Chemical generation of sound waves: shock waves and a "giant" photoacoustic effect

2002 ◽  
Author(s):  
H.X. Chen ◽  
T.E. McGrath ◽  
A.C. Beveridge ◽  
G.J. Diebold
Keyword(s):  
Shock Waves ◽  
Sound Waves ◽  
Photoacoustic Effect

Photoacoustic Calorimetry

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Thermal Expansion ◽  
Chemical Reactions ◽  
Thermodynamic Data ◽  
Chemical Species ◽  
Experimental Methods ◽  
Sound Waves ◽  
Ambient Conditions ◽  
Photoacoustic Effect ◽  
Photoacoustic Calorimetry ◽  
Present Understanding

“Any chemical species, which under ambient conditions (i.e., a temperature around 25°C, and a pressure close to 1 atm) will, for a combination of kinetic and thermodynamic reasons, decay on a timescale ranging from microseconds, or even nanoseconds, to a few minutes” can be classified as a short-lived compound. According to this definition, suggested by Almond, it is clear that the experimental methods described in previous chapters can only be used to study the thermochemistry of long-lived substances. The technique that we address here, known as photoacoustic calorimetry (PAC) or laser-induced optoacoustic calorimetry (LIOAC), is suitable for investigating the energetics of molecules with lifetimes smaller than about 1μs. It relies on the photoacoustic effect, which was discovered by Bell more than 100 years ago. With the assistance of Tainter, he was able to “devise a method of producing sounds by the action of an intermittent beam of light” and conclude that the method “can be adapted to solids, liquids, and gases”. Figure 13.1 shows a photophone, “an apparatus for the production of sound by light,” used by Bell to investigate the photoacoustic effect. The controversy around the origin of this phenomenon was settled by Bell himself and by Lord Rayleigh; their views were rather close to our present understanding: When a light pulse is absorbed by a substance, a given amount of heat is deposited, producing a local thermal expansion; this thermal expansion propagates through the medium, generating sound waves. The basic theory of the photoacoustic effect was described by Tam and Patel and some of its applications were presented in a review by Braslavsky and Heibel. The first use of PAC to determine enthalpies of chemical reactions was reported by the groups of Peters and Braslavsky. The same groups have also played an important role in developing the methodologies to extract those thermodynamic data from the experimentally measured quantities. In the ensuing discussion, we closely follow a publication where the use of the photoacoustic calorimety technique as a thermochemical tool was examined. Consider the elementary design of a photoacoustic calorimeter, shown in figure 13.3. The cell contains the sample, which is, for instance, a dilute solution of a photoreactive species.

scholarly journals Explosion waves and shock waves VI. The disturbance produced by bursting diaphragms with compressed air

1946 ◽  
Vol 186 (1006) ◽  
pp. 293-321 ◽  
Keyword(s):  
Shock Waves ◽  
Vortex Formation ◽  
Pressure Effects ◽  
Sound Waves ◽  
Free Air ◽  
Compressed Gas ◽  
Compression And Expansion ◽  
Uniform Tube ◽  
Set Up ◽  
Different Gases

Experimental verification of the theoretical relationships governing the motion of shock waves has been derived from an investigation into the development of the disturbance set up in a uniform tube when a body of compressed gas, confined at one end by means of a copper diaphragm, is released by rupture of the diaphragm. The wave-speed camera has been used to obtain continuous Schlieren records of the passage of these effects along the tube and to analyse their properties under a variety of experim ental conditions, the main variations being those caused by the use of different thicknesses of diaphragm, different lengths of compression and expansion chambers, and of different gases in these chambers. The pressure effects released on the rupture of the diaphragm are the shock wave, a vortex formation and the expanding gases from behind the diaphragm. Schlieren snapshot (spark) photographs have been obtained showing the structure of these pressure effects when they are projected from the end of the tube into free air. The photographs show, in addition to these details, the establishment of a system of stationary sound waves. Diagrams have been constructed based on the experimental data showing the apparent form of the wave during various phases of its progress.

scholarly journals Bubbles with shock waves and ultrasound: a review

2015 ◽  
Vol 5 (5) ◽  
pp. 20150019 ◽  
Author(s):  
Siew-Wan Ohl ◽  
Evert Klaseboer ◽  
Boo Cheong Khoo
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Biomedical Applications ◽  
High Speed ◽  
Experimental Studies ◽  
High Intensity Focused Ultrasound ◽  
High Speed Photography ◽  
Sound Waves ◽  
Bubble Cloud ◽  
Bubble Interaction

The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed ‘acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics–bubble interactions, with a focus on shock wave–bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the ‘resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave–bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead.

On the interaction of shock waves and sound waves in transonic buffet flow

2013 ◽  
Vol 25 (2) ◽  
pp. 026101 ◽  
Author(s):  
A. Hartmann ◽  
A. Feldhusen ◽  
W. Schröder
Keyword(s):  
Shock Waves ◽  
Sound Waves ◽  
Interaction Of Shock Waves ◽  
Transonic Buffet

A model of sonoluminescence

1994 ◽  
Vol 445 (1924) ◽  
pp. 323-349 ◽  
Keyword(s):  
Shock Wave ◽  
Molecular Weight ◽  
Shock Waves ◽  
Bubble Radius ◽  
Bubble Surface ◽  
The Other ◽  
Sound Waves ◽  
Van Der Waals Gas ◽  
Trapped Gas ◽  
Spherical Container

A bubble of air, trapped at the centre of a spherical container of water on the surface of which spherical sound waves are maintained by transducers, may emit light, a phenomenon known as sonoluminescence. The surface of the bubble expands and contracts in obedience to the Rayleigh–Lamb equation, which requires knowledge of the gas pressure on the surface of the bubble. In many investigations of bubble pulsations, it is assumed that the air in the bubble moves adiabatically. To understand sonoluminescence, however, it is necessary to allow for the possibility that shocks are generated within the bubble. We couple the Rayleigh–Lamb equation governing the bubble radius to Euler’s equations governing the motion of air in the bubble, and solve the two equations simultaneously. The air is modelled by a van der Waals gas. Results are presented for a number of slightly different conditions of excitation, but in which the response of the system is widely different. If the frequency of the sound is high, the gas in the bubble moves adiabatically and no light is emitted. As the frequency is reduced (for the same ambient bubble radius and driving pressure), the incoming bubble surface acts as a piston that generates an ingoing shock wave that passes through the centre of the bubble, and then, when it strikes the bubble surface, halts and reverses its inward motion; a sequence of such inwardly and outwardly moving shocks occur. The shock waves generate such high temperatures that the air near the centre of the bubble is almost completely ionized, and emits light, which we attribute to bremmstrahlung. The light created by the second inwardly moving shock exceeds that created by the first but, as the frequency of the sound is further reduced, the energy from the first shock rises, and the overall luminosity of the bubble increases. When the sound frequency is further reduced, two shocks are launched successively by the inward moving bubble surface, the second colliding with the first after it has passed through the centre of symmetry but before it can collide with the bubble surface. Even higher temperatures are reached and the luminosity of the bubble continues to increase with decreasing frequency. Details of these solutions are presented, and estimates are made of the luminosity of the bubble in different conditions of excitation. Two other families of solutions are presented. In one, the frequency and ambient bubble radius are fixed and the driving amplitude is varied. In the other, the frequency and driving amplitude are fixed and the radius is varied. The effects of changing only the molecular weight of the trapped gas is also examined.

Shock waves and non-stationary flow in a duct of varying cross-section

1971 ◽  
Vol 46 (1) ◽  
pp. 111-128 ◽  
Author(s):  
Naruyoshi Asano
Keyword(s):  
Shock Waves ◽  
Cross Section ◽  
Small Amplitude ◽  
Stationary Flow ◽  
Shock Propagation ◽  
Sound Waves ◽  
One Dimensional ◽  
Dimensional Approximation ◽  
Propagation Law ◽  
Good Agreement

Sound waves of finite but small amplitude propagating into a quasi-steady, supersonic flow in a non-uniform duct are analyzed by means of a perturbation method. General properties of the flow and of the wave propagation are studied using a one-dimensional approximation. A shock propagation law in the unsteady flow is obtained. As an example, the formation and development of shock waves are discussed for a duct with a conical convergence. Comparisons of the theory with an experiment are also made; fairly good agreement is found.

scholarly journals Sound waves and shock waves in high-density deuterium

1991 ◽  
Vol 9 (4) ◽  
pp. 795-816 ◽  
Author(s):  
Kazuko Inoue ◽  
Tomio Ariyasu
Keyword(s):  
Shock Wave ◽  
Surface Tension ◽  
Shock Waves ◽  
Sound Wave ◽  
Weak Shock ◽  
High Density ◽  
Inertial Confinement ◽  
Sound Waves ◽  
Attenuation Constant ◽  
Adiabatic Shock

The possibility of compressing the cryogenic hollow pellet of inertial confinement nuclear fusion with multiple adiabatic shock waves is discussed, on the basis of the estimation of the properties of a high-density deuterium plasma (1024−1027 cm−3, 10−1−104 eV), such as the velocity and the attenuation constant of the adiabatic sound wave, the width of the shock wave, and the surface tension.It is found that in the course of compression the wavelength of the adiabatic sound wave and the width of the weak shock wave sometimes become comparable to or exceed the fuel shell width of the pellet, and that the surface tension is negative. These results show that it is rather difficult to compress stably the hollow pellet with successive weak shock waves.

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