Collision Of Shock Waves Research Articles

QCD-gravity double-copy in the Regge regime: Shock wave propagators

In a previous paper [H. Raj and R. Venugopalan, ], we demonstrated a double-copy relation between inclusive gluon radiation in shock wave collisions of ultrarelativistic nuclei and inclusive graviton radiation in trans-Planckian gravitational shock wave collisions. We compute here the corresponding gravitational shock wave propagators in general relativity and demonstrate that they too obey a double-copy relation to gluon shock wave propagators computed previously. These results provide key input in a renormalization group approach toward computing the high frequency radiation spectrum in close black hole encounters. Published by the American Physical Society 2024

Effects of Particle Migration on the Relaxation of Shock Wave Collisions.

The non-equilibrium characteristics during the shock relaxation process hold a foundational position in various fields. In contrast to the propagation of a single shock wave, the collision process of two shock waves exhibits distinct non-equilibrium features. Employing non-equilibrium molecular dynamics, we simulated the collision of ultra-strong shock waves in a classical gas system, investigating the relationship between equilibrium relaxation time and shock intensity. Tracking the spatial migration of microscopic particles in the shock collision region during the relaxation process, we observed a significant contribution of particle migration to the average energy changes during relaxation. The discussion on particle migration provides a valuable new perspective for understanding the microscopic mechanisms of the relaxation process.

Gravitational wave double copy of radiation from gluon shockwave collisions

In [1], we showed that the gravitational wave spectrum from trans-Planckian shockwave scattering in Einstein gravity is determined by the gravitational Lipatov vertex expressed as the bilinear double copy Γμν=12CμCν−12NμNν where Cμ is the QCD Lipatov vertex and Nμ is the QED soft photon factor. We show here that this result can be directly obtained by careful application of the classical color-kinematic duality to the spectrum obtained in gluon shockwave collisions.

Modeling the Interaction of Proximal Fragments for Destructive Atmospheric Entry Analysis

The destructive atmospheric entry process is distinguished by the formation of several fragments due to the severe aerothermal loads encountered during the descent. The proximity of debris leads to shock wave interactions and collisions between bodies, influencing the overall dynamics of the fragments and affecting the prediction of demise and ground impact location. To account for these effects, the use of computational fluid dynamics is introduced to resolve the shock interaction patterns by employing a quasi-steady approach, and the use of a simple rigid-body collision model is introduced to represent the dynamics of fragments in the cloud of debris. The quasi-steady approach is assessed and validated by comparative analysis with a few studies in the literature. One of these examples is the rebuilding of the VKI’s experiment of a free-flying ring crossing a shock wave generated by the presence of a stationary cylinder. The impact of explicitly modeling collision dynamics in the trajectory of fragments and ground spread distance is validated by considering a set of relevant test cases from the literature and tested them for destructive atmospheric reentry of the Attitude Vernier Upper Module, the launcher VEGA upper stage.

Universal features of 2→N scattering in QCD and gravity from shockwave collisions

A remarkable double-copy relation of Einstein gravity to QCD in Regge asymptotics is Γμν=12CμCν−12NμNν, where Γμν is the gravitational Lipatov vertex in the 2→3 graviton scattering amplitude, Cμ its Yang-Mills counterpart, and Nμ the QED bremsstrahlung vertex. In QCD, the Lipatov vertex is a fundamental building block of the BFKL equation describing the 2→N scattering of gluons at high energies. Likewise, the gravitational Lipatov vertex is a key ingredient in a 2D effective field theory framework describing trans-Planckian 2→N graviton scattering. We construct a quantitative correspondence between a semiclassical Yang-Mills framework for radiation in gluon shockwave collisions and its counterpart in general relativity. In particular, we demonstrate the Lipatov double copy in a dilute-dilute approximation corresponding to RS,L, RS,H≪b, where RS,L, RS,H are the respective emergent Schwarzchild radii generated in shockwave collisions and b is the impact parameter. We outline extensions of the correspondence developed here to the dilute-dense computation of gravitational wave radiation in the close vicinity of one of the black holes, the construction of graviton propagators in the shockwave background, and a renormalization group approach to compute 2→N amplitudes that incorporates graviton Reggeization and coherent graviton multiple scattering. Published by the American Physical Society 2024

Wee partons in QCD and gravity: Double copy and universality

We discuss a quantitative “double copy” between radiation from shockwave collisions in Einstein gravity and in QCD. The correspondence extends to 2 → N amplitudes in Regge asymptotics. The classicalization and unitarization of these amplitudes at maximal occupancy, corresponding to black hole and Color Glass Condensate (CGC) states respectively, are described by the emergent Goldstone dynamics of wee partons. We outline some consequences of the universal dynamics on both sides of the correspondence.

Stability investigation of two-phase n-decane rotating detonation waves

In this paper, three-dimensional rotating detonation combustor fuelled by n-decane sprays is numerically investigated with Eulerian-Lagrangian method. The flow field characteristics, the effects of injection total pressure and oxygen mass fraction on the stability of two-phase rotating detonation wave are analysed. The results show that the mixing-dominance and the reaction-dominance are two mechanisms affecting the stability of two-phase rotating detonation wave. Specifically, injection total pressure mainly affects the fuel mixing in non-premixed configuration. Increasing the total pressure improves the droplet evaporation, such as the reduce of the droplet evaporation distance, Sauter mean diameter and the rise of droplet evaporation rate. Besides, the stability of two-phase rotating detonation wave is nonlinear, the highest stability happens in 1.5MPa, which is due to the collision of shock wave and rotating detonation wave. On the other hand, oxygen mass fraction has a significant effect on the reactivity of reactant and leads to the wave propagation mode transition. The increasing of oxygen mass fraction broadens the high reaction rate zone, which provides a suitable environment for the generation of local explosions. The local explosions gradually develop into detonation waves and form multi-wave mode after a complex self-adjusted process. Moreover, the stability of two-phase rotating detonation wave is in proportion to the oxygen mass fraction. As the increase of oxygen mass fraction, the fluctuations of pressure and detonation speed tend to be smooth, which implied the higher stability in multi-wave mode. The analysis about stability of RDW may be beneficial to the design of two-phase rotating detonation engines.

Fundamental review on collision of blast waves

The introduction and pinnacle of colliding blast waves research commenced in the 1950s following World War II. Since then, sporadic studies have appeared throughout the literature up until the early 1990s, beyond which a significant contributory gap on the topic ensued. With the interminable proactivity of modern civil and aerospace defense research in the past several decades, investigations on the phenomena of blast wave collisions have fallen behind in comparison. Recent events and applications of offensive and defensive operations have slowly begun to rekindle studies on colliding blast waves in the last few years. However, there remains limitations on the extent of analyses which have yet to be adequately addressed. This review attempts to critically compile and analyze all existing research on blast wave collisions to identify pertinent shortcomings of the present state-of-the-art. In addition, related investigations of colliding shock waves and the collision of shock waves and blast waves are also provided to further elaborate on their distinctions to colliding blast waves. Prior to such discussions, the fundamentals of blast wave behaviors in terms of their characteristics, formation, and propagation are presented to pave a background to subsequent advanced topics. Finally, unique classifications of direct and indirect applications of blast wave collisions are presented with modern perspectives. As a result, a classical problem is reawakened toward understanding and addressing highly complex and dynamic shock wave systems in defense applications.

Adaptive simulations of flame acceleration and detonation transition in subsonic and supersonic mixtures

Two-dimensional simulations were carried out to investigate the flame acceleration and deflagration-to-detonation transition (DDT) in a combustion chamber filled with a subsonic or supersonic mixture by employing Navier-Stokes equations together with a detailed chemistry reaction mechanism of 11 species and 27 steps under adaptive mesh refinement. The effects of the initial mixture Mach number and mesh resolution on the flame acceleration and DDT were studied in detail, and the entire processes of the flame acceleration, DDT and detonation propagation were revealed. Two DDT mechanisms are obtained in a chamber having the same low blockage ratio but with different initial velocities of the mixture. Regime I: multiple shock wave collisions, shock focusing and shock reflection result in a rapid energy deposition in a small region; a direct detonation subsequently occurs in the boundary wall for the subsonic mixture. Regime II: the classic hot-spot mechanism due to the reactive gradient mechanism is responsible for the detonation transition in the supersonic mixture when the intense leading shock wave impacts and reflects on the solid surface. By increasing the initial mixture Mach number, the run-up time and distance to DDT are dramatically reduced. The flame front structure and propagation in the supersonic flow demonstrate that the detonation cell size rapidly increases when propagating into the smooth region due to detonation attenuation and resulting pressure decrease. Additionally, a much higher combustion temperature occurs in the upper and lower walls because of the Mach stem. In comparison, the results show that the detonation overdrive degree and pressure gain ratio in the subsonic mixture are higher than in the supersonic mixture. Moreover, flame propagation upstream also suggests that increased pressure and temperature occur in the inlet isolation section, even forming a localized explosion point.

Holographic collisions in large D effective theory

We study collisions of Gaussian mass-density blobs in a holographic plasma, using a large D effective theory, as a model for holographic shockwave collisions. The simplicity of the effective theory allows us to perform the first 4+1 collisions in Einstein-Maxwell theory, which are dual to collisions of matter with non-zero baryonic number. We explore several collision scenarios with different blob shapes, impact parameters and charge values and find that collisions with impact parameter below the transverse width of the blobs are equivalent under rescaling. We also observe that charge weakly affects the rest of quantities. Finally, we study the entropy generated during collisions, both by charge diffusion and viscous dissipation. Multiple stages of linear entropy growth are identified, whose rates are not independent of the initial conditions.

Dynamics and head-on collisions of multidimensional dust acoustic shock waves in a self-gravitating magnetized electron-depleted dusty plasma

The dynamics and collisions of dust acoustic (DA) shock excitations traveling in opposite directions are theoretically investigated in a three-dimensional self-gravitating magnetized electron-depleted dusty plasma whose ingredients are extremely warm positively and negatively charged massive dust grains as well as ions that follow the q-nonextensive distribution. A linear analysis and the extended Poincare–Lighthill–Kuo method are used to derive the dispersion relation, the two-sided Korteweg–de Vries Burgers equations, and the phase shift that occurs due to the wave interaction. It is found that gravitation introduces Jeans-like instability, reduces the wave damping rate, decays the aperiodic oscillatory structure of DA excitations, and strongly affects the amplitude, steepness, and occurrence of monotonic compressive and rarefactive shocks. Numerical simulations also highlighted the stabilizing role of the magnetic field and the singularities of the collision process of monotonic shock fronts as well as the undeniable influence of viscosity, ion nonextensivity, and obliqueness between counter-traveling waves on the phase shift and collision profiles. The present results may be useful to better understand interactions of dust acoustic shock waves in the laboratory and astrophysical scenarios, such as dust clouds in the galactic disk, photo-association regions separating H II regions from dense molecular clouds, Saturn's planetary ring, and Halley Comet.

Numerical simulation on the shock wave focusing detonation process in the semicircle reflector

Shock wave focusing is considered a new type of initiation method that does not require external ignition devices. For this method, understanding the shock wave/flame interaction accurately is one of the critical issues for revealing the ignition and triggering mechanisms during shock wave focusing processes. In this study, numerical simulations were carried out to investigate the detailed flow field evolution of the focusing process with kerosene as fuel. Two detonation initiation modes were found during the shock wave focusing processes, which were the direct initiation mode and the reflected shock wave collision initiation mode, respectively. At the detonation wave propagation stage, the primary detonation wave decouples and fails to propagate out of the cavity. The multiple initiation phenomenon occurs in the cavity, and it dominated detonation waves to propagate outside of the cavity to accomplish one thermal cycle. There is no positive correlation between jet temperature and detonation wave propagation velocity. When the jet temperature is low, the detonation wave velocity dominated by the multiple initiation mode is the fastest. The analysis of the shock wave focusing process under different jet velocities showed that when the jet velocity was lower than 2 Ma, the decoupling of the primary detonation wave failed to induce multiple detonation waves. Driven by the vortex in the semicircular cavity, the flame is almost stationary, which means the failure of the detonation wave propagation process.

Arising of trapped surfaces with nontrivial topology from colliding shock waves

The lightlike limit of boosted black hole solutions with one angular momentum is considered for $D \geq4$ dimensions. The boost is performed parallel to the angular momentum and the lightlike limit is done by means of perturbative expansions. We shown that for $D=4$ and $D> 5$ the lightlike limit cannot be extended inside the ring singularity. Then, for $D = 5$ we discuss the arising of trapped surfaces in the head-on collision. We find that, inside the validity of the perturbative analysis we do, a trapped surface with topology $\mathbb R \times \mathbb S_1 \times\mathbb S_1$ seems to appear over the past light cone of the collision below a critical value $a_c$ of the Kerr parameter $a$.

Linear analysis and head-on collision of dust ion-acoustic shock waves in un-magnetized electronegative collisional plasmas

The linear properties and head-on collision of dust ion-acoustic shock waves (DIASWs) are investigated in un-magnetized electronegative collisional plasmas comprising non-inertial thermal electron and light negative ion, inertial positive ion, and stationary dust grain with negative charges. In this regard, the dispersion relation is derived using the standard normal mode analysis and the two-sided damped Korteweg–deVries (dKdV) equations are derived employing the extended Poincaré Lighthill Kuo (ePLK) method. The effects of physical parameters on linear dispersion relation, formation of shocks, phase shift due to head-on collision, and collision process are studied. It is found that the effect of is more dominant to the wave frequency than that of and in a certain range of the group velocity of the DIASWs is increasing and then decreasing for the effect of the ratio of negative ion to electron density. The amplitude and width of the DIASWs increase with the enhancement of electron temperature and the ion-neutral collision plays a significant role in the formation of shock. The consequence of () the phase shift is increasing (decreasing). The results of this study may be useful to the investigation of space and astrophysical environment where the electronegative collisional plasma exists.

Weak shock wave interactions in isentropic Cargo‐LeRoux model of flux perturbation

In this paper, we explore the weak shock wave interactions in isentropic Cargo‐LeRoux model of flux perturbation which describes strictly hyperbolic quasilinear system of conservation laws. For the Riemann problem, we provide a global existence and uniqueness result of exact solution. Further, we establish the exact solution explicitly in terms of one parameter family of elementary wave curves. We devise a necessary and sufficient condition on initial data for which the solution of the Riemann problem consists of either a shock wave or a simple wave according to one and three family of characteristic curves. Lastly, we analyze the Von Neumann result related to collision of weak shock waves of same family.

Shock-wave Radio Probing of Solar Wind Sources in Coronal Magnetic Fields

Abstract The space weather effects in the near-Earth environment as well as in atmospheres of other terrestrial planets arise by corpuscular radiation from the Sun, known as the solar wind. The solar magnetic fields govern the solar corona structure. Magnetic-field strength values in the solar wind sources—key information for modeling and forecasting the space weather climate—are derived from various solar space- and ground-based observations, but so far not accounting for specific types of radio bursts. These are “fractured” type II radio bursts attributed to collisions of shock waves with coronal structures emitting the solar wind. Here, we report on radio observations of two “fractured” type II bursts to demonstrate a novel tool for probing of magnetic-field variations in the solar wind sources. These results have a direct impact on interpretations of this class of bursts and contribute to the current studies of the solar wind emitters.

Backward Flux Re-Deposition Patterns during Multi-Spot Laser Ablation of Stainless Steel with Picosecond and Femtosecond Pulses in Air.

We report on novel observations of directed re-deposition of ablation debris during the ultrafast laser micro-structuring of stainless steel in the air with multi-beams in close proximity on the surface. This interesting phenomenon is observed with both 10 ps and 600 fs NIR laser pulses at 5 kHz repetition rate. Ablation spot geometries could be altered with the use of beam splitting optics or a phase-only Spatial Light modulator. At low fluence (F ~ 1.0 J cm−2) and pulse exposure of a few hundred pulses, the debris appears as concentrated narrow “filaments” connecting the ablation spots, while at higher fluence, (F ~ 5.0 J cm−2) energetic jets of material emanated symmetrically along the axes of symmetry, depositing debris well beyond the typical re-deposition radius with a single spot. Patterns of backward re-deposition of debris to the surface are likely connected with the colliding shock waves and plasma plumes with the ambient air causing stagnation when the spots are in close proximity. The 2D surface debris patterns are indicative of the complex 3D interactions involved over wide timescales during ablation from picoseconds to microseconds.

3-D structure of the Glasma initial state: Breaking boost-invariance by collisions of extended shock waves in classical Yang-Mills theory

We simulate the 3+1 D classical Yang-Mills dynamics of the collisions of longitudinally extended nuclei, described by eikonal color charges in the Color Glass Condensate framework. By varying the longitudinal thickness of the colliding nuclei, we discuss the violations of boost invariance and explore how the boost invariant high-energy limit is approached. Subsequently, we develop a more realistic model of the three dimensional color charge distributions that connects longitudinal and transverse fluctuations to the $x$ and $k_\bot$ dependence of transverse momentum dependent parton distributions, and explore the resulting rapidity profiles and their longitudinal fluctuations.

Effects of Isothermal Wall Boundary Conditions on Rotating Detonation Engine

ABSTRACT Three-dimensional numerical simulations of rotating detonation engines (RDEs) are reported with stoichiometric hydrogen/air mixtures using Navier-Stokes equations with non-slip walls. The effects of isothermal wall boundary conditions at 300 K, 600 K and 900 K are investigated and further compared with the simulation under adiabatic walls. With isothermal walls of 300 K, axial detonation is formed, which further leads to the quenching of detonation. With 600 K isothermal walls, the detonation wave has a similar stably propagating process as adiabatic walls. However, due to the wall heat loss, a lower detonation velocity is obtained in the simulation with isothermal walls. With 900 K isothermal walls, it is found that detonation quenches at first due to the high temperature of the walls, then re-initiates as a result of the collisions of shock waves. In addition, the temperature and heat flux distributions in the outer wall are analyzed. Both the peak temperature and heat flux are found to appear at the detonation wavefront. The averaged heat flux in the detonation region is about three times of the averaged heat flux evaluated in the outer wall. Moreover, the averaged temperature and heat flux remain nearly unchanged in the post-detonation region. Our results are in agreement with experimental studies and provide some insights for RDE thermal management.

On the Collision of Relativistic Shock Waves and the Large Scale Structure of the Universe

The solution to the problem of symmetric collision of two relativistic shock waves is given and limiting cases are investigated: Newtonian mechanics and ultrarelativistic mechanics. The results are correlated with the presence of known superclusters and "walls" in the Universe.