Kinetic Energy Research Articles

A Systematic Local View of the Long-Term Changes in the Atmospheric Energy Cycle

Abstract The global climatology and long-term changes in the atmospheric energy cycle in the boreal winter are analyzed using a local available potential energy framework using the fifth-generation ECMWF reanalysis data during 1979–2021. In contrast to the classic Lorenz energy cycle, this local framework provides the local information of available potential energy (APE) and its interactions with kinetic energy (KE), allowing the systematic study of barotropic and baroclinic processes. A further systematic decomposition of the APE and KE reservoirs into high- and low-frequency components is conducted to investigate the source and sink terms that account for their spatial variations and long-term changes. The climatology of the local energetic budget terms shows that the interplay between low-frequency APE and KE is mostly over the tropical and polar regions associated with the thermally direct circulation there. Interactions involving high-frequency components are mainly located in the storm-track regions. We show that under recent global warming, a prominent dipolar trend of changes is present over the Asia–Pacific region for all energy forms. The long-term changes in the energy budget reveal how high-frequency APE intensification is due to a stronger conversion from low-frequency APE upstream of the storm track and that this intensification can be compensated by eddy advection away from the storm track, rather than conversion to kinetic energy in the proximity of the mean jet. This provides evidence that a warmer climate substantially affects the energy cycle and, thus, the atmospheric circulation. Significance Statement Potential and kinetic energies are major components of atmospheric circulation. Those energies and their generation, dissipation, and conversions provide insight into the dynamics of atmospheric circulation. The Lorenz energy cycle, based on a global framework, has been fundamental in deepening our understanding of the atmosphere. However, here we use a systematic local framework to gain a better understanding of atmospheric circulation changes and how global warming has affected them. Our study finds a general intensification of the local energy cycle over the last few decades.

Characterizing MICROMEGAS ion detection capabilities at the INFN Pisa ion beam facility

Researchers at INFN Pisa are currently developing a detector based on MICROMEGAS technology, sensitive to atoms with a kinetic energy in the 1-100keV range and operating under low-pressure conditions (100hPa or less). For the detector test, an Ion Beam Facility (IBF) was set up at the INFN laboratory in Pisa in order to have a controlled test bench capable of guaranteeing the stability and repeatability of the measurements. The group effort dedicated to the development of the IBF led to detailed characterization measurements of the MICROMEGAS performance using H2 and He ion beams.

Hydrodynamic analysis of an aquaculture tank-type floating breakwater integrated with perforated baffles

An innovative approach that integrates the floating breakwater (FB) with an offshore aquaculture tank is proposed to enhance economic benefits and hydrodynamic properties. To study the hydrodynamics of the integrated structure, a time-synchronized spatial-separated strategy is proposed and applied to the computational fluid dynamics (CFD) to facilitate the complex coupling between waves, mooring force, sloshing flow with the perforated baffle, and body motion. The mooring constraint was achieved by incorporating the catenary mooring theory, as well as employing the volume-averaged porous theory to simulate the perforated baffle effect to provide a low-energy environment required by aquaculture. Corresponding experimental tests were conducted to validate the reliability of the numerical model. The motion response, transmission and reflection coefficients, and sloshing behavior are analyzed to evaluate the hydrodynamics of the integrated structure. Besides, an index referred to as area-weighted-average velocity is introduced to further quantify the kinetic energy of sloshing flow. Results reveal the proposed aquaculture tank-type floating breakwater (AFB) can serve well as tuned liquid dampers (TLDs) to reduce the roll motion, and greatly improve the wave-attenuating capacity. Furthermore, the perforated baffles effectively weaken the sloshing energy at medium and finite filling depths, which are commonly operating depths for aquaculture in a floating closed containment system (FCCS). Overall, the floating breakwater integrated with the aquaculture tank is feasible due to a series of advantages.

A quadrupole oscillator as an ingtegrable model

A quadrupole oscillator is presented as an integrable model in the Born-Oppenheimer formalism with an electronic Hamiltonian being the quadrupole tensor. The electronic states of present concern are associated with a doubly degenerate positive eigenvalue of the electronic Hamiltonian, and accordingly the nuclear Hamiltonian takes a 2×2 matrix form. While the potential function for nuclear motion is proportional to r2, the kinetic energy operator is rather complicated, containing coupling terms with a Berry connection through adiabatic approximation. The energy eigenvalues, which receive a modification by a Chern number, get closer to those for the 3D isotropic harmonic oscillator if the angular momentum quantum number becomes sufficiently large.

Heat transfer enhancement of solar collector tube enhanced by swirling flow

Heat transfer capability was one of the key factors that restricted the collecting efficiency of the parabolic trough collector tube. In this paper, a swirl-enhanced solar collector tube with a cyclone inserted at the inlet of the metal tube was purposed to improve the heat transfer capability of the collector tube. The cyclone induced a swirling flow and improved the convection inside the tube, thereby enhancing the heat transfer capacity of the tube. The advantage of the cyclone tube was not changing the structure and processing technology of the original heat collector tube. A numerical model was established to study the flow and heat transfer characteristics of the cyclone tube using Ansys CFX software. The results demonstrated that the swirling flow was over a distance exceeding 1 m and the fluctuations in turbulent kinetic energy was within a distance of approximately 0.2 m. The heat transfer capacity was significantly enhanced within this 0.2 m region and the maximum normalized Nusselt number reached 2.81. Finally, the influences of the blade length and the blade numbers on the heat transfer capability were researched. Results showed that cyclone with short blades and more blades resulted in better enhancing effects.

Mode-I dynamic fracture evolution and energy dissipation of basalt fiber reinforced reactive powder concrete

Dynamic fracture experiments on basalt fiber reinforced reactive powder concrete (BFRRPC) were conducted using notched semi-circular bending (NSCB) specimens, aiming to investigate the Mode-I dynamic fracture characteristics. Based on the split Hopkinson pressure bar (SHPB) and digital image correlation (DIC) systems, this study focused on investigating the dynamic fracture toughness, fracture process zone (FPZ), crack propagation, fractal dimension of fracture path, and energy evolution of BFRRPC with different basalt fiber contents. The results show the basalt fiber break, pull-out and interface fracture in the matrix in the microscopic experiment results, which are the intrinsic reasons for the enhancement of fracture toughness in RPC due to the fiber presence. The increases in fracture toughness of BFRRPC range between 24.7% and 42.7%, with a notable enhancement observed when incorporating 1.0% basalt fiber content. The crack and the FPZ tip of BFRRPC can be located effectively by the method of displacement-strain mixed calibration. The addition of 1.0% basalt fiber content effectively delays the crack initiation in specimens, with crack initiation occurring earlier as the loading level increases. The CTOD and FPZ tip opening displacement have nothing to do with the loading level. Basalt fibers can lead to relatively lower and stable fractal dimensions of BFRRPC, effectively reducing the cracking degree and increasing the roughness of cracks. Basalt fiber effectively enhances the fracture energy of RPC. The dissipated energy is mainly composed of the energy consumed by the fracture (fracture energy) of BFRRPC, with the overall residual kinetic energy ratio (the ratio of residual kinetic energy to dissipated energy) generally below 1.90%.

Uma nova formulação para previsão da perfuração de impactos balísticos em concreto

Abstract This work presents a model for determining the depth of projectile perforation based on the RBL formula for ballistic impact, validated with microconcrete specimens made with Portland cement and coarse aggregate of granite and basalt. The model was validated with 7.62 x 51 mm FMJ (Full Metal Jacketed) ammunition on specimens with 5 cm of diameter and a height variation of 5.00 - 10.00 cm The transformation of kinetic energy into heat was found to be one of the forms of energy release. Experimental results showed that the calculation model proposed here predicts penetration depth values closer to the experimental values than current models, which is favorable for the safety.

Discrete variance decay analysis of spurious mixing

This work examines the use of discrete variance decay of tracers to estimate locally in space and time the numerical mixing caused by different processes during a tracer transport step. Expressions for local discrete variance decay (DVD) rates are directly derived from discrete tracer equations without any assumptions on discrete fluxes of the second moment. They relate the DVD rates to the fluxes of the first moment through the faces of scalar control cell. Mixing associated with advective and diffusive fluxes is thus estimated. The new framework avoids the need for second-moment flux definition when solved directly on finite-volume cell faces but still invokes certain second-moment fluxes when the face DVD rates are partitioned to cells sharing the face. These implied discrete fluxes depend on the partitioning and are non-unique. For third- or higher-order advection schemes, the DVD rates are contaminated by dispersive errors intrinsic to the approach, introducing uncertainty to the locality of any estimates produced by it. Additional temporal averaging or coarse-graining is thus necessary. Through the application of this technique, Numerical mixing is found to be correlated with the distribution of eddy kinetic energy. Numerical mixing induced by vertical advection is found to be relatively small and correlated with the distribution of buoyancy fluxes. The explored high-order schemes are found to demonstrate levels of spurious mixing which may locally exceed physical mixing.

Experimental and numerical studies on the hydraulic performance and the internal flow characteristics of lead-bismuth in the main coolant pump of LFR

As the key component of the primary circuit of a lead-cooled fast reactor (LFR), the hydraulic performance and the internal flow characteristics of the main coolant pump (MCP) are significantly important to the long-term safe and efficient operation of LFR. The present study reports an experimental and numerical investigation of the hydraulic performance and the internal flow characteristics of a centrifugal pump, which is considered one of the candidates for the MCP in LFR. Based on the experimental platform of Liquid Metal-Supercritical Fluid coupled heat transfer (LMSF) of Xi’an Jiaotong University, the hydraulic performances of a centrifugal pump like the pump head and its efficiency are studied and the measured data is also used to validate the accuracy of the numerical method which are employed to study the flow characteristics of MCP, as velocity, pressure, turbulent kinetic energy (TKE). The results show that the deviation of experimental and numerical simulation results is less than 5%. The high velocity region in the impeller channel is concentrated near the hub side of the blade inlet, and the significant pressure difference of the blade surface is primarily concentrated in the second half and shroud region. The inlet area of the blade exhibits a concentration of high TKE and the circular distribution of TKE within the impeller exhibits a periodic pattern, with its frequency being consistent with the number of blades.

Experimental and numerical investigations into cold flow characteristics of multiple micro-mixing jets for hydrogen-rich gas turbines

To explore the flow field of micro-mixing jets, cold flow characteristics of a model Micromix burner were investigated by particle image velocimetry (PIV) system and Large-eddy simulation (LES) model. Results show that LES results are in good agreement with experimental results. In the flow field of multiple micro-mixing jets, the jet velocities of nozzles farther away from the burner center have a high increase and decay rate. When the outlet Reynolds number increases, the Reynolds stress increases first and then decreases in the merging region indicating that the velocity fluctuation disappears in the second jet half, but it has little effect on the flow field structure. Comparing the flow fields of round multiple micro-mixing jets, the merging point and combined point in the elliptical jets flow field move backward. Moreover, the maximum velocity for elliptical jets is also faster than the round jets, which is caused by the high turbulent kinetic energy in the elliptical jet flow field. When the tube spacing increases from 2 to 3 times the tube diameter, positions of the two feature points change linearly. Further, the surrounding jets can decrease the velocity attenuation of the center nozzle and elongate the axial length of the two feature regions.

Supercritical n-decane heat transfer in a vertical tube subjected to high-temperature crossflow air

The study presents a numerical investigation of high-temperature supercritical n-decane flowing upward in a tube subjected to non-uniform heating. The aim of the study is to evaluate the heat transfer mechanisms due to the non-uniform heating condition where it can be observed that the radial inner wall temperatures exhibit a typical pendulum-type distribution. In particular, between 140° < θ < 220° (near the cold side of the tube), the temperature at the inner wall is at the lowest and remains essentially constant, which indicates that the n-decane between the hot and cold sides in the tube exhibits poor mixing. Also, the higher the inlet temperature, the more likely heat transfer deterioration (HTD) will occur closer to the tube inlet. Moreover, detailed information on wall temperatures, velocity, and secondary flow of the supercritical n-decane are evaluated and discussed. The results show that Re is affected by the density and kinetic viscosity of n-decane near the pseudocritical temperature so that Re near the wall fluctuates and has an influence on the wall heat transfer in the HTD region. The Pr at the center of the fluid decreases along the axial direction and the fluid boundary layer becomes thinner, resulting in a more pronounced non-uniformity of Pr in the radial direction. Meanwhile, the stability of the turbulent kinetic energy (TKE) distribution and the high intensity of TKE favor the heat transfer of n-decane in the tube.

Characteristics and dynamics of the interannual eddy kinetic energy variation in the Western Equatorial Pacific Ocean

The interannual variations of eddy kinetic energy (EKE) in the western equatorial Pacific Ocean are investigated based on satellite observations and model outputs in this study. Results reveal that the EKE exhibits vigorous interannual variations, especially in the region of North Equatorial Countercurrent (NECC) and north of New Guinea, and the variations differ between the two types of El Niño events. The energy budget diagnosis indicates that the EKE variations are mainly attributed to the barotropic instability associated with the background currents. Specifically, the energetic NECC behaves northward shift and a stronger meander path, which favors the enhancement of EKE variations due to the enhanced barotropic instability. The interannual fluctuations of the strength of the New Guinea Coastal Current/Undercurrent (NGCC/NGCUC) and the eastward current along the equator contribute to the significant EKE interannual variations north of New Guinea. Further, the distinct features of EKE variations in two types of El Niño events are as follows: EKE typically weakens in the western equatorial Pacific during Eastern Pacific El Niño (EP-El Niño) events, whereas it intensifies north of New Guinea during Central Pacific El Niño (CP-El Niño) events. The opposite features north of New Guinea are attributed to the wind work and a stronger eastward current along the equator in CP-El Niño events. These results can contribute to a better understanding of the low-frequency eddy-mean flow interactions.

The Schrödinger Equation Used the Wrong Energy Relationship

According to the energy relationship of the ground state solution of a hydrogen atom using the Schrödinger equation, the kinetic energy of an electron at twice the Bohr radius becomes zero. The electron has zero kinetic energy, which means it is dead, indicating that the energy relationship used in the Schrödinger equation is incorrect. Then, the reasons for both the chaotic energy relationship of the Schrödinger equation and the half frequency problem encountered by Bohr are analyzed. Bohr only considered Coulomb force and established an equation with centrifugal force, but he did not consider Lorentz force. So, the frequency he obtained must be multiplied by 1/2 to match the experimental value. This article also analyzes other issues related to the Schrödinger equation.

Ultra-Low Power Circuit Design Techniques for Audio-Based Environmental Sensing in IoT Networks

Abstract: ULP circuit design consideration is critical in enhancing AS-based ESL in IoT networks essential in designing IoT devices to work with minimal power consumption. These designs enable the sensors to operate continuously interesting environments while at the same time utilizing methods like duty cycling, adaptive sampling, and wake-up circuitries. AFE parts help to minimize pre-ADC signal manipulation within the hardware and true and near-threshold processing, as well as subthreshold processing, decreases the power dissipation even more without affecting utility. Energy harvesting including, solar and piezoelectric handling ensures kinetic energy is accumulated for efficient functioning without batteries. Furthermore, incorporating lightweight machine learning (ML) models allows for audio classification and anomalous event detection on the network edge and with low data transfer. In combination, these developments bring more efficient and resource-saving IoT networks providing essential data for applications in environmental and climate change sensing, smart cities, public safety, and industrial security. This approach is essential when building IoT systems that are to last, to meet the increasing need for intelligent, self-sustaining, energy-efficient systems

Performance analysis of various wall treatments of RANS models for prediction of near-wall turbulence transport characteristics of plane wall jet

PurposeThe present study scrutinizes the relative performance of various near-wall treatments coupled with two-equation RANS models to explore the turbulence transport mechanism in terms of the kinetic energy budget in a plane wall jet and the significance of the near-wall molecular and turbulent shear, to select the best combination among the models which reveals wall jet characteristics most efficiently.Design/methodology/approachA two-dimensional steady incompressible plane wall jet in a quiescent surrounding is simulated using ANSYS-Fluent solver. Three near-wall treatments, namely the Standard Wall Function (SWF), Enhanced Wall Treatment (EWT) and Menter-Lechner (ML) treatment coupled with Realisable, RNG and Standard k-e models and also the Standard and Shear-Stress Transport (SST) k-ω models are employed for this investigation.FindingsThe ML treatment slightly overestimated the budget components on an outer scale, whereas the k-ω models strikingly underestimated them. In the buffer layer at the inner scale, the SWF highly over-predicts turbulent production and dissipation and k-ω models over-predict dissipation. Appreciably accurate inner and outer scale k-budgets are observed with the EWT schemes. With a sufficiently resolved near-wall mesh, the Realisable model with EWT exhibits the mean flow, turbulence characteristics and turbulence energy transport even better than the SST k-ω model.Originality/valueThree distinct near-wall strategies are chosen for comparative performance analysis, focusing not only on the mean flow and turbulence characteristics but the turbulence energy budget as well, for finding the best combination, having potential as a viable and low-cost alternative to LES and DNS for wall jet simulation in industrial application.

Perfecting refrigerator freezers through magnetic resonance velocimetry

Using magnetic resonance velocimetry facilitates precise structural modifications based on flow characteristics and turbulent kinetic energy

The influence of the shock-to-reshock time on the Richtmyer–Meshkov instability in reshock

Experiments on the Richtmyer–Meshkov instability (RMI) in a dual driver vertical shock tube (DDVST) are described. An initially planar, stably stratified membraneless interface is formed by flowing air from above and sulfur hexafluoride from below the interface location using the method of Jones &amp; Jacobs (Phys. Fluids, vol. 9, issue 1997, 1997, pp. 3078–3085). A random three-dimensional, multi-modal initial perturbation is imposed by vertically oscillating the gas column to produce Faraday waves. The DDVST design generates two shock waves, one originating above and one below the interface, with these shocks having independently controllable strengths and interface arrival times. The shock waves have nominal strengths of $M_L=1.17$ and $M_H=1.18$ for the shock wave originating in the light and heavy gas, respectively, with these strengths chosen to result in arrested bulk interface motion following reshock. The influence of the length of the shock-to-reshock time, as well as the order of shock arrival, on the post-reshock RMI is examined. The mixing layer width grows according to $h\propto t^\theta$ , where $\theta _H=0.36\pm 0.018$ (95 %) and $\theta _L=0.38\pm 0.02$ (95 %) for heavy and light shock first experiments, respectively, indicating no strong dependence on the order of shock wave arrival. Volume integrated specific turbulent kinetic energy (TKE) in the mixing layer versus time is found to decay according to $E_{tot}/\bar {\rho }\propto t^p$ with $p_H=-0.823\pm 0.06$ (95 %) and $p_L=-1.061\pm 0.032$ (95 %) for heavy and light shock first experiments, respectively. Notably, the 95 % confidence intervals do not overlap. Analysis on the influence of the shock-to-reshock time on turbulent length scales, transition criteria, spectra and mixing layer anisotropy are also presented.

Strong error bounds for Trotter and strang-splittings and their implications for quantum chemistry

Efficient error estimates for the Trotter product formula are central in quantum computing, mathematical physics, and numerical simulations. However, the Trotter error's dependency on the input state and its application to unbounded operators remains unclear. Here, we present a general theory for error estimation, including higher-order product formulas, with explicit input state dependency. Our approach overcomes two limitations of the existing operator-norm estimates in the literature. First, previous bounds are too pessimistic as they quantify the worst-case scenario. Second, previous bounds become trivial for unbounded operators and cannot be applied to a wide class of Trotter scenarios, including atomic and molecular Hamiltonians. Our method enables analytical treatment of Trotter errors in chemistry simulations, illustrated through a case study on the hydrogen atom. Our findings reveal the following: (i) for states with fat-tailed energy distribution, such as low-angular-momentum states of the hydrogen atom, the Trotter error scales worse than expected (sublinearly) in the number of Trotter steps; (ii) certain states do not admit an advantage in the scaling from higher-order Trotterization and, thus, the higher-order Trotter hierarchy breaks down for these states, including the hydrogen atom's ground state; (iii) the scaling of higher-order Trotter bounds might depend on the order of the Hamiltonians in the Trotter product for states with fat-tailed energy distribution. Physically, the enlarged Trotter error is caused by the atom's ionization due to the Trotter dynamics. Mathematically, we find that certain domain conditions are not satisfied by some states so higher moments of the potential and kinetic energies diverge. Our analytical error analysis agrees with numerical simulations, indicating that we can estimate the state-dependent Trotter error scaling genuinely. Published by the American Physical Society 2024

Kinetic Energy and Angular Momentum of Free Particles in a Class of Rotating Cylindrical Gravitational Waves using the Noether Symmetry Approach

Kinetic Energy and Angular Momentum of Free Particles in a Class of Rotating Cylindrical Gravitational Waves using the Noether Symmetry Approach

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.