55 research outputs found
Differential criterion of a bubble collapse in viscous liquids
The present work is devoted to a model of bubble collapse in a Newtonian
viscous liquid caused by an initial bubble wall motion. The obtained bubble
dynamics described by an analytic solution significantly depends on the liquid
and bubble parameters. The theory gives two types of bubble behavior: collapse
and viscous damping. This results in a general collapse condition proposed as
the sufficient differential criterion. The suggested criterion is discussed and
successfully applied to the analysis of the void and gas bubble collapses.Comment: 5 pages, 3 figure
The Sound of Sonoluminescence
We consider an air bubble in water under conditions of single bubble
sonoluminescence (SBSL) and evaluate the emitted sound field nonperturbatively
for subsonic gas-liquid interface motion. Sound emission being the dominant
damping mechanism, we also implement the nonperturbative sound damping in the
Rayleigh-Plesset equation for the interface motion. We evaluate numerically the
sound pulse emitted during bubble collapse and compare the nonperturbative and
perturbative results, showing that the usual perturbative description leads to
an overestimate of the maximal surface velocity and maximal sound pressure. The
radius vs. time relation for a full SBSL cycle remains deceptively unaffected.Comment: 25 pages; LaTex and 6 attached ps figure files. Accepted for
publication in Physical Review
Coupling of acoustic cavitation with DEM-based particle solvers for modeling de-agglomeration of particle clusters in liquid metals
The aerospace and automotive industries are seeking advanced materials with low weight yet high strength and durability. Aluminum and magnesium-based metal matrix composites with ceramic micro- and nano-reinforcements promise the desirable properties. However, larger surface-area-to-volume ratio in micro- and especially nanoparticles gives rise to van der Waals and adhesion forces that cause the particles to agglomerate in clusters. Such clusters lead to adverse effects on final properties, no longer acting as dislocation anchors but instead becoming defects. Also, agglomeration causes the particle distribution to become uneven, leading to inconsistent properties. To break up clusters, ultrasonic processing may be used via an immersed sonotrode, or alternatively via electromagnetic vibration. This paper combines a fundamental study of acoustic cavitation in liquid aluminum with a study of the interaction forces causing particles to agglomerate, as well as mechanisms of cluster breakup. A non-linear acoustic cavitation model utilizing pressure waves produced by an immersed horn is presented, and then applied to cavitation in liquid aluminum. Physical quantities related to fluid flow and quantities specific to the cavitation solver are passed to a discrete element method particles model. The coupled system is then used for a detailed study of clusters’ breakup by cavitation
Primary Bjerknes forces
When a bubble in a liquid is subjected to a periodic sound field, the resulting bubble oscillations can interact with the sound field, giving rise to the primary Bjerknes force. A simple undergraduate-level derivation, and a graphical illustration of the underlying processes, are give
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