We present detailed observations of the shock waves emitted at collapse single cavitation bubbles using simultaneous time-resolved shadowgraphy and hydrophone pressure measurements. The geometry is systematically varied from spherical to very non-spherical by decreasing their distance a free or rigid surface modulating gravity-induced gradient aboard parabolic flights. produces multiple shocks that are clearly associated with different processes, such as jet impact individual collapses...

Tough bioadhesion has important implications in engineering and medicine but remains challenging to form control. We report an ultrasound (US)-mediated strategy achieve tough with controllability fatigue resistance. Without chemical reaction, the US can amplify adhesion energy interfacial threshold between hydrogels porcine skin by up 100 10 times. Combined experiments theoretical modeling suggest that key mechanism is US-induced cavitation, which propels immobilizes anchoring primers into...

The present paper focuses on the numerical simulation of interaction laser-generated bubbles with a free surface, including comparison results instances from high-speed videos experiment. Volume Of Fluid method was employed for tracking liquid and gas phases while compressibility effects were introduced appropriate equations state each phase. Initial conditions bubble pressure estimated through traditional Rayleigh Plesset equation. simulated expands in non-spherically symmetric way due to...

Fast liquid jets, called micro-jets, are produced within cavitation bubbles experiencing an aspherical collapse. Here we review micro-jets of different origins, scales and appearances, propose a unified framework to describe their dynamics by using anisotropy parameter $\unicode[STIX]{x1D701}\geqslant 0$ , representing dimensionless measure the momentum at collapse point (Kelvin impulse). This is rigorously defined for various jet drivers, including gravity nearby boundaries. Combining...

The present paper focuses on the simulation of expansion and aspherical collapse a laser-generated bubble subjected to an acceleration field comparison results with instances from high-speed videos. interaction liquid gas is handled volume fluid method. Compressibility effects have been included for each phase predict propagation pressure waves. Initial conditions were estimated through Rayleigh Plesset equation, based maximum size time. predictions indicate that during shape very close...

Note: FNSFlash and Splash Reference EPFL-ARTICLE-214200doi:10.1063/1.4931098View record in Web of Science Record created on 2015-12-02, modified 2017-05-10

Laser-induced cavitation bubble dynamics at different distances from a rigid boundary is investigated using high-speed synchrotron x-ray phase-contrast imaging. This achieved through the design of tailored experimental chamber specifically designed to reduce absorption along path length in water while mitigating effects. The highly resolved undistorted radiographs are able visualize sharp interface even upon complex shapes, which can serve as high-quality benchmarks for numerical...

Upon interaction with underwater shock waves, bubbles can collapse and produce high-speed liquid jets in the direction of wave propagation. This work experimentally investigates impact laser-induced impulsive i.e. waves a short, finite width, variable peak pressure on radii range 10–500 $\mathrm {\mu }$ m. The visualisations provide new benchmarking remarkable quality for validation numerical simulations derivation scaling laws. experimental results support laws describing time jet speed...

Wall-attached bubbles can produce repeated jets under gentle ultrasound stimulation through the Faraday instability. We identify three distinct jetting regimes defined by frequency and bubble surface topology. demonstrate that these form via flow-focusing singularities following two collapse modes of interface: conical, producing a jet towards substrate, or parabolic, generating pair oppositely directed jets. Scaling laws governing events are derived, revealing universal self-similar...

This work investigates the fundamental role of cavitation bubble clouds in stone comminution by focused ultrasound. The fragmentation stones ultrasound has applications medical lithotripsy for kidney or gall stones, where their is believed to result from high acoustic wave energy as well formation cavitation. Cavitation known contribute erosion and cause damage away target, yet exact contribution mechanisms remain currently unclear. Based on situ experimental observations, post-exposure...

We investigate the structures generated by vortex shedding mechanism in turbulent axisymmetric wakes of non-axisymmetric plates, including a square plate and series fractal compare results to disk. For given characteristic length ℓ, all plates have same frontal area A, since ℓ = A0.5, but perimeter irregularity were varied manner thus allowing us effect boundary conditions. Measurements taken over large range downstream radial distances order obtain more robust measure for energy. It was...

Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures broad luminescence spectrum (wavelength range, 300-900 nm) from individual collapses laser-induced in water. By varying bubble size, driving pressure, and perceived gravity level aboard parabolic flights, we probed limit aspherical to highly spherical collapses. Luminescence was...

We present detailed visualizations of the micro-jet forming inside an aspherically collapsing cavitation bubble near a free surface. The high-quality large and strongly deformed bubbles disclose so far unseen features dynamics bubble, such as mushroom-like flattened jet-tip, crown formation micro-droplets. also find that jetting surface reduces collapse time relative to Rayleigh time.

This paper is associated with a video winner of 2021 American Physical Society's Division Fluid Dynamics (DFD) Milton van Dyke Award for work presented at the DFD Gallery Motion. The original available online Motion, https://doi.org/10.1103/APS.DFD.2021.GFM.V0038.

Understanding the shell rheology of ultrasound contrast agent microbubbles is vital for anticipating their bioeffects in clinical practice. Past studies using sophisticated acoustic and optical techniques have made enormous progress this direction, enabling development models that adequately reproduce nonlinear behaviour coated microbubble under excitation. However, there also been puzzling discrepancies missing physical explanations dependency viscosity on equilibrium bubble radius, which...

An experimental study of the rebounding dynamics cavitation bubbles deformed by a free surface and variable gravity is presented. It highlights need to consider rebound's sensitivity deformation when comparing experiments with theoretical models describing multiple bubble oscillations.

Microbubble translations driven by ultrasound-induced radiation forces can be beneficial for applications in ultrasound molecular imaging and drug delivery. Here, the effect of size range microbubble populations on their is investigated experimentally theoretically. The displacements within five distinct size-isolated are a standard ultrasound-imaging probe at frequencies ranging from 3 to 7 MHz, measured using multi-gate spectral Doppler approach. Peak displacements, reaching up 10 μm per...

We present experimental observations of microjets formed by cavitation microbubbles. An underwater electric discharge, applied beneath a flat free surface, produces primary compression wave, which undergoes several phase inversions upon reflections from the surface and spark-bubble interface. The first reflection yields tension cloud secondary bubbles in liquid, some form collapse. tuning these enables an effective control microjet direction bubble cloud. All jets microbubbles between spark...

Cylindrical cavitation bubbles, capable of generating extreme strain rates, are experimentally and theoretically studied in shear-thickening suspensions. Starting from the limit between continuous discontinuous shear thickening regimes, bubbles deform increasingly with increasing solid volume fraction until replaced by cavitation-induced fractures.

Ultrasonic atomization is employed to generate size-controllable droplets for a variety of applications. Here, we minimize the number parameters dictating process by studying single drop pending from an ultrasonic horn. Spatiotemporally resolved X-ray phase-contrast imaging measurements show that number-median sizes ejected can be predicted linear Navier–Stokes equations, signifying size distribution controlled fluid properties and driving frequency. Experiments with larger pendant water...

This study presents a general methodology and an experimental approach to identify the gas components within laser-induced cavitation bubbles. A needle electrode inside bubble, which introduces low electric energy into produces homogenous plasma discharge vapor cavity. The primary bubble dynamics remain identical while rebound becomes about twice as large when is applied. effect of non-condensable gases charge on explored theoretically, role found be significant. Optical emission...

High-power ultrasonic horns operating at low frequency are known to generate a cone-shaped cavitation bubble cloud beneath them. The exact physical processes resulting in the conical structure still unclear mainly due challenges associated with their visualization. Herein, we address onset of by exploiting high-speed X-ray phase contrast imaging. It reveals that cone formation is not immediate but results from three-step phenomenology: (i) inception and oscillation single bubbles, (ii)...

Due to the primary radiation force, microbubble displacement has been observed previously in focal region of single-element and array ultrasound probes. This effect harnessed increase contact between microbubbles targeted endothelium for drug delivery molecular imaging. In this study, displacements associated with plane-wave (PW) transmission are thoroughly investigated compared those obtained focused-wave (FW) over a range pulse repetition frequencies, burst lengths (BLs), peak negative...