Rotational Energy Research Articles

Rotational and translational motions in a homogeneously cooling granular gas

A granular gas composed of monodisperse spherical particles was studied in microgravity experiments in a drop tower. Translations and rotations of the particles were extracted from optical video data. Equipartition is violated, the rotational degrees of freedom were excited only to roughly 2/3 of the translational ones. After stopping the mechanical excitation, we observed granular cooling of the ensemble for a period of three times the Haff time, where the kinetic energy dropped to about 5% of its initial value. The cooling rates of all observable degrees of freedom were comparable, and the ratio of rotational and translational kinetic energies fluctuated around a constant value. The distributions of translational and rotational velocity components showed slight but systematic deviations from Gaussians at the start of cooling.

Self-adaptive rotational electromagnetic energy generation as an alternative to triboelectric and piezoelectric transductions

Triboelectric and piezoelectric energy harvesters can hardly power most microelectronic systems. Rotational electromagnetic harvesters are very promising alternatives, but their performance is highly dependent on the varying mechanical sources. This study presents an innovative approach to significantly increase the performance of rotational harvesters, based on dynamic coil switching strategies for optimization of the coil connection architecture during energy generation. Both analytical and experimental validations of the concept of self-adaptive rotational harvester were carried out. The adaptive harvester was able to provide an average power increase of 63.3% and 79.5% when compared to a non-adaptive 16-coil harvester for harmonic translation and harmonic swaying excitations, respectively, and 83.5% and 87.2% when compared to a non-adaptive 8-coil harvester. The estimated energy conversion efficiency was also enhanced from ~80% to 90%. This study unravels an emerging technological approach to power a wide range of applications that cannot be powered by other vibrationally driven harvesters.

Bumpy Superluminous Supernovae Powered by a Magnetar–Star Binary Engine

Wolf–Rayet stars in close binary systems can be tidally spun up by their companions, potentially leaving behind fast-spinning, highly magnetized neutron stars, known as “magnetars,” after core collapse. These newborn magnetars can transfer rotational energy into heating and accelerating the ejecta, producing hydrogen-poor superluminous supernovae (SLSNe). In this Letter, we propose that the magnetar wind of the newborn magnetar could significantly evaporate its companion star, typically a main-sequence or helium star, if the binary system is not disrupted by the abrupt mass loss and supernova (SN) kick. The subsequent heating and acceleration of the evaporated star material along with the SN ejecta by the magnetar wind can produce a postpeak bump in the SLSN lightcurve. Our model can reproduce the primary peaks and postpeak bumps of four example observed multiband SLSN lightcurves, revealing that the mass of the evaporated material could be ∼0.4–0.6 M ⊙ if the material is hydrogen-rich. We propose that the magnetar could induce strongly enhanced evaporation from its companion star near the pericenter if the orbit of the post-SN binary is highly eccentric, ultimately generating multiple postpeak bumps in the SLSN lightcurves. This “magnetar–star binary engine” model may offer a possible explanation for the evolution of polarization, along with the origin and velocity broadening of late-time hydrogen or helium broad spectral features observed in some bumpy SLSNe. The diversity in the lightcurves and spectra of SLSNe may be attributed to the wide variety of companion stars and post-SN binary systems.

A system-level CFD simulation model for investigating the energy dissipation mechanism of seawater pump and rotary energy recovery device in SWRO desalination system

Seawater reverse osmosis (SWRO) technology has been universally adopted because of its high efficiency, economic benefits, easy maintenance, and high-pressure seawater pump (HPSP) and energy recovery device (ERD) are essential components, which determine the specific energy consumption of SWRO system. However, it is still unclear about energy dissipation mechanism and mixing characteristics from the perspective of system. For that, this thesis proposes a novel system-level Computational Fluid Dynamics (CFD) model considering all interfaces in HPSP and integrated energy recovery and pressure boost device (IERPBD). To profoundly investigate the system performance under various operating conditions, the pressure and composition distribution, power loss of each interface and mixing rate are numerically calculated and analyzed. Additionally, experiment of the effect of temperature on SWRO system performance is conducted to practically verify the proposed model, which indicates that the presented model could precisely reflect the energy dissipation and mixing characteristics. Besides, it is advised that the rotating speed of HPSP and IERPBD should not be set too high which could increase the mixing rate and energy consumption, and higher temperature might lower the quality of produced freshwater. This study offers a feasible way to reveal the energy dissipation mechanism of SWRO desalination system.

Design optimisation of roadside safety roller barriers

Safety roller barrier (SRB) is an innovative road safety device that utilises foam rollers to absorb and convert shock energy into rotational energy, showcasing its remarkable ability to minimise the risk and severity of casualties in road accidents. In this study, a simulation-based optimisation approach was employed to obtain the optimal design for the SRB. Quasi-static and dynamic mechanical properties of the construction materials were experimentally obtained. SRB finite element (FE) models were then created based on installed systems in multiple Australian cities. The model was validated using full-scale TL4 crash tests according to the specifications outlined in the Manual for Assessment of Safety Hardware (MASH). Subsequently, a parametric study was conducted to explore the influence of design parameters such as post spacing, rail height, and roller number. Finally, a parallel Bayesian optimisation algorithm was applied to re-design the SRB system with enhanced performance and reduced cost. This optimisation process yielded several sets of optimal parameters, paving the way for a more effective and economically viable SRB design.

Influence of rotations in energy transfer of a particle colliding on a flat surface

To understand the influence of rotations on the dissipation of energy in the interaction between a grain and its environment, we investigate the relaxation process of a single particle bouncing on a flat horizontal surface. For this purpose, faceted particles were used to promote the appearance of rotations in each bounce. The evolution of potential, translational and rotational kinetic energies was analyzed during the whole relaxation process, particularly focusing on the behavior just before and after each collision. The rebounding action of an individual grain results in energy dissipation commonly quantified by ϵ, the coefficient of restitution. This coefficient is defined as the ratio of the normal velocity component prior to impact (Vn) to the corresponding component immediately following the collision (Vn′), i.e. related to translational kinetic energy associated with motion in the normal direction. We identify a critical impact velocity below which, in certain collisions, ϵ>1. This phenomenon can be attributed to stored rotational kinetic energy which is transferred to translational kinetic energy during the collision, thereby increasing the normal velocity Vn′ and resulting in the observed high values of ϵ.

Design of strong-performance, high-heat dissipation rate, and long-lifetime triboelectric nanogenerator based on robust hexagonal boron nitride (hBN) nanosheets/polyvinyl chloride (PVC) composite films for rotational energy harvesting

Here, we design a rotational structure on a triboelectric nanogenerator (TENG) using a robust hexagonal boron nitride nanosheets/polyvinyl chloride (hBN nanosheets/PVC) composite film as a triboelectric material, leading to strong output performance, high heat-dissipation rate, and long lifetime. At a rotor-stator contact pressure of 0.85 N with a rotational speed of 400 r/min, the optimized 2 wt %-hBN nanosheets/PVC-based TENG can produce a peak output voltage of 142 V with a current of 272 μA, leading to a maximum power of 30.7 mW, which can continuously power some tiny electronics. Note that the surface temperature of the device is 2.4 °C lower than that of the pure PVC film-based TENG after 10 min of continuous operation at 250 r/min. Moreover, the 2 wt %-hBN nanosheets/PVC composite film exhibits the surface charge density, the thermal conductivity, and the friction coefficient of 620 μC/m2, 0.26 W/mk and 0.27, which are 87.3 % higher than, 36.8 % higher than, and 32.5 % lower than that of pure PVC film, providing a new strategy for designing triboelectric materials with high surface charge density, good thermal conductivity and low wear resistance.

The Halogenation Effect Induces a Variety of Switchable Phase Transition and Second-Harmonic-Generation Materials.

Halogen engineering offers a means of enhancing the physical properties of materials by fine-tuning the rotational energy barrier and dipole moment, which proved to be effective in achieving switchable phase transitions and optical responses in materials. In this work, by substituting the methyl group in ligand N-ethyl-1,5-diazabicyclo[3.3.0]octane (CH3CH2-3.3.0-Dabco) with halogen atoms X (Cl or Br) and then contining to react it with FeBr3 in a HBr aqueous solution, we successfully synthesized three kinds of organic-inorganic hybrid switchable phase-change materials, [CH3CH2-3.3.0-Dabco]FeBr4 (1), [ClCH2-3.3.0-Dabco]FeBr4 (2), and [BrCH2-3.3.0-Dabco]FeBr4 (3), which were fully characterized by single-crystal X-ray diffraction and variable-temperature powder X-ray diffraction. Compared to compound 1, compounds 2 and 3 show two pairs of reversible phase transitions, dielectric anomalies, and a second-harmonic-generation effect, which are successfully induced due to the halogen substitution. This study offers an effective molecular design strategy for the exploration and construction of iron halide organic-inorganic hybrid materials with temperature-adjustable physical properties.

A high-performance dual-mode energy harvesting with nonlinear pendulum and speed-amplified mechanisms for low-frequency applications

Vibrations induced by human motions and vehicle operations feature low-frequency, broadband, and time-varying. However, enhancing the power density of energy harvesting for various low-frequency applications presents a significant challenge. This paper proposes a high-performance dual-mode energy harvester (DM-EH) incorporating coupled nonlinear pendulum and speed-amplified mechanisms with gears for the simultaneous scavenging vibration and rotation energy. The pendulum serves as the energy capture unit for detecting vibration energy while ensuring the effective operation of the generation unit in rotational environments. The gears amplify the speed of the excitation and enable frequency up-conversion, thereby enhancing the energy conversion. Experimental results substantiate the DM-EH's ability to extract power from vehicle operations at speeds ranging from 60 to 540 rpm, as well as from human motions at frequencies of 0.7–1.5 Hz with 30° amplitudes. In rotation mode, the prototype achieves a maximum average direct current power of 3.79 W, while in vibration mode, it attains 244 mW. The prototype successfully powers portable electronics and supports battery-free triaxial acceleration and temperature multi-sensors during human motions and railway simulation tests. This prototype showcases immense potential as a sustainable power source for portable electronics and self-powered monitoring applications.

An experiment for the study of projectile motion

The classic demonstration experiment of the motion of a point mass thrown at an angle to the horizon is studied. Several measurements of the range of a projectile launched sphere are carried out and compared with the results that were obtained by an analytical approach. The sphere’s motion can be treated as two independent movements, a linear uniform movement in the horizontal direction and a uniformly accelerated motion in the vertical direction. The value of launching velocity obtained by kinematics is compared with those predicted by the law of mechanical energy conservation. The conclusion is that the model of a frictionless sliding sphere is far from explaining the experimental result. The model could be improved proposing that the sphere rolls without sliding (pure rolling) on the platform including the rotational kinetic energy. Finally, the fact that the sphere does not settle completely on the launch rail was considered using an effective radius of rotation. Observed from the three proposed models, the last one is the closest to the obtained experimental value. These activities can also improve students’ understanding of the concept of projectile motion.

Nucleosynthesis in the Innermost Ejecta of Magnetorotational Supernova Explosions in Three Dimensions

Core-collapse supernova (CCSN) explosions powered by rotation and magnetic fields present an interesting astrophysical site for nucleosynthesis that potentially contributes to the production of r-process elements. Here we present yields of the innermost ejecta in 3D magnetorotational CCSN models simulated using the CoCoNuT-FMT code. Strong magnetic fields tap the rotational energy of the proto−neutron star and lead to earlier and more energetic (∼3 × 1051 erg) explosions than typical neutrino-driven CCSNe. Compared to a reference nonmagnetic model, the ejecta in the magnetorotational models have much more neutron-rich components with Y e down to ∼0.25. Our post-processing calculations with the reaction network SkyNet show significant production of weak r-process elements up to mass number ∼130. We find negligible differences in the synthesis of heavy elements between two magnetorotational models with different initial field strengths of 1010 and 1012 G, in accord with their similar explosion dynamics. The magnetorotational models produce about ∼0.19 and 0.14 M ☉ of radioactive 56Ni, on the low end of inferred hypernova nickel masses. The yields are publicly available at Zenodo (doi: 10.5281/zenodo.10578981) for comparison with stellar abundance patterns, inclusion in modeling galactic chemical evolution, and comparison with other yield calculations. Our results add to the yet-restricted corpus of nucleosynthesis yields from 3D magnetorotational supernova simulations and will help quantify yield uncertainties.

Simultaneous Thermally Stimulated Delayed Phosphorescence (TSDP) and Thermally Activated Delayed Fluorescence (TADF) in a Two-Coordinated Au(I) Bimetallic Complex Featuring a Tandem Carbene Structure.

A bimetallic, two-coordinated carbene-metal-amine (cMa) Au(I) complex featuring a twisted tandem carbene structure (NHC1-Au-NHC2-Au-carbazolyl) was synthesized. The molecular structure in single crystals revealed a large dihedral angle between the two carbene ligands, while the bridged carbene NHC2 and carbazolyl (Cz) ligands were coplanar. A bluish green thermally stimulated delayed phosphorescence (TSDP) was observed in crystals with an emission lifetime over 70 μs, which can be attributed to the spin allowed diabatic population of a high-lying emissive triplet state from the 3LE characterized low-lying ones. The small rotation energy barrier of Cz along the coordination bond allowed conformers with large dihedral angles between NHC2 and Cz. The ICT characterized S1 state was consequently stabilized to achieve a thermally accessible energy gap to facilitate ISC between triplets and the S1, leading to the thermally activated delayed fluorescence (TADF). Simultaneous TSDP and TADF dual emission can be recorded in its doped polymer film owing to the coexistence of these different conformers.

Amplification of electromagnetic fields by a rotating body

In 1971, Zel’dovich predicted the amplification of electromagnetic (EM) waves scattered by a rotating metallic cylinder, gaining mechanical rotational energy from the body. This phenomenon was believed to be unobservable with electromagnetic fields due to technological difficulties in meeting the condition of amplification that is, the cylinder must rotate faster than the frequency of the incoming radiation. Here, we measure the amplification of an electromagnetic field, generated by a toroid LC-circuit, scattered by an aluminium cylinder spinning in the toroid gap. We show that when the Zel’dovich condition is met, the resistance induced by the cylinder becomes negative implying amplification of the incoming EM fields. These results reveal the connection between the concept of induction generators and the physics of this fundamental physics effect and open new prospects towards testing the Zel’dovich mechanism in the quantum regime, as well as related quantum friction effects.

Comparison of kinetic energy conversion characteristics of two extreme precipitation episodes during persistent unusually heavy rainfall on 17–23 July 2021 in Henan, China

A persistent heavy rainfall event, contributed by two extreme episodes (P1 and P2), occurred in Henan province of China from 17 to 23 July 2021. An active mesoscale vortex was present in the lower troposphere, along with a shallow trough moving eastward in the upper troposphere. The budgets of rotational kinetic energy (KR) and divergent kinetic energy (KD) at distinct stages are investigated. The lower-level KR anomaly, related to the mesoscale vortex growth therein, was responsible for P1. However, the upper-troposphere KR was dominant and strong during the P2 stage, associated with an eastward-developing upper-level trough. Prior to both P1 and P2, active inner interaction between rotational and divergent winds presented, manifested as a rapid increase of KVRVD signals. KVRVD and precipitation had similar pattern distribution and consistent evolution tendency. Therefore, KVRVD might be a useful indicator for the occurrence and intensification of rainfall. Expect for two components of winds interaction, the external source feeding kinetic energy growth is also explored. For P1, APE (available potential energy)-> KD-> KR was the key path towards rotational kinetic energy, providing energy for mesoscale vortex growth in lower troposphere, which was favorable for the extreme episode of P1. Nevertheless, for P2 stage, APE acted as a direct energy source towards KR in upper troposphere, with higher efficiency (via APE-> KR) and thus stronger KR. This kind of difference in conversion path depended on the vertically-coupled degree between the lower-level mesoscale vortex and the upper-level trough, in addition to the rotational and divergent wind speed. Their tilting/upright configuration produced strong baroclinic/barotropic process, accelerating energy conversion of APE-> KD/APE-> KR via GD/GR (i.e., generating KD/KR by divergent/rotational winds crossing geopotential height contours, usually as a generator resulting from barotropic/baroclinic process). Therefore, kinetic energy budget may be a valuable tool for identifying key weather systems development and forecasting extreme rainfall episodes.

Interaction between lateral jet and hypersonic rarefied flow

Reaction control systems (RCS) are commonly utilized in a variety of air vehicles, and they give rise to complex flow phenomena. For flows dominated by shock waves and expansion, such as lateral jets, a significant gradient is formed in the local region of the flow field, resulting in a high local Knudsen number, and the continuum hypothesis is no longer applicable, even if the freestream belongs to near-continuum flow. As a result, multi-scale simulation approaches should be used to capture the interactions between these multi-scale structures and appropriately determine aerodynamic forces. Our earlier work, which used the conserved discrete unified gas kinetic scheme (CDUGKS) for monatomic gas, studied the flow field features of lateral jets and aerodynamic forces on blunt bodies under various rarefied freestream conditions. In this research, the Rykov model is used to expand the CDUGKS suit for diatomic gas flow while taking into account the excitation of molecular rotational energy. The impact on the flow field and aerodynamic forces from four parameters, namely freestream Mach number, jet Mach number, jet pressure ratio, and nozzle position, is thoroughly investigated. The results show that even if the incoming Mach number is different, the flow field structure and aerodynamic properties don't change much when the jet momentum ratio stays the same. The solid wall stagnation point value and local peak also show some linear relationships. The jet pressure ratio mainly affects the expansion characteristics of the jet, such as the influence range on the solid wall. In addition, with an increase in the distance between the nozzle position and the torque reference point, higher control efficiency can be obtained. The study of these aspects will help us comprehend lateral jet flow and provide reference for the design of an air vehicle's RCS.

A piezoelectric-triboelectric-electromagnetic tri-hybrid energy harvester with dual-frequency-up-conversion mechanism for ultralow-frequency rotational motion

Rotational energy harvesting under ultralow frequencies has always been a great challenge. A piezoelectric-triboelectric-electromagnetic tri-hybrid energy harvester (THEH) with dual-frequency-up-conversion mechanism for ultralow-frequency rotational motion is proposed in this paper. The integration of two piezoelectric nanogenerators (PENG), two triboelectric nanogenerators (TENG), and one electromagnetic generator (EMG) further improves the power output. PENG and TENG can operate at a higher frequency through the magnetic coupling and impact of the center magnet. In the process, the center magnet also causes EMG to generate electricity. The three modules are coupled together by the center magnet to harvest energy continuously. This paper studies the performance of THEH at 0–2.6 Hz and the effects of the key parameter. The maximum average output is obtained as 2.38 mW, 1.3 mW, and 13.3 μW for the PENG, EMG, and TENG components at 1.2 Hz, respectively. Furthermore, a tri-channel power management method is proposed to integrate three modules’ energy in THEH. Some THEH-based self-powered electronic devices are demonstrated, which shows THEH’s great potential for rotational energy harvesting.

Dynamics of the Decomposition of Gas Molecules Containing Sulfur and Nitrogen from Char-S and Char-N Structures in Combustion and Pyrolysis Reactions

ABSTRACT Combustion states of char-S (C14H16O4S) and char-N (C18H19NO3) sub function molecules in a limited number of oxygen environments and pyrolysis states at high temperatures were examined quantum mechanically. In the study, the formation of all gases, with or without carbon, were determined. All the dynamics in which the O2 molecule could be effective in the combustion mechanism and all the elements that could affect the decomposition in the pyrolysis event were determined. The dynamics of the formation and disappearance of the highly stable CO molecule and CH2O (formaldehyde) molecules were shown in detail. It has been shown that the CO molecule is a catalysis that can bond with hydrocarbon groups and decompose them into small hydrocarbon groups at high temperature. In this study, it was shown that high temperature-dependent vibration and rotational energies, CO molecule and H-atom transfers play a role in the decomposition in the pyrolysis system, and the aromatic carbon ring group is the last particle group to decompose. In addition, the formation and dissociation dynamics of sulfoxylic acid, thioformic acid, hydrogen sulfide molecules originating from the Char-S system, as well as the formation conditions of hydrogen cyanide and pyridinyl molecules originating from the Char-N system, were determined. The study also showed that since the N-atom is located in the aromatic carbon ring, it makes the emergence of the nitrous oxide molecule difficult in pyrolysis systems.

An optimal operation strategy of wind farm for frequency regulation reserve considering wake effects

When wind farms (WFs) participate in power system frequency regulation, deloaded control can increase the stored rotational kinetic energy in the wind turbines (WTs), thereby enhancing their frequency support capability. However, due to the wake effects and deloaded control of turbines, this method can also lead to increased power losses. An optimal operation strategy has been proposed to balance power generation and frequency regulation reserve in WFs, taking wake effects into account. Initially, a WF deloaded control model that considers wake effects, and an adaptive combined frequency control model based on kinetic energy reserve, are established for participation in power system frequency regulation. Subsequently, the Covariance Matrix Adaptation Evolution Strategy (CMAES) is utilized to determine the optimal operation allocation of maximum WF output power within the FLORIS wake model, meeting frequency regulation reserve requirements. A comparative analysis of the optimal allocation results under various wind conditions is conducted to test the frequency support capabilities. The results indicate that the proposed strategy can achieve varying levels of frequency regulation reserve, reduce wake losses to maximize output power under deloaded control, and improve frequency support capability.

Gibbs Free Energy and Enthalpy–Entropy Compensation in Protein–Ligand Interactions

The thermodynamics of protein–ligand interactions seems to be associated with a narrow range of Gibbs free energy. As a consequence, a linear enthalpy–entropy relationship showing an apparent enthalpy–entropy compensation (EEC) is frequently associated with protein–ligand interactions. When looking for the most negative values of ∆H to gain affinity, the entropy compensation gives rise to a barely noticeable increase in affinity, therefore negatively affecting the design and discovery of new and more efficient drugs capable of binding protein targets with a higher affinity. Originally attributed to experimental errors, compensation between ∆H and T∆S values is an observable fact, although its molecular origin has remained obscure and controversial. The thermodynamic parameters of a protein–ligand interaction can be interpreted in terms of the changes in molecular weak interactions as well as in vibrational, rotational, and translational energy levels. However, a molecular explanation to an EEC rendering a linear enthalpy–entropy relationship is still lacking. Herein, we show the results of a data search of ∆G values of 3025 protein–ligand interactions and 2558 “in vivo” ligand concentrations from the Protein Data Bank database and the Metabolome Database (2020). These results suggest that the EEC may be plausibly explained as a consequence of the narrow range of ∆G associated with protein–ligand interactions. The Gaussian distribution of the ∆G values matches very well with that of ligands. These results suggest the hypothesis that the set of ∆G values for the protein–ligand interactions is the result of the evolution of proteins. The conformation versatility of present proteins and the exchange of thousands (even millions) of minute amounts of energy with the environment may have functioned as a homeostatic mechanism to make the ∆G of proteins adaptive to changes in the availability of ligands and therefore achieve the maximum regulatory capacity of the protein function. Finally, plausible strategies to avoid the EEC consequences are suggested.

Dynamics modeling and trajectory tracking control of a life support robot using sliding-mode control with extended state observer

This paper investigates the trajectory tracking control problem of a life support robot chassis under the slipping disturbances. First, a novel dynamics model for the robot chassis is proposed based on Lagrange equation. The constructed model incorporates the effects of rotational kinetic energy from the driving wheels, providing a more comprehensive representation of the chassis dynamics. Then, on the basis of the innovative framework, the dual-loop trajectory tracking control is derived for the chassis, via the kinematics-based backstepping controller and the dynamics-based sliding-mode controller. Moreover, an extended state observer is designed to reduce the influence caused by external disturbances. Finally, the effectiveness and superiority of the proposed tracking control approach are verified through simulation experiments.