Applications of Ultrasound to Materials Chemistry

MRS Bulletin ◽  
1995 ◽  
Vol 20 (4) ◽  
pp. 29-34 ◽  
Author(s):  
Kenneth S. Suslick
Keyword(s):  
Physical Phenomenon ◽  
Direct Interaction ◽  
Acoustic Cavitation ◽  
Expansion Wave ◽  
Materials Chemistry ◽  
Metal Powders ◽  
Heterogenous Catalysis ◽  
Compression Waves ◽  
Expansion Waves ◽  
Chemical Effects

This article will begin with an introduction to acoustic cavitation, the physical phenomenon responsible for the chemical effects of ultrasound. Some recent applications of sonochemistry to the synthesis of nanophase and amorphous metals, as well as to heterogenous catalysis, will then be highlighted. Finally, we will examine the effects of ultrasound on metal powders in liquid-solid slurries.The chemical effects of ultrasound do not come from a direct interaction of sound with molecular species. Ultrasound has frequencies from around 15 kilohertz to tens of megahertz. In liquids, this means wavelengths from centimeters down to microns, which are not molecular dimensions. Instead, when sound passes through a liquid, the formation, growth, and implosive collapse of bubbles can occur, as depicted in Figure 1. This process is called acoustic cavitation.More specifically, sound passing through a liquid consists of expansion waves and compression waves. As sound passes through a liquid, if the expansion wave is intense enough (that is, if the sound is loud enough), it can pull the liquid apart and form a bubble (a cavity). The compression wave comes along and compresses this cavity, then another expansion wave re-expands it. So we have an oscillating bubble going back and forth, say, 20,000 times a second.

On expansion waves generated by the refraction of a plane shock at a gas interface

1967 ◽  
Vol 30 (2) ◽  
pp. 385-402 ◽  
Author(s):  
L. F. Henderson
Keyword(s):  
Expansion Wave ◽  
Plane Shock ◽  
Wave System ◽  
Expansion Waves ◽  
Reflected Wave ◽  
Expansion Fan ◽  
New Type ◽  
Self Similar ◽  
Fixed Boundaries ◽  
Mapping Theory

The paper deals with the regular refraction of a plane shock at a gas interface for the particular case where the reflected wave is an expansion fan. Numerical results are presented for the air–CH4 and air–CO2 gas combinations which are respectively examples of ‘slow–fast’ and ‘fast–slow’ refractions. It is found that a previously unreported condition exists in which the reflected wave solutions may be multi-valued. The hodograph mapping theory predicts a new type of regular–irregular transition for a refraction in this condition. The continuous expansion wave type of irregular refraction is also examined. The existence of this wave system is found to depend on the flow being self-similar. By contrast the expansion wave becomes centred when the flow becomes steady. Transitions within the ordered set of regular solutions are examined and it is shown that they may be either continuous or discontinuous. The continuous types appear to be associated with fixed boundaries and the discontinuous types with movable boundaries. Finally, a number of almost linear relations between the wave strengths are noted.

Acoustic cavitation in phacoemulsification: chemical effects, modes of action and cavitation index

2002 ◽  
Vol 28 (6) ◽  
pp. 775-784 ◽  
Author(s):  
Moris Topaz ◽  
Menachem Motiei ◽  
Ehud Assia ◽  
Dan Meyerstein ◽  
Naomi Meyerstein ◽  
...  
Keyword(s):  
Acoustic Cavitation ◽  
Modes Of Action ◽  
Chemical Effects

Detection of HO2•/O2•- Radicals Formed in Aqueous Solutions Irradiated with Megasonic Waves Using a Cavitation Threshold (CT) Cell Set-Up

2014 ◽  
Vol 219 ◽  
pp. 170-173
Author(s):  
Zhen Xing Han ◽  
Bing Wu ◽  
Ian Brown ◽  
Mark Beck ◽  
Srini Raghavan
Keyword(s):  
Acoustic Cavitation ◽  
Water Molecules ◽  
Chemical Effects ◽  
High Temperature And Pressure ◽  
Cavitation Threshold ◽  
Temperature And Pressure ◽  
Hydrogen Radical ◽  
Set Up ◽  
Physical And Chemical ◽  
Reducing Properties

Acoustic cavitation, especially transient cavitation, in solutions is accompanied by a number of physical and chemical effects. Due to high temperature and pressure conditions inside bubbles at their collapse, excitation of various species as well as formation of radicals occurs in solution [1-4]. Water molecules excited by megasonic irradiation typically dissociate to hydrogen and hydroxyl radicals (H• and OH•) [5]. The hydroxyl radical is a strong oxidant while the hydrogen radical has reducing properties. In presence of O2 in the solution, H• reacts with O2 to form hydroperoxyl (HO2•) radicals, which act as a reducing as well as a (weak) oxidizing agent [6]. Dissociation of hydroperoxyl radicals result in the formation of superoxide anion radicals (O2•-) as follows [6]:

Expansion Waves in Two-Phase Pipelines

2006 ◽  
Author(s):  
Alessandro Terenzi
Keyword(s):  
Sound Velocity ◽  
Slip Flow ◽  
Expansion Wave ◽  
Two Phase ◽  
Expansion Waves ◽  
Internal Fluid ◽  
Pressurized Pipelines ◽  
The Impact ◽  
Phase Fluid ◽  
Wave Calculation

The analysis of the expansion wave propagation generated by full-bore ruptures of pressurized pipelines containing compressible fluids must be carried out during the assessment of the possible use of crack arrestors. If the internal fluid is two-phase, the sound velocity dependence from the local void fraction and flow regime has to be taken into account, by considering that it may be much lower than for single phase gases, thus promoting crack propagation. In this paper a model for the simulation of an expansion wave in a two-phase fluid pipeline is presented; this model includes several possible descriptions of the thermodynamics and flow regimes, ranging from the simpler homogeneous equilibrium approach to the non-equilibrium slip flow evaluation. The sound velocity trend inside a rarefaction wave can give rise to particular phenomena as curve inversions and jumps. The impact of different formulations on the expansion wave calculation is discussed, giving hints for the design of the pipelines under consideration.

scholarly journals Physical and chemical effects of acoustic cavitation in selected ultrasonic cleaning applications

2016 ◽  
Vol 29 ◽  
pp. 568-576 ◽  
Author(s):  
Nor Saadah Mohd Yusof ◽  
Bandar Babgi ◽  
Yousef Alghamdi ◽  
Mecit Aksu ◽  
Jagannathan Madhavan ◽  
...  
Keyword(s):  
Acoustic Cavitation ◽  
Ultrasonic Cleaning ◽  
Chemical Effects ◽  
Physical And Chemical

Waves near a Sonic Line in Non-Homentropic Flow

1972 ◽  
Vol 23 (1) ◽  
pp. 7-14 ◽  
Author(s):  
B L Hunt
Keyword(s):  
Compression Waves ◽  
Expansion Waves ◽  
Sonic Line ◽  
Wave Patterns

SummaryThis paper gives qualitative descriptions of the wave patterns near a sonic line in non-homentropic flow. It is found that these wave patterns can be quite different from the homentropic forms. The most striking differences are that, under appropriate circumstances, the sonic line can produce expansion waves and receive compression waves. Three particular flow situations are then examined with the aid of the new descriptions.

scholarly journals Numerical solutions of the unsteady Fanno model for compressible pipe flow

2007 ◽  
Vol 579 ◽  
pp. 493-507 ◽  
Author(s):  
A. NOVIKOVS ◽  
H. OCKENDON ◽  
J. R. OCKENDON
Keyword(s):  
Pipe Flow ◽  
Large Time ◽  
Numerical Solutions ◽  
Travelling Waves ◽  
Nonlinear Effects ◽  
Numerical Results ◽  
Time Behaviour ◽  
Large Time Behaviour ◽  
Compression Waves ◽  
Expansion Waves

This paper presents numerical results on the evolution of the solutions of the Fanno model for compressible pipe flow. The principal results concern the large-time behaviour when nonlinear effects are appreciable throughout the evolution. Our computations show that compression waves can be expected to evolve into travelling waves for large times whereas expansion waves cannot.

A study of the flow structure for Mach reflection in steady supersonic flow

2010 ◽  
Vol 656 ◽  
pp. 29-50 ◽  
Author(s):  
B. GAO ◽  
Z. N. WU
Keyword(s):  
Shock Wave ◽  
Supersonic Flow ◽  
Mach Reflection ◽  
Reflected Shock Wave ◽  
Inflexion Point ◽  
Compression Waves ◽  
Expansion Waves ◽  
Sonic Line ◽  
Reflected Shock ◽  
Starting Point

In this paper we study the waves generated over the slipline and their interactions with other waves for Mach reflection in steady two-dimensional supersonic flow. We find that a series of expansion and compression waves exist over the slip line, even in the region immediately behind the leading part of the reflected shock wave, previously regarded as a uniform flow. These waves make the leading part of the slipline, previously regarded as straight, deviate nonlinearly towards the reflecting surface. When the transmitted expansion waves from the upper corner first intersect the slipline, an inflexion point is produced. Downstream of this inflexion point, compression waves are produced over the slipline. By considering the interaction between the various expansion or compression waves, we obtain a Mach stem height, the shape and position of the slipline and reflected shock wave, compared well to computational fluid dynamics (CFD) results. We also briefly consider the case with a subsonic portion behind the reflected shock wave. The global flow pattern is obtained through CFD and the starting point of the sonic line is identified through a simple analysis. The sonic line appears to coincide with the first Mach wave from the upper corner expansion fan after transmitted from the reflected shock wave.

The interaction region in the boundary layer of a shock tube

1969 ◽  
Vol 38 (1) ◽  
pp. 109-125 ◽  
Author(s):  
S. D. Ban ◽  
G. Kuerti
Keyword(s):  
Boundary Layer ◽  
Shock Tube ◽  
Elliptic Equations ◽  
Weak Shock ◽  
Flow Fields ◽  
Interaction Region ◽  
Expansion Wave ◽  
Expansion Waves ◽  
Consistent Linearization ◽  
Singular Parabolic Equations

Velocity and temperature boundary layers developed on a plane wall by ideal shock-tube flow are considered for weak shock and expansion waves. Analytically, the boundary layer consists of three regions, bounded by (1) expansion-wave head, (2) diaphragm location, (3) contact discontinuity, (4) shock. The flow fields (1, 2) and (3, 4) are, essentially, known. In the interaction region (2, 3), these flow fields merge, the governing equations are ‘singular parabolic’ and admit boundary conditions usually associated with elliptic equations. It is convenient to replace the weak expansion wave in the main flow by a line discontinuity. A consistent linearization scheme can now be devised to obtain the solution in the three regions. In (2, 3), the resulting linear singular parabolic equations for the first-order solutions are solved successfully by an iterative finite difference method, normally applied to elliptic equations.

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