Low Kinetic Energy Research Articles

SN 1054 as a Pulsar-Driven Supernova: Implications for the Crab Pulsar and Remnant Evolution

Abstract One of the most studied objects in astronomy, the Crab Nebula, is the remnant of the historical supernova SN 1054. Historical observations of the supernova imply a typical supernova luminosity, but contemporary observations of the remnant imply a low explosion energy and low ejecta kinetic energy. These observations are incompatible with a standard 56Ni-powered supernova, hinting at an an alternate power source such as circumstellar interaction or a central engine. We examine SN 1054 using a pulsar-driven supernova model, similar to those used for superluminous supernovae. The model can reproduce the luminosity and velocity of SN 1054 for an initial spin period of ∼ 14 ms and an initial dipole magnetic field of 1014 − 15 G. We discuss the implications of these results, including the evolution of the Crab pulsar, the evolution of the remnant structure, formation of filaments, and limits on freely expanding ejecta. We discuss how our model could be tested further through potential light echo photometry and spectroscopy, as well as the modern analogues of SN 1054.

Detection of a Planar Tetracoordinate Hydrogen within the Indium Framework by Quantum Dynamics Theory.

In this work, we consider the question how to detect the planar tetracoordination hydrogen geometry which was recently proposed by electronic structure calculations on the In4H+ system (Angew. Chem. Int. Ed. 2024, 63, e202317312; e202400927; e202403214). Keeping the C4v symmetry, a two-dimensional model of In4H+ is designed to build the nonadiabatic Hamiltonian operator with the lowest-lying singlet and triplet states coupled with spin-orbit coupling. The electronic energies in fitting the potential energy matrix are computed at either the MRCI or CCSD (T) level. Having constructed Hamiltonian, the multiconfigurational time-dependent Hartree product method predicts vibrational eigenstates for spectrum and recrossing probability of the proton. These quantum dynamics calculations predict a period of ∼60 fs for the proton recrossing the In4 moiety and further indicate that experimental observation of the D4h geometry for the triplet state is highly probable at room temperature even though the present MRCI and previous CASPT2 calculations (Angew. Chem. Int. Ed. 2024, 63, e202400927) both predict the C4v symmetry. To measure the C4v geometry, a low temperature of ≲30 K could be adopted. Despite the low temperature, the experiment might still miss the C4v geometry due to the nonzero recrossing probability of H at the low kinetic energy region. Further, a new type of hydrogen bonding in the D4h geometry is proposed to explain the interaction between the C4v geometries.

Interatomic and intermolecular decay processes in quantum fluid clusters.

In this comprehensive review, we explore interatomic and intermolecular correlated electronic decay phenomena observed in superfluid helium nanodroplets subjected to extreme ultraviolet (XUV) radiation. Helium nanodroplets, known for their distinctive electronic and quantum fluid properties, provide an ideal environment for examining a variety of non-local electronic decay processes involving the transfer of energy, charge, or both between neighboring sites and resulting in ionization and the emission of low-kinetic energy electrons. Key processes include interatomic or intermolecular Coulombic decay (ICD) and its variants, such as electron transfer-mediated decay (ETMD). Insights gained from studying these light-matter interactions in helium nanodroplets enhance our understanding of the effects of ionizing radiation on other condensed-phase systems, including biological matter. We also emphasize the advanced experimental and computational techniques that make it possible to resolve electronic decay processes with high spectral and temporal precision. Utilizing ultrashort pulses from free-electron lasers, the temporal evolution of these processes can be
followed, significantly advancing our comprehension of the dynamics within quantum fluid clusters and non-local electronic interactions in nanoscale systems.

Atom-Vacancy-Defect-Derived Electric Hysteresis Loops and Stochastic Low-Frequency Noises in Few-Atom Layer MoS2.

Atom-vacancy-defects present in various materials yield numerous interesting physical phenomena, even obstructing high performance in some cases. On the other hand, their valuable applications to novel devices, such as nitrogen vacancy centers in diamond for quantum bits, have gathered significant attention. In particular, these tendencies become more substantial in two-dimensional (2D) (atomically) thin van der Waals layers. However, correlations with various kinds of atom defects are still under exploration. Herein, we find the stochastic behaviors of large hysteresis loops with strong photoresponse in the static electrical properties in few-atom layer semiconductors, molybdenum disulfide (MoS2). The temperature dependence and transmission electron microscopy reveal that they arise from pairs of two neighboring in-plane S-vacancy defects, which predominantly present only around the interface at the MoS2 flake/substrate, with activation energies ∼0.35 eV. The low-frequency (f) (LF) noise measurements clarify a high f shift in the two 1/f2-dependent regimes, implying stochastic behaviors of electric charges through the S-vacancy pairs with high-speed charge(spin) transitions across low kinetic energy barriers between narrow discrete states. The shallow energy sates are formed from the highly uniform S-vacancy pairs interacting with Mo atoms, which act like quantum dots. The observed stochastic operation holds promise for various application, particularly for probabilistic neuromorphic computation in artificial intelligence.

Parametric modeling and optimization of the intake port in a naturally aspirated opposed rotary piston engine across the full speed range

The opposed rotary piston (ORP) engine offers advantages such as compact size, simple structure, and high power density, making it highly promising for long-endurance unmanned aerial vehicles (UAVs). Parametric modeling of intake ports and the investigation of structural parameters on intake characteristics for ORP engines are crucial for improving the intake performance. In this paper, based on the kinematic model of the ORP engine, parametric modeling of the intake and exhaust ports are performed, a 3D numerical model is established to explore the intake characteristics at different engine speeds. The impact of intake delayed closing angle (IDCA), intake inclination angle (IIA), and dual intake ports on the intake characteristics of the ORP engine are investigated. Finally, the combustion characteristics and performance metrics of the engine using optimized intake ports are compared against the baseline intake phase. The results indicate that the CGE and pumping loss of the ORP engine initially increase and then decrease with rising engine speed. The CGE exceeds 92 % at 1000 r·min−1 and 94 % at 5000 r·min−1 when the IDCA are set at 8° and the IIA at −20°. The pumping losses at 4000 r·min−1 and 5000 r·min−1 are reduced by 33.3 % and 30.9 %, respectively, after intake port optimization. The performance metrics at 1000 r·min−1 and 2000 r·min−1 show a slight decline compared to pre-optimization due to lower turbulence kinetic energy (TKE) and intake backflow. However, at 3000–5000 r·min−1, the optimized intake port structure significantly improves performance metrics of the ORP engine.

Deep Kinetic Energy Response to the Variability of the Kuroshio Extension

AbstractThe transfer of energy from the upper to deep oceans is a well‐known and challenging subject in physical oceanography. This research investigates the intricate relationship between surface and deep ocean currents. Utilizing nearly 2 years of observations from the Kuroshio Extension System Study (KESS), our study unveils the deep‐ocean kinetic energy response to the Kuroshio Extension (KE) variability. We introduce the Kuroshio Extension Jet Path Index (KEJPI), which identifies two distinct modes of the KE jet on an intra‐seasonal timescale. Our findings reveal a strong correlation (0.73) between KEJPI and the mean kinetic energy of deep‐ocean geostrophic circulation, suggesting that the KE jet's large amplitude meanders have a significant impact on deep‐ocean kinetic energy. Singular Value Decomposition (SVD) analysis further unveils a co‐evolving spatial pattern between upper and lower ocean kinetic energy. We investigate the dynamic vertical coupling (DVC) mechanism by examining the coherent variation among the sea surface height (SSH), 15°C isotherm (Z15), deep pressure anomaly, and abyssal flow. The KE jet migration can induce net divergence and convergence within the water column, which in turn generates deep‐ocean quasi‐geostrophic currents. These currents show a marked increase in kinetic energy, reaching levels three times higher than the background. This DVC‐driven kinetic energy can further cascade into near‐inertial and high‐frequency internal waves, contributing to abyssal mixing. Our study underscores the role of large current system instabilities in transferring energy to the deep ocean and facilitating deep mixing processes.

Non-Radiative Deactivation in Isolated Quinoline.

The photophysics of the S2 1(ππ*) state of the polycyclic aromatic nitrogen-containing hydrocarbon (PANH) quinoline is investigated in a free jet using a picosecond laser system. A [1 + 1] multiphoton ionization spectrum yields the S2 origin at around 32 200 cm-1 and reveals several vibronic bands. In time-resolved experiments, quinoline is then excited between 312.2 and 279.7 nm. Probe wavelengths of 351 and 263.5 nm are employed. The dynamics is monitored by time-resolved photoelectron imaging. The images reveal a short-lived band at high electron kinetic energies with a ps lifetime and a band at lower electron kinetic energies that shows an offset at long delay times. In comparison with previous work, the offset is assigned to ionization from the T1 state. Lifetimes decrease from 45 ps at the S2 origin to 11 ps at +3550 cm-1. Most likely, the S2 1(ππ*) state deactivates by internal conversion to the S1 1(nπ*) state, followed by intersystem crossing to the triplet manifold.

Predicting particle catchment areas of deep-ocean sediment traps using machine learning

Abstract. The ocean's biological carbon pump plays a major role in climate and biogeochemical cycles. Photosynthesis at the surface produces particles that are exported to the deep ocean by gravity. Sediment traps, which measure deep-carbon fluxes, help to quantify the carbon stored by this process. However, it is challenging to precisely identify the surface origin of particles trapped thousands of meters deep due to the influence of ocean circulation on the sinking path of carbon. In this study, we conducted a series of numerical Lagrangian experiments in the Porcupine Abyssal Plain region of the North Atlantic and developed a machine learning approach to predict the surface origin of particles trapped in a deep-ocean sediment trap. Our numerical experiments support the predictive performance of the machine learning approach, and surface conditions appear to provide valuable information for accurately predicting the source area, suggesting a potential application with satellite data. We also identify factors that potentially affect prediction efficiency, and we show that the best predictions are associated with low kinetic energy and the presence of mesoscale eddies above the trap. This new tool could provide a better link between satellite-derived sea surface observations and deep-ocean sediment trap measurements, ultimately improving our understanding of the biological-carbon-pump mechanism.

Gas-solid flow behavior and heat transfer in a spiral-based reactor for calcium-based thermochemical energy storage

Calcium-based thermochemical energy storage presents a viable solution to bridge the gap between energy supply and demand during periods of off-sunlight due to its high energy density, low cost, and widespread availability. However, this technology faces a challenge in enhancing heat and mass transfer in the reactor, largely due to its low thermal conductivity. This study investigated the flow behavior and heat transfer in a spiral-based reactor, both with and without the inclusion of calcium-based particles during pneumatic conveying. The results indicate that, for flow behavior, the variation in Re number with a limited amount of particle mass in the spiral-based reactor is similar to that without particle conveying, increasing with an increase in gas velocity. However, an increased amount of particle mass can lead to clogging in the spiral-based reactor, resulting in notches in the Re number variation. Furthermore, the kinetic energy variation of calcium-based particles during pneumatic conveying follows four distinct stages: rapid growth, transient stationary, secondary growth, and secondary stationary, which increases with an increase in particle mass and gas velocity. For heat transfer, the temperature remains constant in the spiral-based reactor without particle conveying. However, the variation in gas temperature is opposite to that of particle temperature due to heat transfer between them in the spiral-based reactor during pneumatic conveying. The particle temperature increases with a reduction in particle size and feeding rate, and an increase in gas velocity. Additionally, the heat transfer rate increases with a reduction in particle size and an increase in gas velocity, but the particle feeding rate has a limited effect on heat transfer rate due to the same particle size. Finally, the research on effect of flow behavior on heat transfer suggests that superior heat transfer performance is more readily achieved under the gas-solid flow condition characterized by the lower kinetic energy and larger Re number.

Determining the stopping power of low kinetic energy Ne+ projectiles in self-Assembled monolayers

Neutral impact collision ion scattering spectroscopy (NICISS) is used to measure the energy loss in organic self-assembled monolayers (SAMs) on Au using Ne+ with low kinetic energies from 3 to 5 keV. With increasing film thickness, the energy loss of the projectiles increases because the projectile experiences more collisions with target atoms.Through comparing Monte-Carlo simulations with the NICISS experiments, it was found that contributions from nuclear stopping for Ne+ were significantly larger than for He+ mainly due to the stronger contribution of small-angle scattering of Ne+ making Ne NICISS unsuitable for depth profiling at energies of 5 keV or lower. The measured Ne+ electronic stopping in SAMs is small despite the large atomic number of Ne. Comparing experiments and DFT calculations shows that the latter accurately reproduce stopping powers for Ne+, while SRIM overestimates the stopping power. This contrasts He+ ions, where DFT and SRIM align closely with experiments.

Understanding the Role of Strain on Electrochemical Reaction Kinetics: Oxygen Evolution on Mechanically Strained Rutile TiO2 As a Model System

Electrocatalysis offers a green alternative (when coupled with renewably-sourced electrons) to conventional carbon-intensive chemical fuel and commodity production processes. Electrochemical device efficiency, however, is limited by the sluggish kinetics of multi-electron transfer reactions, such as the oxygen evolution reaction (OER). Theoretical adsorption free energy scaling relationships predict large oxygen evolution overpotentials (>370 mV) for metal oxides performing the adsorbate evolution mechanism, a series of four proton-concerted electron transfer steps.1 Identifying catalyst design strategies that overcome or “break” scaling relations (i.e. strain,2 high entropy alloys,3 non-concerted proton and electron transfer mechanisms4,5) would provide a means to lower kinetic potential energy penalties and enhance the efficiency and economic incentives for further development of renewably-driven electrochemical reactions.Here we investigate the role of mechanically induced strain on the OER activity of polycrystalline rutile TiO2 thin films, grown on the super elastic alloy nitinol (NiTi) and mechanically strained by tensile tester. Our work characterizes how strain manifests in these complex polycrystalline systems with complementary physical characterization techniques (e.g. X-ray diffraction and Raman spectroscopy) and relates strain to OER performance in alkaline electrolytes. We contextualize our results within the framework of conventional adsorption scaling relationships to hypothesize how tensile strain influences reaction intermediate adsorption affinities, inferring implications for the OER kinetics of benchmark IrO2 and RuO2 catalysts that share the same crystal structure as the rutile TiO2 considered here.(1) Jaramillo, T. F.; Nørskov, J. K.; Rossmeisl, J. Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces. ChemCatChem 2011, 3 (7), 1159–1165. https://doi.org/10.1002/cctc.201000397.(2) Khorshidi, A.; Violet, J.; Hashemi, J.; Peterson, A. A. How Strain Can Break the Scaling Relations of Catalysis. Nat Catal 2018, 1 (4), 263–268. https://doi.org/10.1038/s41929-018-0054-0.(3) Kante, M. V.; Weber, M. L.; Ni, S.; van den Bosch, I. C. G.; van der Minne, E.; Heymann, L.; Falling, L. J.; Gauquelin, N.; Tsvetanova, M.; Cunha, D. M.; Koster, G.; Gunkel, F.; Nemšák, S.; Hahn, H.; Velasco Estrada, L.; Baeumer, C. A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation. ACS Nano 2023, 17 (6), 5329–5339. https://doi.org/10.1021/acsnano.2c08096.(4) Grimaud, A.; Diaz-Morales, O.; Han, B.; Hong, W. T.; Lee, Y.-L.; Giordano, L.; Stoerzinger, K. A.; Koper, M. T. M.; Shao-Horn, Y. Activating Lattice Oxygen Redox Reactions in Metal Oxides to Catalyse Oxygen Evolution. Nature Chem 2017, 9 (5), 457–465. https://doi.org/10.1038/nchem.2695.(5) Yoo, J. S.; Rong, X.; Liu, Y.; Kolpak, A. M. Role of Lattice Oxygen Participation in Understanding Trends in the Oxygen Evolution Reaction on Perovskites. ACS Catal. 2018, 8 (5), 4628–4636. https://doi.org/10.1021/acscatal.8b00612.

High-latitude coronal mass ejections on the young solar-like star AB Dor

ABSTRACT AB Dor is a young solar-type star with a surface large-scale magnetic field $10^2$ to $10^3$ times stronger than the that of the Sun. Although strong magnetic fields are thought to inhibit coronal mass ejections (CMEs), dimming signatures typically associated with an eruptive CME were recently observed in AB Dor. The uninterrupted, long-duration dimming signal suggests that a CME took place at a high latitude, where it remained in view as the star rotates. A high-latitude CME is also consistent with observations that indicate that AB Dor hosts polar active regions. To investigate magnetic confinement in AB Dor, we conduct a parametric modelling study of 21 CMEs at latitudes ${\sim} 60^\circ$, varying the location, mass, and magnetic field strength of an injected flux rope. 12 models had the flux rope located in an open magnetic field region, while the remaining nine were in a closed region. Results show that CMEs in open-field regions are in general more likely to erupt. The four eruptive CMEs from closed regions had high free magnetic energies ${\gtrsim} 3\times 10^{35}$ erg, and 10 CMEs predominantly from the closed-field regions (8/10) were confined. CMEs in closed-field regions exhibited lower kinetic energies, since part of the CME energy was expended to overcome magnetic tension and break open the overlying field. In conclusion our work suggests that eruptive CMEs in AB Dor may occur in high-latitude regions of open magnetic field, as the magnetic tension in such regions does not significantly inhibit the eruption.

Dissociative Ionization of the CHBr2Cl Molecule in 800 nm and 400 nm Femtosecond Laser Fields

The dissociative ionization of CHBr2Cl molecules in femtosecond laser fields at 800 nm and 400 nm is investigated to enhance the comprehension of ultrafast dynamics phenomena. The kinetic energy distribution of the resulting ions following photo-dissociation is analyzed using time-of-flight mass spectrometry in combination with DC-sliced ion velocity map imaging. The findings from the experimental study indicate that the presence of low kinetic energy components is attributed to the dissociative ionization processes of CHBr2Cl molecules. The complexity of individual dissociation pathways remains unaffected by the laser fields but is determined by factors such as bond energy, ionization energy of neutral groups, and charge distribution. In the case of 400 nm laser fields, distinct elimination channels enable CHBr2Cl+ ions to circumvent the transition state, leading to the formation of BrCl+ and Br2+ fragments.

Numerical simulation and dynamic experimental investigation on vibration control of a structural system with a stacked single particle‐inerter damper

AbstractTo overcome the deficiencies of large particle radius, strict vibration conditions, and low kinetic energy exchange rate of traditional particle dampers, it is proposed to organically combine the rack and pinion inerter device with a stacked single particle damper (SSPD) to form a novel stacked single particle‐inerter damping system (SSPIS). Based on a detailed analysis of the force state of particles at various stages, the vibration damping mechanism of SSPIS is analyzed, and a mechanical model of a single‐degree‐of‐freedom (SDOF) structure equipped with an SSPIS is established. The numerical simulation and analysis process of SSPIS is provided, and a parametric design method of inerter device based on the structural performance requirements is proposed. The accuracy of the theoretical mechanical model and numerical simulation analysis process of SSPIS is verified through shaking table tests of a single‐story steel frame, and the actual damping control effect of SSPIS on the controlled structure is investigated. Both test and theoretical results show that the numerical simulation analysis process of SSPIS is clear and accurate, and the mechanical model of the SSPIS‐SDOF structural system is highly accurate. The inerter device in SSPIS can significantly improve the momentum exchange efficiency between particles and structures, and SSPIS could adaptively adjust the particle radius size on demand compared with the traditional particle dampers, with a high damping frequency band, and can realize good damping control effect under the earthquake with various types of sites, which has expansive engineering application scenarios.

Transient behaviour analysis in silicon carbide alpha particle detector using TCAD and SRIM simulation

Time response characteristics of α particle detector are crucial for monitoring radiation fields varied with time and its characterization of pulse radiation field. Here, SRIM-informed TCAD simulation is utilized to visually investigate the transient behaviors of carriers and alpha particles in 4H-SiC Schottky barrier detectors for the time response characteristics. We identified external bias voltage and incident particle energy as key factors to influence transient current pulse broadening. Low-energy alpha particles result in low initial kinetic energy of the ionization-generated carriers, leading to transient current broadening and reduced time resolution characteristics. Conversely, high-energy alpha particles ionize carrier with high drift velocity, preventing the broadening effect. Our simulation provides a planform and valuable guidance for optimizing alpha particle detector, selecting appropriate bias voltages, and enhancing time resolution capabilities.

Solid–Liquid Two-Phase Flowmeter Flow-Passage Wall Erosion Evolution Characteristics and Calibration of Measurement Accuracy

Solid–liquid two-phase flowmeters are widely used in critical sectors, such as petrochemicals, energy, manufacturing, the environment, and various other fields. They are indispensable devices for measuring flow. Currently, research has primarily focused on gas–liquid two-phase flow within the flowmeter, giving limited attention to the impact of solid phases. In practical applications, crude oil frequently contains solid particles and other impurities, leading to equipment deformation and a subsequent reduction in measuring accuracy. This paper investigates how particle dynamic parameters affect the erosion evolution characteristics of flowmeters operating in solid–liquid two-phase conditions, employing the dynamic boundary erosion prediction method. The results indicate that the erosion range and peak erosion position on the overcurrent wall of the solid–liquid two-phase flowmeter vary with different particle dynamic parameters. Erosion mainly occurs at the contraction section of the solid–liquid two-phase flowmeter. When the particle inflow velocity increases, the erosion range shows no significant change, but the peak erosion position shifts to the right, primarily due to the evolution of the erosion process. With an increase in particle diameter, the erosion range expands along the inlet direction due to turbulent diffusion, as particles with lower kinetic energy exhibit better followability. There is no significant change in the erosion range and peak erosion position with an increase in particle volume fraction and particle sphericity. With a particle inflow velocity of 8.4 m/s, the maximum erosion depth reaches 750 μm. In contrast, at a particle sphericity of 0.58, the minimum erosion depth is 251 μm. Furthermore, a particle volume fraction of 0.5 results in a maximum flow coefficient increase of 1.99 × 10−3.

Towards ion stopping power experiments with the laser-driven LIGHT beamline

The main emphasis of the Laser Ion Generation, Handling and Transport (LIGHT) beamline at GSI Helmholtzzentrum für Schwerionenforschung GmbH are phase-space manipulations of laser-generated ion beams. In recent years, the LIGHT collaboration has successfully generated and focused intense proton bunches with an energy of 8 MeV and a temporal duration shorter than 1 ns (FWHM). An interesting area of application that exploits the short ion bunch properties of LIGHT is the study of ion-stopping power in plasmas, a key process in inertial confinement fusion for understanding energy deposition in dense plasmas. The most challenging regime is found when the projectile velocity closely approaches the thermal plasma electron velocity ( $v_{i}\approx v_{e,\text {th}}$ ), for which existing theories show high discrepancies. Since conclusive experimental data are scarce in this regime, we plan to conduct experiments on laser-generated plasma probed with ions generated with LIGHT at a higher temporal resolution than previously achievable. The high temporal resolution is important because the parameters of laser-generated plasmas are changing on the nanosecond time scale. To meet this goal, our recent studies have dealt with ions of lower kinetic energies. In 2021, laser accelerated carbon ions were transported with two solenoids and focused temporally with LIGHT's radio frequency cavity. A bunch length of 1.2 ns (FWHM) at an energy of 0.6 MeV u $^{-1}$ was achieved. In 2022, protons with an energy of 0.6 MeV were transported and temporally compressed to a bunch length of 0.8 ns. The proton beam was used to measure the energy loss in a cold foil. Both the ion and proton beams will also be employed for energy loss measurements in a plasma target.

Swimming behaviour of downstream migrating carp in accelerating flows

The downstream migration of fish is impacted by accelerating flow. This study coupled computational fluid dynamics (CFD) modelling and laboratory observations to investigate the effects of two different accelerating flow hydrodynamics on the swimming behaviours of two fish species. The silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) were chosen as target fish species and four hydrodynamic parameters were selected as main indicators to affect fish swimming behaviours. Four specific swimming behaviours were classified in the contraction flume based on fish downstream trajectories. The results indicated that high accelerating flow, low turbulent kinetic energy (Tke ) and shear stress generated the symmetric distribution of fish along two boundaries of the contraction flume. It also indicated that discharge increase would increase the fish entrainment risk from intakes to diversion pipe, while two fish species exhibited different swimming behaviour patterns. Velocity and velocity gradient had more significant effects than other hydrodynamic parameters on fish swimming strategies. There was mutual compensation among fish tail-beat frequency, angle and amplitude. The results illustrated the relationship between the swimming behaviours and hydrodynamics, which could contribute to understanding the fish downstream migration behaviours in accelerating flow.

Dynamic response and damage behavior of impact wear for polycrystalline diamond compact under low kinetic energy impact

Polycrystalline diamond compact (PDC) cutters are the main load-bearing components in shale gas drilling, and their performance significantly affects the efficiency of shale gas extraction. One of the primary reasons for cutter failure is the dynamic impact between the rock and the cutter due to the complex geological conditions of shale gas extraction. Investigating the impact wear behavior and damage mechanisms is vital to designing superior-performing PDC structures and improving their effectiveness in engineering applications. This work investigates the kinetic response and damage behavior of PDCs under low kinetic energy impacts to explain the characteristics and mechanisms of PDC impact wear. The results show that the impact force fluctuates with impact owing to changes in the interface state. Owing to the elastic-plastic properties of PDC, 87 % of the kinetic energy is used for plastic deformation and fracture. Secondly, the contact time and kinetic energy absorption rate only relate to the impact mass. The contact time positively correlates with mass, while the kinetic energy absorption rate changes in the opposite direction. In addition, diamond fracture occurs with a low kinetic energy accumulation of only 0.059 J. Cobalt catalysis and stress effects were found to induce graphitization and carbon rehybridization jointly during impact wear. It is concluded that the PDC impact wear mechanism under low kinetic energy impact is a brittle fracture with a combination of transcrystalline fracture and intergranular fracture. This work provides referable basic research data for designing impact-wear resistant PDC structures and improving the efficiency of shale gas extraction.

Wake Formation Flow Physics and Boundary Layer Analysis on the Sides of the Isosceles Triangular Cylinder with Apex Pointing Downstream

Boundary layer interaction with downstream flow structures was numerically studied to find the region of inactivity behind an 75° isosceles triangular cylinder with apex pointing downstream at intermediate Reynolds numbers (Re = 520, 640, 840 and 1040). The Standard k-ε model in OpenFOAM was used in the study. Numerical results were validated against Particle Image Velocimetry data. Results revealed the stable region of inactivity characterized by low turbulent kinetic energy and vorticity. The onset of secondary vortex and separation point, independent of Reynolds number, was identified. The onset of the secondary vortex was located at (x = 2 mm) from the base and (y = 1.5 mm) from the apex on either side of the cylinder. The ratio of modulus of absolute primary z-component of vorticity, |ω_z^1 |, to the modulus of secondary z-component of vorticity, |ω_z^2 |, was found to be approximately equal to 1.2. This ratio is invariant of the Reynolds number of the study. These findings have practical implications. The unique properties of the inactivity region forms an ideal location that can be used for injecting fluid, placing measurement probe, active flow control and drag reduction. The research problem is formulated in the introduction. Literature is reviewed next providing the background. Details about the range of parameters, governing equations, numerical study details and software used are given in the methodology section. The results section gives the numerical results, verified by mesh refinement test and validated against experimental results. The results are finally discussed in the next section.