Jetting bubbles observed by x-ray holography at a free-electron laser: internal structure and the effect of non-axisymmetric boundary conditions

In this work, we study the jetting dynamics of individual cavitation bubbles using x-ray holographic imaging and high-speed optical shadowgraphy. The bubbles are induced by a focused infrared laser pulse in water near the surface of a flat, circular glass plate, and later probed with ultrashort x-ra...

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Bibliographic Details
Published in:Experiments in fluids 2024, Vol.65 (2), p.20-20, Article 20
Main Authors: Rosselló, Juan M., Hoeppe, Hannes P., Koch, Max, Lechner, Christiane, Osterhoff, Markus, Vassholz, Malte, Hagemann, Johannes, Möller, Johannes, Scholz, Markus, Boesenberg, Ulrike, Hallmann, Jörg, Kim, Chan, Zozulya, Alexey, Lu, Wei, Shayduk, Roman, Madsen, Anders, Salditt, Tim, Mettin, Robert
Format: Article
Language:English
Subjects:
Asymmetry
Boundary conditions
Bubbles
Cavitation
Compressibility
Engineering
Engineering Fluid Dynamics
Engineering Thermodynamics
Filaments
Fluid- and Aerodynamics
Free electron lasers
Glass plates
Heat and Mass Transfer
Infrared lasers
Lasers
Optical microscopy
Research Article
Stagnation point
X ray holography
X ray imagery
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Summary:In this work, we study the jetting dynamics of individual cavitation bubbles using x-ray holographic imaging and high-speed optical shadowgraphy. The bubbles are induced by a focused infrared laser pulse in water near the surface of a flat, circular glass plate, and later probed with ultrashort x-ray pulses produced by an x-ray free-electron laser (XFEL). The holographic imaging can reveal essential information of the bubble interior that would otherwise not be accessible in the optical regime due to obscuration or diffraction. The influence of asymmetric boundary conditions on the jet’s characteristics is analysed for cases where the axial symmetry is perturbed and curved liquid filaments can form inside the cavity. The x-ray images demonstrate that when oblique jets impact the rigid boundary, they produce a non-axisymmetric splash which grows from a moving stagnation point. Additionally, the images reveal the formation of complex gas/liquid structures inside the jetting bubbles that are invisible to standard optical microscopy. The experimental results are analysed with the assistance of full three-dimensional numerical simulations of the Navier–Stokes equations in their compressible formulation, which allow a deeper understanding of the distinctive features observed in the x-ray holographic images. In particular, the effects of varying the dimensionless stand-off distances measured from the initial bubble location to the surface of the solid plate and also to its nearest edge are addressed using both experiments and simulations. A relation between the jet tilting angle and the dimensionless bubble position asymmetry is derived. The present study provides new insights into bubble jetting and demonstrates the potential of x-ray holography for future investigations in this field.
ISSN:0723-4864
1432-1114
DOI:10.1007/s00348-023-03759-9