A5068731631- Ultrasound and Cavitation Phenomena
- Ultrasound and Hyperthermia Applications
- Microfluidic and Bio-sensing Technologies
- Fluid Dynamics and Mixing
- Fluid Dynamics and Heat Transfer
- Electrohydrodynamics and Fluid Dynamics
- Nuclear Physics and Applications
- Cavitation Phenomena in Pumps
- Underwater Acoustics Research
- Innovative Microfluidic and Catalytic Techniques Innovation
- Electrostatics and Colloid Interactions
- Chaos control and synchronization
- Quantum chaos and dynamical systems
- Laser-Ablation Synthesis of Nanoparticles
- Nonlinear Dynamics and Pattern Formation
- nanoparticles nucleation surface interactions
- Combustion and Detonation Processes
- Calcium Carbonate Crystallization and Inhibition
- Advanced X-ray Imaging Techniques
- Methane Hydrates and Related Phenomena
- Particle Dynamics in Fluid Flows
- Minerals Flotation and Separation Techniques
- Mathematical Dynamics and Fractals
- Photoacoustic and Ultrasonic Imaging
- Oceanographic and Atmospheric Processes
University of Göttingen
2016-2025
Czech Academy of Sciences, Institute of Physics
2020-2025
Christian Doppler Laboratory for Thermoelectricity
2014
Universitätsmedizin Göttingen
1998-2014
Technical University of Darmstadt
1998
Darmstadt University of Applied Sciences
1996-1997
Institut für Technische und Angewandte Physik (Germany)
1993-1995
University of Illinois Urbana-Champaign
1995
A strong laser pulse that is focused into a liquid produces vapor cavity, which first expands and then collapses with subsequent rebounds. In this paper mathematical model of the spherically symmetric motion laser-induced bubble proposed. It describes gas dynamics including compressibility, heat, mass transfer effects nonequilibrium processes evaporation condensation on wall. accounts also for occurrence supercritical conditions at collapse. Numerical investigations collapse rebound have...
The mutual interaction between small oscillating cavitation bubbles ${(R}_{0}<10\ensuremath{\mu}\mathrm{m})$ in a strong acoustic field (${P}_{a}>1\mathrm{bar},$ $f=20\mathrm{kHz}$) is investigated numerically. We assume spherical symmetry and coupling of the bubble oscillations. Our results show that strength even directions resulting secondary Bjerknes forces differ considerably from predictions well-known linear theory. This immediate consequence for understanding modeling structure...
Technologies including (3D-) (bio-)printing, diesel engines, laser-induced forward transfer, and spray cleaning require optimization therefore understanding of micrometer-sized droplets impacting at velocities beyond 10 m s<sup>−1</sup>.
The interaction of two laser-induced bubbles in bulk water is investigated. strength and direction the emerging liquid jets can be controlled by adjusting relative bubble positions, time difference between generation, laser pulse energies determining sizes. Experimental numerical studies are performed for millimetre-sized pairs. Taking equal energy, a maximum jet velocity found close anti-phase bubbles, i.e. when second produced at volume first one walls almost touching not merging. Under...
The dynamics of collapsing bubbles close to a flat solid is investigated with respect its potential for removal surface attached particles. Individual are created by nanosecond Nd:YAG laser pulses focused into water glass plates contaminated melamine resin micro-particles. bubble analysed means synchronous high-speed recordings. Due the boundary, collapses well-known liquid jet phenomenon. Subsequent microscopic inspection substrates reveals circular areas clean particles after single...
A bubble expanding and collapsing in water near a flat solid boundary is studied numerically. According to current knowledge, it develops high-speed liquid jet towards the of typically ∼100 m/s. However, character formation properties alter strongly when expands collapses very close boundary. In this case, much thinner faster ∼1000 m/s generated. The respective mechanism demonstrated by solving Navier-Stokes equations for model laser-induced bubble. results add substantially understanding...
Bubble expansion and collapse in a Newtonian liquid is studied numerically for range of dimensionless initial distances from solid boundary. Bubbles farther the develop well-known microjet during collapse. However, bubbles very close to solid, different jet mechanism leads formation fast, thin jets. The results are relevant better understanding cavitational erosion.
Bubble clouds forming in an extended volume of liquid acoustic cavitation show a slowly varying filamentary structure, whose origin is still not completely understood. Experimental observations are reported that provide some characteristics the phenomenon, such as bubble distributions and sound–field measurements. A discussion relevant physical interactions bubbly liquids comprised wave dynamics, Bjerknes drag forces, nucleation coalescence. For describing structure formation process,...
Intense microscale convection is produced by single cavitation bubbles. Ring vortices can be formed bubbles collapsing near solid surfaces. Such unsteady flow fields are measured with a high-speed particle imaging velocimetry (\textmu{}PIV) setup. Net liquid displacement tracked and visualized synthesized Lagrangian ink maps.
Ultrasonic horn transducers are frequently used in applications of acoustic cavitation liquids. It has been observed that if the tip is sufficiently small and driven at high amplitude, very strong, can be covered entirely by gas/vapor phase for longer time intervals. A peculiar dynamics attached cavity emerge with expansion collapse a self-generated frequency subharmonic range, i.e. below driving frequency. The term "acoustic supercavitation" was proposed this type Žnidarčič et al. (2014)...
The acoustic waves being generated during the motion of a bubble in water near solid boundary are calculated numerically. open source package OpenFOAM is used for solving Navier-Stokes equation and extended to include nonlinear wave effects via Tait water. A model with small amount gas chosen, obeying an adiabatic law. starting from size high internal pressure flat, studied. sequence events growth axial microjet formation, jet impact, annular nanojet torus-bubble collapse, rebound second...
The dynamics of a laser-induced bubble on top solid cylinder is studied both experimentally and numerically. When the generated close to flat along axis its maximum radius exceeds one surface, it collapses in form mushroom with footing cylinder, long stem hat-like cap typical for head. head may collapse forming thin, fast liquid jet into stem, depending size distance cylinder. Several experimental numerical examples are given. results represent contribution understand behavior bubbles...
An investigation of the primary Bjerknes force acting on a bubble in strong acoustic field is presented. The approach takes into account nonlinear resonancelike response small bubbles to pressure amplitudes. It shown that for high amplitudes even very are repelled from antinode. This result contrast predictions using forces based harmonic oscillations. relevance this instability single sonoluminescence experiments discussed.
The bifurcation set in the three-dimensional parameter space of periodically driven van der Pol oscillator has been investigated by continuation local curves. two regions which driving frequency ω is greater or less than limit cycle 0 nondriven are considered separately. For case > , subharmonic region, extent and location largest Arnol'd tongues shown, as well period-doubling cascades chaotic attractors that appear within most them. Special attention paid to pattern curves transitional...
In analytical and numerical studies on bubbles in liquids, often the Rayleigh initial condition of a spherical bubble at maximum radius is used: case. This cannot be realized practice, instead need first to generated expanded. The energy-deposit case with its small, high internal pressure that expands into water atmospheric studied for comparison From many possible configurations, single near flat solid boundary chosen as this basic configuration study erosion cleaning phenomena. contains...
X-ray free-electron lasers (XFELs) have opened up unprecedented opportunities for time-resolved nano-scale imaging with X-rays. Near-field propagation-based imaging, and in particular near-field holography (NFH) its high-resolution implementation cone-beam geometry, can offer full-field views of a specimen's dynamics captured by single XFEL pulses. To exploit this capability, example optical-pump/X-ray-probe schemes, the stochastic nature self-amplified spontaneous emission pulses, i.e. beam...