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1	Drop-impact Singular Jets, Acoustic Sound and Bouncing with Filaments Yang, Zi Qiang 30 October 2022 (has links) This dissertation talks about the dynamics of the drop impact in two parts, the impact of the drop on the deep liquid pool with singular jet and sound emission, and the bouncing drop with filaments on the superhydrophoic solid surface. First, we use experiments and simulations to study drop impacts on a deep liquid pool, with a focus on fine vertical jetting and underwater sound emission from entrapped bubbles, during the rebounding of the hemispherical crater. The much larger parametric complexity introduced by the use of two immiscible liquids, compared to that for the same liquid, leads to an extended variety of compound-dimple shapes. The fastest jet occurs from the rebounding of a telescope dimple shape without bubble pinch-off, at around 45 m/s, which leaves a toroidal micro-bubbles from the air-cusp at the base of the dimple. The finest jets have diameter of only 12 µm. A new focusing mechanism for singular jetting from collapsing drop-impact craters is then proposed based on high-resolution numerical simulations. The fastest jet is confined in a converging conical channel with the entrained air sheet providing a free-slip outer boundary condition. Sound can be emitted from the oscillation of the entrapped dimple-bubble, while the tiny bubble from the initial impact is induced to oscillate with the entrapped bubble, triggering the double crest of the acoustic signal. We track the compression of the bubble volume from the high-speed imaging and relate it to the hydrophone signal. In the second part, we investigate the impact of a polymeric drop on a superhydrophobic solid substrate with micropillar structure. The drop spreads on the substrate, wets the tops of the pillars, and rebounds out of the superhydrophobic soild surface. Numerous liquid filaments are stretched from the liquid drop to the attached adjacent pillars, and minuscule threads would be left on the top of the pillars using the inclined superhydrophobic solid surface. The well-organized exposed polymer threads are left on the top of the pillars after solvent evaporation. The thickness of the deposition of filament bundles using the bouncing method are thinner than those formed by drop evaporation or drop rolling from SEM (scanning electron microscope) observation. Drop impact Singular jet Acoustics Bubble oscillation Drop bouncing Filaments
2	Partikelmodellierung der Strukturbildung akustischer Kavitationsblasen in Wechselwirkung mit dem Schalldruckfeld / Particle modeling of acoustic cavitation bubble structure formation and interaction with the acoustic pressure field Koch, Philipp 29 August 2006 (has links) No description available. 530 Physik Mathematics and Computer Science akustische Kavitation Strukturbildung akustische Lichtenbergfigur nichtlineare radiale Blasendynamik Keller-Miksis-Modell Oberflächenstabilität Gasdiffusion Partikelmodellierung primäre und sekundäre Bjerkneskraft Reibungskraft virtuelle Masse Ultraschallfeld Helmholtz-Gleichung stehende Schallfeldmode Resonanzverschiebung Blasen-Flüssigkeits-Gemisch van Wijngaarden-Wellengleichung Einzelblase Vielblasensysteme Hochgeschwindigkeitsaufnahme acoustic cavitation structure formation acoustic Lichtenberg figur nonlinear radial bubble oscillation Keller-Miksis model surface stability gas diffusion particel modeling primary and sekundary Bjerknes force drag force added mass ultrasonic field Helmholtz equation standing wave field resonance shift bubble liquid mixture van Wijngaarden wave equation single bubble multi bubble systems high-speed video observations 33.12 30.20 RHK 000: Ultraschall {Physik: Akustik} RHH 150: Schallausbreitung -reflexion in Flüssigkeiten {Physik: Akustik}

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Drop-impact Singular Jets, Acoustic Sound and Bouncing with Filaments

Partikelmodellierung der Strukturbildung akustischer Kavitationsblasen in Wechselwirkung mit dem Schalldruckfeld / Particle modeling of acoustic cavitation bubble structure formation and interaction with the acoustic pressure field