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José Manuel Gordillo

Publications and source records attributed to José Manuel Gordillo.

8 recordsLinked to original sources
arXiv2026

Aerosol generation by the splashing of low viscosity drops impacting liquid layers

Using theory and numerical simulations, here we describe the early stages of the impact with a velocity $V$ of a drop of radius $R_d$ of a low viscosity liquid such as water against a layer of generic thickness $H$ of the same liquid. Our predictions for the initial velocity $V_t\gg V$ and the diameter $H_t\ll R_d$ of the toroidal rim bordering the edge of the thin lamella which is ejected radially outwards after the impact, are in fair agreement with both the numerical results and also with the experimental measurements reported by Zhang et al [J. Fluid Mech, 690, 5, 2012]. Consequently, the present findings can be employed, for instance, to predict the initial diameters and velocities of the fastest tiny droplets which are ejected right after a rain drop falls on a liquid pool, an ubiquitous phenomenon with implications in the dispersal of contaminants and in the generation of aerosols and of ice condensation nuclei

physics.flu-dyn↗
arXiv2020

The direction of the microjet produced by the collapse of a cavitation bubble locatedin between a wall and a free surface

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

physics.flu-dyn↗
arXiv2019

Axisymmetric bubble pinch-off at high Reynolds numbers

Analytical considerations and potential flow numerical simulations of the pinch-off of bubbles at high Reynolds numbers reveal that the bubble minimum radius, $r_n$, decreases as $τ\propto r_n^2 \, (-\ln{r_n^2})^{1/2}$, where $τ$ is the time to break-up, when the local shape of the bubble near the singularity is symmetric. However, if the gas convective terms in the momentum equation become of the order of those of the liquid, the bubble shape is no longer symmetric and the evolution of the neck changes to a $r_n\proptoτ^{1/3}$ power law. These findings are verified experimentally.

physics.flu-dyn↗
arXiv2019

On the thinnest steady threads obtained by gravitational stretching of capillary jets

Experiments and global linear stability analysis are used to obtain the critical flow rate below which the highly stretched capillary jet generated when a Newtonian liquid issues from a vertically oriented tube, is no longer steady. The theoretical description, based on the one-dimensional mass and momentum equations retaining the exact expression of the interfacial curvature, accurately predicts the onset of jet self-excited oscillations experimentally observed for wide ranges of liquid viscosity and nozzle diameter. Our analysis, which extends the work by Sauter & Buggisch (2005), reveals the essential stabilizing role played by the axial curvature of the jet, being the latter effect especially relevant for injectors with a large enough diameter. Our findings allow us to conclude that, surprisingly, the size of the steady threads produced at a given distance from the exit can be reduced by increasing the nozzle diameter.

physics.flu-dyn↗
arXiv2014

The critical impact speed for the splash of a drop

Making use of experimental and theoretical considerations, in this Letter we deduce a criterion to determine the critical velocity for which a drop impacting a smooth dry surface either spreads over the substrate or disintegrates into smaller droplets. The derived equation, which expresses the splash threshold velocity as a function of the material properties of the two fluids involved, the drop radius and the mean free path of the molecules composing the surrounding gaseous atmosphere, has been thoroughly validated experimentally at normal atmospheric conditions using eight different liquids, with viscosities ranging from $3\times 10^{-4}$ to $10^{-2}$ Pa$\cdot$s and interfacial tension coefficients which vary between $17$ and $72$ mN$\cdot$m$^{-1}$.

physics.flu-dyn↗
arXiv2013

Global stability of stretched jets: conditions for the generation of monodisperse micro-emulsions using coflows

In this paper we reveal the physics underlying the conditions needed for the generation of emulsions composed of uniformly sized drops of micrometric or submicrometric diameters when two immiscible streams flow in parallel under the so-called tip streaming regime after Suryo & Basaran (2006). Indeed, when inertial effects in both liquid streams are negligible, the inner to outer flow-rate and viscosity ratios are small enough and the capillary number is above an experimentally determined threshold which is predicted by our theoretical results with small relative errors, a steady micron-sized jet is issued from the apex of a conical drop. Under these conditions, the jet disintegrates into drops with a very well defined mean diameter, giving rise to a monodisperse micro-emulsion. Here, we demonstrate that the regime in which uniformly-sized drops are produced corresponds to values of the capillary number for which the cone-jet system is globally stable. Interestingly enough, our general stability theory reveals that liquid jets with a cone-jet structure are much more stable than their cylindrical counterparts thanks, mostly, to a capillary stabilization mechanism described here for the first time. Our findings also limit the validity of the type of stability analysis based on the common parallel flow assumption to only those situations in which the liquid jet diameter is almost constant.

physics.flu-dyn↗
arXiv2008

High-speed Jet Formation after Solid Object Impact

A circular disc impacting on a water surface creates a remarkably vigorous jet. Upon impact an axisymmetric air cavity forms and eventually pinches off in a single point halfway down the cavity. Immediately after closure two fast sharp-pointed jets are observed shooting up- and downwards from the closure location, which by then has turned into a stagnation point surrounded by a locally hyperbolic flow pattern. This flow, however, is {\it not} the mechanism feeding the two jets. Using high-speed imaging and numerical simulations we show that jetting is fed by the local flow around the base of the jet, which is forced by the colliding cavity walls. Based on this insight, we then show how the analytical description of a collapsing void (using a line of sinks along the axis of symmetry) can be continued beyond the time of pinch-off to obtain a quantitative model for jet formation which is in good agreement with the numerical and experimental data.

physics.flu-dyn↗