Mach Cone Research Articles

Prediction and observation of regional infrasound from the OSIRIS REx re-entry capsule

Infrasonic signals produced by bolides and space debris passing through atmosphere are frequently observed at notable stand-off distances. The acoustic energy radiated from such objects is dominated by the aero-acoustic Mach cone which exhibits a highly directional radiation pattern dependent on the velocity of the object relative to the surrounding atmosphere. Recently, a mapping of the Mach cone geometry into acoustic ray tracing methods has enabled efficient regional simulation of infrasonic ensonification from such sources. In September 2023, the OSIRIS REx sample capsule returned to Earth as part of a NASA supported asteroid study and a number of institutions deployed sensors to measure geophysical signatures of the event. The anticipated capsule trajectory was combined with historical atmospheric data for September in the western United States to predict likely regional ensonification during re-entry. Los Alamos National Laboratory infrasound experts deployed microbarometer arrays in locations predicted to be ensonified and were able to identify signals with arrival times and direction-of-arrival consistent with the capsule re-entry. An overview of the predictions, field deployments, and identified signals will be presented.

Anisotropic Mach Cone Aligned Mesh Adaptation for Low Boom Simulations

An automated off-body Mach cone aligned structured curvilinear grid generation procedure is presented for near-field computational fluid dynamics simulations. This procedure combines output-based indicators and mesh redistribution to perform anisotropic mesh adaptation while maintaining Mach cone alignment. Automation is achieved through a novel direction-based adaptation indicator formulation. The adaptation procedure is demonstrated on the JAXA Wing Body geometry and X-59 C608 demonstrator models from the Second and Third AIAA Sonic Boom Prediction Workshops, respectively. It is demonstrated that anisotropic mesh adaptation may result in a greater than 50% reduction in the resource usage required to achieve the same level of accuracy as uniform and user-constructed Mach cone aligned grids for near-field pressure signatures, ground-level overpressure signatures, and loudness metrics.

Prediction of regional infrasound produced by supersonic sources using a ray-based Mach cone source.

The geometry of the Mach cone produced by a supersonic source is analyzed and mapped into initial conditions used in acoustic ray tracing. The resulting source model is combined with spherical geometry ray tracing methods to enable propagation simulations for infrasonic signals produced by bolides, space debris, rockets, aircraft, and other fast-than-sound sources out to typical infrasonic observation distances of hundreds or thousands of kilometers. Idealized linear and parabolic trajectories typical of bolides and rockets, respectively, are used to demonstrate the calculation of regional infrasonic signals produced by such sources and characteristics of the radiated infrasonic waves are found to vary strongly with the geometry of the trajectory and atmospheric structure. Predicted regional infrasonic signals are compared with those observed from a November 2020 bolide that passed over Scandinavia using a combination of institutionally maintained infrasound stations and "citizen scientist" data from the Raspberry Shake data repository.

The field theory of collective Cherenkov radiation associated with electron beams

Classical Cherenkov radiation is a celebrated physics phenomenon of electromagnetic (EM) radiation stimulated by an electric charge moving with constant velocity in a three-dimensional dielectric medium. Cherenkov radiation has a wide spectrum and a particular distribution in space similar to the Mach cone created by a supersonic source. It is also characterized by the energy transfer from the charge's kinetic energy to the EM radiation. In the case of an electron beam passing through the middle of an EM waveguide, the radiation is manifested as collective Cherenkov radiation. In this case, the electron beam can be viewed as a one-dimensional non-neutral plasma, whereas the waveguide can be viewed as a slow wave structure. This collective radiation occurs, in particular, in traveling wave tubes (TWTs), and it features the energy transfer from the electron beam to the EM radiation in the waveguide. Based on a first principles Lagrangian field theory, we develop a convincing argument that the collective Cherenkov effect in TWTs is, in fact, a convective instability, that is, amplification. We also recover Pierce's theory as a high-frequency limit of our generalized Lagrangian theory. Finally, we derive for the first time expressions identifying low- and high-frequency cutoffs for amplification in TWTs.

Particle-resolved study of the onset of turbulence

The transition from laminar to turbulent flow is an immensely important topic that is still being studied. Here we show that complex plasmas, i.e., microparticles immersed in a low temperature plasma, make it possible to study the particle-resolved onset of turbulence under the influence of damping, a feat not possible with conventional systems. We performed three-dimensional (3D) molecular dynamics (MD) simulations of complex plasmas flowing past an obstacle and observed 3D turbulence in the wake and forewake region of this obstacle. We found that we could reliably trigger the onset of turbulence by changing key parameters such as the flow speed and particle charge, which can be controlled in experiments, and show that the transition to turbulence follows the conventional pathway involving the intermittent emergence of turbulent puffs. The power spectra for fully developed turbulence in our simulations followed the −5/3 power law of Kolmogorovian turbulence in both time and space. We demonstrate that turbulence in simulations with damping occurs after the formation of shock fronts, such as bow shocks and Mach cones. By reducing the strength of damping in the simulations, we could trigger a transition to turbulence in an undamped system. This work opens the pathway to detailed experimental and simulation studies of the onset of turbulence on the level of the carriers of the turbulent interactions, i.e., the microparticles. Published by the American Physical Society 2024

Jet-flow coupling in heavy-ion collisions and the jetinduced diffusion wake

The diffusion wake accompanying the jet-induced Mach cone serves as a distinctive tool for investigating the characteristics of quark-gluon plasma(QGP) in high-energy heavy-ion collisions. This phenomenon results in a reduction of soft hadrons opposite to the direction of the propagating jet. Our study explores the 3D structure of the diffusion wake induced by γ-triggered jets in Pb+Pb collisions at the LHC energy, utilizing the coupled linear Boltzmann transport and hydro model. We identify a valley structure caused by the diffusion wake, superimposed on the initial multiple parton interaction (MPI) ridge in both rapidity and azimuthal angle. This leads to a double-peak pattern in the rapidity distribution of soft hadrons opposite to the jets. In addition, when jet goes through the QGP medium, it will be affected by the flow velocity. So we take a new method to detect the effect of jet-flow coupling in heavy-ion collisions.

Three-dimensional simulation of laser-induced Mach cones in complex plasmas under microgravity conditions

The three-dimensional density distribution of dust particles in complex plasma under microgravity condition has received much attention. Based on the three-dimensional hydrodynamic simulation, the influences of different coupling parameters, shielding parameters, charge of dust particles and plasma density on the Mach cone by laser-induced are studied in complex plasma under microgravity conditions. When the shielding parameters are large, it is found that three different formulas of coupling parameters <inline-formula><tex-math id="M1">\begin{document}$ \varGamma = \dfrac{{Z_{\text{d}}^{2}{e^2}}}{{d \cdot {T_{\text{d}}}}} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20231849_M1.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20231849_M1.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M2">\begin{document}$ \varGamma ' = \dfrac{{Z_{\text{d}}^{2}{e^2}}}{{d \cdot {T_{\text{d}}}}}\exp ( - \kappa ) $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20231849_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20231849_M2.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M3">\begin{document}$ \varGamma ' = \dfrac{{Z_{\text{d}}^{2}{e^2}}}{{d \cdot {T_{\text{d}}}}}(1{+}\kappa {+}\dfrac{{{\kappa ^2}}}{2})\exp ( - \kappa ) $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20231849_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="8-20231849_M3.png"/></alternatives></inline-formula> have a great influence on the disturbance density of dust particles, and the simulation results are in better agreement with the theoretical expectations under the third formulas. In addition, when the laser radiation force is parallel or vertical to the laser movement speed, the Mach cone structure is symmetrical or antisymmetric in the three-dimensional space, which is mainly based on the asymmetry of the laser disturbance mode. Besides, increasing the shielding parameters, or reducing the charge of dust particles, or reducing the plasma density, the shielding interaction between the dust particles is enhanced, making the Mach cone formed by the dust disturbance density more localized around the laser spot, which is characterized by narrowing the disturbance range and increasing density value. It is expected that this work can provide some reference for the theoretical and experimental studies of laser-induced Mach cone in three-dimensional complex plasma under microgravity conditions.

The optical, seismic, and infrasound signature of the March 5 2022, bolide over Central Italy

On March 5, 2022, a 12 kg meteoroid crossed the sky above Central Italy and was observed by three different observational systems: the PRISMA all-sky camera network (10 stations), the Italian national seismic network (61 stations), and a 4-element infrasound array. The corresponding datasets, each with its own resolution, provided three independent assessments of the trajectory, size and speed of the meteoroid. The bolide traveled across central Italy with an azimuth of 102 degrees, becoming visible at about 91 km above sea level with a velocity of about 15.4 km/s. Its visible trajectory lasted about 15 s. Reasonably, the residual portion of the ablated bolide terminated its path in the Adriatic Sea and could not be recovered. Seismic and infrasound data well match optical observations detecting the bolide Mach cone at 68 km above sea level with a back azimuth of 25 degrees with respect to the array. By comparing results from the three different systems, discrepancies are within the estimated uncertainties, thus confirming the mutual consistency of the adopted methodologies. Therefore, this study shows that different approaches can be integrated to improve the detection capability for bolide crossing the sky in monitored regions.

Deep learning assisted jet tomography for the study of Mach cones in QGP

Mach cones are expected to form in the expanding quark-gluon plasma (QGP) when energetic quarks and gluons traverse the hot medium at a velocity faster than the speed of sound in high-energy heavy-ion collisions. The shape of the Mach cone and the associated diffusion wake are sensitive to the initial jet production location and the propagation direction of the parton shower relative to the radial flow because of the distortion caused by the collective expansion of the QGP and the large density gradient. The shape of jet-induced Mach cones and their distortions in heavy-ion collisions provide a unique and direct probe of the dynamical evolution and the equation of state of QGP. However, it is difficult to identify the Mach cone and the diffusion wake in current experimental measurements of final hadron distributions because they are averaged over all possible initial jet production locations and parton-shower propagation directions. To overcome this difficulty, we develop a deep learning assisted jet tomography which uses the full information of the final hadrons from jets to localize the initial jet production positions. This method can help to constrain the initial regions of jet production in heavy-ion collisions and enable a differential study of Mach-cones with different path lengths and orientations relative to the radial flow of the QGP in heavy-ion collisions.

Three-dimensional Particle-in-cell Simulations of the Solar Wind Interaction with Asteroid 2016 HO3

The recently discovered asteroid 2016 HO3 is the most stable quasi-satellite of our Earth. Several missions to 2016 HO3 have been proposed, including the Tianwen-2 mission of China. Here we study the solar wind interaction with 2016 HO3 with three-dimensional particle-in-cell simulations. It is found that the sunlit surface can be positively charged to more than +10 V, and the shadowed surface is negatively charged to lower than −30 V. The typical electric field on the sunlit surface is about 2 V m−1 but can increase up to 20 V m−1 near the terminator. There is a plasma wake behind 2016 HO3 with a reduced plasma density. Normally, the ion density can be reduced to about 0.3 of the solar wind density at 100 m downstream from 2016 HO3, and the plasma wake is confined by a Mach cone with a cone angle of about 6.°5. In addition, we find that both the solar wind parameters and the secondary electron emission can affect the surface charging, which, in return, changes the wake structure.

Enhanced mixed boundary for modeling infinite domain in 2.5D soil vibration analysis

In this paper, an enhanced mixed 2.5D boundary for treating the infinite domains of the half-space is proposed. Unlike the perfectly matched layer (PML) that has a fixed outer boundary, the proposed method replaces the fixed outer boundary by infinite elements (IFE) to allow waves to propagate uninterruptedly to infinity. Such an approach not only improves the absorption capacity of the PML, but reduces its dependence on the attenuation function. The proposed boundary in the stretched coordinates is formulated in detail, for which the criteria for selecting the reference wavenumbers for multi types of waves are deliberately analyzed. A comprehensive parametric study for assessing the accuracy of the proposed boundary is presented, where the superiority of the proposed boundary relative to the pure PML and IFE is demonstrated. Particularly, the optimal ranges of parameters of the proposed boundary are identified. For illustration, the proposed boundary is applied to analyzing the frequency and time domain responses of a surface train moving at sub- and super-critical speeds. The results indicate that the proposed method can accurately predict the wave propagation characteristics, including the Mach cone at super-critical speeds.

Effectiveness of Cone Angle on Surface Pressure Distribution along Slant Length of a Cone at Hypersonic Mach Numbers

In the present study, the prime attention is to numerically simulate the surface pressure distribution over the slant length of the cone at the various Mach numbers and for the considerable range of semi-cone angles. The Computational Fluid Dynamics (CFD) analysis is used to simulate the surface pressure distribution numerically. The hypersonic Mach numbers, semi-cone angle, and various locations along the slant length of a cone are considered parameters for this research work. The Mach numbers (M) considered for the research work are 5, 7, 9, 11, 13, and 15. The cone angle (θ) from 5° to 25° is considered. The results of pressure (P/Pa) are recorded at various locations (x/L) along the slant length of the cone as 0.1 to 1. The pressure distribution results are obtained by CFD analysis and compared with the analytical results available in the literature for Mach number 5. The findings obtained by CFD analysis and analytical results show good agreement. In this investigation, it is observed that the Mach number, cone angle, and slant length of the cone are the highly influential parameters for the surface pressure distribution. The pressure distribution over the slant length of the cone increases with an increase in the Mach number and the semi-cone angle.

Artificial neural network-based streamline tracing strategy applied to hypersonic waverider design

Streamline tracing in hypersonic flows is essential for designing a high-performance waverider and intake. Conventionally, the streamline equations are solved after obtaining the velocity field over a basic flow field from simplified flow differential equations or three-dimensional computational fluid dynamics. The hypersonic waverider shape is generated by repeatedly applying the streamline tracing approach along several planes. This approach is computationally expensive for iterative waverider optimization. We provide a novel strategy where an Artificial Neural Network (ANN) is trained to directly predict the streamlines without solving the differential equations. We consider the standard simple cone-derived waverider using Taylor–Maccoll equations for the conical flow field as a template for the study. First, the streamlines from the shock are solved for a wide range of cone angle and Mach number conditions resulting in an extensive database. The streamlines are parameterized by a third-order polynomial, and an ANN is trained to predict the coefficients of the polynomial for arbitrary inputs of Mach number, cone angle, and streamline originating locations. We apply this strategy to design a cone-derived waverider and compare the geometry obtained with the standard conical waverider design method and the simplified waverider design method. The ANN technique is highly accurate, with a difference of 0.68% from the standard method in the coordinates of the waverider. The performance of the three waveriders is compared using Reynolds averaged Navier–Stokes simulations. The ANN-derived waverider does not indicate severe flow spillage at the leading edge. The new ANN-based approach is 20 times faster than the standard method.

Sonic boom, more than two centuries of investigation !

Seventy-five years ago, Chuck Yeager on Bell-X1 broke the sound barrier. Five years later, Whitham published his seminal paper linking the shape of a supersonic body to its boom. In 1962, the French-British agreement was signed, launching the Concorde program. First flight occurred seven years later, a climax period for sonic boom research, before its current renewal following the first SSBD demonstration of in-flight boom reduction in 2003. Before this "golden-age", sonic boom, though not known under this name, was not ignored. Booms from meteoroids may have been one of the clues proving their extraterrestrial origin (Biot, 1803) following the hypothesis of Chladni (1794). Infrasound of great Siberian meteorite was recorded in 1908. Shock from the tip of a cracking-whip, the oldest human-made supersonic object, was visualised by Carrière's schlieren shadow photographies in 1927. This method was already used by Mach in 1887, exhibiting the conical shockfront produced by a bullet, now bearing his name but earlier conceptualised by Doppler. During World War One, trying to localise acoustically artillery guns, Esclangon established the modern ray-tracing equations launched from the Mach cone of a supersonic gun shell. The paper will briefly discuss these early works and some others.

3D Structure of Jet-Induced Diffusion Wake in an Expanding Quark-Gluon Plasma.

The diffusion wake accompanying the jet-induced Mach cone provides a unique probe of the properties of quark-gluon plasma in high-energy heavy-ion collisions. It can be characterized by a depletion of soft hadrons in the opposite direction of the propagating jet. We explore the 3D structure of the diffusion wake induced by γ-triggered jets in Pb+Pb collisions at the LHC energy within the coupled linear Boltzmann transport and hydro model. We identify a valley structure caused by the diffusion wake on top of a ridge from the initial multiple parton interaction (MPI) in jet-hadron correlation as a function of rapidity and azimuthal angle. This leads to a double-peak structure in the rapidity distribution of soft hadrons in the opposite direction of the jets as an unambiguous signal of the diffusion wake. Using a two-Gaussian fit, we extract the diffusion wake and MPI contributions to the double peak. The diffusion wake valley is found to deepen with the jet energy loss as characterized by the γ-jet asymmetry. Its sensitivity to the equation of state and shear viscosity is also studied.

Revealing the role of forests in the mobility of geophysical flows

Forests cover 39% of low-altitude mountainous areas globally, and they are considered natural barriers against geophysical flows. Owing to the complexity of flows, the protective effects of forests can hardly be considered in hazard management. In this study, the interactions between granular geophysical flows and forests are explored using a MPM-DEM simulator from a viewpoint of supersonic bow shocks. We show that bow shocks can be approximated by a non-linear analytical framework based on the Mach cone theory. To generate evidence of flow–forest interactions, a new experimental model forest is built. Then, a computational model of granular impact on trees is calibrated and solved by the MPM-DEM method. The results reveal that interactions between overlapping bow shocks considerably affect the flow mobility. Bow shocks either reduce flow momentum or concentrate momentum to increase the runout distance by a factor of up to 1.5 compared with the runout distance of a non-forested area. The revealed bow shock effects on flow momentum can guide the assessment of cultivated forests in impeding geophysical flows. The revealed bow shocks and their ability to change the flow runout highlight the need to explore new models other than classical models based only on basal friction.

Modeling regional propagation of infrasonic Mach cone energy from a supersonic source

Supersonic sources such as bolides, aircraft, and rocket launches are known to produce a wide range of acoustic and infrasonic signals. The lower frequency infrasonic component of these signals can propagate large distances through the atmosphere due to the decreased thermo-viscous losses at low frequency and presence of temperature and wind induced infrasonic waveguides so that signals are often detected at regional distances of hundreds of kilometers. The dominant radiator of energy from such sources is the Mach cone signal that emanates from the source with very specific geometry. Ray tracing analysis using a Mach cone source model to predict infrasonic signals at regional distances will be presented and several parametric studies and comparisons with observed signals from several representative supersonic sources will be presented.

Investigation on anti-penetration capability of water filled aluminum alloy cell structure to the shaped charge jet

Passive protective armor is reliable and cheap, and is favored by many armored weapons and equipment. However, reports on metal-liquid composite armor are not sufficient and systematic. Based on the shaped charge jet (SCJ), the anti-penetration capabilities of water filled aluminum alloy cell structure were studied. The hourglass cell structure (HCS) was designed according to the shock wave propagation characteristics in liquid, and the expansion-convergence cell structure (E-CCS) was derived. Based on the virtual origin theory, the residual tip velocity of jet after SCJ penetrated the cell structure was calculated. According to the theory of supersonic disturbance propagation, the Mach cone half angle of SCJ shock wave propagation in liquid was defined and corrected. The propagation and reflection behavior of shock wave were discussed to analysis the radial convergence of liquid. Via the Van Leer Arbitrary Lagrangian Euler finite element simulation model verified by experiments, the simulation studies of SCJ penetrated the circular cell structure (CCS), HCS, E-CCS and convergence/expansion multi-cell structure were performed. The results show that HCS has better effect of interfering with SCJ than that of CCS and E-CCS. An important discovery is that when the liquid composite multi-cell structure is penetrated by SCJ, the attacked cell will not affect other cells due to the shock wave has been trapped in a single cell.

Three-dimensional wavefront modeling of secondary sonic booms

There is an abundance of previous work in the literature regarding the Mach cone of a supersonic vehicle and its associated ground intercepts identifying where and when the primary sonic boom reaches the ground. Likewise, there is excellent past research that models where the secondary sonic boom reaches the ground due to the reflection and refraction of the sonic boom emanating from above and below a supersonic vehicle. This work will provide a bridge between the two aforementioned aspects of past research. The Mach cone for both above the aircraft and below the aircraft after it reaches the ground will be extended to model the three-dimensional wavefront evolution of the secondary sonic boom as it propagates to the ground. The secondary sonic boom wavefronts modeled in this work will only consist of rays that refract in the vicinity of the stratosphere. The present work will show several cases of the secondary sonic boom wavefront propagation in three dimensions for a variety of aircraft headings and geographic locations around the world with representative upper air temperature and wind conditions.

Fast rupture of the 2009Mw 6.9 Canal de Ballenas earthquake in the Gulf of California dynamically triggers seismicity in California

SUMMARYIn the Gulf of California, Mexico, the relative motion across the North America–Pacific boundary is accommodated by a series of marine transform faults and spreading centres. About 40 M> 6 earthquakes have occurred in the region since 1960. On 2009 August 3, an Mw 6.9 earthquake occurred near Canal de Ballenas in the region. The earthquake was a strike-slip event with a shallow hypocentre that is likely close to the seafloor. In contrast to an adjacent M7 earthquake, this earthquake triggered a ground-motion-based earthquake early warning algorithm being tested in southern California (∼600 km away). This observation suggests that the abnormally large ground motions and dynamic strains observed for this earthquake relate to its rupture properties. To investigate this possibility, we image the rupture process and resolve the slip distribution of the event using a P-wave backprojection approach and a teleseismic, finite-fault inversion method. Results from these two independent analyses indicate a relatively simple, unilateral rupture propagation directed along-strike in the northward direction. However, the average rupture speed is estimated around 4 km s−1, suggesting a possible supershear rupture. The supershear speed is also supported by a Rayleigh wave Mach cone analysis, although uncertainties in local velocity structure preclude a definitive conclusion. The Canal de Ballenas earthquake dynamically triggered seismicity at multiple sites in California, with triggering response characteristics varying from location-to-location. For instance, some of the triggered earthquakes in California occurred up to 24 hr later, suggesting that nonlinear triggering mechanisms likely have modulated their occurrence.