Evolution Of Shock Waves Research Articles

The propagation of shock waves with THz frequency in field-effect transistors

The investigation on propagation of shock waves with terahertz frequency in field-effect transistors has promoted the development of terahertz radiators and detectors. In this paper, we analyze the nonlinear behavior of shock waves with THz frequency in field-effect transistors and study their propagation characteristics at different viscosity coefficients and times. Using reductive perturbation expansion, the hydrodynamic equations are reduced to a Burgers equation governing the characteristic of shock structures in field-effect transistors. We investigate the evolution of shock waves with different viscosity coefficients and times numerically. The analytical and numerical results show that there are monotone shock waves and oscillatory shock waves in this system and an increase in the viscosity coefficient will lead to the diminishment of oscillation. These properties could make the field-effect transistors advantageous for realization of practical terahertz radiation and detection.

WITHDRAWN: Shock wave implosion in water

Analytical modeling of the evolution of cylindrical and spherical shock waves (shocks) during an implosion in water is presented for an intermediate range of convergence, which is not described by the models of self-similar shock propagation far from and in the vicinity of the piston. The model is based on an analysis of the change in pressure and kinetic energy density, as well as on the corresponding fluxes of internal and kinetic energy densities behind the shock front. The model shows that the spatial evolution of the shock velocity strongly depends on the initial compression, the adiabatic index of water, and the geometry of convergence. The model also explains the transition to a rapid increase in the shock velocity at only a certain radius of the shock that is observed in experiments. The dependence of the threshold radius, where the shock implosion follows the power law (quasi self-similarity), on the initial compression is determined. It is stated that in the entire range of the shock radii the internal and kinetic energy density fluxes are equal, which is in agreement with known experimental data.

Shock compression of magnesium alloy by ultrashort loads driven by sub-picosecond laser pulses

The shock compression of magnesium (Mg-4Al-2Zn) alloy polycrystalline films on glass under ultrashort loads driven by sub-picosecond laser pulses was investigated. The continuous diagnostics of motion and reflectivity changes of the free rear surface of the samples was carried out in the picosecond range (≤200 ps) in a single pulse mode using ultrafast spectral interferometry. We present the data on elastoplastic shock wave evolution at a propagation distance of several hundreds of nanometers, elastic precursor decay, shear, and tensile strengths at the extreme strain rate of ∼109 s−1.

Extinction of multiple shocks in the modular Burgers’ equation

We consider multiple shock waves in the Burgers’ equation with a modular advection term. It was previously shown that the modular Burgers’ equation admits a traveling viscous shock with a single interface, which is stable against smooth and exponentially localized perturbations. In contrast, we suggest in the present work with the help of energy estimates and numerical simulations that the evolution of shock waves with multiple interfaces leads to finite-time coalescence of two consecutive interfaces. We formulate a precise scaling law of the finite-time extinction supported by the interface equations and by numerical simulations.

Evolution of ion-acoustic shock waves in magnetized plasma with hybrid Cairns–Tsallis distributed electrons

Abstract The propagation of nonlinear electrostatic ion-acoustic (IA) shock waves in presence of external magnetic field having Cairns–Tsallis distributed electrons and ion kinematic viscosity is investigated. In the linear regime, the dispersion relation of the ion acoustic shock wave is found to be modified by the external magnetic field. Adopting reductive perturbation approach, it is shown that the dynamics of shocks is modeled by a hybrid Ostrovsky–Burgers’ equation. The influence of relevant physical parameters such as nonthermality and nonextensivity of electrons, magnetic field strength, and ion kinematic viscosity on the time evolution of the shock structure is numerically examined. It is observed the present plasma system supports both compressive and rarefactive shock waves. Furthermore, the analysis is performed through dynamical system approach to elucidate the various aspects of the phase-space shock dynamics.

Numerical simulation of the evolution of shock waves and plasma kernels of multi-point laser-induced plasma in supersonic flow

Compared with single-point laser-induced plasma, multi-point laser-induced plasma shows some advantages in ignition and flameholding, but with little research. Therefore, numerical studies of multi-point laser-induced plasma in supersonic flow are conducted using an instantaneous energy deposition model. In the studies, the single-pulse laser energy of every laser focus is 50 mJ, the laser focus configuration is linear, the inflow velocities are from Ma 1.5 to Ma 2.5, and the distances between adjacent focal spots are from 2 to 4 mm. The evolution process of shock waves and plasma kernels in supersonic flow has been described in detail when the inflow velocity is Ma 2 and when the distance between adjacent focal spots is 2 mm. Besides, the evolution law of the velocity field, the streamline, and the plasma kernel position in the flow field have also been analyzed. The results reveal that the volume of the plasma kernel increases rapidly within 15 µs and that the initial shock wave has a strong deflection effect on the supersonic flow. Moreover, the effects of inflow velocities and distances between adjacent focal spots on multi-point laser-induced plasma are compared using the plasma kernel’s average temperature, volume, and specific surface area. Under the conditions of the studies, the results show that the distance between adjacent focal spots is the main reason affecting the evolution. Thus, a distance longer than 4 mm between adjacent focal spots should be avoided for multi-point laser-induced plasma in supersonic flow because the plasma kernel could not be fused in a timely manner.

Image-based characterization of the bubbly shock wave generation and evolution in aviation fuel cavitation

An experimental investigation of cavitation in aviation fuel (JP-8 and JP-5) in a converging-diverging nozzle geometry is presented. A novel enhanced gradient shadowgraphy image processing technique is developed and employed in order to characterize the fundamental processes involved in unsteady bubbly shock wave generation and evolution, both with and without micro-air bubble injection at the inlet. We clarify the sequence of unsteady processes at play in aviation fuel cavitation and provide new perspectives regarding the damaging impact of shock waves that will lead to improved design of fuel system components.

Shock wave characteristics and spalling behavior of non-coherent Cu/Nb multilayers

We investigate shock wave characteristics and spalling failure of Cu/Nb nanolaminates under shock loading via molecular dynamics simulations. The features of stress wave propagation in the Cu/Nb multilayers, including the reflection-loading and reflection-unloading of wave-front stress, and the strong interfacial discontinuities of transverse normal stress components, maximum shear stress and average kinetic energy are revealed by atomistic simulations. Continuum models are proposed to explain these shock wave evolution characteristics. In addition, the simulations well reproduce experimentally observed abnormal ductile damage distribution, i.e., voids nucleate in the Cu phase rather than in the Nb phase or interfaces. Such abnormality is intrinsic dynamic characteristics of nanolaminates, independent of layer thickness and shock intensity. Differences in theoretical spall strengths of Cu, Nb and the interfaces are calculated using the Cauchy-Born kinematic constraint. Moreover, we bring novel insight into the cause of the abnormality from a dynamic perspective that the maximum tensile stress in the stronger Nb phase is restricted by the spall strength of the weaker Cu phase, sound velocity, strain rate and layer thickness. The simulations also indicate that dynamic ductility can be enhanced by reducing the layer thickness, due to that more spall fracture surfaces are generated in nanolaminates with finer layer thickness.

Flame and shock wave evolution characteristics of methane explosion in a closed horizontal pipeline filled with a three-dimensional mesh porous material

In the energy security field, porous materials are regarded as superb explosive attenuators that quench flames and dissipate explosion energy waves. Traditional porous materials based on polymer have been extensively explored for their flame and explosion-proof capabilities, but their applications are limited due to the lack of indispensable physical properties such as flame-retardant and antistatic properties. The polymer composites may contaminate the oil medium, as does the deterioration of their properties. By designing the material's structure and formula, a new three-dimensional mesh porous flame and explosion-proof material (TFEP) is developed through melt blending—extrusion spinning technology and material's explosion-proof performance will also be enhanced. This porous material integrates flame-retardant, antistatic, and oil-resistant performances. The TFEP's suppression effect on 9.5 vol% CH4/air premixed gas explosion was investigated under various filling conditions, and the optimal filling condition of TFEP was explored. Under these conditions, TFEP completely quenches the explosion flame, and the maximum explosion overpressure decay ratio for the upstream and downstream of the pipeline are 87.5% and 82.5%, respectively. TFEP eliminates the electrostatic risk generated by long-term friction of traditional polymer materials. It has moderate oil resistance and may be a candidate for explosion-proof materials in the fuel oil field.

Shock wave evolution into strain solitary wave in nonlinearly elastic solid bar

In this paper we present thorough experimental observation of the process of shock wave transformation into a bulk strain solitary wave in a nonlinearly elastic solid bar made of polystyrene. A theoretical model based on the describing propagation of a plane elastic wave in a bar is developed with account made for material nonlinearity and viscosity. Numerical modeling performed on the base of the developed model with and without regard to viscosity demonstrated formation of a long stable disturbance at proper account made for viscoelastic properties of the bar material.

Shockwave effects in the technology of meat raw material processing

Meat tenderness is recognized as the most important quality characteristic determining consumer acceptability of fresh meat and meat products. Therefore, the development of effective methods for meat tenderization is a topical direction. The review considers the main aspects of the development of shockwave (SW) technology as an alternative method for meat tenderization. The paper analyzes the means of shockwave formation as well as possible mechanisms responsible for meat tenderization caused by shockwave treatment and related to the energy dissipation and mechanical load on the boundary zones of a biological material under processing. The results of the investigations of a shockwave effect on meat tenderness, microbial inactivation, structure and assimilability of muscle protein and other functional and technological properties of a product are presented. The majority of researchers who studied a SW effect on meat tenderization showed different degrees of the improvement in the Warner-Bratzler shear force and increase in sensory scores of meat tenderness. This review shows the main problems linked with commercialization of the meat treatment process using SW based on electrical discharges under water. This method of SW generation is considered safest but infeasible today due to occurrence of restrictions such as damage of packaging materials after treatment, a need to ensure effective SW propagation in a commercial unit and determine optimal treatment parameters in the process of shockwave tenderization. Furthermore, potential possibilities of using shockwave technologies in the food industry are discussed. In particular, shockwave treatment upon extraction is an effective method for extracting juice/ oil/ bioactive components from various plant materials, which can be used as the pretreatment or independent process.

Three-dimensional numerical simulation on near-field pressure evolution of dual-tube underwater detonation

The detonation-powered underwater engine, with the advantages of high specific impulse, high speed, and simple structure, has very broad application prospects in the field of underwater propulsion, and dual-tube combination is an effective means to improve its propulsion performance. In this work, near-field pressure evolution of shock waves and high-pressure zones between two detonation tubes is numerically studied. The two-fluid model and three-dimensional conservation element and solution element method are adopted to reveal the formation, intersection, and interaction of shock waves. Detonation waves generated by two detonation tubes decouple into shock waves after penetrating into water and form a high-pressure zone near each tube exit. The two leading shock waves intersect with each other in the propagation, creating the second high-pressure zone between two tubes. Then, a propagating forward merged new shock wave covers the two original wave-fronts and maintains higher pressure. Pressure evolution under different tube intervals, ignition delays, and filling conditions is also presented to discuss their influence on the performance of dual-tube detonation. The intensity and directivity of shock waves are found to be sensitive to these factors, complexly affecting the thrust components, which provides a depth understanding of dual-tube combination in the application.

Recording of Long Low-Amplitude Bulk Elastic Waves in Transparent Solid Waveguides by Digital and Classical Holography

In this paper we compare two implementations of the holographic technique for recording long, nonlinear, elastic waves of low amplitude in solid polymer waveguides: classical holographic interferometry and digital holography. Both implementations are realized in transmission configuration, with recording in the off-axis schematic. The advantages and disadvantages of these implementations are discussed as applied to the investigation of the evolution of shock waves and strain solitons in transparent solid waveguides.

The effect of dust particles on the evolution of planar and non-planar shock wave in two-dimensional supersonic flow of van der Waals gas

The effect of dust particles on the evolution of planar and non-planar shock wave in two-dimensional supersonic flow of van der Waals gas

Optimization of the composition of Al-Mg alloy films for laser-driven flyer

Laser-driven flyer technology attracts tremendous interests owing to the advantage of generating high pressure shocks at a relative simple and low-cost way. However, low energy conversion efficiency between flyer and laser restricts the further application of this technology. To improve the energy conversion efficiency in a laser-driven flyer assembly, Al-Mg alloy films with three varied compositions were fabricated via magnetron sputtering. The composition, surface morphology, light absorption and thermal properties of the films were investigated using energy dispersive spectrometer, atomic force microscopy, ultraviolet–visible spectrophotometer and laser flash method. The reflectivity of the Al-Mg alloy film at 1064-nm wavelength decreases from 87.2% to 69.3% in comparison with Al film. Moreover, the thermal diffusivity of all the Al-Mg alloy films is lower than that of Al film and varies with the composition. The behavior of the plasma induced shock wave evolution was investigated by shadowgraph imaging technique, indicating that the spatial and temporal evolution of the shock wave agrees well with the form of a Taylor-Sedov spherical shock and the calculated shock wave energy of the Al-Mg alloy films can reach up to 1.19 times that of Al film. Furthermore, the ability to launch a 17-μm-thick Al flyer was characterized by a Photonic Doppler Velocimetry, and there is a 20.9% and 46.12% increase in the terminal velocity and energy conversion efficiency of the Al flyers for Al-Mg alloy films compared with Al film, respectively. Therefore, the performance of laser-driven flyer can be significantly improved by adjusting the composition of Al-Mg alloy films.

On the evolution of magnetic shock wave in the mixture of gas and small solid dust particles

The paper aims to analyze the evolutionary behavior of weakly nonlinear waves propagating in one-dimensional unsteady flow of perfectly conducting compressible fluid subjected to a transverse magnetic field with dust particles. The method of progressive wave approach is utilized to determine the evolution equation characterizing the propagation of wave and also obtained the condition for first wave breaking at finite time. Further, we analyze the behavior of acceleration wave propagating in the medium considered. Also, the propagation of disturbances in the form of sawtooth wave (half N-wave) is studied here. It is observed that the presence of mass fraction of solid particles (kp) and β both causes to slow down the decay process. Also, the effect of axial magnetic field is to increase the growth rate of sawtooth wave (Half N-wave) as compared to in the absence of axial magnetic field. Further, the effect of magnetic field is to slow down the decay process in the presence of mass fraction of solid particles (kp).

Energy density balance during shock wave implosion in water

Analytical modeling of the evolution of cylindrical and spherical shock waves (shocks) during an implosion in water is presented for an intermediate range of convergence radii. This range of radii was observed in experiments when the exploding wire expansion dynamics does not influence on shock propagation, but not yet described by well-known self-similar solutions. The model is based on an analysis of the change in pressure and kinetic energy density as well as on the corresponding fluxes of internal and kinetic energy densities behind the shock front. It shows that the spatial evolution of the shock velocity strongly depends on the initial compression, the adiabatic index of water, and the geometry of convergence. The model also explains the transition to a rapid like a self-similar increase in the shock velocity at only a certain radius of the shock that is observed in experiments. The dependence of the threshold radius, where the shock implosion follows the power law (quasi self-similarity), on the initial compression is determined. It is stated that in the entire range of the shock radii, the internal and kinetic energy density fluxes are equal, which agrees with known experimental data.

Limitation in velocity of converging shock wave

The commonly applied self-similar solution of the problem of the converging shock wave (shock) evolution with constant compression of the medium behind the shock front results in an unlimited increase in the medium velocity in the vicinity of the implosion. In this paper, the convergence of cylindrical shocks in water is analyzed using the mass conservation law, when the water compression behind the shock front is a variable. The model predicts a finite range of radii, which depends on the adiabatic index of water and where the increase in pressure exceeds the sum of the change in the kinetic and internal energy densities behind the shock front. In this range of radii, only the finite increase in the shock and water flow velocities is realized.

Localized Measurement of a Sub-Nanosecond Shockwave Pressure Rise Time.

In a growing number of applications, fast and localized pressure measurement in aqueous media is desired. To perform such measurements, a custom-made single-mode fiber-optic probe hydrophone (FOPH) was designed and used to measure the pressure pulse generated by laser-induced breakdown (LIB) in water. The sensor enabled sub-nanosecond pressure rise time measurement. Both the rise time and the duration of the shockwave were found to be shorter in the direction perpendicular to the breakdown generating laser beam, compared to the shockwave observed in the parallel direction. Simultaneous high-frame-rate imaging was used to qualitatively validate the novel hydrophone data and to observe the shockwave evolution. The measurements were performed also on pressure pulses emitted during the generation of miniature ( [Formula: see text] diameter) laser-induced bubbles at very small distances (down to [Formula: see text]), further demonstrating the capabilities of the small-size sensor and the ability to measure locally. The results improve understanding of LIB shockwave characteristics dependence on laser pulse energy and duration.

Application of Particular Solutions of the Burgers Equation to Describe the Evolution of Shock Waves of Density of Elementary Steps

Particular solutions of the Burgers equations (BE) with zero boundary conditions are investigated in an analytical form. For values of the shape parameter greater than 1, but approximately equal to 1, the amplitude of the initial periodic perturbations depends nonmonotonically on the spatial coordinate, i.e. the initial perturbation can be considered as a shock wave. Particular BE solutions with zero boundary conditions describe a time decrease of the amplitude of initial nonmonotonic perturbations, which indicates the decay of the initial shock wave. At large values of the shape parameter , the amplitude of the initial periodic perturbations depends harmoniously on the spatial coordinate. It is shown that over time, the amplitude and the spatial derivative of the profile of such a perturbation decrease and tend to zero. Emphasis was put on the fact that particular BE solutions can be used to control numerical calculations related to the BE-based description of shock waves in the region of large spatial gradients, that is, under conditions of a manifold increase in spatial derivatives. These solutions are employed to describe the profile of a one-dimensional train of elementary steps with an orientation near <100>, formed during the growth of a NaCl single crystal from the vapor phase at the base of a macroscopic cleavage step. It is shown that the distribution of the step concentration with distance from the initial position of the macrostep adequately reflects the shock wave profile at the decay stage. The dimensionless parameters of the wave are determined, on the basis of which the estimates of the characteristic time of the shock wave decay are made.