Shock Wave Velocity Research Articles

Shock wave reflection from a short orifice open to vacuum

We study axisymmetric time-dependent problem of reflection of a shock wave running into the wall with a short orifice and associated rarefied gas flow into vacuum through a pipe. The main characteristics under consideration are the mass flow rate through the pipe and its transition to the constant value, the influence of the orifice presence, pipe relative length and Knudsen number on the reflected shock wave velocity. The analysis is based on the numerical solution of the S-model kinetic equation using the second-order accurate finite volume method, implemented into the “Nesvetay-3D” software package.

Shockwave phenomena in an inhibited gas‐to‐liquid hydrocarbon transformer oil under lightning impulse voltages

Gas-to-liquid (GTL) transformer oil is increasingly considered as an alternative to conventional mineral oils, due to its consistent performance, high purity and essentially free of sulphur. This high interest has led to growing research attention on streamer and breakdown performance of GTL oil. A large effort has been made to characterise the streamer phenomena of GTL oil. However, the secondary effect of shockwaves, which are produced synchronously with the propagation of streamers, is not well studied. Shockwave phenomena in a GTL oil under standard lightning impulse voltages were studied using a 10 mm point-plane gap and the Schlieren photograph technology. Shockwave propagation velocity and shape were measured in order to quantitatively describe the pressure profiles inside the streamer channels.

Characterization of laser-driven shock compression by time-resolved Raman spectroscopy

To characterize the laser-driven shock wave propagation process in anthracene molecules, the time-resolved Raman spectroscopy experiments were performed. After establishing a pressure distribution formula and using Lorenz profile to simulate the experimental Raman spectrum, the pressure distribution in the gauge layer during the pressure loading and unloading processes will be clarified in real time. The velocity of shock wave in the gauge layer, calculated through the shock front location at various delay time, is about 2.99 km s−1. Noticing that the relative intensity of compressed Raman mode is proportional to the velocity of the shock wave, in this work, this relationship was identified in a new mathematical expression after establishing a physical model. The velocity of shock wave calculated from the new formula is about 3.02 km s−1, which was in great agreement with the previous method and both methods are corresponded to practice.

A simple electrometric method for parametric determination of Jones-Wilkins-Lee equation of state from underwater explosion test

The parametric determination of the Jones-Wilkins-Lee equation of state (JWL-EOS) of condensed explosives was mostly dependent on a cylinder test using a high-speed photography technique. In the present work, a simple electrometric method based on the underwater explosion test was developed with a novel pressure-conducted velocity probe permitting recording the detonation and shock wave velocity in a single test. Specifically, a velocity probe-based testing setup for the underwater explosion was designed at first to measure the oblique shock wave front of the cylinder charge. We carried out four tests using powdery cyclotrimethylenetrinitramine (RDX) and obtained the curves of detonation-shock front position versus time. The oblique shock wave fronts were then determined based on the analysis of two-dimensional steady flow, and some other parameters such as detonation pressure, adiabatic exponent, Mach number, and gas-water interface angle were calculated combining the Prandtl-Mayer expansion law. Excellent agreements with the calculation results of Kamlet’s semi-empirical formulas were achieved. By applying a numerical calculation and test-and-error process, we adjusted the six JWL-EOS parameters (A, B, C, R1, R2, and ω) constantly to make the error between numerical and experimental results of oblique shock front fall within ±2%. Finally, the JWL-EOS of powdery RDX in each test was determined, and the curves of adiabatic pressure versus relative volume were plotted as well to demonstrate the accuracy of the present method.

Extracting mole fraction measurements from the visualization of a shock reflection

A novel method of determining the local mole fraction in a binary mixture from the visualization of a shock reflection was developed and tested in a shock tube. Incident and reflected shock wave velocities extracted from high-speed shadowgraphy and surface pressure data obtained from piezoelectric pressure sensors were used in combination with classical shock theory to perform the measurements. The mole fraction was determined from the analysis of the mixture properties, including the specific heat capacity and molecular weight. The sensitivity of measurement uncertainty to the camera resolution and framing rate was analyzed. Based on shock tube tests of helium–nitrogen mixtures, the accuracy of the mole fraction measurement technique is 4%.

Shock Initiation of the Triaminotrinitrobenzene‐Based Explosive JBO‐9021 Measured with a Photon Doppler Velocimeter

AbstractTriaminotrinitrobenzene (TATB) is an important insensitive high explosive because of its low shock sensitivity and high energy. The evolution of shock into the detonation of TATB requires academic attention and research. A multi‐points laser interferometer termed a photon Doppler velocimeter and a rotating mirror streak camera were used to study the shock initiation of detonation in a pressed solid explosive formulation, JBO‐9021, which contained 85 wt.% TATB, 10 wt.% HMX and 5 wt.% Kel‐F binder. In conventional experiments, the test explosive was assembled by using several columniform explosives with different external diameters. A new device was designed to solve complex problems. This device comprised a wedge‐shaped explosive sample and a transparent window, and by using this device, the particle‐velocity histories of eight shock positions and the shockwave velocity could be obtained. A series of shock‐initiation experiments on high explosive JBO‐9021 was performed, and the explosive samples were initiated at different intensity input shocks by an explosive‐driven attenuator. The photon Doppler velocimeter was used to detail the growth from an input shock to detonation, and the increase in particle velocity in unreacted JBO‐9021 was also obtained in low‐intensity shock‐initiation experiments. The shock velocity was measured with a rotating mirror streak camera in one experiment. Hugoniot data for JBO‐9021 in the form of a shock velocity versus a particle velocity and the initial shock pressure versus a distance‐to‐detonation relationship (Pop‐plot) were obtained. Based on the experimental results, the shock‐sensitivity characteristic of JBO‐9021 was described.

Measurement of shock pressure and shock-wave attenuation near a blast hole in rock

The objective of this study was to investigate granite responses to blasting. The focus was on the pressure and attenuation of shock waves in granite. Tests are reported on ten cylinders subjected to explosions from central pressed trinitrotoluene (TNT) charges with approximate density of 1.6 g/cm3. Three cylinders had dimensions Ø150 mm × 200 mm; seven, Ø240 mm × 300 mm. Specimens had concentric holes drilled from both ends: one 20-mm hole to position the explosive charge and one 50-mm hole to insert a granite plug equipped with Manganin gauges, which were applied to monitor the pressures of the shock waves. The configuration of the gauges was analyzed before testing to investigate how precisely they could measure shock waves in the granite. One or two gauges were used in each cylinder at distances of 7, 15, 22 or 35 mm from the explosive charge in the cylinder axis. At detonation of the charge, the measured peak pressure values ranged from 15.9–4.4 GPa depending on distance from the explosive, with pressure rise times of ∼0.5 μs. In one specimen, deflagration occurred, resulting in a low peak pressure of 1.35 GPa 11 mm from the explosive and a 16-μs pressure rise time. For specimens with two gauges, shock-wave velocities were found to depend strongly on the distance from the explosive. Fitting a curve to the experimental data, an exponential relation for the shock-wave peak pressure and its attenuation was obtained, expressing pressure (GPa) as a function of increasing distance (mm) from the explosive: p=19.4exp(−0.04x). The findings, especially regarding the damping term, may for instance be useful for verification of numerical models for blasting simulation.

Dust Motions in Magnetized Turbulence: Source of Chemical Complexity

Abstract In addition to the manufacture of complex organic molecules from impacting cometary and icy planet surface analogs, which is well-established, dust grain–grain collisions driven by turbulence in interstellar or circumstellar regions may represent a parallel chemical route toward the shock synthesis of prebiotically relevant species. Here we report on a study, based on the multi-scale shock-compression technique combined with ab initio molecular dynamics approaches, where the shock-wave-driven chemistry of mutually colliding isocyanic acid (HNCO) containing icy grains has been simulated by first principles. At the shock-wave velocity threshold triggering the chemical transformation of the sample (7 km s−1), formamide is the first synthesized species, thus being the springboard for the further complexification of the system. Also, upon increasing the shock impact velocity, formamide is formed in progressively larger amounts. More interestingly, at the highest velocity considered (10 km s−1), impacts drive the production of diverse carbon–carbon bonded species. In addition to glycine, the building block of alanine (i.e., ethanimine) and one of the major components of a plethora of amino acids including, e.g., asparagine, cysteine, and leucine (i.e., vinylamine), have been detected after shock compression of samples containing the most widespread molecule in the universe (H2) and the simplest compound bearing all of the primary biogenic elements (HNCO). The present results indicate novel chemical pathways toward the chemical complexity typical of interstellar and circumstellar regions.

Real-time distributed monitoring of pressure and shock velocity by ultrafast spectrometry with Chirped Fiber Bragg Gratings: Experimental vs calculated wavelength-to-pressure sensitivities in the range [0–4 GPa

Fiber Bragg Gratings (FBGs) are gaining acceptance as velocity/pressure gauges in the fields of detonation and shock physics on account of their sensitivity, small size, flexibility, electromagnetic immunity, and wavelength-encoded feature. Chirped FBGs (CFBGs) are investigated as wavelength-to-position discriminators with the purpose of monitoring pressure/velocity profiles over a distance range of typically 100 mm. The use of CFBGs simplifies both sensor deployment and data retrieval and finally improves the accuracy due to the increased number of measurement data. In this paper, the metrological performance of CFBGs used as in situ distributed shock pressure/velocity gauges is investigated both theoretically and experimentally in a planar shock loading configuration with an aluminum-based flyer and target. In the intermediate range for shock stress, i.e., less than the Hugoniot Elastic Limit (HEL) of silica, CFBGs provide simultaneous measurements of both shockwave velocity and stress within the target material. A Bragg wavelength-to-stress model is proposed that takes into account (i) the state-of-stress within the target material, (ii) the stress coupling coefficient due to imperfect impedance matching between the target material and the silica fiber, (iii) the conversion of the state-of-stress into a state-of-strain within the silica fiber, and (iv) the conversion of strain data into observable Bragg wavelength shifts. Finally, the model also takes into account the pressure dependence of constitutive parameters for silica and aluminum. Experiments were performed in planar shock loading using CFBGs as stress gauges, bonded along the target axis with Araldite glue. 6061-T6 aluminum flyers were launched at several velocities by a gas gun onto targets of the same material. A free-space Czerny-Turner (CT) spectrometer and an integrated-optics Arrayed-Waveguide Grating (AWG) were both used as dynamic spectrum analyzers. Experimental Bragg wavelength shifts agree well with theoretical predictions for both elastic and hydrodynamic planar shock loading of 6061-T6 aluminum, opening up large perspectives for shock physics experiments.

The non-self-similar Riemann solutions to a compressible fluid described by the generalized Chaplygin gas

In this paper, we concern with the Riemann solutions to a compressible fluid described by the generalized Chaplygin gas, where the external force is a constant. Five exact solutions are given. In particular, the delta shock wave with a Dirac delta function in density and internal energy occurs in some solutions, and the location, velocity and weights of the delta shock wave are explicitly described. It is also noticed that because of the effect of the external force, these exact solutions are not self-similar.

Molecular dynamics modeling of the Hugoniot states of aluminum

In this study, molecular dynamics (MD) simulations coupled with multi-scale shock technique (MSST) are used to predict the Hugoniot curve PH, Grüneisen coefficient γ and melting temperature Tm of single crystal (SC) and nanocrystalline (NC) aluminum (Al) with grain sizes of 6 and 60 nm at dynamic high pressure. The linear relation between the shock wave velocity and particle velocity is reproduced, and the results indicate that there is nearly no difference for the Hugoniot of SC and NC Al, which could be explained by the fact that the grain size effect on PH can be negligible at high pressure. Some empirical models are used to predict γ and Tm, which exhibit an opposite behavior. In addition, it is found that the melting pressure and temperature are 107.5 GPa, 3063 K for SC Al, while they are 109.5 GPa, 3082 K for NC Al, which have a reasonable agreement with the published work.

Laser-driven hydrothermal wave speed in low-Z foam of overcritical density

The speed of the laser-supported hydrothermal wave is experimentally measured in porous polystyrene with overcritical average density. The results of the experiments are in agreement with the simulations performed with the MULTI-FM code, modeling the state of partly homogenized plasma. The measured velocity is 2 times smaller than the shock wave velocity calculated in simulations under the same conditions of laser irradiation in a homogeneous substance of the same density. The obtained results allow us to better investigate the possibility of using porous matter of overcritical density as an effective absorber-ablator in laser thermonuclear fusion targets.

Theoretical study for anisotropic responses of the condensed-phase RDX under shock loadings

We have performed quantum-based molecular dynamics (MD) simulations in conjunction with multiscale shock technique (MSST) to investigate the initial chemical processes and the anisotropy of shock sensitivity of the RDX under shock loading applied along the different directions. The results show that there is a difference between x (or y)-direction and z-direction in the response to a shock wave velocity of 12 km/s. It was shown that detonation temperature and pressure in the z-direction lags behind that of x-direction (or y-direction). Moreover, from the time evolution of the population of various key fragments, we also observe that along with z-direction significantly later than that of x (or y)-direction, which the reaction rate is also slower. Thus, we draw a conclusion that sensitive for shock propagation along x or y-direction, but less sensitive for shock propagation along z-direction.

Kinetics of nonequilibrium processes in air plasma formed behind shock waves: state-to-state consideration

A new kinetic thermal nonequilibrium model for air plasma, considering vibrations of , and molecules in both the ground and electronically excited states in a state-to-state approach, was developed. The model treats in a consistent way the coupling of vibrational–electronic excitation of molecules and plasma chemical reactions as well as thermal nonequilibrium between translational degrees of freedom of electrons and heavy particles. The model was validated against the values of the radiation intensity of the and bands measured in the shock-tube experiments in an – mixture at shock wave speeds up to . Numerical analysis of thermally nonequilibrium processes in shock wave air plasma using the developed state-to-state model was conducted. It was shown that behind the shock front, a non-Boltzmann distribution over vibrational levels of , and molecules in both the ground and electronically excited states forms, but at the same time low vibration levels of these molecules are still populated in line with the local Boltzmann distribution with its own vibrational temperature. However, at extremely high shock wave velocities () disruption of the Boltzmann distribution of and molecules starts from vibrational levels with quantum numbers , so it is worth using the state-to-state consideration in such cases.

Propagation of shock waves in dry and wet sandstone: Experimental observations, theoretical analysis and meso-scale modeling

Abstract Methods of experimental observations, theoretical analysis and meso-scale modeling were used to study the propagation processes of shock waves in dry and wet sandstone under dynamic impact in this paper. According to the results from the dynamic impact experiments with velocity of 0.2–0.5 km/s, it was found that the velocity of shock wave increases linearly with water content. Additionally, the velocity of the shock wave in the sandstone showed a linearly increased regularity with the increasement of the impact velocity, which was proved by theory in this paper. Furthermore, meso-scale simulation models were performed and the simulation results showed that sandstone's porosity reduced the shock waves velocity compared to nonporous materials. Pore space filled with water counteracts the effects of porosity, resulted in larger shock wave velocity.

A new model for the time delay between elastic and plastic wave fronts for shock waves propagating in solids

A time delay is created between elastic and plastic wave fronts because of the difference between the elastic longitudinal sound speed and the plastic shock wave velocity. Over a short propagation distance, the time delay between the elastic and plastic wave fronts at the Hugoniot elastic limit (HEL) is nonlinear, while at larger distances, the time delay is linear. In this work, a new time delay model is introduced that is based on the distance traveled by the waves and using the Rayleigh–Hugoniot jump relations for elastic–perfectly plastic materials. The results of the model have shown in FCC metals the subsonic shock velocity is due to the reduction of shear stress in an unsteady wave being greater than the one in the steady wave. The reduction of the plastic shock wave speed and formation of the elastic shock at the moment of impact are found to result in the nonlinear relationship of the lag between elastic and plastic wave fronts. For calculating the nonlinear time delay in a relaxing material, the lower HEL must be used; the elastic shock is important when the difference between the longitudinal elastic sound speed and the plastic shock wave speed is very small or when the ratio of the HEL to the applied stress is high. In BCC metals, V, Cr, and W, a different behavior has been observed which is in contrast to FCC metals, Ag, Al, and Cu. Therefore, the different behavior is due to a different mechanism that occurs in BCC metals.

Ultrafast dynamics of hard tissue ablation using femtosecond-lasers.

Several studies on hard tissue laser ablation demonstrated that ultrafast lasers enable precise material removal without thermal side effects. Although the principle ablation mechanisms have been thoroughly investigated, there are still open questions regarding the influence of material properties on transient dynamics. In this investigation, we applied pump-probe microscopy to record ablation dynamics of biomaterials with different tensile strengths (dentin, chicken bone, gallstone and kidney stones) at delay times between 1 picosecond and 10 microseconds. Transient reflectivity changes, pressure and shock wave velocities and elastic constants were determined. The result revealed that absorption and excitation show the typical well-known transient behavior of dielectric materials. We observed for all samples a photomechanical laser ablation process, where ultrafast expansion of the excited volume generates pressure waves leading to fragmentation around the excited region. In addition, we identified tensile-strength-related differences in the size of ablated craters and ejected particles. The elastic constants derived were in agreement with literature values. In conclusion, pressure-wave-assisted material removal seems to be a general mechanism for hard tissue ablation with ultrafast lasers. This photomechanical process increases ablation efficiency and removes heated material, thus ultrafast laser ablation is of interest for clinical application where heating of the tissue must be avoided.

Ultrafast dynamic response of single-crystal β-HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)

We report experimental and computational studies of shock wave dynamics in single-crystal β-HMX on an ultrafast time scale. Here, a laser-based compression drive (∼1 ns in duration; stresses of up to ∼40 GPa) is used to propagate shock waves normal to the (110) and (010) lattice planes. Ultrafast time-domain interferometry measurements reveal distinct, time-dependent relationships between the shock wave velocity and particle velocity for each crystal orientation, which suggest evolving physical processes on a sub-nanosecond time scale. To help interpret the experimental data, elastic shock wave response was simulated using a finite-strain model of crystal thermoelasticity. At early propagation times (<500 ps), the model is in agreement with the data, which indicates that the mechanical response is dominated by thermoelastic deformation. The model agreement depends on the inclusion of nonlinear elastic effects in both the spherical and deviatoric stress-strain responses. This is achieved by employing an equation-of-state and a pressure-dependent stiffness tensor, which was computed via atomistic simulation. At later times (>500 ps), the crystal samples exhibit signatures of inelastic deformation, structural phase transformation, or chemical reaction, depending on the direction of wave propagation.

Relating a small-scale shock sensitivity experiment to large-scale failure diameter in an aluminized ammonium nitrate non-ideal explosive

The detonation failure process, specifically where a transient reaction occurs in an overdriven explosive due to a sub-critical charge diameter, has remained relatively unexplored, particularly regarding its relationship to shock initiation mechanisms. Detonation failure, here defined as a weakly supported shock wave traveling with a decaying velocity, of aluminized ammonium nitrate (AN/Al) was considered to investigate the relationship between the detonation failure process and shock sensitivity. Previous work has shown that the Al additive particle size alters the failure diameter, a measure of shock sensitivity, of AN/Al. Microwave interferometry was used to measure the transient shock wave velocity in the explosive system, which was lightly confined at a diameter below its critical diameter, in response to an overdriven shock insult in a small-scale experiment. An array of mixture ratios and particle size distributions of the explosive system was used to vary the sensitivity of the explosive and to facilitate exploration of the relationship between the shock velocity decay rate, initiation mechanisms, and large-scale shock sensitivity. Resulting shock velocity profiles in AN/Al indicate that micron-sized and larger Al particles can contribute to the detonation process. It is concluded that the rate at which the transient shock velocity approaches that of a compressive wave with no supporting reaction corresponds to the relative shock sensitivity of the system; it is therefore proposed that the measured shock velocity decay rate of an overdriven sub-critical diameter charge of AN/Al reveals quantifiable information about the relative shock sensitivity of a large-scale charge.

Shock wave attenuation in a micro-channel

This work presents optical measurements of shock wave attenuation in a glass micro-channel. This transparent facility, with a cross section ranging from $$1\,\hbox {mm}\times 150\,\upmu \hbox {m}$$ to $$1\,\hbox {mm}\times 500\,\upmu \hbox {m}$$ , allowed for the use of high-speed schlieren videography to visualize the propagation of a shock wave within the entire micro-channel and to quantify velocity attenuation of the wave due to wall effects. In this paper, we present the experimental technique and the relevant data treatment we have used to increase the sensitivity of shock wave detection. Then, we compared our experimental results for different channel widths, lengths, and shock wave velocities with the analytical model for shock attenuation proposed by Russell (J Fluid Mech 27(2):305–314, 1967), which assumes laminar flow, and by Mirels (Attenuation in a shock tube due to unsteady-boundary-layer action, NACA Report 1333, 1957) for turbulent flow. We found that these models are inadequate to predict the observed data, owing to the presence of fully developed flow which violates the basic assumption of these models. The data are also compared with the empirical shock attenuation models proposed by Zeitoun (Phys Fluids 27(1):011701, 2015) and Deshpande and Puranik (Shock Waves 26(4):465–475, 2016), where better agreement is observed. Finally, we presented experimental data for the flow field behind the shock wave from measurements of the Mach wave angle which shows globally decreasing flow Mach numbers due to viscous wall effects.