Publications by Philippe Kobel

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We describe a recently realized experiment producing the most spherical cavitation bubbles today. The bubbles grow inside a liquid from a point plasma generated by a nanosecond laser pulse. Unlike in previous studies, the laser is focussed by a parabolic m ...

Recent investigations of the magnetic field vector properties in the solar internetwork have provided diverging results. While some works found that the internetwork is mostly pervaded by horizontal magnetic fields, other works argued in favor of an isotro ...

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, and propose a unified framework to describe their dynamics by using an ...

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 a broad luminescence spectrum (wavelengt ...

Context. To deepen our understanding of the role of small-scale magnetic fields in active regions (ARs) and in the quiet Sun (QS) on the solar irradiance, it is fundamental to investigate the physical processes underlying their continuum brightness. Previo ...

This paper describes the techniques and physical parameters used to produce stable centimetric water drops in microgravity, and to study single cavitation bubbles inside such drops (Parabolic Flight Campaigns, European Space Agency ESA). While the main sci ...

We present high-precision experiments conducted with the aim to better characterise weak deformations of single cavitation bubbles. Using two needle hydrophones and a high-speed photodetector, we record the timings of shock waves and luminescence emitted a ...

The unique confinement of shock waves inside isolated liquid volumes amplifies the density of shock–liquid interactions. We investigate this universal principle through an interdisciplinary study of shock-induced cavitation inside liquid volumes, isolated ...

We report a fundamental study of single cavitation bubbles inside quasi-spherical water drops produced in microgravity (42nd ESA parabolic flight campaign, 8th ESA student parabolic flight campaign). High-speed imaging revealed implications of isolated, fi ...

We propose an experiment for studying the final stages of collapse of a single laser generated cavitation bubble in microgravity. Unlike previous investigations, the goal of the study is to examine the direct effects of gravity on the cavity collapse. In this paper we present ground-based research on these effects and outline a microgravity experiment destined for ESA Microgravity Research Campaign. The proposed experiment uses a focused laser to generate a highly spherical bubble in an extended water volum

Background Conflicting reports in the literature have raised the question whether radial extracorporeal shock wave therapy (rESWT) devices and vibrating massage devices have similar energy signatures and, hence, cause similar bioeffects in treated tissues. ...

We realized an experimental setup to study the dynamics of cavitation bubbles inside spherical water drops produced in microgravity (8th Student Parabolic Flight Campaign, European Space Agency ESA). Water volumes of up to 8 ml (25 mm diameter) were expelled through a specially designed injector tube. The latter contained a porous hydrophilic foam and was particularly coated to ensure a stable and attached water drop. Single cavitation bubbles were then generated by an electrical discharge inside the drop.

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

The dynamic of a cavitation bubble inside a water drop is investigated in microgravity in order to analyze the interaction between the collapsing bubble and a quasispherical free surface. Tests are carried in the frame of the 42nd parabolic flight campaign ...

We studied spark-generated shockwaves propagating inside stable water drops produced in microgravity. The closed and isolated liquid geometry results in a unique confinement of shockwaves, since the latter bounce of the free surface. This setting results in an amplified form of secondary cavitation, and proved particularly useful to study the coupling between shockwaves and secondary cavitation. High-speed visualizations and 3D computer simulations reveal that focus zones in the shockwave propagation lead t

Poster session on microgravity experiments 2006.

Philippe Kobel

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The quest for the most spherical bubble: experimental setup and data overview

Inferring the magnetic field vector in the quiet Sun III. Disk variation of the Stokes profiles and isotropism of the magnetic field

Scaling laws for jets of single cavitation bubbles

Luminescence from cavitation bubbles deformed in uniform pressure gradients

The continuum intensity as a function of magnetic field II. Local magnetic flux and convective flows

Techniques for generating centimetric drops in microgravity and application to cavitation studies

Detailed experiments on weakly deformed cavitation bubbles

Confined shocks inside isolated liquid volumes: A new path of erosion?

Cavitation Bubble Dynamics inside Liquid Drops in Microgravity

Direct effects of gravity on cavitation bubble collapse

Radial Shock Wave Devices Generate Cavitation

Water drops and cavitation bubbles in microgravity

Detailed Jet Dynamics in a Collapsing Bubble

Interaction of a cavitation bubble with a spherical free surface

Secondary Cavitation and Shockwaves in Isolated Volumes

Bubbles in drops: from cavitation to exploding stars

The inner world of a collapsing bubble

Microgravity Experiment: Cavitation Studies Inside Water Drops