Local Shock Research Articles

Quantitative measure and visualization for local shock strength in two-dimensional flow

Quantitative measure and visualization for local shock strength in two-dimensional flow

Развитие турбулентности за околоземной ударной волной в периоды спокойного и возмущенного солнечного ветра

Magnetosheath is a transition layer between the solar wind and the magnetosphere and may contribute to the geoeffectiveness of various large-scale interplanetary phenomena. In this paper, we examine the dynamics of the turbulent fluctuation spectra behind the bow shock during undisturbed solar wind and when interplanetary coronal mass ejections and corotation interaction regions interact with the magnetosphere. The study is based on statistical analysis of the turbulence features inside the magnetosheath at different distances from the bow shock. We demonstrate that the turbulence features change when plasma crosses the bow shock for the solar wind of all types and they usually recover when plasma moves away from the bow shock. However, peculiarities in the turbulence development occur during interplanetary coronal mass ejections. Moreover, during disturbed solar wind there are relations between the turbulence features at the sub-ion scales and background plasma parameters such as plasma parameter β, the angle θBN between the interplanetary magnetic field and the local bow shock normal, solar wind bulk velocity, and the distance to the magnetosheath boundaries.

Turbulence development behind the bow shock during disturbed and undisturbed solar wind

Magnetosheath is a transition layer between the solar wind and the magnetosphere and may contribute to the geoeffectiveness of various large-scale interplanetary phenomena. In this paper, we examine the dynamics of the turbulent fluctuation spectra behind the bow shock during undisturbed solar wind and when interplanetary coronal mass ejections and corotation interaction regions interact with the magnetosphere. The study is based on statistical analysis of the turbulence features inside the magnetosheath at different distances from the bow shock. We demonstrate that the turbulence features change when plasma crosses the bow shock for the solar wind of all types and they usually recover when plasma moves away from the bow shock. However, peculiarities in the turbulence development occur during interplanetary coronal mass ejections. Moreover, during disturbed solar wind there are relations between the turbulence features at the sub-ion scales and background plasma parameters such as plasma parameter β, the angle θBN between the interplanetary magnetic field and the local bow shock normal, solar wind bulk velocity, and the distance to the magnetosheath boundaries.

Design and characterization of a pyroshock reduction structure based on local resonance mechanisms

In the spacecraft Pyrotechnic shock process, the explosion generated by the strong shock wave and preload force release of the vehicle structure produces a transient, high-frequency, and high-amplitude shock response, resulting in a harsh shock environment prone to failure or damage to many precision equipment or components on the spacecraft, a fatal impact on the launch mission. This paper designed a local resonance shock mitigation structure based on local resonance theory for the Pyrotechnic shock environment and optimized the parameters of the structure by the genetic algorithm. A Pyrotechnic shock simulation experimental device was built to verify the impact reduction effect of the designed shock reduction structure. This experimental device can well restore the pyrotechnic shock environment. In addition, a finite element simulation model was established, and the impact reduction effect of the protective structure was verified both numerically and experimentally. The experimental and numerical analysis results show that the impact response decays significantly in the structural band gap range with the same transfer path, and the shock response spectrum amplitude decreases 9.8 dB in the 100–10,000 Hz frequency band.

A Local Inverse Conical Shock Problem for the Steady Supersonic Potential Flow

A Local Inverse Conical Shock Problem for the Steady Supersonic Potential Flow

Micro-jetting and Transverse Waves in Oblique Detonations

We present a highly-resolved 2D numerical simulation of a wedge-induced Oblique Detonation Wave (ODW) using a 9-species 21-reaction chemical kinetic mechanism for a stoichiometric H2-air mixture. Adaptive Mesh Refinement (AMR) is leveraged to obtain a resolution close to the continuum limit at the finest level (Δxfinest=0.78μm=20λ, where λ is the mean-free path of the fuel–air mixture), which spans the ODW front and its transverse waves. The simulation is performed for a sufficiently large domain, enabling us to unveil the multi-zonal structure of the ODW. We capture, for the first time, the onset of microscopic hypersonic jets (micro-jets) far downstream of the wedge tip associated with cellular structures resembling those of a multi-headed Normal Detonation Wave (NDW). In contrast, the upstream “cell-like” structure (christened as “pseudo-cellular” hence) are found to be devoid of these micro-jets with a morphology similar to that of single-headed NDWs, such as spinning/zig-zag detonations in tubes/2D channels, respectively. A detailed investigation into the transverse-shock structure downstream reveals that a colliding pair of transverse waves lead to the micro-jetting phenomenon. The absence of one of the pair of transverse waves in the upstream region results in the observed pseudo-cellular structures. The origin of these transverse waves in an ODW, unclear in previous literature, is shown to arise from coalescing and strengthening of Compression Waves (CWs) that are produced from two distinct mechanisms. During the “early” phase of the ODW stabilization, CWs are formed as a result of local blast events. In the subsequent “middle” phase, these are formed as a result of the shear-layer instabilities coupling with the local shock structure, leading to the so-called left-running transverse waves (LRTWs) upstream and the right-running transverse waves (RRTWs) downstream. The identified mechanisms offer a plausible explanation on why ODWs exhibit a multi-zonal morphology.Novelty and Significance StatementThe present study is one of the very few studies in the Oblique Detonation Wave (ODW) literature that includes multi-step chemistry while solving for the compressible reacting Navier-Stokes equations on a large simulation domain revealing the multi-zonal structure of the ODW. Furthermore, the resolution employed for the study approaches the continuum limit, making it on-par with the current state-of-the-art for ODW simulation. For the first time, this study has demonstrated the existence of microscopic hypersonic jets (micro-jets) far downstream of the wedge tip in a wedge-induced ODW and a method to isolate them in numerical simulations, leading to insights on the broader micro-jetting phenomenon in detonations. The existence of a cell-like (which we term as “pseudo-cellular”) region bearing similarity with that of single-headed spinning detonations is also noted due to the absence of a transverse wave family upstream. The exact physical mechanisms leading to the formation of transverse waves in ODW are also investigated, which were previously ambiguous in the literature.

Environmental impacts of underground nuclear weapons testing

ABSTRACT Each nuclear weapon test contributes to a global burden of released radioactivity. Between 1945 and 1996, more than 2,000 nuclear tests were conducted, three-quarters of which were underground. Underground nuclear tests involved placing the nuclear device in a cavity drilled or excavated beneath the surface. The goal was to contain the explosion and its effects to the immediate vicinity of the detonation point, ultimately minimizing the release of radioactive materials into the atmosphere. While these tests successfully curtailed the atmospheric release and radioactive fallout, they created dynamic responses within crustal formations caused by local shock waves from the explosion. This paper discusses the legacy of underground nuclear testing, addressing issues from containment failure to the phenomenological effects after underground detonations and the pathways of subsequent dispersal of radionuclides to the environment.

Numerical investigation of optical distortions by turbulent wake and shock wave in the transonic flow

Large eddy simulation with the explicit fifth-order weighted compact nonlinear schemes is performed to investigate the aero-optical distortion caused by a transonic flow over a cylinder at Reynolds numbers of Re = 1 × 105, Re = 2 × 105, and Re = 4 × 105. Proper orthogonal decomposition identifies two dominant modes: the antisymmetric “shifting” mode and the symmetric “breathing” mode, both peaking at the non-dimensionalized Strouhal number StD = 0.18. Optical distortion refers to the phenomenon where a beam passes through a non-uniform and fluctuating flow field, resulting in defocus, jitter, and significant energy reduction. Optical calculations for 12 cases demonstrate that local shock waves and turbulent wakes notably exacerbate optical distortion. In terms of temporal results, the peak frequency of the beam aligns with StD = 0.18 when passing through the cylinder shockwave and falls within StD = 0.16–0.42 as it crosses the shear layer. Significant fluctuations are observed in the turbulent wake and local shock wave, with frequency peaks ranging from StD = 0.12–0.72. Additionally, streamwise flow structures are found to primarily impact optical distortion. Comparative analysis across the three Reynolds numbers indicates that optical distortion is insensitive to Reynolds number variations within the same order of magnitude. The employed grid sufficiently resolves key flow structures impacting beam transmission.

Transition of Edney shock–shock interactions due to the whipping phenomenon of liquid jet in supersonic crossflow

In this paper, we experimentally study the unsteady dynamics of shock–shock interaction between the bow shock generated by a liquid jet in supersonic crossflow (LJISC) and an oblique shock. Images of shock–shock interactions were captured using high-speed focusing schlieren. Due to the whipping nature of the liquid jet, a coupling happens between the instantaneous bow shock shape and violent oscillations of the liquid jet. Proper orthogonal decomposition reveals that the dominant coherent structures of LJISC are convective and flapping modes, and these modes are responsible for unsteady variation in the local bow shock angle. An oblique shock emanating from a wedge is made to interact with the oscillating bow shock of a liquid jet near the sonic line. At this shock interaction location and for a constant momentum flux ratio between liquid jet and crossflow, unsteady transitions between the types of Edney shock–shock interactions were observed. The types of Edney shock–shock interactions that can occur depend on the local average bow shock angle and the momentum flux ratio. Support vector machine (SVM) model was used to classify three types of Edney shock–shock interactions based on ten features related to the nearest knee point, shock interaction point, and maximum penetration height. Using the SVM model, three dominant features that affect the type of shock–shock interaction were identified. Experimental results, when compared with shock polar, reveal some short-duration abnormal presence of overall regular interaction instead of overall Mach interaction regime.

Shockwave velocimetry using wave-based image processing to measure anisotropic shock emission

Noninvasive optical measurements of the shockwave propagation velocity using multiple pulse illumination allow deducing the shockwave pressure amplitude through Hugoniot relations and an appropriate equation of state of the medium. This technique is particularly useful for spatially resolved measurements near the shockwave emission site. Due to diffraction, however, a shockwave front can significantly change its morphology, rendering precise velocity measurements non-trivial. As solution we propose a wave front evolution (WaFE) velocimetry technique, which applies Huygens principle. We take a shadowgraph of the wave front at subsequent times as initial condition for the acoustic Helmholtz equation and numerically propagate the fronts in time. From the instance of time, when two subsequently taken wave front shadows numerically interfere and form one sharp wave front, the local shock velocity is obtained and the local shock pressure amplitude measured. With artificial test images, it is shown that this technique has excellent sub-pixel accuracy, robustness to noise, and can work with low contrast images and even overlapping and interfering wave fronts. The software is made available freely and can be applied to general shock front velocity measurements. We apply WaFE to determine the anisotropic shockwave emission from an elongated laser-induced plasma in water from shadowgraphs of the shockwave front imaged four times onto the same camera frame using multiple pulse illumination at a repetition rate of 60 MHz. The direction dependence of attenuation of the shockwave pressure amplitude is measured at distances of 50–300 μm to the plasma.

Local bow shock environment during magnetosheath jet formation: results from a hybrid-Vlasov simulation

Abstract. Magnetosheath jets are plasma structures that are characterised by enhanced dynamic pressure and/or plasma velocity. In this study, we investigate the formation of magnetosheath jets in four two-dimensional simulation runs of the global magnetospheric hybrid-Vlasov model Vlasiator. We focus on jets whose origins were not clearly determined in a previous study using the same simulations (Suni et al., 2021) to have been associated with foreshock structures of enhanced dynamic pressure and magnetic field. We find that these jets can be divided into two categories based on their direction of propagation, either predominantly antisunward or predominantly toward the flanks of the magnetosphere. As antisunward-propagating jets can potentially impact the magnetopause and have effects on the magnetosphere, understanding which foreshock and bow shock phenomena are associated with them is important. The antisunward-propagating jets have properties indistinguishable from those of the jets found in the previous study. This indicates that the antisunward jets investigated in this paper belong to the same continuum as the jets previously found to be caused by foreshock structures; however, due to the criteria used in the previous study, they did not appear in this category before. These jets together make up 86 % of all jets in this study. The flankward-propagating jets make up 14 % of all jets and are different, showing no clear association with foreshock structures and exhibiting temperature anisotropy unlike the other jets. We suggest that they could consist of quasi-perpendicular magnetosheath plasma, indicating that these jets could be associated with local turning of the shock geometry from quasi-parallel to quasi-perpendicular. This turning could be due to bow shock reformation at the oblique shock caused by foreshock ultralow-frequency (ULF) wave activity.

Shocked quartz in sandstone from the buried Ilkurlka impact structure, Officer Basin, Western Australia

AbstractThe Ilkurlka structure is an ~12 km diameter buried circular aeromagnetic anomaly within the Officer Basin in Western Australia. Prior studies postulated a range of origins, including meteorite impact. We report the presence of pervasive deformation in the first drill cores from the structure. Brecciated sandstone and siltstone contain arrays of quartz grains with concussion fractures and rare shocked quartz grains with planar deformation features (PDF). Universal stage measurements of two quartz grains reveal one grain with PDF parallel to (0001) orientation and three PDF sets parallel to . A second grain contains three PDF sets parallel to and one set parallel to . The shocked grains are interpreted to have formed in situ, rather than representing transported detrital shocked grains. These results suggest local shock compression of at least 10 GPa; however, preservation of primary porosity and overall paucity of shocked grains may indicate lower mean shock pressures. (U‐Th)/He dating of 58 apatite grains from four samples across both cores shows a dominant age population at ~265 Ma and a minor age population at ~135 Ma. These dates overlap with regional events and thus do not provide an unambiguous impact age. An upper Carboniferous to lower Permian maximum impact age is provisionally proposed based on inferred missing target rock stratigraphy.

Do Local and International Shocks Matter in the Interconnectedness amid Exchange Rates and Energy Commodities? Insights into BRICS Economies

The study examined the interdependence structure among energy (brent, natural gas and petroleum) commodities returns, crude oil implied volatility, and exchange rate returns and volatilities in the context of BRICS across time and/or frequencies. The wavelet approaches (bi-wavelet, partial wavelet and wavelet multiple) were employed for the period from May 07, 2012, to March 31, 2021. It was revealed that co-movements between exchange rate returns and energy commodities were negative and significant at certain times and frequencies. In this case, causality emanated from exchange rate returns. Moreover, in most instances, implied volatilities strongly impacted the exchange rate and energy interconnectedness returns. We found strong integration levels among the financial time series with Petroleum having the most likelihood to lead or lag. Findings from the study imply that co-movements between exchange rate returns and energy commodities are heterogeneous and adaptive. Also, local shocks (exchange rate volatilities), have the greatest spillover effect between exchange rate returns and energy commodities relative to implied crude oil volatility. This is the first study that employs the wavelet approaches to investigate the conditional effects of local and external shock on the comovement between exchange rate returns and energy commodities’ returns.

Numerical Investigation of the Dynamic Instability of a Reentry Capsule in Transonic Flow

This study presents a numerical investigation of transonic flow characteristics over a reentry capsule at Mach 1.05, employing a detached eddy simulation. The simulated flowfields demonstrate that the recompression shock wave oscillates back and forth at a Strouhal number of the order of 0.01. Frequency analysis of fluctuations in the drag coefficient and base pressure reveals that these fluctuations can be predominantly attributed to oscillations in the recompression shock wave. While the recompression shock wave propagates upstream, local shock waves occur alternately in the upper and lower free-shear layers, with a Strouhal number of the order 0.1, due to the instability of free-shear layers. The repeated occurrence of these local shock waves causes the recirculation region to shrink, resulting in a decrease in the base pressure. Conversely, while the recompression shock wave propagates downstream, no local shock wave occurs and the recirculation region expands, leading to an increase in the base pressure. These results suggest that the interactions among the recompression shock wave, local shock wave, and free shear layer give rise to fluctuations in the base pressure of the capsule, which in turn can affect its dynamic instability.

Saint‐Pierre‐le‐Viger (L5‐6) from asteroid 2023 CX1recovered in the Normandy, France—220 years after the historic fall of L'Aigle (L6 breccia) in the neighborhood

AbstractOn February 13, 2023, a huge fireball was visible over Western Europe (fireball event 2023 CX1). After the possible strewn field was calculated, the first of several recovered samples, with a mass of about 100 g, was discovered just 2 days after the fireball event on the ground of the village of Saint‐Pierre‐le‐Viger. Meanwhile, more than 60 samples with a total mass of more than 1 kg were recovered and a piece of one of these is studied here. The fall occurred 220 years after the historic meteorite fall of L'Aigle on April 26, 1803, <120 km south. L'Aigle is the closest meteorite fall to Saint‐Pierre‐le‐Viger and belongs to the same chondrite group. Both meteorites are breccias containing only clasts of high metamorphic degree (type 5 and type 6). Since only 20% of the L chondrites are breccias this coincidence is remarkable. As just mentioned, both samples studied from these rocks in this work are ordinary chondrite breccias and consist of equilibrated and recrystallized lithologies of petrologic type 6. The brecciated texture in L'Aigle, resulting in a remarkable light–dark structure, is more pronounced than the brecciated features in Saint‐Pierre‐le‐Viger, from which also type 5 fragments have been reported. The compositions of low‐Ca pyroxene and olivine grains in Saint‐Pierre‐le‐Viger (Fs21.2and Fa23.4, respectively) clearly require an L‐group classification. L'Aigle was classified as an L6 breccia in the past, and this has now been confirmed by new data on low‐Ca pyroxene and olivine (Fs20.7and Fa23.8, respectively). Saint‐Pierre‐le‐Viger contains local thin shock veins, and both meteorites are moderately shocked. Most olivines in the studied samples have planar fractures, but the estimated abundance of mosaicized olivines of 30%–40% among the large grains require a S4 shock classification. Oxygen isotope and bulk chemical data of Saint‐Pierre‐le‐Viger certainly support the L chondrite classification. Bulk spectral data of Saint‐Pierre‐le‐Viger are dominated by silicate minerals, that is, Fe‐bearing low‐Ca pyroxene, olivine, and plagioclase. Isotopic, chemical, and spectral data of the L'Aigle meteorite are shown for comparison and are very similar, providing additional circumstantial evidence of Saint‐Pierre‐le‐Viger's L chondritic nature.

Investigation of multi-stage evaporation and wave multiplicity of two-phase rotating detonation waves fueled by ethanol

In this study, a numerical investigation based on the Eulerian-Lagrangian model is conducted to explore a rotating detonation engine (RDE) fueled by liquid ethanol. The focus is on examining the characteristic phenomena of the two-phase rotating detonation wave (RDW) caused by droplet evaporation and varying inlet conditions. To enhance the evaporation of liquid fuel, pre-heated air is used, and both liquid and pre-vaporized ethanol are simultaneously injected. The distribution of ethanol droplets reveals an initial concentration near the injection surface and accumulation in the fuel-refill zone. Here, liquid droplets gradually evaporate after absorbing latent heat from the surrounding gas. The subsequent interactions between the evaporating droplets and the RDW vary with the droplet size. For droplets with diameters of d0 = 5–15 μm, after being swept by the RDW, a secondary evaporation process occurs, leading to an enlargement of the width of the reaction zone. However, the chemical reactions still predominantly take place in close proximity to the detonation front. As d0 further increases, droplet evaporation persists in the post-detonation expansion zone over a long distance until the remaining droplets are fully evaporated and eventually burned in this region. The study also analyzes the extinction of rotating detonations and the emergence of new detonation waves resulting from local explosions and consequent shock collisions. It is demonstrated that variations in the diameter of injected droplets and inlet temperature can lead to different operating modes with varying numbers of RDWs.

Preface

The 20th Annual International Astrophysics Conference (AIAC) was held at the La Posada de Santa Fe Hotel, Santa Fe, New Mexico, USA from October 31 to November 4, 2022. This year’s meeting followed in the footsteps of 2020’s COVID-19-affected meeting and was the first AIAC since the pandemic. Understandably, the re-opening of the AIAC meetings proceeded cautiously but we are happy to report that the meeting went exceptionally smoothly, safety protocols were followed, and an enjoyable and stimulating meeting was held. Leading the way in ensuring a safe and successful meeting was of course the conference organizer Adele Corona of ICNS and her assistant Kathy Tolbert, and the staff at the La Posada. With the successful conclusion of this meeting, we look forward to a degree of normalcy in organizing meetings and conferences in future.The theme of the 20th AIAC was “From the Depths of the Solar Corona to the Darkness of Interstellar Space: A 20 Year Perspective” with our now traditional format of 25-minute presentations punctuated by selected 40-minute invited talks that explored various themes in greater detail.The intent of the 20th AIAC was twofold – retrospective, celebrating the solar, space, and astrophysical accomplishments of the past 20 years as expressed in the 19 prior AIAC conferences, and perspective, i.e., examining some of the pressing questions that taxed our community over the past 20 years from the perspective of what we think we now know and understand. Since the 19 previous meetings addressed the broad themes of the interaction of the outer heliosphere and the local interstellar medium, shock waves and nonlinear processes, energetic particles, particle acceleration and transport, the heating and physics of the solar corona and solar wind, turbulence processes, and much more, these were the themes of the 20th iteration of the AIAC. A characteristic theme of previous meetings was the universality of many of the physical processes that informed the conference, and this was a central element of the 20th celebration.Finally, let me thank again Adele Corona for another outstanding meeting. Her ability to create and organize superbly run and efficient conferences is unmatched. Likewise, we thank her long-time assistant Kathy Tolbert for her excellent help. Finally, thanks as always to Adele for her help in providing the logistical support for this volume of papers.

High-energy (>40 MeV) Proton Intensity Enhancements Associated with the Passage of Interplanetary Shocks at 1 au

We analyze periods with elevated >40 MeV proton intensities observed near Earth over a time span of 43 yr (1973–2016) that coincide with the passage of interplanetary (IP) shocks. Typically, elevated proton intensities result from large solar energetic particle (SEP) events. The IP shocks observed during these elevated-intensity periods may or may not be related to the origin of the SEP events. By choosing those cases when the shocks can be confidently associated with the solar eruption that generated the SEP event, we analyze the components of these SEP events that are localized in the vicinity of the shock (so-called “energetic storm particles”, ESPs), focusing on those events where the ESP component exceeds 40 MeV. We examine the interdependence of these high-energy ESPs with (i) the properties of the solar eruptions that generated the shocks and the SEP events, and (ii) the parameters of the shocks at their arrival at 1 au. The solar eruptions at the origin of the shocks producing >40 MeV proton ESP intensity enhancements are within ±50° longitude of central meridian and are associated with fast coronal mass ejections (plane-of-sky speeds ≳1000 km s−1). The ESP events with the largest >40 MeV proton intensity increases tend to occur when there are structures such as intervening IP coronal mass ejections and other unrelated shocks present in the solar wind through which the shock is propagating. Among the various local shock parameters considered, only the shock speed shows a certain degree of correlation with the observed ESP intensity increase.

Tests on the incline rectification of suction bucket foundation installation under local cyclic shock loading

ABSTRACT There are many problems with the vertical installation of suction buckets due to the complex ocean wave current and seabed geological conditions. In this paper, a set of tests were developed to study the mechanism of incline rectification of the suction bucket foundation based on resistance-reduced vibration on local side walls (RRV-LSW). In this experiment, the dynamic evolution process of pore water pressure around the suction barrel foundation was monitored from three angles of vibration frequency, initial inclination angle and load, and the influence of local cyclic vibration parameters on the slope velocity of the suction barrel foundation was quantified. The results indicate that a tilted suction caisson foundation can be effectively corrected through lateral wall vibration, and the correction effect is closely related to the vibration frequency, initial tilt angle, and static pressure load.

Effect of inlet Mach number on performance and flow structure of an axial supersonic through-flow fan cascade

Ensuring the high efficiency and stable operation of a supersonic through-flow fan (STFF) in a wide range of inlet Mach numbers is of vital importance. The influence of inlet Mach number (M) ranging from 0.3 to 2.36 on the aerodynamic performance and flow structure in the STFF cascade is studied. The results indicate that at design incidence, the transonic inflow condition has a greater loss, a lower static pressure ratio, and a larger flow turning than the non-transonic inflow condition. The evolution of shock structure with the increasing inlet Mach number is as follows: shock-free → passage quasi-normal shock → leading edge (LE) local normal shock + λ shock → LE normal shock + trailing edge (TE) fishtail shock → LE bow shock + TE fishtail shock + multiple reflected oblique shocks → multiple oblique shocks. Under subsonic inflow conditions, the blade loss is dominated by boundary layer friction loss and wake loss. Under transonic inflow conditions, when the inlet Mach number rises from 0.66 to 0.86, the rear branch of passage λ shock impinges on the thickened separation region of the adjacent blade. This increases the loss. When the inlet Mach number rises to 1.06, the λ shock evolves into fishtail shocks, and the LE shock becomes stronger, reducing shock loss and separation loss significantly. As the inlet Mach number goes up to 1.26, the LE normal shock evolves into a bow shock, inducing a sharp reduction in LE shock loss. Under the supersonic inflow conditions, when the inlet Mach number rises from 1.96 to 2.36, the loss variation is mainly stemmed from LE bluntness loss, accounting for 66% of overall loss change.