Specific Kinetic Energy Research Articles

Simulation Study on the Average Specific Kinetic Energy and Safety Radius of Stun Grenade Fragments for Different Initiation Point

In order to evaluate the lethality and injury radius of fragments and weaken the average specific kinetic energy, the calculation model of average specific kinetic energy of stun grenade fragments is established based on the Monte Carlo subdivision projection simulation. With the joint simulation method of LS-DYNA and programming, the calculation model of the specific kinetic energy of the semi-prefabricated fragments is solved and compared at different initiation points of the same charge. The mass distribution, vertical target distribution, average specific kinetic energy threshold and safety radius of the whole time-domain fragments at the initiation points 1.5cm, 3cm, 4.5cm, 6cm, 7.5cm and 9cm from the top of the shell are obtained. For the same charge parameters, the results show that the number of fragments near the initiation point of the charge center is less, the mass mean value and standard deviation are larger, and the threshold value of specific kinetic energy is lower than that of both ends of charge; the injury radius of the initiation points 1.5cm, 6cm and 9cm is 4.9m, 2.94m and 4.1m respectively. The initiation point near the charge center can significantly reduce the injury radius of the fragments and improve the safety of the stun grenade.

Effect of elevated pressure on air-assisted primary atomization of coaxial liquid jets: Basic research for entrained flow gasification

Highly resolved numerical simulations have been conducted for a generic, coaxial air-blast atomizer designed for fundamental research of entrained flow gasification processes. Objective of the work is to gain a detailed knowledge of the influence of elevated reactor pressure on the primary atomization behaviour of high-viscous liquid jets. In agreement with measured breakup morphology and breakup regimes proposed in literature, the simulations yield a pulsating mode instability of liquid jet, along with disintegrations of fibre-type liquid fragments for different pressures. From the mechanism point of view, the breakup process has been shown to be triggered by concentric, axisymmetric ring vortices, which disturb the liquid jet surface in a first stage and penetrate further into the intact core, leading to interfacial instabilities and pinch-off of liquid ligaments. The liquid jet breaks up faster at elevated pressure, leading to a shorter core length LC. The calculated exponent (b≈−0.5) of the power law for fitting the decrease of LC with p agrees well with measured correlations from literature in terms of varied momentum flux ratio M and Weber number WeG, although water jets, atmospheric pressure and different air-assisted, external mixing nozzles were used in these works. Therefore, the effect of elevated pressure is equivalent to that of increased M or WeG, which scale linearly with p or the gas density for the current setup. The specific kinetic energy of liquid kL has been found to be increased with p, which is particularly pronounced in the high frequency range. A first-order estimate has been proposed, which can be used for the evaluation of liquid kinetic energy or droplet velocity within the spray. The results have been validated by simulations with twice-refined resolution, yielding a grid-independence behaviour with respect to the primary breakup characteristics. However, the follow-up processes with secondary breakup and spray dispersion are reproduced better by using the finer grid.

Performance optimization of core-shell HMX@(Al@GAP) aluminized explosives

The energy release of aluminized explosives was impeded by the aggregation of aluminum powders, especially for nano-aluminum powders. The core-shell HMX@(Al@GAP) explosives with 5 wt% to 15 wt% aluminum were fabricated, with systematical investigation of morphology, mechanical properties, thermal decomposition, combustion and detonation properties. Compared with the physical mixtures, the aluminized explosives with core-shell microstructure showed better creep resistance and mechanical strength. The thermal decomposition of HMX in core-shell HMX@(Al@GAP) was slightly advanced due to good dispersion of Al@GAP particles. Delayed but more vigorous and longer burning during combustion process was witnessed for the core-shell explosive. For HMX@15 wt%(Al@GAP) aluminized explosives, the detonation velocity and specific kinetic energy was 8567 m/s and 1.412 kJ/g, which was 1.3% and 5.1% higher than the corresponding physical mixtures. The reaction of the core-shell HMX@(Al@GAP) and the physical mixtures were calculated by ReacFF-/g force field, showing remarkable dependent of the average temperature on the microstructure. Present research might provide new insight for synergistically improvement of mechanical and detonation properties in aluminized explosives.

Experiments on burst pressure and fragment dispersion effects of small-sized pressure vessel BLEVE

With the purpose of researching the bursting of a small-sized pressure vessel containing high pressure carbon dioxide (CO2) and the dispersion and distribution of the prefabricated fragments, experimental tests were conducted for pressure vessels with V-shaped grooves and X-shaped grooves. Depending on the experimental results, the rupture positions of the two types grooved pressure vessels were different, and the resistance to the pressure of the V-shaped grooved pressure vessels was higher than the resistance to the pressure of the X-shaped grooved pressure vessels. The maximum burst pressure and the average burst pressure of the V-shaped grooved pressure vessels were both higher than those of X-shaped grooved pressure vessels. For the distribution range of the prefabricated fragments, the fragments were concentrated in the range of the fragment radial scattering azimuth angles from −15° to 15° and the axial scattering azimuth angles was from 65.77° to 113.02°. The initial velocity of a fragment was 272.79 m/s, and the prefabricated fragment with that initial velocity had a residual specific kinetic energy of 101.97 J/cm2 when it dispersed beyond 7 m, which could cause damage to organisms.

Ram Pompasının Basma Hattındaki Su Debisinin Artırılmasına Yönelik Bir Çalışma

Tarımda sulama, zirai ürün fiyatını artışına neden olan girdi maliyetinden biridir. Sulamada kullanılan pompa sadece ürün maliyetini arttırmasının yanında kullanılan fosil yakıtlar nedeniyle çevre kirliliğine de sebep olur. Birçok ülkede sulamada uygulaması görünen RAM pompası suyun herhangi bir yükseklikten pompaya düşmesi ilkesine göre çalışır. Bir su pompası olan RAM pompa mekanizmasına düşen suyun en az onda birini su düşme yüksekliğinin on katına kadar basabilir ve bu işlemi suyun kendi özgül ağırlığı ve kinetik enerjisinden yararlanarak yapmaktadır. Yani suyu terfi ettirmek için herhangi bir fosil yakıt ve/veya elektrik enerjisi sarf etmemektedir. Böylece bu pompa ile terfi ettirilen su yüksek bir depoda biriktirilebilir istendiği zaman tarım alanları cazibe ve benzeri yöntemler ile sulanabilir. Bu çalışma ile RAM pompası geliştirilerek, basma debisi %16-%20 oranında artırılmış, pompa imalat maliyeti %50 düşürülmüştür. Böylece geliştirilmiş bu RAM pompa ile herhangi bir enerji kullanmadan suyun bulunduğu yerden daha yüksek yerdeki tarım alanlarına daha fazla suyun daha düşük imalat maliyetiyle iletilmesi sağlanmıştır.

Optimization of the specific kinetic energy of the pre-grooved stun grenade fragments based on HyperMesh, LS-DYNA and Matlab

Large-scale fragments formed by packaging shell of stun grenade are easy to cause irreversible damage to human body in close range. In order to reduce the specific kinetic energy of shell fragments as much as possible, the pre-grooving method is proposed to optimize the safety of packaging shell. According to the process of fragment forming, flying and impacting, the shell breaking model, fragment dispersion model and average specific kinetic energy calculation model are established respectively. The non-grooved shell and inner grooved shell are simulated by the joint simulation method of HyperMesh, LS-DYNA and Matlab. The fragment mass distribution, initial velocity and average specific kinetic energy are obtained and compared. The results show that under the same main charge parameters, the mass distribution of fragments is more concentrated and the large mass fragments are less in the inner grooved shell than in the non-grooved shell; the average initial velocity of fragments in the inner grooved shell is lower than that in the non-grooved shell; the attenuation of average specific kinetic energy in the inner grooved shell is faster than that in the non-grooved shell, which is safer than that in the non-grooved structure.

The rise and fall of an extraordinary Ca-rich transient

This work presents the observations and analysis of ATLAS19dqr/SN 2019bkc, an extraordinary rapidly evolving transient event located in an isolated environment, tens of kiloparsecs from any likely host. Its light curves rise to maximum light in 5−6 d and then display a decline of Δm15 ∼ 5 mag. With such a pronounced decay, it has one of the most rapidly evolving light curves known for a stellar explosion. The early spectra show similarities to normal and “ultra-stripped” type Ic SNe, but the early nebular phase spectra, which were reached just over two weeks after explosion, display prominent calcium lines, marking SN 2019bkc as a Ca-rich transient. The Ca emission lines at this phase show an unprecedented and unexplained blueshift of 10 000–12 000 km s−1. Modelling of the light curve and the early spectra suggests that the transient had a low ejecta mass of 0.2−0.4 M⊙ and a low kinetic energy of (2−4) × 1050 erg, giving a specific kinetic energy Ek/Mej ∼ 1 [1051 erg]/M⊙. The origin of this event cannot be unambiguously defined. While the abundance distribution used to model the spectra marginally favours a progenitor of white dwarf origin through the tentative identification of Ar II, the specific kinetic energy, which is defined by the explosion mechanism, is found to be more similar to an ultra-stripped core-collapse events. SN 2019bkc adds to the diverse range of physical properties shown by Ca-rich events.

Afterglow light curves from misaligned structured jets

ABSTRACT GRB 170817A/GW 170817 is the first gamma-ray burst (GRB) clearly viewed far from the GRB jet’s symmetry axis. Its afterglow was densely monitored over a wide range of frequencies and times. It has been modelled extensively, primarily numerically, and although this endeavour was very fruitful, many of the underlying model parameters remain undetermined. We provide analytic modelling of GRB afterglows observed off-axis, considering jets with a narrow core (of half-opening angle θc) and power-law wings in energy per unit solid angle (ϵ = ϵcΘ−a where Θ = [1 + (θ/θc)2]1/2) and initial specific kinetic energy (Γ0 − 1 = [Γc, 0 − 1]Θ−b), as well as briefly discuss Gaussian jets. Our study reveals qualitatively different types of light curves that can be viewed in future off-axis GRBs, with either single or double peaks, depending on the jet structure and the viewing angle. Considering the light-curve shape rather than the absolute normalizations of times and/or fluxes, removes the dependence of the light curve on many of the highly degenerate burst parameters. This study can be easily used to determine the underlying jet structure, significantly reduce the effective parameter space for numerical fitting attempts and provide physical insights. As an illustration, we show that for GRB 170817A, there is a strong correlation between the allowed values of Γc, 0 and b, leading to a narrow strip of allowed solutions in the Γc, 0–b plane above some minimal values Γc, 0 ≳ 40, b ≳ 1.2. Furthermore, the Lorentz factor of the material dominating the early light curve can be constrained by three independent techniques to be Γ0(θmin, 0) ≈ 5–7.

Simulation of bubble–plate attachment and estimation of induction time using smoothed particle hydrodynamics

Induction time, an important factor in the adhesion process of mineral particles to bubble surfaces, has been determined only by experimental methods that are time consuming and expensive. This study aims to introduce a numerical approach to describe bubble–plate attachment by determining the induction time using smoothed particle hydrodynamics (SPH). Each subprocesses of bubble-plate attachment process including liquid film thinning, liquid film rupture, three-phase contact line extension, and stable three-phase contact line formation are distinguished by both qualitative images and four different specific kinetic energy profiles of simulation results. Most notably, numerical results indicated that our SPH model can successfully simulate a dynamic process of bubble–plate attachment in the context of kinetic time. Both the scale and dependence of the induction time on different bubble sizes agreed well with the experimental results. This approach can thus be the stepping stone for modeling attachment probability and can be further employed for the multiscale modeling of froth flotation.

Use of the optioelectronic ВБХ 731.4 measuring complex in ballistic research

The practice describes the use of certain measuring equipment to determine the affiliation of certain items to firearms. The author analyzes the study of firearms, and conducts an experiment to determine the specific kinetic energy of projectiles to hit a target. To conduct the experiment, the author uses the ВБХ 731.4 measuring complex in accordance with current methods.

Relaxation times and ergodic properties in a realistic ionic-crystal model, and the modern form of the FPU problem

It is well known that Gibbs’ statistical mechanics is not justified for systems presenting long-range interactions, such as plasmas or galaxies. In a previous work we considered a realistic FPU-like model of an ionic crystal (and thus with long-range interactions), and showed that it reproduces the experimental infrared spectra from 1000 K down to 7 K, provided one abandons the Gibbs identification of temperature in terms of specific kinetic energy, at low temperatures. Here we investigate such a model in connection with its ergodic properties. The conclusion we reach is that at low temperatures ergodicity does not occur, and thus the Gibbs prescriptions are not dynamically justified, up to geological time scales. We finally give a preliminary result indicating how the so-called “nonclassical” q-statistics show up in the realistic ionic-crystal model. How to formulate a consistent statistical mechanics, with the corresponding suitable identification of temperature in such nonergodicity conditions, remains an open problem, which apparently constitutes the modern form of the FPU problem.

A Physical Basis for the H-band Blue-edge Velocity and Light-curve Shape Correlation in Context of Type Ia Supernova Explosion Physics

Abstract Our recent work demonstrates a correlation between the high-velocity blue edge, v edge, of the iron-peak Fe/Co/Ni H-band emission feature and the optical light-curve (LC) shape of normal, transitional and subluminous SNe Ia. We explain this correlation in terms of SN Ia physics. v edge corresponds to the sharp transition between the complete and incomplete silicon burning regions in the ejecta. It measures the point in velocity space where the outer 56Ni mass fraction, X Ni, falls to the order of 0.03–0.10. For a given 56Ni mass, M(56Ni), v edge is sensitive to the specific kinetic energy E kin(M(56Ni)/M WD) of the corresponding region. Combining v edge with LC parameters (i.e., s BV , in B and V) allows us to distinguish between explosion scenarios. The correlation between v edge and light-curve shape is consistent with explosion models near the Chandrasekhar limit. However, the available sub-M Ch WD explosion model based on SN 1999by exhibits velocities that are too large to explain the observations. Finally, the subluminous SN 2015bo exhibits signatures of a dynamical merger of two WDs demonstrating diversity among explosion scenarios at the faint end of the SNe Ia population.

The experimental and numerical investigation on the ballistic limit of BB—Gun pellet versus skin simulant

The insufficient recognition of injuries by the BB-gun (regarded as toys for children) has led to its increasing misuse without permission, which has caused many public safety issues. Aiming to enhance the understanding of the injuries by the BB-gun, the experimental and numerical study of BB-Gun pellet penetrating “cowhide + gelatine” composite target was comprehensively carried out. It was confirmed from the experiment that BB-Gun is capable of inflicting severe or fatal wounds to important organs, and perforating the skin or not could be employed to evaluate the safety of BB-guns. Moreover, three forms of ballistic limit (including: velocity, kinetic energy and specific kinetic energy) of typical BB were calculated and analyzed by reasonably validated numerical simulation method. Additionally, a formulation was acquired by dimensional analysis based on the simulation results and was verified to accurately predict the ballistic limit velocity of BB with different mechanical properties. The method may help to improve the understanding on the minimal velocity needed to perforate skin and may be advised as the determination of the safety of BB-gun.

Internal energy and hydrostatic pressure of a quantum relativistic ideal gas

ABSTRACTIn the classical case, the hydrostatic pressure of an ideal gas is defined as being two-thirds of the specific kinetic energy of the gas: , where is the average kinetic energy of the particles. However, this is no longer the case when relativistic cases are considered. Further concerns may be raised by quantum considerations. In the present paper, both pressure and kinetic energy are calculated taking the appropriate averages weighted with the equilibrium distribution function of the gas. For the purpose of this work the quantum relativistic Fermi–Dirac and Bose–Einstein distribution functions, will be considered for the cases of bosons and weakly degenerate fermions. Integration yields results in a closed form containing modified Bessel functions. A large-argument approximation is then taken, leading to an equation of state composed of the classic part plus correction terms.

A study on the comprehension of differences in specific kinetic energy of TKX-50 and HMX from the perspective of gas products.

5,5'-Bitetrazole-1,1'-dioxydihydroxylamine salt (TKX-50), a high-energy energetic material, possesses good safety and energy properties. The energy characteristic data of TKX-50 are commonly generated via theoretical simulation and experimental measurements. Interestingly, the detonation velocity of TKX-50 is higher than HMX, but the specific kinetic energy of TKX-50 is the opposite. Thus, a systematic study on the decomposition mechanism of TKX-50 is important to establish the reasons for this variation in specific kinetic energy. Although the thermal decomposition mechanism of TKX-50 has been reported, the specific compositional changes of its gas products under different heating conditions remain unknown, hindering a comprehensive understanding of the mechanism from the perspective of gas products. Herein, the gas products of TKX-50 and HMX in thermal decomposition and thermal explosion are investigated and compared. It was found that more TKX-50 is converted to ABTOX for further decomposition when the heating rate increases. ABTOX can decompose to C2N2, which is prone to polymerization, generating a solid residue under high temperature and pressure. Although polymerized C2N2 decomposes and burns during the explosion, it delays the time of TKX-50 reaching its maximum amount of outgassing, thereby affecting its specific kinetic energy. Furthermore, in the thermal explosion, compared with HMX, TKX-50 generates less H2 and CO. Since the combustion heat of hydrogen is much higher than that of carbon, the more hydrogen generated, the higher the detonation heat obtained. Therefore, TKX-50 has a lower detonation heat, which also affects its specific kinetic energy.

Horizontally polarized shear waves in stratified anisotropic (monoclinic) media

The dispersion relations are derived for the horizontally polarized shear (SH) waves in stratified anisotropic plates with arbitrary elastic anisotropy. Analytical expressions for the vectorial group and ray velocities of SH waves propagating in anisotropic layers with monoclinic symmetry are obtained. Closed form relations between velocities and specific kinetic and strain energy for SH waves are derived and analyzed.

Optimization of an inerter-based vibration isolation system and helical spring fatigue life assessment

This paper presents an analytical analysis and optimization of vibration-induced fatigue in a generalized, linear two-degree-of-freedom inerter-based vibration isolation system. The system consists of a source body and a receiving body, coupled through an isolator. The isolator consists of a spring, a damper, and an inerter. A broadband frequency force excitation of the source body is assumed throughout the investigation. Optimized system, in which the kinetic energy of the receiving body is minimized, is compared with sub-optimal systems by contrasting the fatigue life of a receiving body helical spring with several alternative isolator setup cases. The optimization is based on minimizing specific kinetic energy, but it also increases the number of cycles to fatigue failure of the considered helical spring. A significant portion of this improvement is due to the inclusion of an optimally tuned inerter in the isolator. Various helical spring deflection and stress correction factors from referent literature are discussed. Most convenient spring stress and deflection correction factors are adopted and employed in conjunction with pure shear governed proportional stress in the context of high-cycle fatigue.

Development of customised 3D printed biodegradable projectile for administrating extended-release contraceptive to wildlife

Customisation of sustained and controlled release of contraceptives plays a key role in veterinary applications. A biodegradable projectile containing different doses of contraceptive progesterone was prepared using fused deposition modelling 3D printing. Three concentrations of progesterone (2, 5 and 10% w/w) with polylactic acid was prepared as a 1.75 mm filament by hot melt extrusion. Solvent dissolution tests confirmed the successful incorporation of progesterone in the polymer while microscopic (SEM) studies indicated the drug was melted and thoroughly mixed with the polymer matrix and pore-formation after dissolution. A significant suppression of melting temperature of polymer from 166 to 145 °C was noted by thermal analysis (DSC) studies of the drug loaded systems. Interaction between the contraceptive drug and the polymer via hydrogen bonding was revealed from the spectroscopic (FTIR) studies. In vitro release behaviour was assessed over a five-month period, for 2% and 5% progesterone loaded projectiles release profiles fitted zero order whereas 10% loaded projectiles fitted the Higuchi model. Penetration assessment confirmed the drug loaded PLA projectiles provided sufficient specific kinetic energy required to penetrate thin and medium-thickness skins. This work demonstrates the feasibility of fused deposition modelling 3D printing as suitable process for manufacturing ballistic customised drug delivery devices.

Late-time mixing and turbulent behavior in high-energy-density shear experiments at high Atwood numbers

The LANL Shear Campaign uses millimeter-scale initially solid shock tubes on the National Ignition Facility to conduct high-energy-density hydrodynamic plasma experiments, capable of reaching energy densities exceeding 100 kJ/cm3. These shock-tube experiments have for the first time reproduced spontaneously emergent coherent structures due to shear-based fluid instabilities [i.e., Kelvin-Helmholtz (KH)], demonstrating hydrodynamic scaling over 8 orders of magnitude in time and velocity. The KH vortices, referred to as “rollers,” and the secondary instabilities, referred to as “ribs,” are used to understand the turbulent kinetic energy contained in the system. Their evolution is used to understand the transition to turbulence and that transition's dependence on initial conditions. Experimental results from these studies are well modeled by the RAGE (Radiation Adaptive Grid Eulerian) hydro-code using the Besnard-Harlow-Rauenzahn turbulent mix model. Information inferred from both the experimental data and the mix model allows us to demonstrate that the specific Turbulent Kinetic Energy (sTKE) in the layer, as calculated from the plan-view structure data, is consistent with the mixing width growth and the RAGE simulations of sTKE.

SH waves in anisotropic (monoclinic) media

The dispersion relations are derived for SH waves in stratified anisotropic plates with arbitrary elastic anisotropy. Analytical expressions for vectorial group and ray velocities of SH waves propagating in anisotropic layers with monoclinic symmetry are obtained. Closed-form relations between velocities and specific kinetic and strain energy for SH waves are derived and analyzed.