Types Of Shock Waves Research Articles

Analysis of the building on the air shock wave by direct dy-namic method (with LIRA-FEM soft-ware)

Calculation of the impact of air shock waves on buildings is extremely important for our country, which is in a state of war. Studying the structural safety and survivability of load-bearing reinforced concrete structures under influence is an important task, especially for critical infrastructure facilities. A blast scenario can be carried out directly in an FEA program as a time history analysis evaluate varying levels of structural damage and to minimize loss of life.The article is devoted to the features of the calcula-tion of buildings under the influence of air shock waves using the finite element method using the LIRA-FEM software complex. The features of ex-plosive loads, typical shock wave parameters, and the order of analysis for explosive loads are taken into consideration. The primary distinctions be-tween shock or explosion impacts and regular loads are explained. In-depth consideration is given to the problems of determining shock wave parameters and how they affect structures. Also included are the techniques for evaluating structures for explosive impacts.Using LIRA-FEM software, a preliminary analysis of the explosion resistance of a one-story building with a metal frame and sheet metal wall infill is carried out. It is demonstrated how to define impulse loads from a shock wave to the side walls, roofs, rear walls, and walls facing the explosion. The article describes the peculiarities of the "Time History Analysis" system in the LIRA-FEM program for ex-plosion dynamics problems.This analysis helps in the assessment of risks in the design of protective structures, development of pro-ject solutions and conducting research in the field of explosion safety.

Mathematical-Physics Analyses of the Nozzle Shaping at the Aperture Gas Outlet into Free Space under ESEM Pressure Conditions.

The paper presents a methodology that combines experimental measurements and mathematical-physics analyses to investigate the flow behavior in a nozzle-equipped aperture associated with the solution of its impact on electron beam dispersion in an environmental scanning electron microscope (ESEM). The shape of the nozzle significantly influences the character of the supersonic flow beyond the aperture, especially the shape and type of shock waves, which are highly dense compared to the surrounding gas. These significantly affect the electron scattering, which influences the resulting image. This paper analyzes the effect of aperture and nozzle shaping under specific low-pressure conditions and its impact on the electron dispersion of the primary electron beam.

Generation and modulation of shock waves in two-dimensional polariton condensates

Due to the ability of exciton-polariton condensates formed in semiconductor microcavities to be achieved at room temperature and their characteristics such as non-equilibrium and strong interactions, they have become an ideal platform for studying the nonlinear properties of non-equilibrium quantum systems. In 2013, the research group led by L. Dominici observed two-dimensional symmetric shock waves in the polariton condensate driven by coherent pump. However, owing to the characteristics of this system, theoretical researches have lagged behind. In one-dimensional polariton condensates, disregarding cross-interaction of the system, a type of asymmetric shock wave was respectively discovered by A. M. Kamchatnov in 2012 and A. M. Belounis in 2017. In 2023, utilizing the adiabatic approximation, our research team not only uncovered sparse wave, symmetric, and asymmetric shock waves in the system, but also revealed that the symmetric shock waves are triggered by cross-interaction. At present, there is no theoretical research on shock waves in two-dimensional polariton condensate. In this paper, spectral methods and fourth-order Runge-Kutta methods are used to explore the generation and control of shock waves in two-dimensional polariton condensates. It is found that when the cross-interaction between the condensate and the polariton thermal reservoir is quenched at high condensation rates, the initially prepared bright solitons can be modulated into two types of rotationally symmetric shock waves with different velocities, while the initial dark-like solitons can only transform into a single velocity rotationally symmetric shock wave. If quenching the external potential, the dark-like solitons can be transformed into anisotropic supersonic shock waves, and the dependence of shock wave on the width of the external potential is also shown. When the external potential and incoherent pumping are controlled at low condensation rates, multiple anisotropic shock waves can be excited in a uniform condensate, and their amplitudes can be used to control the wave number and amplitude of the shock waves and the range of widths for the external potential or incoherent pumping to excite shock waves is also demonstrated. The proposed methods in this paper not only provide theoretical guidance for the generation and control of shock waves in exciton-polariton condensates, but also find symmetric shock waves similar to experiments (<ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.nature.com/articles/ncomms9993"><i>Nat. Commun.</i> <b>6</b> , 8993</ext-link>) without adopting any approximation, and open up a universal pathway for exciting shock waves in non-equilibrium or non-integrable systems, which may become a paradigm for transforming solitons into shock waves and significantly propel the rapid development of shock wave theory in different domains.

General concept for autoignitive reaction wave covering from subsonic to supersonic regimes

We consider a one-dimensional (1D) autoignitive reaction wave in a reactive flow system comprising unburned premixed gas entering from the inlet boundary and burned gas exiting from the outlet boundary. In such a 1D system at given initial temperature, it is generally accepted that steady-state solutions can only exist if the inlet velocity matches either the velocity of deflagration wave, as determined by the burning rate eigenvalue in the subsonic regime, or the velocity of detonation wave as dictated by the Chapman–Jouguet condition in the supersonic regime. Based on our recently published theory that ignition is equivalent to deflagration wave with unity Lewis number, we believe that it is possible to redefine deflagration wave from ignition. Thus, we have developed the general concept of “autoignitive reaction wave” and shown theoretically that there are two distinct regions that can maintain steady-state solutions in both the subsonic and supersonic regimes. Based on this theory, we selected inlet velocities that are predicted to yield either steady-state or flashback solutions and conducted numerical simulations. This novel approach revealed that steady-state solutions are possible not only at the velocity of the deflagration wave in the subsonic regime and the velocity of the detonation wave in the supersonic regime, but also across a broad range of inlet velocities. Furthermore, we identify a highly stable autoignitive reaction wave that emerges when the inlet velocity surpasses the velocity of detonation wave, devoid of the typical shock wave commonly seen in detonation waves. This “supersonic autoignitive reaction wave” lacks the instability-inducing detonation cell structure, suggesting the potential for the development of novel combustor concepts.

Effect of dimensionless vent ratio on the flame-shock wave evolution dynamics of blended LPG/DME gas explosion venting

To reveal the flow field-shock wave-flame coupling evolution law of LPG/DME blended gas explosion venting under different dimensionless vent ratio(KV), the numerical model for multi-blended gas explosion venting was established and research of blended gas explosion venting at KV = 0.02–0.21 was carried out based on experimental verification. The results show that, after the vent opens, the turbulence intensity increases, the velocity gradient of the flow field increases, the maximum explosion wind velocity(Vmax) of the outfield varies linearly with KV, and the flame of “mushroom shape” is elongated, and “break flame” occurs under the action of the relative motion of “primary and secondary vortex group”. When KV＞0.02, the flame propagation velocity increases locally because of the thermal-mass diffusion instability, and with increasing KV, the average flame propagation velocity decreases from 258.29 m/s to 226.58 m/s. In the process of explosion venting, a typical shock wave fluctuating pressure waveform curve is formed in the outfield. Under the combined action of the infield pressure venting effect and the outfield turbulence intensity, the maximum explosion overpressure in the outfield (Pmax) reaches maximum 423.97 kPa at KV = 0.07. Meanwhile, the larger the KV, the greater the shock wave velocity due to the lead role of the infield explosion venting shock wave and outfield flame compression shock wave on the shock wave propagation velocity.

Detection of Transdermal Drug Delivery Efficiency by Shock Wave.

This study aimed to observe the drug distribution ex-vivo after transdermal drug delivery (TDD) by Shock Wave (SW) and to explore the different effects of the two types of shock waves. Nine female Sprague-Dawley (SD) rats were randomly divided into 3 groups: (i) control group; (ii) RESW group (0.35mJ/mm2, 2 Hz, 400 pulse); (iii) FESW group (0.16mJ/mm2, 2 Hz, 400 pulse). Micro positron emission tomography/computed tomography (PET/CT) was used to observe the distribution of [18]F-NaF. Furthermore, 12 SD rats were randomly divided into 4 groups: (i) control group; (ii) FESW group 1 (0.03mJ/mm2, 2 Hz, 400 pulse); (iii) FESW group 2 (0.16mJ/mm2, 2 Hz, 400 pulse); (iv) FESW group 3 (0.35mJ/mm2, 2 Hz, 400 pulse). High-performance liquid chromatography (HPLC) tested diclofenac sodium and glucose percutaneously TDD by FESW. Statistical significance was conducted by analysis of variance of repeated measurement. The micro PET/CT observed FESW could penetrate [18]F-NaF through the skin, while RESW could not. The second study found the higher the energy of the FESW, the more diclofenac sodium and glucose penetration. Repeated measures analysis of variance found a within-subject effect (diclofenac sodium, F = 4.77, p = 0.03), (glucose, F = 8.95, p = 0.006), significant differences between the control group, FESW group 1, and FESW group 2 (p < 0.05). The study found that FESW can penetrate [18]F-NaF, sugar and diclofenac sodium into the rat body. FESW has a good indication of drug penetration, which provides new biological evidence for route administration.

Methodology for the Identification of Shock Wave Type and Speed in a Traffic Stream Using Connected Vehicle Data

The concept of traffic shock waves was first theorized by Lighthill and Whitham in 1955. The identification of shock wave type and speed in a traffic stream provides critical information about the queue formation and its dissipation. This information can be utilized by various stakeholders for traffic management, emergency response, etc. Such information can also be integrated into the travel time prediction models and real-time route diversions for navigation. Past efforts at identifying shock waves used simulation or analysis based on location-based sensors such as loop detectors. This paper describes scalable methodologies for measuring shock wave propagation using Connected Vehicle (CV) data. The techniques to identify the six different types of shock waves are illustrated through case studies from Indiana highways that use both CV data and the corresponding surveillance camera images. The shock wave speeds for each event are estimated using the linear regression model, with most shock wave speed estimates having a coefficient of determination (R2) of 0.9 or better. Although shock wave speeds vary by traffic flow rates and geometry, the typical backward forming shock wave speeds ranged from 1.75 to 11.76 mph whereas the backward recovery shock wave speeds were observed to be between 5.78 and 16.54 mph. These techniques can be adapted for real-time use to assist traffic management centers with estimating upstream propagation and recovery time. A case study with a car fire is used to illustrate how this shock wave speed data can be used to frame discussions with first responders regarding how reducing incident clearance time can reduce the risk of secondary crashes.

Numerical Simulation of Acoustic Wave Generated by DC Corona Discharge Based on the Shock Wave Theory

The audible noise generated by corona discharge has the N-type characteristic at the initial generation stage, and it is a typical shock wave. This shock wave usually only exists around the corona source with a tiny range, making it difficult to obtain its characteristics through experimental measurements. An electrosound-combined simulation of the corona discharge based on the shock wave theory was conducted, and the development process involving the corona discharge, shock wave, and sound wave was simulated. First, the corona was numerically simulated based on the 2D pin–plate axisymmetric hydrodynamic model. It was found that the plasma was mainly distributed near the axis of the corona field where the electric field changed violently, and the maximum value of the electric field appeared at the head of the discharge channel. Then, the plasma energy was equivalent to the explosive energy, and a plasma explosion shock model was established. It was found that the shock wave pressure had obvious positive and negative pressure zones, and the propagation velocity decays to the sound velocity gradually. Finally, the shock wave pressure derived by the explosion model was used as the acoustic source, and the acoustic wave propagation process was simulated. The simulated sound pressure waveform had the same characteristics as the relevant experimental measurement results, proving that the developed method possessed strong applicability and gave rise to a new angle for the simulation of corona-generated audible noise.

Generation and Control of Shock Waves in Exciton-Polariton Condensates

We propose a scheme to generate and control supersonic shock waves in a non-resonantly incoherent pumped exciton-polariton condensate, and different types of shock waves can be generated. Under conditions of different initial step waves, the ranges of parameters about various shock waves are determined by the initial incidence function and the cross-interaction between the polariton condensate and the reservoir. In addition, shock waves are successfully found by regulating the incoherent pump. In the case of low condensation rate from polariton to condensate, these results are similar to the classical nonlinear Schrödinger equation, and the effect of saturated nonlinearity resulted from cross interaction is equivalent to the self-interaction between polariton condensates. At high condensation rates, profiles of shock waves become symmetrical due to the saturated nonlinearity. Compared to the previous studies in which the shock wave can only be found in the system with repulsive self-interaction (defocusing nonlinearity), we not only discuss the shock wave in the exciton-polariton condensate system with the repulsive self-interaction, but also find the shock wave in the condensates system with attractive self-interaction. Our proposal may provide a simple way to generate and control shock waves in non-resonantly pumped exciton-polariton systems.

Asymptotic step-like solutions of the singularly perturbed Burgers equation

This paper deals with a problem of asymptotic step-like solutions of the Burgers equation with variable coefficients and a small parameter. By means of the nonlinear Wentzel–Kramers–Brillouin method, the algorithm of constructing these asymptotic solutions is proposed and statements on justification of the algorithm are proved. The obtained results are illustrated by an example, for which the first asymptotic step-like approximation is explicitly found. The asymptotic solution is global and has a form of the shock wave type function. There are also given graphs of these approximate solutions for certain numerical parameters.

Deforming soft algebras for gauge theory

Symmetry algebras deriving from towers of soft theorems can be deformed by a short list of higher-dimension Wilsonian corrections to the effective action. We study the simplest of these deformations in gauge theory arising from a massless complex scalar coupled to F2. The soft gauge symmetry ‘s-algebra’, compactly realized as a higher-spin current algebra acting on the celestial sphere, is deformed and enlarged to an associative algebra containing soft scalar generators. This deformed soft algebra is found to be non-abelian even in abelian gauge theory. A two-parameter family of central extensions of the s-subalgebra are generated by shifting and decoupling the scalar generators. It is shown that these central extensions can also be generated by expanding around a certain non-trivial but Lorentz invariant shockwave type background for the scalar field.

Прикатодные плазменные и газодинамические процессы при формировании искрового разряда в воздухе атмосферного давления в промежутке острие-плоскость

Using the method of shadow photographing, the formation of a spark discharge in the "tip (cathode) – plane" interval with a length of 1.5 mm is investigated. Two types of shock waves have been registered – cylindrical, created when the discharge channel expands, and cathode, presumably generated by cathode flares near the surface of the tip electrode. The computational and theoretical consideration of the proposed mechanism is carried out.

Near-cathode plasma and gas-dynamic processes during the formation of a spark discharge in air at atmospheric pressure in the gap point-plane

Using the method of shadow photographing, the formation of a spark discharge in the &amp;quot;tip (cathode)-plane&amp;quot; interval with a length of 1.5 mm is investigated. Two types of shock waves have been registered cylindrical, created when the discharge channel expands, and cathode, presumably generated by cathode flares near the surface of the tip electrode. The computational and theoretical consideration of the proposed mechanism is carried out. Keywords: gas discharge, microstructure, electron temperature, degree of gas ionization.

Weight-Based Evaluation of the Explosive Power of New Energetic Materials

Accurately evaluating the explosive performance of newly developed energetic materials is important for the design of high-energy warheads. Different energetic materials have distinct effects in terms of thermal damage and damage caused by the pressure of the shock wave. In this study, the authors seek to quantitatively evaluate the explosive power of new energetic materials on the basis of the above factors. We consider single-parameter models for the evaluation of both the pressure of the shock wave and the thermal dose and use them to propose a comprehensive method to assess the explosive effects of new energetic materials based on their weight distribution. We first build a test system to obtain the thermal dose corresponding to the typical proportional distance based on the typical peak pressure. We then construct a normalized model of the surface-reflected pressure and the thermal dose by using the proportional distance related to a typical shock wave. Finally, we calculate the specific equivalent of new energetic materials relative to trinitrotoluene (TNT) and use it to quantitatively evaluate its explosive power. The results of experiments to assess the performance of the proposed method show that it is applicable and can be used to assess the explosive effects of new energetic materials.

Epistemology in Practice: Ernst Mach’s Experiments on Shock Waves and The Place of Philosophy

The present paper studies Ernst Mach’s experimental work with “spark waves” and other types of shock waves, which brought him to the 1887–88 famous schlieren photographs of supersonic phenomena triggered by bullets shot at high speed. Against what it is traditionally argued, I show (1) that Ernst Mach’s visualization attempts do not depend on his commitment to any particular philosophical doctrine about the role of sensations as the foundation of empirical science, and (2) that his inclination toward experimental research may have crucially contributed to the development of his epistemological and ontological views.

Numerical Simulation of Jet Interaction Flow Field with Different Flow Rates

In this paper, the complex disturbance flow caused by the interaction of jets with different flow rates and hypersonic incoming flow on a cone-cylinder-skirt of revolution is numerically studied, the typical shock wave structure and the influence range caused by the jet interaction are given, and the effect of the jet flow rate on the interaction flow field is discussed. The results show that the interaction between the jet flow and the incoming flow increases with the rise of the jet flow rate, and the influence range of the wrapping effect enlarges. If the jet flow rate is equivalent to the incoming flow rate, the leading edge separation line forms a closed loop.

Numerical Investigation on Unsteady Shock Wave/Vortex/Turbulent Boundary Layer Interactions of a Hypersonic Vehicle during Its Shroud Separation

Hypersonic vehicles are drawing more and more attention now and for the near future, especially in the low-altitudes near space, from 20 km to 45 km. The reliable separation of the protecting shroud from the hypersonic vehicle is a prerequisite and critical issue for the success of the entire flight mission. The unsteady multi-body separation characteristics and flow characteristics of hypersonic shroud separation at Mach 7.0 are investigated based on numerical simulation in this paper. The improved delayed detached eddy simulation (IDDES) method, dynamic hybrid overset mesh method, and HLLE++ numerical scheme are used to ensure numerical accuracy. Numerical results show that there are four types of vortexes and three types of shock waves inside the shrouds during the separation process, which generate complex shock wave/vortex/boundary layer interactions. Further, an unsteady process of the expansion-transfer-dissipation of an A-type vortex is found, which is the result of strong shock/vortex/boundary layer interactions. The adverse pressure gradient is the root cause driving the generation and transfer of the A-type vortex during the shroud separation. Furthermore, the transfer process of the A-type vortex only lasts for 5.52 ms but causes a large disturbance to the aerodynamic force of the shroud. The results of this paper could provide a reference for the design of near-space hypersonic vehicles.

Patient Outcomes on Treatment of Insertional Achilles Tendinopathy with Extracorporeal Shockwave Therapy: A Retrospective Study

Category: Ankle; Other Introduction/Purpose: Insertional achilles tendinopathy (IAT) affects approximately one-third of patients who report achilles tendon pain during their lifetime. It is characterized by stiffness and pain that are aggravated by prolonged rest and physical activity, respectively. Known treatments for IAT include eccentric exercises, night splints, pharmacologic or biologic injections, and extracorporeal shockwave therapy (ESWT). However, pain and functional outcomes following ESWT treatment for IAT vary throughout the literature. In addition, ESWT protocols have varied across studies. This retrospective study aimed to collect information on patient outcomes following ESWT treatment for IAT at a single institution to better characterize patient-reported pain and functional outcomes and to determine if patient-reported outcomes differ according to varying ESWT protocols. Methods: 44 patients who presented with IAT and received ESWT from 2/1/2016 to 10/1/2021 were included. Confirmation of IAT was determined by a review of each patient's chart. Patient-reported outcomes included NRS or VAS scores and PROMIS-10 were collected prior to ESWT sessions and at follow-up time points. Additionally, demographic information for each patient was collected including age, gender, race, ethnicity. Information regarding their achilles tendinopathy included symptom duration, laterality, prior interventions before ESWT, concurrent foot or ankle injuries on the same side, pain (baseline and follow-ups), PROMIS-10 (baseline and follow-ups) was also collected. Finally, ESWT information was reviewed including focused vs radial, number of sessions, number of pulses, energy intensity, frequency, any adverse outcomes after ESWT (e.g., tendon rupture, increase in pain; immediate or delayed), and if any interventions were needed during or after ESWT (physical therapy, cortisone injection, PRP, surgery, medications, orthotics). Results: Out of the 44 patients who were included in the study, 27 were female and 17 male. Mean symptom duration was 23.3 months (SD 26.7 months). 34 patients had unilateral pain while 5 had bilateral pain. Every patient had undergone previous treatment with a majority having tried physical therapy (n=33) and bracing (n=21). Mean number of ESWT sessions between patients was 3.3 (SD 1.5 sessions). 30 patients received focused shockwave therapy, 3 received radial shockwave therapy and 1 received both. The remaining 10 patient charts were inconclusive as to which type of shockwave was performed. 13 patients reported no improvement whereas the remaining 31 patients reported improvement, with a majority (n=18) reporting at least 50% improvement or greater. Conclusion: Insertional achilles tendinopathy can be treated with a wide variety of modalities, therapies and adjuncts. When considering treatment for cases that do not respond to the traditional methods including physical therapy, bracing and injections, ESWT shows promising data to be an effective treatment option, regardless of type or intensity. Most patients require more than 1 ESWT to be effective.

OpenFOAMTM Simulation of the Shock Wave Reflection in Unsteady Flow

This work studies the impact of a shock wave traveling with non-constant velocity over straight surfaces, generating an unsteady and complex reflection process. Two types of shock waves generated by sudden energy released are studied: cylindrical and spherical. Several numerical tests were developed considering different distances between the shock wave origin and the reflecting surface. The Kurganov, Noelle, and Petrova (KNP) scheme implemented in the rhoCentralFoam solver of the OpenFOAMTM software is used to reproduce the different shock wave reflections and their transitions. The numerical simulations of the reflected angle, Mach number of the shock wave, and position of the triple point are compared with pseudo-steady theory numerical and experimental studies. The numerical results show good accuracy for the reflected angle and minor differences for the Mach number. However, the triple point position is more difficult to predict. The KNP scheme in the form used in this work demonstrates the ability to capture the phenomena involved in the unsteady reflections.

Turbulence Model Comparative Study for Complex Phenomena in Supersonic Steam Ejectors with Double Choking Mode.

Scholars usually ignore the non-equilibrium condensing effects in turbulence-model comparative studies on supersonic steam ejectors. In this study, a non-equilibrium condensation model considering real physical properties was coupled respectively with seven turbulence models. They are the k-ε Standard, k-ε RNG, k-ε Realizable, k-ω Standard, k-ω SST, Transition SST, and Linear Reynolds Stress Model. Simulation results were compared with the experiment results globally and locally. The complex flow phenomena in the steam ejector captured by different models, including shock waves, choking, non-equilibrium condensation, boundary layer separation, and vortices were discussed. The reasons for the differences in simulation results were explained and compared. The relationship between ejector performance and local flow phenomena was illustrated. The novelty lies in the conclusions that consider the non-equilibrium condensing effects. Results show that the number and type of shock waves predicted by different turbulence models are different. Non-equilibrium condensation and boundary layer separation regions obtained by various turbulence models are different. Comparing the ejector performance and the complex flow phenomena with the experimental results, the k-ω SST model is proposed to simulate supersonic steam ejectors.