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Empirical Analysis of the Dissipated...

Francke, Kristina.

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Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking./
Author:	Francke, Kristina.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2020,
Description:	111 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-12, Section: B.
Contained By:	Dissertations Abstracts International81-12B.
Subject:	Ocean engineering. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=27957837
ISBN:	9798645497989

Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking.
Francke, Kristina.

Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking. - Ann Arbor : ProQuest Dissertations & Theses, 2020 - 111 p.

Source: Dissertations Abstracts International, Volume: 81-12, Section: B.

Thesis (Ph.D.)--Florida Atlantic University, 2020.

This item must not be sold to any third party vendors.

In this research an attempt is made at explaining the physical processes behind energy dissipation during wave breaking, through spectral analysis of the resulting sound. The size of an air bubble can be directly linked to the frequency of the sound that is heard using the simple harmonic solution to the Rayleigh- Plesset equation. It indicates the inverse relationship between frequency and bubble size. And this relationship has been used to identify wave breaking in general [MANASSEH 2006]. Now this research goes a step farther and looks at how the frequency spectrum of the sound changes with time, in an effort to understand the general pattern and from that to deduce an empirical equation that describes the breaking down of turbulence during a wave breaking event.Two main processes have been identified, with the second process having three main indicators that are necessary to evidence wave breaking. The first process is a near instantaneous shattering of the initial air bubble into much smaller metastable bubbles of a size that appears to be common for all waves independent of wave height. Then in the second process, the bubbles continue to break down following a recognisable pattern.For the indicators of the continuous movement into higher frequencies (smaller bubble sizes), there has to be a negative phase shift as frequency of the sound increases. Simply said the higher frequencies get more pronounced as time passes. The amplitude decreases with increasing frequency. And finally, there is a sinusoidal pattern in the manner in which the power is distributed throughout the frequencies.It can be concluded from data that the sinusoidal pattern is most likely due to the probability of how bubbles break down. This probability function is not universally constant but depends on the physical properties of the medium the wave is travelling through, or in the case of ocean waves it depends on the properties of water. Two new parameters are proposed to help describe wave breaking severity, the angle of the time vector, which shows how much of the original wave energy is being dissipated, and another describing how fast the energy is being moved into higher frequency bands.

ISBN: 9798645497989Subjects--Topical Terms:

660731
Ocean engineering.
Subjects--Index Terms:

Acoustics

Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking.
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245 1 0 $a Empirical Analysis of the Dissipated Acoustic Energy in Wave Breaking.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2020
300 $a 111 p.
500 $a Source: Dissertations Abstracts International, Volume: 81-12, Section: B.
500 $a Advisor: Dhanak, Manhar.
502 $a Thesis (Ph.D.)--Florida Atlantic University, 2020.
506 $a This item must not be sold to any third party vendors.
520 $a In this research an attempt is made at explaining the physical processes behind energy dissipation during wave breaking, through spectral analysis of the resulting sound. The size of an air bubble can be directly linked to the frequency of the sound that is heard using the simple harmonic solution to the Rayleigh- Plesset equation. It indicates the inverse relationship between frequency and bubble size. And this relationship has been used to identify wave breaking in general [MANASSEH 2006]. Now this research goes a step farther and looks at how the frequency spectrum of the sound changes with time, in an effort to understand the general pattern and from that to deduce an empirical equation that describes the breaking down of turbulence during a wave breaking event.Two main processes have been identified, with the second process having three main indicators that are necessary to evidence wave breaking. The first process is a near instantaneous shattering of the initial air bubble into much smaller metastable bubbles of a size that appears to be common for all waves independent of wave height. Then in the second process, the bubbles continue to break down following a recognisable pattern.For the indicators of the continuous movement into higher frequencies (smaller bubble sizes), there has to be a negative phase shift as frequency of the sound increases. Simply said the higher frequencies get more pronounced as time passes. The amplitude decreases with increasing frequency. And finally, there is a sinusoidal pattern in the manner in which the power is distributed throughout the frequencies.It can be concluded from data that the sinusoidal pattern is most likely due to the probability of how bubbles break down. This probability function is not universally constant but depends on the physical properties of the medium the wave is travelling through, or in the case of ocean waves it depends on the properties of water. Two new parameters are proposed to help describe wave breaking severity, the angle of the time vector, which shows how much of the original wave energy is being dissipated, and another describing how fast the energy is being moved into higher frequency bands.
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653 $a Signal processing
653 $a Spectral analysis
653 $a Wave breaking
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