Acoustic Shock Waves Research Articles

Bulk micro-machined wide-band aero-acoustic microphone and its application to acoustic ranging

A wide-band aero-acoustic microphone was realized using a bulk micro-machining process based on the deep reactive-ion etching of silicon. The sensing diaphragm is completely sealed, thus eliminating the loss of low-frequency response resulting from pressure equalization through the release etch-holes present on the diaphragm of a previously reported microphone implemented using a surface-micro-machining process. A dynamic sensitivity of ∼0.33 µV/V/Pa was estimated using an acoustic shockwave (‘N-wave’) generated using a custom-built high-voltage electrical spark-discharge system. This value is comparable to the effective static sensitivity of ∼0.28 µV/V/Pa measured using a commercial nano-indenter system. The response of the microphone is relatively flat from 6 to 500 kHz, with a resonance frequency of ∼715 kHz. An array of three microphones was also constructed and tested to demonstrate the application of these microphones to the localization of high frequency and short duration acoustic sources.

Propagation of ion acoustic shock waves in negative ion plasmas with nonextensive electrons

Nonlinear ion acoustic shocks (monotonic as well as oscillatory) waves in negative ion plasmas are investigated. The inertialess electron species are assumed to be nonthermal and follow Tsallis distribution. The dissipation in the plasma is considered via kinematic viscosities of both positive and negative ion species. The Korteweg-de Vries Burgers (KdVB) equation is derived using small amplitude reductive perturbation technique and its analytical solution is presented. The effects of variation of density and temperature of negative ions and nonthermal parameter q of electrons on the strength of the shock structures are plotted for illustration. The numerical solutions of KdVB equation using Runge Kutta method are obtained, and transition from oscillatory to monotonic shock structures is also discussed in detail for negative ions nonthermal plasmas.

Ablation of Bone without Thermal or Acoustic Injury via a Novel Ultrafast Picosecond Infrared Laser

Objectives: A precise method to ablate bone without significant thermal or acoustic injury has remained elusive. A novel non-ionizing ultrafast pulsed picosecond infrared laser (PIRL) may provide the solution. The PIRL ablates tissue through purely photomechanical means, via a thermoelastic front spallation effect, with near complete thermal and acoustic transient confinement. In contrast, the Er:YAG laser ablates tissue via a micro-explosive vaporization mechanism. This study compares PIRL and Er:YAG laser ablation of bone by infrared thermography (IRT), digital microscopy, and electron microscopy. Methods: Ten cuts were made in fresh ex-vivo cortical bone via PIRL and Er:YAG laser ablation under IRT imaging. Lasers were operated using similar average power settings (68 mW) at fluence levels (0.78 J/cm2 and 8.15 J/cm2) in the treatment window above the ablation threshold and below ionization threshold for the PIRL and Er:YAG laser respectively. Digital and electron microscopy were used to image the ablation zones. Results: Peak temperature was negligible and significantly lower for PIRL in comparison to Er:YAG laser ablation (1.56 ± 2.71°C vs. 12.99 ± 2.71°C, P = 0.008). Digital microscopy revealed similar cortical surface ablation volumes for both lasers. Electron microscopy demonstrated well delineated ablation zone margins with no sign of micro-fracture or thermal injury for PIRL ablation. Conclusions: The PIRL provides a means of bone ablation without acoustic shockwave induced micro-fractures or thermal injury. This novel laser has great potential in advancing surgical techniques and outcomes in otologic, neurotologic, implant, cranio-maxillofacial, and head and neck reconstructive surgery.

Oblique ion acoustic shock waves in a magnetized plasma

Ion acoustic (IA) shock waves are studied in a magnetized plasma consisting of a cold viscous ion fluid and Maxwellian electrons. The Korteweg–de Vries–Burgers equation is derived by using the reductive perturbation method. It is shown that the combined effects of external magnetic field and obliqueness significantly modify the basic properties (viz., amplitude, width, speed, etc.) of the IA shock waves. It is observed that the ion-viscosity is a source of dissipation, and is responsible for the formation of IA shock structures. The implications of our results in some space and laboratory plasma situations are discussed.

Experimental study of the pressure field of an electric explosion of plane ring foil

Results of an experimental study of the pressure field of a shock acoustic wave in a closed chamber with condensed matter are presented; this wave results from the electric explosion of a plane ring foil, on which discharge current passes in the radial direction. The presence of a pronounced pressure maximum with regard to the electrode-system axis can be interpreted as the effect of nonlinear interaction of elements of the shock acoustic waves excited on diametrically opposite sides of the exploding ring foil.

Disinfection and toxicological assessments of pulsed UV and pulsed-plasma gas-discharge treated-water containing the waterborne protozoan enteroparasite Cryptosporidium parvum

We report for the first time on the comparative use of pulsed-plasma gas-discharge (PPGD) and pulsed UV light (PUV) for the novel destruction of the waterborne enteroparasite Cryptosporidium parvum. It also describes the first cyto-, geno- and ecotoxicological assays undertaken to assess the safety of water decontaminated using PPGD and PUV. During PPGD treatments, the application of high voltage pulses (16kV, 10pps) to gas-injected water (N2 or O2, flow rate 2.5L/min) resulted in the formation of a plasma that generated free radicals, ultraviolet light, acoustic shock waves and electric fields that killed ca. 4 log C. parvum oocysts in 32min exposure. Findings showed that PPGD-treated water produced significant cytotoxic properties (as determined by MTT and neutral red assays), genotoxic properties (as determined by comet and Ames assays), and ecotoxic properties (as determined by Microtox™, Thamnotox™ and Daphnotox™ assays) that are representative of different trophic levels in aquatic environment (p<0.05). Depending in part on the type of injected gas used, PPGD-treated water became either alkaline (pH≤8.58, using O2) or acidic (pH≥3.21, using N2) and contained varying levels of reactive free radicals such as ozone (0.8mg/L) and/or dissociated nitric and nitrous acid that contributed to the observed disinfection and toxicity. Chemical analysis of PPGD-treated water revealed increasing levels of electrode metals that were present at ≤30 times the tolerated respective values for EU drinking water. PUV-treated water did not exhibit any toxicity and was shown to be far superior to that of PPGD for killing C. parvum oocysts taking only 90s of pulsing [UV dose of 6.29μJ/cm2] to produce a 4-log reduction compared to a similar reduction level achieved after 32min PPGD treatment as determined by combined in vitro CaCo-2 cell culture-qPCR.

Incidence of a Shock Wave on a Cantilever Plate Coupled with an Elastic Rod

Experimental results on the deformation of a coupled elastic system consisting of a cantilever plate and a support rod and subjected to a long plane acoustic shock wave are discussed. Nonstationary strains were measured using a PC with an LMS SCADAS Mobile high-precision eight-channel front-end (Belgium)

Gunshot induced indirect femoral fracture: mechanism of injury and fracture morphology

IntroductionIndirect ballistic fractures occur when a projectile passes close to, but not contacting, the bone. The mechanism of how these fractures occur is not yet proven, but recently the acoustic...

Ion acoustic shock waves in plasmas with warm ions and kappa distributed electrons and positrons

The monotonic and oscillatory ion acoustic shock waves are investigated in electron-positron-ion plasmas (e-p-i) with warm ions (adiabatically heated) and nonthermal kappa distributed electrons and positrons. The dissipation effects are included in the model due to kinematic viscosity of the ions. Using reductive perturbation technique, the Kadomtsev-Petviashvili-Burgers (KPB) equation is derived containing dispersion, dissipation, and diffraction effects (due to perturbation in the transverse direction) in e-p-i plasmas. The analytical solution of KPB equation is obtained by employing tangent hyperbolic (Tanh) method. The analytical condition for the propagation of oscillatory and monotonic shock structures are also discussed in detail. The numerical results of two dimensional monotonic shock structures are obtained for graphical representation. The dependence of shock structures on positron equilibrium density, ion temperature, nonthermal spectral index kappa, and the kinematic viscosity of ions are also discussed.

Time-fractional Burgers equation for dust acoustic waves in a two different temperatures dusty plasma

The reductive perturbation method has been used to derive the Burgers equation for dust acoustic shock waves in unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The time-fractional Burgers equation is formulated using Euler-Lagrange variational technique and is solved using the variational-iteration method. The effect of time fractional parameter on the behavior of the shock waves in the dusty plasma has been investigated.

Nonextensive dust acoustic shock structures in complex plasmas

Nonlinear dust acoustic (DA) shock waves are studied in a nonextensive charge varying complex plasma. A burger-like equation the coefficients of which is significantly modified by nonextensivity and dust charge fluctuation is derived. It is found that the influence of particle (electrons and ions) nonextensivity and dust charge fluctuation affect the basic properties of the collisionless DA shock wave drastically.

Planar and nonplanar ion acoustic shock waves in relativistic degenerate astrophysical electron-positron-ion plasmas

We have studied the propagation of ion acoustic shock waves involving planar and non-planar geometries in an unmagnetized plasma, whose constituents are non-degenerate ultra-cold ions, relativistically degenerate electrons, and positrons. By using the reductive perturbation technique, Korteweg–deVries Burger and modified Korteweg–deVries Burger equations are derived. It is shown that only compressive shock waves can propagate in such a plasma system. The effects of geometry, the ion kinematic viscosity, and the positron concentration are examined on the ion acoustic shock potential and electric field profiles. It is found that the properties of ion acoustic shock waves in a non-planar geometry significantly differ from those in planar geometry. The present study has relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments) and in dense astrophysical objects.

Nonplanar electron acoustic shock waves

The properties of cylindrical and spherical electron acoustic shock waves (EASWs) in an unmagnetized plasma consisting of cold electrons, immobile ions and Boltzmann distributed hot electrons are investigated by employing the reductive perturbation method. A Korteweg–de Vries Burgers (KdVB) equation is derived and its numerical solution is obtained. The effects of several parameters and ion kinematic viscosity on the basic features of EA shock waves are discussed in nonplanar geometry. It is found that nonplanar EA shock waves behave quite differently from their one-dimensional planar counterpart.

Ionospheric anomaly at the occurring time of China’s May 12, 2008, M = 7.9 Wenchuan Earthquake using nonlinear principal component analyses and image decoding

Nonlinear principal component analysis (NLPCA) and image decoding are used to determine the spatial pattern of a total electron content (TEC) map anomaly in the ionosphere above China’s Wenchuan earthquake of 12 May, 2008 (UT) (Mw=7.9). The earthquake occurred at 06:28:01UT and the time period examined using NLPCA is 06:00 to 08:00UT. The TEC map of previous time period is transformed to an input matrix of NLPCA using image decoding, and then the TEC anomaly found is widespread and less intense at an altitude of 200km using NLPCA; however, it becomes more intense and localized with height up to an altitude of 300km. This paper discusses potential causes of the anomaly with emphasis on very rising acoustic shockwaves and snow-plow effects on ionospheric electron plasma resulting from the mainshock of the earthquake.

IL12 THERMOACOUSTIC INSTABILITY AND ITS RELATED FLUID DYNAMICAL PROBLEMS

This paper introduces thermoacoustic instability of a quiescent gas enclosed in a channel (or a tube) caused by thermoviscous diffusion under an axial temperature gradient. This instability may be regarded as that of heat flowing in background. Once the heat flow becomes unstable, it entails motions of the gas, which spread as acoustic waves. If the instability is promoted by an acoustic resonance of the gas column, then there emerge its oscillations. They are called thermoacoustic oscillations and exploited as a novel means of heat engines. To consider the instability, a thermoacoustic-wave equation is first introduced. This describes a spatial and temporal behavior of an excess pressure in the channel. While the equation is valid generally in linear theory, it may be approximated for short- and long-time behaviors. Linear stability analysis is briefly outlined and marginal conditions of instability are considered. As the amplitude of oscillations becomes higher, nonlinear effects tend to suppress the linear growth. The thermoacoustic oscillations observed in reality occur as outcome of a balance between linear instability and weak nonlinearity. Origins of nonlinearity may be classified into the one as wave and the other as vortex. The former concerns with emergence of an acoustic streaming and an acoustic shock wave, while the latter concerns with formation of jets, wakes and separated flows. Discussions are given on these problems.

Ionospheric Anomaly due to the volcanic eruption in Colima, Mexico, 06 January 2013: Two-Dimensional Principal Component Analysis

The ionospheric total electron content (TEC) data from 05 to 10 January 2013 (UT) were examined by two-dimensional principal component analysis (2DPCA) and revealed a TEC anomaly related to the volcanic eruption in Colima, Mexico on 06 January, 2013. A TEC anomaly was detected above the volcano from 21:00 to 21:05 on 06 January 2013 (UT). The anomaly occurred for at least 5 minutes, during this time period we could identify the equatorial ionization anomaly (EIA). The shock acoustic wave produced by eruption-induced seismic activity may be the cause of the observed TEC anomaly. We show that it is possible to monitor or predict volcanic eruptions and their associated seismic activity through the use of two-dimensional principal component analysis of the resulting TEC anomalies.

Shock wave negative pressure characteristics of underwater plasma sound source

The propagation process of intense acoustic shock wave, generated by the discharge of underwater plasma sound source, is analyzed based on a modified Rayleigh model. The bunching sound field model of underwater plasma sound source is established by using the Euler equation as the control equations. The formation mechanism of the shock wave negative pressure is analyzed theoretically and intuitively through the sound field charts obtained by simulation. The results demonstrate that the waters around the bunching wave will be stretched and form a zone of negative pressure with the combination of the rarefaction wave and the inertia of water. It will make the waters to form a discontinuous phenomenon if the stretching force is great than the ultimate tensile strength of the water, the phenomenon of cavitation bubble will appear at this time. Besides that, negative pressure will be aggravated by the diffracted wave generated at the edge of the energy-gathered reflector, and the shock wave negative pressure will reach the maximum value by the superimposition of the edge diffraction wave and the stretch wave. The reasons for the formation of the shock wave negative pressure is testified and revealed further by comparing the waveforms of simulation and experiment. The study results provide a theoretical guide for understanding the propagation law of underwater shock wave and further improving the design of the underwater plasma sound source.

Development of a Consistent and Stable Fully Implicit Moment Method for Vlasov--Ampère Particle in Cell (PIC) System

In this study, we advance the classic implicit moment method (IMM) particle simulation approach for the coupled Vlasov--Ampère system. We extend the IMM concept by (1) enforcing discrete consistency between the moment and kinetic system by introducing the concept of discrete consistency term and (2) efficiently converging the moment and kinetic system within a time step using a density normalized stress tensor. The new approach is energy conserving and is second-order accurate in time. The advantageous accuracy properties of the scheme are demonstrated with several numerical experiments including the challenging case of an ion acoustic shockwave problem.

Electron acoustic shock waves in a collisional plasma

A nonlinear analysis for the finite amplitude electron acoustic wave (EAW) is considered in a collisional plasma. The fluid model is used to describe the two-temperature electron species in a fixed ion background. In general, in electron-ion plasma, the presence of wave nonlinearity, dispersion, and dissipation (arising from fluid viscosity) give rise to the Korteweg-de Vries Burgers (KdVB) equation which exhibits shock wave. In this work, it is shown that the dissipation due to the collision between electron and ion in the presence of collective phenomena (plasma current) can also introduce an anomalous dissipation that causes the Burgers term and thus leads to the generation of electron acoustic shock wave. Both analytical and numerical analysis show the formation of transient shock wave. Relevance of the results are discussed in the context of space plasma.

Astrophysical naturally moderated classical positron beam interaction with nonlinear waves in nonextensive astrophysical plasmas

The positron acoustic shock and solitary wave are explored in nonextensive electron-positron-ion plasma. The plasma system under-consideration, consists of a classical positron beam, q distributed electrons and positively charged bulky ions constitute a neutralizing background. The nonlinear Korteweg-de Vries and Burger equations are derived by employing the standard reductive perturbation method. The positron acoustic wave in linear limit is also discussed for dissipative as well as nondissipative cases of nonextensive plasmas. The plasma parameters such as, the concentration of neutralizing ions background, beam velocity, temperature and q parameter of the nonextensive electrons are noticed to significantly affect the positron acoustic shock and solitary waves. Our findings may be helpful in the understanding of laboratory beam plasma interaction experiments as well as the astrophysical nonextensive plasmas interacting with positron beam.