1/3 power law. These findings are verified experimentally.

A circular disc hitting a water surface creates an impact crater which after collapse leads to vigorous jet. Upon axisymmetric air cavity forms and eventually pinches off in single point halfway down the cavity. Two fast sharp-pointed jets are observed shooting up- downwards from closure location, by then has turned into stagnation surrounded locally hyperbolic flow pattern. This flow, however, is not mechanism feeding jets. Using high-speed imaging numerical simulations we show that jetting...

We perform extensive experiments with coflowing liquids in microfluidic devices and provide a closed expression for the drop size as function of measurable parameters jetting regime that accounts experimental observations; this works irrespective how jets are produced, providing powerful design tool type experiments.

When a drop impacts smooth, dry surface at velocity above the so-called critical speed for splashing, initial liquid volume loses its integrity, fragmenting into tiny droplets that are violently ejected radially outwards. Here, we make use of model Riboux & Gordillo ( Phys. Rev. Lett. , vol. 113, 2014, 024507), together with one-dimensional approximation describing flow in sheet and balances mass momentum border sheet, to calculate mean sizes velocities drops. The predictions good...

Abstract

In this paper we present a new method for the production of bubble-liquid suspensions (from now on BLS) composed micron-sized bubbles and with gas to liquid volume ratios larger than unity. We show that BLS fraction λ=Qg/Ql, being Qg Ql flow rates liquid, respectively, is controlled by dimensionless parameter which accounts ratio pressure inside device viscous drop from orifices where injected exit, obtained. This permits correct scaling all experiments presented.

A solid object impacting on liquid creates a jet due to the collapse of impact cavity. Using visualization experiments with smoke particles and multiscale simulations we show that in addition high-speed air-jet is pushed out Despite an velocity only 1 m/s, this attains \emph{supersonic} speeds already when cavity slightly larger than mm diameter. The structure air flow resembles closely compressible through nozzle -- key difference here "nozzle" \emph{liquid} shrinking rapidly time.

The capillary breakup of the high-speed Worthington jets ejected after a cavity collapse in water occurs due to high-Reynolds-number version end-pinching mechanism first described, creeping flow limit, by Stone & Leal ( J. Fluid Mech. , vol. 198, 1989, p. 399). Using potential numerical simulations and theory, we find that resulting drop ejection process does not depend on external noise can be described as function single dimensionless parameter, We S = ρ R 3 0 2 /σ, which expresses...

A drop of radius $R$ a liquid density $\unicode[STIX]{x1D70C}$ , viscosity $\unicode[STIX]{x1D707}$ and interfacial tension coefficient $\unicode[STIX]{x1D70E}$ impacting superhydrophobic substrate at velocity $V$ keeps its integrity spreads over the solid for $V<V_{c}$ or splashes, disintegrating into tiny droplets violently ejected radially outwards $V\geqslant V_{c}$ with $V_{c}$ critical splashing. In contrast case impact onto partially wetting substrate, Riboux & Gordillo ( Phys....

In this paper, we present a simplified theoretical model based on the method of images that predicts direction microjet produced after implosion cavitation bubble created in between free interface and rigid wall. Our predictions have been verified by means thorough experimental study which distances pulsed-laser to wall surface are varied systematic manner. addition, extend arbitrary values corner angle, $\pi/(2n)$ with $n$ natural number. The analytical solution will be useful design new...

The physical mechanism behind the beauty of iconic image a drop detaching from tip jet produced when or stone falls on pond, is identical to one driving 1000 m/s jets impacting solid substrate liquid cavitates near solid, causing structural damage, micron-sized bubbles ingested by breaking waves burst at ocean's surface, ejecting nanometric with velocities up 100 that produce part sea spray aerosols which favors cloud formation. We show that, due large inertia, radial flow rate established...

A temporal, inviscid, linear stability analysis of a liquid jet and the co-flowing gas stream surrounding has been performed. The basic velocity profiles have computed self-consistently by solving numerically appropriate set coupled Navier–Stokes equations reduced using slenderness approximation. in case uniform profile recovers classical Rayleigh Weber non-viscous results as limiting cases for well-developed very thin boundary layers respectively, but consideration realistic brings to light...

Abstract In this paper we reveal the physics underlying conditions needed for generation of emulsions composed uniformly sized drops micrometric or submicrometric diameters when two immiscible streams flow in parallel under so-called tip streaming regime after Suryo and Basaran (Phys. Fluids, vol. 18, 2006, 082102). Indeed, inertial effects both liquid are negligible, inner to outer flow-rate viscosity ratios small enough capillary number is above an experimentally determined threshold which...