Large Amount Of Kinetic Energy Research Articles

Ultrastretchable Helical Carbon Nanotube-Woven Film.

Helical carbon nanotube (HCNT) is regarded as one of the most promising nanomaterials due to its excellent tensile strength and superhigh stretchability. Here, a novel HCNT-woven film (HWF) is proposed, and its in-plane and out-of-plane mechanical properties are systematically investigated via molecular dynamics (MD) simulation. The MD results show that HWF possesses highly stretchable capability resulting from sliding and straightening of CNT segments, and the maximum tensile strain can reach 2113%. Furthermore, the HWF presents an obvious tensile mechanical anisotropy. The torsion failure is the main fracture mode when the HWF is stretched along the longitudinal direction. However, when the HWF is stretched along the transverse direction, the fracture is mainly caused by intertube compression. On the other hand, the HWF can dissipate large amount of kinetic energy of projectile via sliding and fracture of HCNTs, leading to high specific penetration energy. This work provides a theoretical guidance for designing and fabricating next-generation superstrong two-dimensional CNT-based nanomaterials.

Magnetic Reconnection in the Wakes of Cosmic Strings

The motion of cosmic strings in the universe leads to the generation of wakes behind them. We study magnetized wakes of cosmic strings moving in the postrecombination plasma. We show that magnetic reconnection can occur in the postshock region. Since the width of the cosmic-string wake is very small, the reconnection occurs over a very short length scale. The reconnection leads to a large amount of kinetic energy being released in the postshock region of the cosmic-string wake. This enhances the kinetic energy released during the reconnection. We make a rudimentary estimate of the kinetic energy released by the magnetic reconnection in cosmic-string wakes and show that it can account for low-energy gamma-ray bursts in the postrecombination era.

CFD modeling of a horizontal wind turbine by utilizing solar nozzle for power production

Abstract In this study, utilizing air velocity by converting wind kinetic energy into mechanical energy due to the converging area, has been numerically studied by proposing a 3D novel model and using ANSYS Fluent 19 software. Solar radiation by using the radiation model (S2S) has been considered to benefit from the heat energy to be converted into kinetic energy of the flow. Ultimate dimensions were calculated for the proposed nozzle is made of glass material. The study concentrates on the utilization of solar nozzles and their effect on wind energy. This study focused on and attempted to increase the local wind velocity (1 m/s) in Kirkuk city in Iraq, to a higher velocity that could produce a large amount of kinetic energy which is then converted to generate power. Hence, increasing the efficiency of the plant. Results showed that wind velocity increases as the heat gain increases and the area decreased. The velocity at the converging position without including the solar radiation model reached about (15.1 m/s), while in the case of enabling the solar radiation, it showed a value of (15.75 m/s). As a result, the power produced from this proposed method has increased by a value of 74 W.

A new experimental method to study the convective heat transfer characteristics of the interior passages of ventilated disc brakes

Vehicle braking systems use sliding friction between discs and pads to convert large amounts of kinetic energy into heat. Thus, sufficient cooling of disc brakes is needed. Convective heat transfer is an efficient way to cool disc brakes and prevent very high temperatures. To enhance convective heat transfer, ventilated disc brakes are commonly used. Therefore, the heat transfer characteristics of the internal passages of ventilated discs are of special interest. This paper describes a new experimental method to study the convective heat transfer characteristics of the interior passages of ventilated disc brakes, in which a wheel rolled a ventilated disc with tapered radial vanes on a circular track to simulate the real working conditions of a ventilated disc brake. The naphthalene sublimation method was used to obtain convective heat transfer characteristics by the heat/mass transfer analogy principle. Different data reduction methods were used to present the experimental results. The correlations among the Nusselt number, Reynolds number and other geometric parameters of the tapered radial vanes are reported in this paper. The results indicate that the heat transfer coefficient has a close relationship with Coriolis acceleration. Thus, this paper reports a correlation between Coriolis acceleration and the convective heat transfer coefficient, which can be used to extend the results obtained by the tested discs to realistic cases.

Exciton properties, optical phonon modes, polaron characteristics and plasma frequency of GaSb upon compression

The pressure dependence of exciton properties, optical phonon modes, polaron characteristics and plasma frequency of GaSb has been investigated using a pseudopotential approach combined with Harrison and Adachi's models. The obtained results show reasonable accord with data available in the literature. The enhanced pressure from 0 to 40 kbar increases the exciton reduced mass monotonously and in a non-linear way. The screening effect makes the Bohr radius much larger than the lattice parameter of these semiconductor materials. The phonon frequency modes increase with increasing pressure. This is due to the pressure effect that brought atoms closer to each other and thus they sit in steeper potential wells. The Fröhlich coupling constant decreases monotonously with increasing pressure. This reflects the reduction of the lattice asymmetrical local deformation when GaSb is subjected to pressure. The applied pressure makes the plasma system of GaSb creates longer wavelengths which give ions a large amount of kinetic energy. The information obtained from this contribution may become good guidance for use of the material in question in several device applications, e.g., in infrared optical sources and thermo photovoltaic systems.

Machine Learning Based Design of Open Cell Foams for Crash Energy Absorption - A Pilot Study

<div class="section abstract"><div class="htmlview paragraph">Cellular solids are excellent energy absorbers and widely applied in the automotive passive safety area. Their microstructures offer the ability to undergo large plastic deformation at nearly constant nominal stress and thus can absorb a large amount of kinetic energy before collapsing to a more stable configuration or fracture. To further improve their performance, it is imperative to develop a systematic design method, to tailor microstructures’ behavior by adjusting their geometric parameters, especially for those with irregular, random shapes.</div><div class="htmlview paragraph">In this research, we proposed a machine learning based method, which combines the finite element (FE) analysis to design open cell foams for crash energy absorption. The foam geometry is generated utilizing a large number of core points and convex polygons, known as the Voronoi diagram, and then converted to the FE model to compute the plateau stress under crush loading. Based on the simulation dataset, principal component analysis (PCA) is performed to significantly reduce the dimension of design variables. Then, the relationship between the structural response and reduced design variables are established using a linear regression function. The results of the case study demonstrate that the proposed method can effectively and efficiently design the cellular energy absorbers with stochastic, truss-type microstructures at a relatively low computational cost.</div></div>

A new criterion of coalescence-induced microbubble detachment in three-dimensional microfluidic channel

This work is motivated by an experiment of microbubble transport in a polymer microfluidic gas generation device where coalescence-induced detachment exhibits. We numerically study three-dimensional microbubble coalescence using the graphics processing unit accelerating free energy lattice Boltzmann method with cubic polynomial boundary conditions. The focus is on the coalescence-induced microbubble detachment (CIMD) in microfluidics. From the experimental observation, we identified that size inequality between two-parent bubbles and the size of the father (large) bubble are key factors to determine if a CIMD will occur. First, the analytical relationship between equilibrium contact angle and dimensionless wetting potential and experimental results of coalescence with and without CIMD are employed for the verification and validation, respectively. From eighteen experimental and computational cases, we derive a new criterion for CIMD: CIMD occurs when the two-parent bubbles are (nearly) equal with a relatively large radius. The underlying mechanism behind this criterion is explored by the time evolution of the velocity vector field, vorticity field, and kinetic energy in the entire coalescence. It is found that the symmetric capillary force drives the formation of vertical flow stream to the horizontal alignment of parent bubbles and the blockage of the downward stream due to the solid interface promotes the intensity of the upward stream. Meanwhile, large-sized parent bubbles transfer a large amount of kinetic energy from the initial free surface energy, which is essential to lead a CIMD in the post-coalescence stage. Such a new criterion is expected to impact the design and optimization of microfluidics in various applications.

Surface and Buried Explosions: An Explorative Review with Recent Advances

Partially or fully buried explosive on detonation releases a large amount of kinetic energy a part of which gets dissipated during creation of crater and the rest gets converted into ground shock. Both phenomena are of complex nature with involvement of non-linearity in both loading and material characteristics. This review aims at providing an insight into mechanisms involved during an event of buried explosion with varying degree of confinement. Factors affecting crater formation and ground shock propagation in media are discussed in detail. An overview of various prediction methods developed over the years based on dimensional analysis and theory of similarity to estimate crater dimensions and magnitude of ground shock and ground motion along with their limitations is presented. Prediction models used to define and optimise rock fragmentation distribution in surface mining operations are additionally reviewed and discussed. Various state-of-the-art experimental and numerical techniques are discussed in brief. Finally, it discusses the challenges involved in both experimental and numerical analysis and thereby provides alternative solutions and suggestions for further investigations in specific areas of lacuna.

Ricochet of steel spheres on sand with varying water content

The explosion of a building generates plenty of debris that flies far away. The flying debris is hazardous because it contains large amounts of kinetic energy. Therefore, determining the safety distance from the debris is essential. However, debris ricochet that collides onto the ground affects the safety distance because the ricochet phenomenon is influenced by the condition of the medium. In this study, experiments and finite element analysis were performed to investigate the ricochet based on the water content of sand. From a direct shear test, the internal friction angle and cohesion of sand were obtained based on the water content. The effects of internal friction angle and adhesion on the yield stress and ricochet were investigated. The results indicated that as the water content increased, the internal friction angle increased and then decreased, and the cohesion continued to decrease. The yield stress was proportional to the internal friction angle and inversely proportional to adhesion. Therefore, lower yield stress resulted in deeper penetration of debris, leading to higher energy loss, which increased the kinetic energy loss factor. Thus, the condition of the medium should be considered for setting a proper safety distance suitable for the surrounding environment of the building.

Design and analysis of a scheme for the naval gun test shell entering the bore

The test shell without projectile belt is widely used in the teaching, inspection and maintenance of modern automatic naval guns. In order to ensure the normal work of each mechanism, it is very important to design the buffer and limit of the test shell during the process of entering the bore. Taking a certain type of medium caliber naval gun as the research object, the design of colloidal fluid damper and cartridge lock was proposed to ensure the reliability of entering the bore and closing the breechblock. By combining the simulation methods of computational fluid dynamics (CFD) and multibody system dynamic (MBD), it was analyzed whether the structural design can meet the engineering requirements. The research results show that the colloidal fluid damper can dissipate a large amount of kinetic energy of the shell, and the cartridge lock can limit the rebound movement. The combination of the two ensures the smooth process of closing the breechblock. The research provides a design method for the process of the test shell entering the bore, and provides theoretical support for the feasibility of the method.

TOLUENIUM AND OTHER GASEOUS METHYLBENZENIUM IONS: COMPLEX INTERPLAY OF PROTONATED ARENES AND CYCLO‐OLEFINS

The development of the current knowledge of the gas-phase chemistry of protonated methylbenzenes, such as toluenium, xylenium and mesitylenium ions, their higher congeners as well as of their mostly cyclo-olefinic isomers by mass spectrometric methodology is presented. Starting from the observation of the characteristic expulsion of dihydrogen from metastable C7 H9 + ions, which is associated with the release of large amounts of kinetic energy, and the composite C- and H-scrambling prior to the loss of methane, in particular, insights into the isomerization scenario of various isomeric C7 H9 + , C8 H11 + , and C9 H13 + ions, based on a large variety of independent techniques, are discussed. Besides isotope labeling and metastable ion methodology, these include flowing afterglow mass spectrometry, gas-phase titration and infrared spectroscopy of mass-selected ions. The particularly complex energy hypersurface of isomerizing and fragmenting toluenium ions, which has been elaborated in various reports over the years, is presented in a combined way to assess the role of protonated cycloheptatriene, norbornadiene, and 6-methylfulvene as well as a number of further C7 H9 + isomers. The formation and nature of C7 H9 + ions generated by fragmentation of various hydrocarbon precursors, such as monoterpenes and adamantane, is also addressed. The contribution of infrared multiphoton dissociation spectroscopy (IRMPD)and tagged-ion infrared photodissociation (IRPD) of the gaseous C7 H9 + ions as compared to the wealth of previous understanding of their chemistry is commented on as well. Finally, remarkable parallels of the gas-phase chemistry of methylbenzenium ions and the role of such species within the cavities of acidic zeolite catalysts in the course of the industrially important methanol-to-hydrocarbon reaction are discussed. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

A triboelectric and pyroelectric hybrid energy harvester for recovering energy from low-grade waste fluids

Low-grade waste energy is widely available in industrial processes, and it typically appears in the form of thermal fluids. Types of technologies are developed for harvesting the thermal energy from these fluids. However, the thermal fluid not only possesses thermal energy, but also contains a large amount of kinetic energy. In this study, a hybrid device is proposed for harvesting both the thermal and kinetic energy of the thermal fluids. A free-standing type triboelectric nanogenerator (TENG) is employed for harvesting the kinetic energy, while a pyroelectric generator (PENG) is used for harvesting the thermal energy. Output performance of discrete water droplets with temperature of 5 °C, 25 °C, 45 °C and 65 °C are compared in both the TENG and PENG devices. The effects of the device inclination angle, and droplet released height are discussed. The analyses are conducted based on high-speed video recording of the droplet dynamics on the device as well as numerical simulation. The results indicate the droplet temperature, device inclination angle and droplet released height affect the droplet dynamics significantly. Further, the variation of droplet dynamics greatly affects the output performance of both the TENG and PENG. The peak output power of the TENG decreases with the increase of droplet temperature, while the output power of the PENG increases with the temperature variation. A hybrid energy harvester was fabricated and a peak power density of 2.6 μW/cm2 was achieved. A maximum energy increment of 238% was obtained by the hybrid harvester, as compared to the pure PENG device. The harvested energy was able to light up 28 commercial LED light bulbs.

Pressure influence on heating of ventilating disc brakes for passenger cars

The braking system is one of the most important elements in vehicle systems from the aspect of vehicle safety, besides the steering system and the internal combustion engine. During the braking process, the disc and pads absorb a large amount of kinetic energy that converted to heat. Owing to this frictional heating, it is necessary to compute the temperature distribution that will be appeared during the braking process, which is the main goal of this research paper. There are many factors that can be influenced to the distribution of frictional heat generated. One of the significant factors is the applied pressure by the brake pad on the braking disc. The results proved that when increased the applied pressure then the frictional heat generated increased too. It was developed a new finite element model based on observed data from real vehicle. It was used ANSYS/WORKBENCH 14.5 software to perform the numerical analysis, module Transient Structural. Parts that are the most disposed to the thermal stress are braking pads. Also, it was found time period from 0 to 0.1 second is the most critical period during the whole braking period, because in this period, temperature rises rapidly, the maximum temperature occurred at 1.338 seconds, and after that it falls.

A developed flywheel energy storage with built-in rotating supercapacitors

Flywheel energy storage can store large amounts of kinetic energy in its rotating parts, but its inertia restricts the rate of power exchange. On the other hand, there is supercapacitor with the ability of exchanging large amounts of instantaneous power. Therefore, the combination of these two systems can significantly improve the dynamic response of conventional flywheel energy storage. This paper proposes a novel design for this combined system in which supercapacitors are located inside the rotating disk. Therefore, supercapacitors can significantly improve the dynamic performance of the flywheel energy storage with trivial effects on its size and weight. Moreover, the ability of rotating supercapacitors to store electrical as well as kinetic energy increases the energy storage capacity of the proposed flywheel energy storage. This developed system with its improved performance can be widely employed instead of the conventional flywheel energy storage in various applications. In this paper, the proposed structures with built-in rotating supercapacitors are mechanically analyzed by CATIA and ABAQUS. In addition, the developed flywheel energy storage, which is equipped with a permanent magnet synchronous machine and its modified indirect vector controller, is simulated in MATLAB/Simulink under various conditions.

Progress and perspective on interactions between ocean and typhoon

Typhoon is one of the most destructive natural disasters on the earth. A lot of fruitful research has been conducted, especially from the perspective of atmospheric sciences. During a typhoon, the ocean also undergoes dramatic variabilities, which can have significant feedbacks to the atmosphere and typhoon. Generally, the sea surface temperatures (SST) decrease and inertial oscillations are greatly enhanced. The fingerprints of typhoon on the ocean are not constrained to the local sea surface, but can be extended to the ocean interior and remote areas, which play an important role in the climate change on a much longer and larger spatiotemporal scales. In addition, the mesoscale eddy accounts for a large amount of kinetic energy in the ocean. Much progress has been achieved on the responses and feedbacks of ocean eddy to typhoon, but it remains a large uncertainty for the ocean-typhoon interaction. Particularly, the three-dimensional structure of ocean eddy during typhoon is unclear due to the lack of observations. Overall, so far, there have been no comprehensive understandings of the ocean-typhoon interactions, which are believed to be a bottleneck for improving the typhoon prediction. Therefore, the mechanisms of ocean-typhoon interactions at various spatiotemporal scales, as well as their contributions to the short-term and long-term typhoon forecast, have become a hot and challenging topic for both the oceanic and the atmospheric sciences. In this paper, recent progress in the ocean-typhoon interactions is reviewed, based on several collaborative projects in China. The foci are on the local responses and feedbacks between mesoscale variabilities in the upper ocean and typhoon, the ocean-typhoon interactions at low frequency and the impacts on global climate, data assimilation during typhoon, and typhoon forecast in the ocean-atmosphere coupled framework. The major challenge to the ocean-typhoon interactions resides in the lack of persistent and reliable observations, especially the synchronized observations in both the ocean and the atmosphere. Some valuable experiments have been conducted recently and are summarized in this study. For example, mooring/buoy arrays are carefully designed and deployed in the northern South China Sea consecutively from 2014 up to now. The monitoring for a long period accumulates very useful in-situ data for the study on the ocean-typhoon interactions. In addition, several novel technics are also proposed and tested recently, such as the one using rocket-deployed dropsondes to obtain vertical profiles in the atmosphere within a typhoon, and the Iridium Argo the sampling frequency of which can be remotely and manually increased when a typhoon is coming. On the mechanisms of ocean-typhoon interaction, a hypothesis of cold suction in the ocean is proposed and examined, which is another avenue for the typhoons impacts on the subsurface in the ocean, except for the traditional concept of heat pump. Evidence for cold suction is found in in-situ observations. The new concept makes the theory for ocean-typhoon interactions more comprehensive. For the practical application, the improvement of typhoon prediction is the golden goal. A lot of efforts have been put into the data assimilation, which synthesizes data from different resources, such as the remote sensing data of the sea surface properties and the Argo data for the ocean interior. Improved data assimilation methods are proposed to facilitate the extreme conditions during typhoon. Until now, most operational typhoon forecast still rely on the atmosphere-only model. Nevertheless, the atmosphere-ocean-wave coupled systems have been established and evaluated. Some improvement has been shown for the operational typhoon forecast. Finally, some key scientific problems and technical challenges are raised in this paper, which are expected to shed light on the future studies on the ocean-typhoon interaction.

Comparing Eddy‐Permitting Ocean Model Parameterizations via Lagrangian Particle Statistics in a Quasigeostrophic Setting

AbstractThis paper uses Lagrangian statistics—absolute dispersion, pair dispersion, and particle forecasting—to compare four eddy‐permitting models of idealized mesoscale ocean dynamics. The baseline model uses scale‐selective biharmonic damping of momentum to keep the velocity field smooth at the grid scale without overly smearing the partially resolved eddies. The second model uses a nonlinear space‐ and time‐varying Leith viscosity to absorb enstrophy near the grid scale without dissipating too much energy. The last two models use a strong biharmonic damping of momentum to keep the velocity field smooth at the grid scale; this dissipates an unrealistically large amount of kinetic energy, and the models add either deterministic or stochastic forcing to reinject this energy at larger scales. These models are called Jansen and Held models after Jansen and Held (2014, https://doi.org/10.1016/j.ocemod.2014.06.002). All four models correctly model the diffusive transport of particles over time scales more than a few weeks, as measured by the Lagrangian absolute dispersion, showing that all models correctly reproduce the large scales of coherent eddies. The Lagrangian relative dispersion (or pair dispersion) is more sensitive to structure at smaller scales in the velocity field. The Leith model has the least‐accurate relative dispersion, while the two Jansen and Held models have the most accurate. In initialized forecast experiments, there is very little difference in performance between the models.

Green energy harvesting from human footsteps

The need for a sustainable green energy is increasing, while the availability of energy itself is not comparable to the needs. One of the most rapid activities in human life is footstepping. The large amounts of kinetic energy in term of pressure force are generated in every footstep activities at the crosswalk space, lecture building, office, shopping centre or market area. As an alternative energy that still has not been exploited, these human steps can be used to power some low voltage loads. In this study, a tile constructed with some piezoelectric transducers are designed and implemented to generate electrical pulses and harvesting human feet step energies. The piezoelectric transducers used in this study is Lead Zirconate Titanate type. From the pizoelectric floor energy harvester system, a tile consists of 20 pieces parallel connected piezoelectric transducer can produce AC voltage up to 71.20 V. While the average generated voltage is 63.98 V. So the average power is 0.0604 watt/10 footsteps. We conclude that this piezoelectric generator can be generated more power when arranged with some tiles arrangement, so we can harvest this energy efficiently.

A velocity map imaging mass spectrometer for photofragments of fast ion beams.

We present the details of a fast ion velocity map imaging mass spectrometer that is capable of imaging the photofragments of trap-cooled (≥7 K) ions produced in a versatile ion source. The new instrument has been used to study the predissociation of N2O+ produced by electric discharge and the direct dissociation of Al2+ formed by laser ablation. The instrument's resolution is currently limited by the diameter of the collimating iris to a value of Δv/v = 7.6%. Photofragment images of N2O+ show that when the predissociative state is changed from 2Σ+(200) to 2Σ+(300) the dominant product channel shifts from a spin-forbidden ground state, N (4S) + NO+(v = 5), to a spin-allowed pathway, N*(2D) + NO+. The first photofragment images of Al2+ confirm the existence of a directly dissociative parallel transition (2Σ+u ← 2Σ+g) that yields products with a large amount of kinetic energy. D0 of ground state Al2+ (2Σ+g) measured from these images is 138 ± 5 kJ/mol, which is consistent with the published literature.

An Efficient Thermo‐Kinematic (ETK) Model for Long‐Time Simulation of High Speed Railway Brake Dynamics

AbstractHigh speed railway brakes transfer a large amount of kinetic energy into heat during the brake operation. Due to its design one major problem is tapered wear, which could significantly reduce brake performance and safety as well as increase aftermarket costs. Modeling and simulation of these brake systems is rather complicated with respect to the coupled multiphysics, multiscaled phenomena, friction and wear, especially on long time scale. Here, we present the so‐called Efficient Thermo‐Kinematic (ETK) model, which include the complexities of the multiphysics of the brake process in the efficient way. Using this model, we are able to proceed the simulation of the brake dynamics in long‐time scale. The partial differential equations are derived based on the coupled manner. The simulation with ETK model shows reasonable results with very fast computational time. The ratio of computing time to real time can reach 1:2000 (with a standard personal computer). Thus, investigations on tapered wear can be performed not only in one brake operation but in many times of brake operations. The simulation results will support the development process of railway brakes in order to mitigate tapered wear of the brake pads. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Short-Term Frequency Response of a DFIG-Based Wind Turbine Generator for Rapid Frequency Stabilization

This paper proposes a short-term frequency-response scheme of a doubly-fed induction generator (DFIG)-based wind turbine generator (WTG) for improving rotor speed recovery and frequency nadir. In the energy-releasing period, to improve the frequency nadir and rotor speed convergence by releasing a large amount of kinetic energy stored in the rotating masses in a DFIG-based WTG, the power reference is increased up to the torque limit referred to the power and reduces along with it for a predefined period which is determined based on the occurrence time of the frequency nadir in a power grid. Then, the reference decreases so that the rotor speed is forced to be converged to the preset value in the stable operating region of the rotor speed. In the energy-absorbing period, to quickly recover the rotor speed, the reference smoothly decreases with the rotor speed and time during a predefined period until it intersects with the maximum power point tracking curve. The simulation results demonstrate that the proposed scheme successfully achieves rapid frequency stabilization with the improved frequency nadir under various wind conditions based on the IEEE 14-bus system.