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Shape stability and violent collapse...

Calvisi, Michael Louis.

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Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks./
作者:	Calvisi, Michael Louis.
面頁冊數:	179 p.
附註:	Adviser: Andrew J. Szeri.
Contained By:	Dissertation Abstracts International68-02B.
標題:	Applied Mechanics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3253794

Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks.
Calvisi, Michael Louis.

Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks. - 179 p.

Adviser: Andrew J. Szeri.

Thesis (Ph.D.)--University of California, Berkeley, 2006.

This dissertation elucidates the effect of nonspherical perturbations on the energy-focusing properties of bubble collapses driven by acoustic and shock wave forcing. First, the influence of acoustic forcing on shape stability is explored and two models of bubble breakup---one based on perturbation analysis and the other based on numerical solution of the Laplace equation---are compared, showing remarkably good agreement. The Laplace equation for axisymmetric geometry is solved through use of a Boundary Integral Method that can efficiently model highly deformed; even toroidal bubble geometries. This model is based on the work of previous researchers but is significantly augmented for our purposes to simulate extremely violent, acoustically-driven collapses. Our numerical model based on the Boundary Integral Method is then used to explore the effect of shape stability on energy concentration in the bubble interior by comparing the peak temperatures and pressures of spherical to nonspherical bubble collapses. It is demonstrated that for very intense collapses, nonspherical bubbles do not focus the energy as efficiently as spherical collapses due to the conversion of some of the incident acoustic energy into kinetic energy of a liquid jet that pierces the bubble near the point of minimum volume. This is clarified by a calculation of the (gas) thermal equivalent of this liquid kinetic energy. Finally, the effect of shock wave forcing on bubbles is analyzed in the vicinity of a rigid boundary. Through calculation of quantities such as kinetic energy and Kelvin impulse of the surrounding liquid, the physics of shock-bubble interaction near a wall is illuminated. A key finding is that reflection of the incident shock wave enhances the intensity of bubble collapse in the near region due to constructive interference between the incident and reflected shock waves. Conversely, destructive interference suppresses the intensity of such collapses further away from the surface. The work done by the shock wave on the bubble is shown to strongly predict the maximum bubble volume regardless of the standoff distance and the presence or absence of reflection; furthermore, with appropriate interpretation, these predictions match almost exactly those of a spherical model.Subjects--Topical Terms:

1018410
Applied Mechanics.

Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks.
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245 1 0 $a Shape stability and violent collapse of microbubbles interacting with acoustic waves and shocks.
300 $a 179 p.
500 $a Adviser: Andrew J. Szeri.
500 $a Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1042.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2006.
520 $a This dissertation elucidates the effect of nonspherical perturbations on the energy-focusing properties of bubble collapses driven by acoustic and shock wave forcing. First, the influence of acoustic forcing on shape stability is explored and two models of bubble breakup---one based on perturbation analysis and the other based on numerical solution of the Laplace equation---are compared, showing remarkably good agreement. The Laplace equation for axisymmetric geometry is solved through use of a Boundary Integral Method that can efficiently model highly deformed; even toroidal bubble geometries. This model is based on the work of previous researchers but is significantly augmented for our purposes to simulate extremely violent, acoustically-driven collapses. Our numerical model based on the Boundary Integral Method is then used to explore the effect of shape stability on energy concentration in the bubble interior by comparing the peak temperatures and pressures of spherical to nonspherical bubble collapses. It is demonstrated that for very intense collapses, nonspherical bubbles do not focus the energy as efficiently as spherical collapses due to the conversion of some of the incident acoustic energy into kinetic energy of a liquid jet that pierces the bubble near the point of minimum volume. This is clarified by a calculation of the (gas) thermal equivalent of this liquid kinetic energy. Finally, the effect of shock wave forcing on bubbles is analyzed in the vicinity of a rigid boundary. Through calculation of quantities such as kinetic energy and Kelvin impulse of the surrounding liquid, the physics of shock-bubble interaction near a wall is illuminated. A key finding is that reflection of the incident shock wave enhances the intensity of bubble collapse in the near region due to constructive interference between the incident and reflected shock waves. Conversely, destructive interference suppresses the intensity of such collapses further away from the surface. The work done by the shock wave on the bubble is shown to strongly predict the maximum bubble volume regardless of the standoff distance and the presence or absence of reflection; furthermore, with appropriate interpretation, these predictions match almost exactly those of a spherical model.
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