Total Kinetic Energy Research Articles

Photodissociation dynamics of H2S+ via the A2A1 (0, 8, 0) state.

The photodissociation dynamics of the hydrogen sulfide cation (H2S+) (X2B1) were investigated using the time-sliced velocity map ion imaging technique. S+ (4Su) product images were measured at four photolysis wavelengths around 393.70nm, corresponding to the excitation of the H2S+ (X2B1) cation to the A2A1 (0, 8, 0) state. The raw images and the derived total kinetic energy releases (TKERs) spectra exhibited partial rotational resolution for the H2 products. A sensitive dependence on the photolysis wavelength was observed in the TKER spectra and anisotropy parameters. Within a narrow excitation energy range of ∼12cm-1, the H2 products showed two distinct rotational excitations. Furthermore, clear differences in anisotropy parameters were observed. These phenomena indicate that the rotational excitation of the H2S+ ions plays a role in the non-adiabatic photodissociation dynamics.

Charge distribution and total kinetic energy in the fission of Rn, Ra and U

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Variable droop gain frequency supporting control with maximum rotor kinetic energy utilization for wind-storage system

To address the emerging frequency stability issue brought by the large replacement of synchronous generators with renewable generations, wind turbine generators are required to possess frequency-supporting capability. However, existing frequency-supporting control strategies lack the assessment of the frequency support capability of wind turbine generators, leading to degraded control performance under various situations. Aiming to solve this problem, this paper proposes a variable-droop-gain control for wind turbine generators with maximum rotor kinetic energy utilization. Firstly, an analytical relationship was established between droop gain, disturbance scale, and rotor speed. Subsequently, the released energy of the wind turbine generator is evaluated, which equals the difference in the rotor kinetic energy under the initial and the post-disturbance steady-state rotor speed. It was proved that the released kinetic energy cannot exceed a certain proportion of total rotor kinetic energy. Accordingly, a variable initial gain scheme is proposed, which determines the initial droop gain as per the disturbance scale for maximizing the kinetic energy release of wind turbines. Moreover, an additional real-time droop gain adjustment rule is added to prevent the over-deceleration of wind turbines. The simulation results show that the proposed scheme may provide the maximum KE release and effectively improve the system frequency nadir while ensuring the safe operation of wind turbine generators.

A DATA DRIVEN METHOD FOR THE DERIVATION OF EXPLICIT ALGEBRAIC REYNOLDS STRESS MODELS APPLIED TO THE WAKE LOSSES OF LOW-PRESSURE TURBINE CASCADES

Abstract This paper introduces and validates a data-driven approach to improve the prediction of linear eddy viscosity models (LEVMs). The general approach is adopted in order to improve the wake mixing of low-pressure turbine (LPT) cascades. The approach follows the rationale applied in the derivation of explicit algebraic Reynolds stress models (EARSMs) by including additional second-order tensors in the Boussinesq assumption. The unknown scalar functions that determine the contributions of each second-order tensor to the Reynolds stresses are approximated as polynomials. A metamodel-assisted multi-objective optimization determines the value of each of the polynomial coefficients by minimizing the difference between the result of the EARSM simulation and reference data provided by a high fidelity large eddy simulation (LES). In this study, tailor made EARSMs are calibrated to improve the prediction of the kinetic energy loss distribution in the wake of the T106C LPT cascade. We investigated the influence of each polynomial coefficient of the EARSM on the results. The models generated by the approach reduced the deviations in total kinetic energy loss between the LES reference solution and the baseline model by approximately 70%. The turbulent quantities are analyzed to identify the physical correlations between the model inputs and the improvement. The transferability of the models to unseen test cases was assessed using the MTU-T161 LPT cascade. In summary, the suggested approach was able to generate tailor made EARSM models that reduce the deviations between RANS and LES for the mixing of turbulent wake flows.

Research on the Influence of Particles and Blade Tip Clearance on the Wear Characteristics of a Submersible Sewage Pump

A submersible sewage pump is designed for conveying solid–liquid two-phase media containing sewage, waste, and fiber components, through its small and compact design and its excellent anti-winding and anti-clogging capabilities. In this paper, the computational fluid dynamics–discrete element method (CFD-DEM) coupling model is used to study the influence of different conveying conditions and particle parameters on the wear of the flow components in a submersible sewage pump. At the same time, the energy balance equation is used to explore the influence mechanism of different tip clearance sizes on the internal flow pattern, wear, and energy conversion mechanism of the pump. This study demonstrates that increasing the particle volume fraction decreases the inlet particle velocity and intensifies wear in critical areas. When enlarging the tip clearance thickness from 0.4 mm to 1.0 mm, the leakage vortex formation at the inlet is enhanced, leading to increased wear rates in terms of the blade and volute. Consequently, the total energy loss and turbulent kinetic energy generation increased by 3.57% and 2.25%, respectively, while the local loss coefficient in regard to the impeller channel cross-section increased significantly. The findings in this study offer essential knowledge for enhancing the performance and ensuring the stable operation of pumps under solid–liquid two-phase flow conditions.

Effects of multi-scale turbulent motions on aerodynamic performance of wind turbine under sand-laden conditions

Wind turbine installation in the desert and Gobi regions offers a promising approach for meeting long-term energy demands. However, the effect of multi-scale characteristics in sand-laden atmosphere flows on wind turbine aerodynamic performance has not been evaluated. In this study, wind velocity data collected from the Qingtu Lake Observation Array (QLOA) were employed to address this gap. Results show that up to 58% of the total turbulent kinetic energy (TKE) is accounted for by very large-scale motions (VLSMs), which make up a considerable portion of the TKE. The contributions of the large-scale motions (LSMs) and the small-scale motions (SSMs) to TKE are 36% and 6%, respectively. The contribution of multi-scale turbulent motions to the aerodynamic loads of wind turbine under sand-laden conditions has been quantified for the first time. The comparison demonstrates that while LSMs and SSMs exhibit a rapid drop in their contributions to wind turbine loads with height, VLSMs show a rapid increase. Wavelet analysis revealed a strong correlation between VLSMs and power, thrust, and blade root flapwise moment at periods ranging from 256 to 1024 s. This correlation weakens as the streamwise length scale of the turbulent coherent structure decreases. This study provides essential insights for optimizing wind turbine design and site selection in sand-laden environments.

A wind farm control strategy for frequency regulation reserve: Optimize wake loss and frequency support capability

—With a high proportion of renewable energy, the issue of grid frequency fluctuations is becoming increasingly prominent. To tackle this challenge, wind farms can enhance frequency regulation response by increasing rotational kinetic energy through overspeed control. However, this approach may result in energy losses due to the wake effect. This paper proposes an optimized configuration strategy for wind farm frequency regulation reserve (FRR), utilizing pitch angle cooperative control to reduce wake losses. The objective is to explore the optimal configuration for maximizing wind energy utilization under FRR conditions. A genetic algorithm is used to find the optimal control parameters in the established FLORIS-based wind farm power reserve wake model, which involves rotor speed and pitch angle control, to maximize output power and rotational kinetic energy. Based on this, a lookup table is constructed to map wind conditions to the optimal control parameters for different FRR level. According to the reserve power schedule, optimization control is applied to the wind farm. Simulation results show that, compared to the traditional equal distribution strategy for FRR power, the proposed control strategy can enhance the total kinetic energy reserve of the wind farm by optimizing wake loss, thereby improving frequency support capability.

Effects of axisymmetric confinement on vortical structures emanating from round turbulent jets

Confined jets occur in many engineering applications including combustion chambers, jet pumps, and chemical reactors. The effects of axisymmetric confinement on the vortical structures identified in a turbulent jet are investigated using large eddy simulation at a Reynolds number of 30 000 (based on nozzle exit conditions) and expansion ratio (chamber-to-nozzle diameter ratio) of five. The results obtained from the confined jet are compared with those of a free jet under the same nozzle exit flow conditions. A prominent recirculation zone forms between the expanding jet and the confining wall, resulting in early shear layer distortion and a shorter interaction length in the confined jet (0.85 jet diameters) compared to the free jet (1.15 jet diameters). Using the λ2 criterion for vortex identification, two dominant structural modes are identified in the near-exit region of the free jet: ring and helical modes. However, in the confined jet, the helical mode is absent, and the turbulent confined fluid accelerates the breakup of the ring vortices. The interaction of the secondary line vortices with the breaking structures leads to the formation of new hairpin-like vortices, which also contribute to further vortex breakup. These results explain the enhanced mixing performance of confined jets as the mixing is directly tied to the breakup of large vortical structures. Proper orthogonal decomposition modes are also presented to identify the structures/events with the highest contribution to the total turbulent kinetic energy in both flow fields.

Electrodynamic model of ball lightning

The paper considers a hypothesis of the structure of ball lightning core as an ensemble of dynamic electric capacitors. The dynamic capacitor is an object consisting of spatially separated charges – electrons and protons. Electrons, due to the action of mutually orthogonal electric and magnetic fields, move in a circle, oscillating in the radial direction. The magnetic field is generated by the movement of protons around the electron ring. The number of protons exceeds the number of electrons, due to which the dynamic capacitor has a positive electric charge. The system of dynamic capacitors is located inside a spherical shell consisting of water molecules polarized in the electric field of the charge of the dynamic capacitor. The shell creates a force that prevents the expansion of dynamic capacitors. It is shown that 1900 dynamic capacitors with a radius of 0.5 cm with a total kinetic energy of 6.36 MJ can fit in ball lightning with an internal shell radius of 6.2 cm. In this case, the energy density in the core of ball lightning can be about 6.4·109 J/m3. This is comparable with the result of measurements of energy density of natural ball lightning.

Effects of structural configuration on perforation/spalling damage and secondary fragment velocity of reinforced concrete slabs subjected to close-in explosion

Reinforced concrete (RC) slabs are vulnerable to localized damage from close-in TNT explosions, suffering perforation and extensive spalling damages that generate high-velocity secondary fragments posing severe risks to nearby facilities and personnel. Current numerical methods such as the Finite Element Method (FEM) face challenges in accurately predicting fragmentation due to mesh distortion caused by large deformations and discontinuities, underscoring the need for enhanced modelling techniques. As a result, although numerous studies have numerically investigated how structural configurations influence RC slab damage under blast loads, the issue of mesh distortion and element erosion in FEM has led to the inability in reliably predicting the associated threats from high-velocity fragments. This study numerically investigates the influences of structural configuration (e.g., concrete strength, reinforcement ratio and layout, dimensions of slabs, and concrete cover depth) on the perforation/spalling area and fragment ejecting velocity of one-way RC slabs subjected to close-in explosions through an ALE-FEM-SPH numerical model, which has been demonstrated effective and reliable in the authors’ previous studies. The results indicate that concrete strength and slab thickness most significantly affect both the damage and fragment characteristics, while the slab's width-to-height ratio, reinforcement ratio, and layout, have less influence, particularly on fragment velocity. Empirical equations derived from extensive numerical data are provided to help engineers and security personnel quickly evaluate the blast effects on RC slabs. The accuracy and robustness of the proposed formulae, which can be straightforwardly used to predict blast fragments of reinforced concrete slabs, have been statistically evaluated and the proposed formulae demonstrate satisfactory precision, with less than 20 % error in estimating damage area, maximum fragment velocity, and total kinetic energy of fragments.

Effect of voltage amplitude and frequency on the characteristic parameters of a piezoelectric actuated micro-blower

Micro-blower is an innovative device that is used for sensitive applications such as electronics cooling, avionics and the medical field. It features a piezoelectric disc (PED)-diaphragm assembly. A 3D computational model of micro-blower is developed and simulated using COMSOL Multiphysics and studied its characteristic parameters such as maximum displacement (w), average velocity (w̅’), maximum von Mises stress (Tv), total kinetic energy (EK), total elastic strain energy (EU) and total electric energy (EE). The frequency-dependent electric potential difference was supplied to the Lead Zirconate Titanate (PZT-5H) PED. Seven different square wave ultrasonic frequencies were used as input for the PED ranging from 22 to 28 kHz, a resonance frequency is proposed in the study. There were three peak-to-peak voltages, Vp-p, of 10, 15 and 20 V were used. The characteristic parameters were estimated for the diaphragm, PED and PED-diaphragm assembly. For a 20 Vp-p and at 27 kHz, the maximum w reached 1.987 µm. The maximum Tv on the diaphragm surface and EE developed in the PED were 29.925 MPa and 442.98 nJ, respectively. The present numerical results were validated with previous studies on a similar domain and were in good agreement.

A more quiescent deep ocean under global warming

The ocean is a magnificent reservoir of kinetic energy possessed by currents at diverse spatio-temporal scales. These currents transport heat and material, regulating the regional and global climate. It is generally thought that large-scale ocean circulations should become more energetic under global warming, especially in the ocean’s upper layer. However, using high-resolution global climate simulations, here we demonstrate that the total ocean kinetic energy is projected to be significantly reduced in a warming climate, despite overall acceleration of large-scale ocean circulations in the upper layer. This reduction is primarily attributed to weakened ocean mesoscale eddies in the deep ocean. Enhanced vertical stratification under global warming reduces the available potential energy stored in large-scale ocean circulations, diminishing its conversion into eddy kinetic energy. Our findings reveal a more quiescent deep ocean under global warming and suggest a crucial role of mesoscale eddies in determining the anthropogenic change of total ocean kinetic energy.

Energetic Information from Information-Theoretic Approach in Density Functional Theory as Quantitative Measures of Physicochemical Properties.

The Hohenberg-Kohn theorem of density functional theory (DFT) stipulates that energy is a universal functional of electron density in the ground state, so energy can be thought of having encoded essential information for the density. Based on this, we recently proposed to quantify energetic information within the framework of information-theoretic approach (ITA) of DFT (J. Chem. Phys. 2022, 157, 101103). In this study, we systematically apply energetic information to a variety of chemical phenomena to validate the use of energetic information as quantitative measures of physicochemical properties. To that end, we employed six ITA quantities such as Shannon entropy and Fisher information for five energetic densities, yielding twenty-six viable energetic information quantities. Then, they are applied to correlate with physicochemical properties of molecular systems, including chemical bonding, conformational stability, intermolecular interactions, acidity, aromaticity, cooperativity, electrophilicity, nucleophilicity, and reactivity. Our results show that different quantities of energetic information often behave differently for different properties but a few of them, such as Shannon entropy of the total kinetic energy density and information gain of the Pauli energy density, stand out and strongly correlate with several properties across different categories of molecular systems. These results suggest that they can be employed as quantitative measures of physicochemical properties. This work not only enriches the body of our knowledge about the relationship between energy and information, but also provides scores of newly introduced explicit density functionals to quantify physicochemical properties, which can serve as robust features for building machine learning models in future studies.

SN 2019tua: A Type IIb Supernova with Multiple Bumps in the Light Curves

We present photometric and spectroscopic observations and analysis of the Type IIb supernova (SN) SN 2019tua, which exhibits multiple bumps in its declining light curves between 40 and 65 days after discovery. SN 2019tua shows a time to peak of about 25 days, similar to other Type IIb SNe. Our observations indicate a decrease in its brightness of about 1 mag in the 60 days after the peak. At about days 50 and 60, its multiband light curves exhibit bumpy behavior. The complex luminosity evolution of SN 2019tua could not be well modeled with a single currently popular energy source model, e.g., radioactive decay of 56Ni, magnetar, interaction between the ejecta and a circumstellar shell. Even though the magnetar model has a smaller χ 2/dof value, the complex changes in SN 2019tua’s brightness suggest that more than one physical process might be involved. We propose a hybrid circumstellar medium (CSM) interaction plus 56Ni model to explain the bolometric light curve of SN 2019tua. The fitting results show that the ejecta mass M ej ≈ 2.4 M ⊙, the total CSM mass M CSM ≈ 1.0 M ⊙, and the 56Ni mass M Ni ≈ 0.4 M ⊙. The total kinetic energy of the ejecta is E k ≈ 0.5 × 1051 erg. Preexisting multiple shells suggest that the progenitor of SN 2019tua experienced mass ejections within approximately ∼6–44 yr prior to the explosion.

Mechanistic investigation of nucleation kinetics in heterogeneous ice crystallization: the role of cooling rate, surface energy, surface nanostructure, and wetting state

The mechanism of nucleation in heterogeneous ice crystallization is important but remains unclear in spite of decades-long research. This study aims at investigating the nucleation kinetics in heterogeneous ice crystallization through molecular dynamics simulations, and comprehensively elucidating the effect of cooling rate, surface energy, surface nanostructure, and wetting state on the nucleation behaviours. More than 300 cases were simulated using monatomic water (mW) model based on a modified Stillinger-Weber (SW) potential. The dynamic nucleation and crystallization behaviours, along with the evolution of the largest ice nucleus, total ice clusters, kinetic energy, and interaction energy between nanodroplet and substrate, were investigated. Increasing the cooling rate and higher surface energy could promote the ice nucleation, but may lead to a tendency to transform into metastable interfacial ice and 4-coordinated molecule types, and create ice-free layer near the substrate due to the strong interaction strength. What's more, the effect of size match between the accessible width and ice lattice constant depends on the wetting states. In Cassie-Baxter state, the size match effect could promote the ice nucleation, while in Wenzel state it is not pronounced and decreasing the contact area by increasing the nanogroove width would inhibit the nucleation process. This work will be valuable in understanding the mechanism of nucleation kinetics in heterogeneous ice crystallization and provide guidance in promoting or inhibiting ice formation.

An Application of DC Motor Modelled Classical Sliding Mode Control with Moving Sliding Surface to Rotary Inverted Pendulum System

The rotary inverted pendulum system (RIP), which is highly favored in control applications, is examined in this work. By determining the coordinates of the Rip elements' centers of gravity, the system's total kinetic and potential energies were determined. The kinetic and potential energy expressions were used to generate the Lagrangian function. Expressions providing the system's equations of motion were discovered by taking the Lagrangian approach into consideration. The motor's equations, which will initiate the system, have also been considered. Through the use of state variables and a Matlab program, the system's pendulum angle was managed by using a moving sliding surface and the traditional sliding mode control technique. Based on the dynamics, the slip surface's slope was computed. The sliding surface's slope was computed based on the system's dynamics. The genetic algorithm was utilized to determine the ideal values for the coefficients employed in the control structure. The findings showed that the inaccuracy was roughly zero and that the pendulum angle took around 1.5 seconds to reach the intended reference value. Furthermore, it noted that the motor torque and current values are 12 Nm and 2.5 amps, respectively. The findings show that the motor values are reasonably similar to the values seen in real-world applications. Control in real-time applications won't be an issue if the motor is chosen based on these values

Influence of In-Cylinder Turbulence Kinetic Energy on the Mixing Uniformity within Gaseous-Fuel Engines under Various Intake Pressure Conditions

To explore the potential for further enhancing the gas mixing uniformity of natural gas (NG) engines, this paper identifies turbulent kinetic energy (TKE), which has an essential impact on gas mixing, as the entry point of the research. After establishing a computational fluid dynamics (CFD) model for NG engines’ direct injection and mixing processes, the inlet pressure is selected as the experimental variable to investigate the influence of TKE on gas mixing uniformity. In particular, by proposing the theoretical concept of the core mixing stage, the numerical variation rule between the best mixture concentration region (BMCR) percentage and the mean turbulent kinetic energy (MTKE) of the core mixing stage is analyzed under certain injection timing conditions. The results indicate that, with identical intake pressures, an advanced gas injection timing elevates the total turbulence kinetic energy (TTKE) during the core mixing stage, thereby amplifying the uniformity of the gas mixture at the ignition. In specific scenarios, as the intake pressure increases, the decreasing trend in the BMCR proportion closely resembles the diminishing trend in the MTKE during the core mixing stage. Scrutinizing the variation trend in either parameter allows for an approximate prediction of the variation trend in the other parameter. When the intake pressure is gradually raised from the naturally aspirated state, the adequacy of the gas jet development is progressively reduced by the increasing back pressure in the cylinder.

JWST Reveals Powerful Feedback from Radio Jets in a Massive Galaxy at z = 4.1

We report observations of a powerful ionized gas outflow in the z = 4.1 luminous radio galaxy TNJ1338-1942 hosting an obscured quasar using the Near Infrared Spectrograph (NIRSpec) on board JWST. We spatially resolve a large-scale (∼15 kpc) outflow and measure outflow rates. The outflowing gas shows velocities exceeding 900 km s−1 and broad line profiles with widths exceeding 1200 km s−1 located at an ∼10 kpc projected distance from the central nucleus. The outflowing nebula spatially overlaps with the brightest radio lobe, indicating that the powerful radio jets are responsible for the outflow kinematics. The gas is possibly ionized by the obscured quasar with a contribution from shocks induced by the jets. The mass outflow rate map shows that the region with the broadest line profiles exhibits the strongest outflow rates. The total mass outflow rate is ∼500 M ⊙ yr−1, and the mass loading factor is ∼1, indicating that a significant part of the gas is displaced outwards by the outflow. Our hypothesis is that the overpressured shocked jet fluid expands laterally to create an expanding ellipsoidal “cocoon” that causes the surrounding gas to accelerate outwards. The total kinetic energy injected by the radio jet is about 3 orders of magnitude larger than the energy in the outflowing ionized gas. This implies that kinetic energy must be transferred inefficiently from the jets to the gas. The bulk of the deposited energy possibly lies in the form of hot X-ray-emitting gas.

Stability and dynamic analyses of hybrid laminates using refined higher-order zigzag theory

This article presents a comparative study on the stability and dynamic response of hybrid laminated composite plates over monolithically produced laminated composite plates. A Refined Higher-order Zigzag Theory (RHZT) is formulated and implemented using finite element method for the analysis of hybrid laminates. This formulation considers both the interlaminar shear stress continuity and shear-free boundary conditions at surfaces of the plates. The numerical implementation employs C 0 continuous eight-noded isoparametric plate elements considering geometric nonlinearity. The element stiffness matrix is formulated to consider both the linear and nonlinear terms of the strain-displacement equations. Derivation of the consistent mass matrix for a plate element is presented following the approximation of total kinetic energy and utilising Hamilton’s principle. Numerical examples are provided to demonstrate buckling and free vibration analyses (as eigenvalue problems). The results are numerically verified and validated using data from published literature. Finally, parametric studies are presented to demonstrate the effectiveness of fibre hybridisation approach on the buckling and free vibration behaviour of laminated composites.

The Behavior of Thin-Walled Cylinders with Ribs Regarding the Energy Absorption Capability on High-Velocity Impact

Many industries and automotive companies use thin-walled cylinders as energy-absorbing devices. Researchers have previously investigated various parameters related to thin-walled cylinders and their behavior under impact loads. When the impactor hits the thin-walled cylinder from the axial direction, it causes the bending of the cylinder wall on an axisymmetric or non-axisymmetric pattern, depending on the ratio of diameter divided by wall thickness. In addition, the length of the specimen influences the deformation mode that occurs. This study discusses how installing ribs on the cylinder walls affects energy absorption capabilities. We conducted the research by making modeling based on the finite element method by making various specimens according to the experimental scenarios. We experimented with an aluminum alloy cylinder with a diameter of 50 cm, a thickness of 1.5 mm, and a length of 200 mm. Then, successively, we installed ribs with a length of 2 mm and a thickness of 3.5 mm, one rib, two ribs, three ribs, four ribs, and five ribs. The impactor hits the specimen from the axial direction to one end at high speed while the other is given fixed support. The results obtained from the experiment are total deformation, reaction force, absorbed energy, and deformation pattern. The experimental results show that adding ribs changes the deformation pattern from previously non-axis-symmetric to axis-symmetric. The total deformation decreases, the reaction force becomes smaller, and the ability to absorb energy equals the total kinetic energy. This result is a recommendation for manufacturing in an energy absorption structural system. Keywords: rib, deformation mode, wall thickness, energy absorption, reaction force.