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• Impinging paper-thin sheets of liquids produces high energy dissipation rates. • The volume of energy dissipation is equal to the volume of the impingement zone. • A new expression for the energy dissipation rate was derived and compared with turbulence theory. • Large-eddy turnover time is approximately equal to liquid residence time in impingement zone. • Large-eddy kinetic energy decays exponentially in the impingement zone. The micromixing time of impinging thin liquid sheets depends upon the energy dissipation rate (∊). The kinetic energy released by the impingement has been previously studied and was found to be a function of the coefficient of restitution of the collision. In this work, the volume within which the released kinetic energy is dissipated was investigated. The volume of energy dissipation was determined by measuring the time required for the velocity of the liquid prior to the collision to be reduced to the velocity after the collision. High-speed video was used to measure the velocity of features, generated in the front single sheet, as they passed through the impingement zone and into the mixed sheet. The experimental results showed that the time required for the velocity change was approximately equal to the residence time of liquid in the impingement zone (t r). A new equation for ∊ was developed and compared with ∊ derived from turbulence energy-cascade theory. This comparison showed that the large-eddy turnover time (t Λ) was approximately equal to t r ; a result that is in accordance with the notion from turbulence energy-cascade theory that large, energy-containing eddies lose their energy within t Λ. Within the impingement zone, the large-eddy kinetic energy was found to decay exponentially with time. [ABSTRACT FROM AUTHOR]

Linear propulsion electromagnetic energy equipment can convert electromagnetic energy to kinetic energy instantaneously and has many advantages, such as high kinetic energy, efficiency, precision, and strong controllability. It surpasses traditional mechanical and chemical energy methods, significantly impacting various fields. Aiming at the numerical simulation method, which has problems with large computation volume and a long time of physical field simulation, the current field prediction method of linear propulsion electromagnetic energy equipment based on a Deep Generation Adversarial Operator Network is proposed. Firstly, deep operator network is combined with conditional generative adversarial network to obtain the knowledge-embedded conditional adversarial operator network (CGAONet) model. Then, Res-Transformer-Unet (RTUnet) is used as a branch network of CGAONet to establish the RTUnet-CGAONet model, and the current field method using a deep adversarial operator network is proposed. Finally, the finite element simulation model of the US public linear propulsion electromagnetic energy equipment calculation example is established to construct the simulation dataset from 1D excitation current value and time data to a 2D current field. The trained RTUnet-CGAONet model predicts the mean absolute percentage error of 2.94% in the 2D current field, and the model is minimally affected by the number of samples in the dataset. The results of this paper can achieve the second-level calculation of the current field under different excitation currents, which provides a new way of thinking for the analysis of dynamic characteristics of linear propulsion electromagnetic energy equipment. [ABSTRACT FROM AUTHOR]

Environmentally friendly, high-output, high-efficiency compact pumps are in high demand in industrial fields such as chemical analysis and medical care. The efficiency of many small pumps is rather low, with peak efficiencies on the order of about 2%, even for commercially available pumps. Considering current environmental issues, improving the efficiency of motors and pumps is an important issue for preventing global warming. In this research, a small two-valve pump that can suck and discharge water by converting the energy of electromagnetic-vibration component resonance into kinetic energy was newly developed. In actual machine tests, two types of electromagnetic vibration pumps (I and II) with two-valve structures and different shapes were prototyped, and the shapes were optimized for efficiency. The type II vibration pump with an acrylic rod attached to the type I pump had excellent suction and discharge characteristics. The maximum efficiency was 12.2%, which is exceptional for a small pump. In addition, it was clarified by the actual machine test that the type II pump can stably discharge water at a high head of 2000 mm. The two types of pumps proposed in this paper were shown to be highly useful industrially in terms of performance, simplicity, cost, and operability and can be used selectively according to the application. Furthermore, since these pumps can be manufactured with a small number of parts, this paper shows their potential to contribute to environmental issues. [ABSTRACT FROM AUTHOR]

The synchronous virtualmachine uses inverter power to imitate the performance of the conventional synchronous machine. It also has the same inertia, damping, frequency, voltage regulation, and other external performance as the generator. It is the key technology to realize new energy grid connections' stable and reliable operation. This project studies a dynamic simulation model of an extensive new energy power system based on the virtual synchronous motor. A new energy storage method is proposed. The mathematical energy storage model is established by combining the fixed rotor model of a synchronous virtual machinewith the charge-discharge power, state of charge, operation efficiency, dead zone, and inverter constraint. The rapid conversion of energy storage devices absorbs the excess instantaneous kinetic energy caused by interference. The branch transient of the critical cut set in the system can be confined to a limited area. Thus, the virtual synchronizer's kinetic and potential energy can be efficiently converted into an instantaneous state. The simulation of power system analysis software package (PSASP) verifies the correctness of the theory and algorithm in this paper. This paper provides a theoretical basis for improving the transient stability of new energy-connected power grids. [ABSTRACT FROM AUTHOR]

In order to analyze the relay action process from an imaging perspective and further investigate the bounce phenomenon of relay contacts during the contact process, this paper utilizes a high-speed shooting platform to capture images of relay action. In light of the situation where the stationary contact in the image is inclined and continuously changing, a rotation template matching algorithm based on adaptive weight is proposed. The algorithm identifies and obtains the inclination angle of the stationary contact, enabling the study of the relay contact bounce process. By extracting contact bounce distance data from the images, a bounce process curve is plotted. Combined with the analysis of the contact bounce process, the reasons for the bounce are explored. The results indicate that the proposed rotation template matching algorithm can accurately identify stationary contacts and their angles at different angles. By analyzing the contact status and bounce process of the relay contacts in conjunction with the relay structure, parameters such as the bounce time, bounce height, and time required to reach the maximum distance can be calculated. Additionally, the main reason for contact bounce in the relay studied in this paper is the limitation imposed on the continued movement of the stationary contact by the presence of the relay brackets when the kinetic energy of the contact is too high. This phenomenon occurs during the first vibration peak in the vibration process after the moving contact contacts the stationary contact. The research results provide a reference for further studying the relay contact bounce process, optimizing relay structure, and suppressing contact bounce. [ABSTRACT FROM AUTHOR]

Copyright of Zhejiang Electric Power is the property of Zhejiang Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we present a compressive study on the design and development of a MEMS ring resonator and its dynamic behavior under electrostatic force when supported by twin circular curve beams. Finite element analysis (FEA)-based modeling techniques are used to simulate and refine the resonator geometry and transduction. In proper FEA or analytical modeling, the explicit description and accurate values of the effective mass and stiffness of the resonator structure are needed. Therefore, here we outlined an analytical model approach to calculate those values using the first principles of kinetic and potential energy analyses. The natural frequencies of the structure were then calculated using those parameters and compared with those that were simulated using the FEA tool ANSYS. Dynamic analysis was performed to calculate the pull-in voltage, shift of resonance frequency, and harmonic analyses of the ring to understand how the ring resonator is affected by the applied voltage. Additional analysis was performed for different orientations of silicon and assessing the frequency response and frequency shifts. The prototype was fabricated using the standard silicon-on-insulator (SOI)-based MEMS fabrication process and the experimental results for resonances showed good agreement with the developed model approach. The model approach presented in this paper can be used to provide valuable insights for the optimization of MEMS resonators for various operating conditions. [ABSTRACT FROM AUTHOR]

With the continuous improvement of wind power penetration in the power system, the volatility and unpredictability of wind power generation have increased the burden of system frequency regulation. With its flexible control mode and fast power adjustment speed, energy storage has obvious advantages in participating in power grid frequency regulation. Therefore, this paper studies the control strategy of wind energy storage combined with primary frequency regulation and proposes a control method of wind energy storage combined with primary frequency regulation based on the operation state of wind turbines. This paper analyzes the reserve power and rotor reserve kinetic energy of wind turbines operating in different wind speed ranges, introduces the fan frequency regulation operation state coefficient to quantify the real-time frequency regulation ability of the unit, regards the fan and energy storage system as independent frequency regulation sources, and designs the control strategy of joint frequency regulation of wind and storage in different wind speed ranges. The energy storage system is employed to participate in frequency control in the low-wind-speed range, thereby addressing the "blind spot" issue of wind turbine unit frequency control alone. In the medium- and high-wind-speed ranges, the real-time complementary output of wind and energy storage power is achieved by assigning weights based on the frequency control operation status coefficient. Finally, the effectiveness of the joint frequency modulation control strategy of wind storage in low-, medium-, and high-wind-speed regions is verified in the simulation model. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper established a three-dimensional transient MHD model of a high-current multi-component vacuum arc under a transverse magnetic field (TMF) to simulate the dynamic characteristics of plasma parameters in the uniform motion mode of a contracted arc under lower TMF. The model considered the ionization–recombination process among the multi-components and used the P1 model to calculate the thermal radiation losses. The simulation results show that the ion number density of The TMF arc is on the order 1024 m−3, and when the plasma temperature reaches 4.3 eV, the effects of thermal radiation cannot be ignored. The majority of the plasma from the cathode and anode undergo acceleration and then deceleration before finally intersecting at the center of the arc, creating an extreme value of the density and the pressure, where a large amount of kinetic energy is converted into internal energy. The arc will be bent and deflected under the action of the ampere force, and the deflection of Cu3+ is especially obvious. The TMF affects the collision strength of the jet in the intersection area and, thus, affects the ion density, in which the change of Cu2+ is dominant. The ionization–recombination process of ions is mainly determined by the electron temperature, which is affected by the arc current. As the current decreases, Cu1+ increases and Cu2+ and Cu3+ decrease, and the change in ionization rate is the main reason for the change in the proportion of each ionic component; the heat flux density to the anode and cathode is on the order of 1010 W/m2, which heats the front of the arc and ensures the stable movement of the arc. Meanwhile, due to the high ion number density, the ion heat flux accounts for the main part of the heat flux, and the anode exhibits a higher proportion of ion heat flux. [ABSTRACT FROM AUTHOR]

The most important event in astronomy and celestial physics in the early 21st century is the fall of the Chelyabinsk meteoroid with a kinetic energy of nearly 440 kt TNT. Such an event occurs once every 65 years on average. The effects of this celestial body are considered in more than 200 scientific papers. At the same time, less than 25 papers are devoted to the fall of another large meteoroid called the Kamchatka meteoroid on December 18, 2018, at 23:48:20 UT (Universal time). Meanwhile, the parameters of this meteoroid are quite unique. The velocity components are vx = 6.3, vy = –3, and vz = –31.2 km/s, and the velocity magnitude was 32 km/s. The total optical radiated energy was Er = 1.3 × 1014 J (31 kt of TNT), the fireball explosion altitude was zr = 26 km, and the coordinates are 56.9° N, 172.4° E. The angle of entry into the atmosphere with respect to the horizon was close to 68.6°. The meteoroid had the initial kinetic energy of 173 kt of TNT, the mass of 1.41 kt, and the size of nearly 9.4 m. The fall of such bodies occurs at a frequency of once every 30 years. It is of interest to perform the further study of its ionospheric effects and compare the results measured by ground-based and satellite methods with each other. The objective of this study is to analyze the results of GPS observations for the ionospheric effects to compare them with the results measured by the method of ground-based oblique incidence sounding of the ionosphere. To observe the ionospheric disturbances following the fall of the Kamchatka meteoroid, an AC60 receiving station (geographic coordinates, 53° N, 173° E) located at a distance of 450 km from the Kamchatka meteoroid explosion site and six GPS satellites (PRN02, PRN05, PRN07, PRN09, PRN29, and PRN30) were used. The principal results of these studies are the following. GPS technologies were used to estimate the delay times of ionospheric response to the Kamchatka meteoroid explosion, the horizontal propagation velocities of disturbances (504–520 m/s) and their periods (11–18 min), durations (22–35 min), wavelengths (333–530 km), and the relative amplitudes of electron density disturbances (3–4%). The estimate obtained for the relative amplitudes of wave disturbances in the electron density by the ground-based and satellite methods have proven to be close to each other (3–4%). Their periods also have close values (10–15 min). The ground-based and satellite methods also revealed the wave disturbances associated with both atmospheric gravity and seismic waves. [ABSTRACT FROM AUTHOR]

The Pauli kinetic energy functional and its functional derivative, termed Pauli potential, play a crucial role in the successful implementation of orbital-free density functional theory for electronic structure calculations. However, the exact forms of these two quantities are not known. Therefore, perforce, one employs the approximate forms for the Pauli functional or Pauli potential for performing orbital-free density functional calculations. In the present study, we developed a feed-forward neural network-based representation for the Pauli potential using a 1-dimensional (1-D) model system. We expanded density in terms of basis functions, and the coefficients of the expansion were used as input to a feed-forward neural network. Using the neural network-based representation of the Pauli potential, we calculated the ground-state densities of the 1-D model system by solving the Euler equation. We calculated the Pauli kinetic energy using the neural network-based Pauli potential employing the exact relation between the Pauli kinetic energy functional and the potential. The sum of the neural network-based Pauli kinetic energy and the von Weizsäcker kinetic energy resulted in an accurate estimation of the total kinetic energy. The approach presented in this paper can be employed for the calculation of Pauli potential and Pauli kinetic energy, obviating the need for a functional derivative. The present study is an important step in the advancement of application of machine learning-based techniques toward the orbital-free density functional theory-based methods. [ABSTRACT FROM AUTHOR]

The accurate calculation of natural frequencies is important for vibration and earthquake analyses of structural frames. For this purpose, it is necessary to discretize each beam or column of the frame into one or more smaller elements. The required number of elements per member increases when the frame's modal shapes have wavelengths similar to the beam lengths. This paper presents a method that reduces the number of elements needed for a precise calculation. This is achieved by implementing a straightforward local correction to the kinetic and elastic energy of certain elements, resulting in a substantial decrease in error. The validity of this method is demonstrated through a range of examples, from simple canonical cases to more realistic ones. Additionally, the paper discusses the unique features of this method and examines its relationship with other approaches. [ABSTRACT FROM AUTHOR]

This paper investigates the relationship between unsteady flow and radiated noise in the near wake of a wind turbine tower due to the blade tower interaction (BTI) in Wind tunnel experiments. The two-dimensional hot-wire probe is used to collect the instantaneous velocity field in the BTI region, and the microphone sensor is used to collect sound field information. The effects of Reynolds stress and turbulent kinetic energy on BTI noise are further analyzed based on the instantaneous velocity field. The results show that the blade's passing effect causes irregular velocity distribution and vortex migration and mixing in the near wake of the tower, resulting in the most significant difference in Reynolds shear stress at the 0.71R position of the blade during the blade's transition from an azimuthal angle of 180°–210°(upward). Furthermore, a strong correlation is identified between the peak turbulent kinetic energy and the peak acoustic pressure value measured during the rotational cycle when the blade ran up to 210° azimuth angle. It is deduced that the aerodynamic noise at the rear of the tower is attributed to the increase in momentum exchange caused by fluid doping and bursting, which are driven by Reynolds shear stress. Momentum exchange induces an increase in turbulent kinetic energy, which results in fluid velocity pulsations, pressure pulsations, and, thus, noise. The reduction in fluid mixing and the reduction in pressure pulsation subsequently lead to a reduction in the noise generated by the tower. Therefore, a viable approach to reducing BTI noise involves minimizing momentum exchange. [ABSTRACT FROM AUTHOR]

The accurate computation of different turbulent statistics poses different requirements on numerical methods. In this paper, we investigate the capabilities of two representative numerical schemes in predicting mean velocities, Reynolds stress and budget of turbulent kinetic energy (TKE) in low Mach number flows. With concerns on numerical order of accuracy, dissipation and dispersion properties, a high-order upwind scheme with relatively good dispersion and dissipation and a second-order non-dissipative central scheme with perfect dissipation but poor dispersion are adopted for this comparative study. By carrying out a series of numerical simulations including Taylor-Green vortex, turbulent channel flow at R e τ = 180 and turbulent flow over periodic hill at R e b = 10595 , it can be obtained that although the high-order upwind scheme lacks perfection of dissipation in high wave number range, it still demonstrates superior predictive capability compared with the second-order non-dissipative central scheme, especially with relatively coarse grids. Finally, by taking the high-order upwind scheme as a suitable selection for turbulence simulation, the turbulent flow over a 30P30N multi-element airfoil is investigated as an application study. After briefly comparing the simulated profiles and spectrum with reference experimental results as validation, the budget of TKE is analyzed to locate the dominant flow structures and regions. It is found that the production and dissipation terms behave in a "monopole" pattern in the locations with strong shears and wakes. Whereas the advection and diffusion terms show an "inward" pattern and an "outward" pattern, which indicate the spatial transport of TKE between the center of the shear layer and nearby locations. [ABSTRACT FROM AUTHOR]

This paper investigates numerically the shock wave interaction with a V-shaped heavy/light interface. For numerical simulations, we choose six distinct vertex angles ( θ = 40 ∘ , 60 ∘ , 90 ∘ , 120 ∘ , 150 ∘ , and 170 ∘) , five distinct shock wave strengths ( M s = 1.12 , 1.22 , 1.30 , 1.60 , and 2.0 ), and three different Atwood numbers ( A t = − 0.32 , − 0.77 , and − 0.87 ). A two-dimensional space of compressible two-component Euler equations are solved using a third-order modal discontinuous Galerkin approach for the simulations. The present findings demonstrate that the vertex angle has a crucial influence on the shock wave interaction with the V-shaped heavy/light interface. The vertex angle significantly affects the flow field, interface deformation, wave patterns, spike generation, and vorticity production. As the vertex angle decreases, the vorticity production becomes more dominant. A thorough analysis of the vertex angle effect identifies the factors that propel the creation of vorticity during the interaction phase. Notably, smaller vertex angles lead to stronger vorticity generation due to a steeper density gradient, while larger angles result in weaker, more dispersed vorticity and a less complex interaction. Moreover, kinetic energy and enstrophy both dramatically rise with decreasing vortex angles. A detailed analysis is also carried out to analyze the vertex angle effects on the temporal variations of interface features. Finally, the impacts of different Mach and Atwood numbers on the V-shaped interface are briefly presented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The chip compression ratio is the most important characteristic of various machining processes with chip generation. This characteristic enables the determination of kinetic and other energy loads on the tool and the machined material. This provides an overall evaluation of the machining process and the possibility of its subsequent optimization. This paper presents the results of determining this cutting characteristic by experimental method, analytical calculation, and numerical modeling. For the analytical calculation of the chip compression ratio, an analytical cutting model developed based on the variational principle of the minimum potential energy was used. A finite element model of orthogonal cutting was used for the numerical simulation of the above process characteristic. Experimentally, the chip compression ratio was determined by the ratio of the chip thickness to the cutting depth (undeformed cutting thickness). The chip thickness was determined by direct measurement using chip slices obtained during the cutting process. The Johnson–Cook constitutive equation was used as the machined material model and the Coulomb model was used as the friction model. The generalized parameters' determination of the constitutive equation was performed through a DOE (Design of Experiment) sensitivity analysis. The variation range of these parameters was chosen based on the analysis of the effect of individual parameters of the constitutive equation on the chip compression ratio value. The largest deviations between the experimental and analytically calculated values of the chip compression ratio did not exceed 21%. At the same time, the largest deviations of simulated values of the indicated cutting characteristic and its experimental values did not exceed 20%. When comparing the experimental values of the chip compression ratio with the corresponding calculated and simulated values, the deviations were within 22%. [ABSTRACT FROM AUTHOR]

The shape of the connecting section of the shaft spillway directly affects the flow pattern of the tunnel, the vibration characteristics of the shaft and the energy dissipation effect. At present, the research on the shape of connecting section is mostly single factor, and few multi-factor studies. In engineering design practice, the optimization of shaft shape mostly refers to similar engineering experience, and there is no more systematic optimization method. In this paper, the numerical orthogonal test is used to analyze the sensitivity of the length-width ratio, the contraction ratio of the exit pressure slope and the compression slope ratio of the connecting section. The results show that the length-width ratio has the most significant effect on the outlet turbulent kinetic energy, followed by the compression slope ratio and the lowest contraction ratio. The research results can provide some reference for the optimization of the joint shape of the shaft spillway tunnel in engineering design. [ABSTRACT FROM AUTHOR]

Supersonic ion jets produced in vacuum arc discharges have a wide range of applications, where precise control of ion kinetic energy is crucial. However, a comprehensive understanding of the ion acceleration mechanism remains elusive, particularly regarding whether there is ion velocity separation in the vacuum spark stage. In this paper, a 1D spherical implicit particle-in-cell (PIC) with Monte Carlo collision (MCC) model is employed to investigate the ion velocity separation in multi-charged vacuum arc plasma with varying electrode bias voltages and plasma ion densities. The results show that ion kinetic energy can reach hundreds of electron volts due to continuous acceleration by the formed potential valley, which leads to ion velocity separation at low electrode bias voltage or low plasma density. An increasing electrode bias voltage flattens the potential valley, reducing the electric field acceleration. While increasing the plasma density deepens the valley and intensifies Coulomb collisions, resulting in nearly-equal velocities across ions in different charge states. These findings can theoretically explain the discrepancies observed in previous experiments regarding the dependence of the ion velocity on its charge state during the vacuum spark stage. [ABSTRACT FROM AUTHOR]

Launcher efficiency is an important index for evaluating the performance of the electromagnetic launcher, and it reflects the ability of the launcher to convert input electrical energy into kinetic energy of the armature. In this paper, the launcher efficiency is taken as the objective function of bore parameter optimization, and particle swarm optimization is used to optimize the initial parameters of the BP neural network to improve the accuracy of the neural network in predicting launcher efficiency. The results show the following: (1) The predicted efficiency of the launcher shows the same trend as the experimental results. When the ratio of rail separation and rail height is greater than 1.75, the rate of change in the launcher efficiency curve decreases as the rail separation increases. (2) The weight of the influence of each parameter on the launcher efficiency follows the following law: convex arc height > rail separation > rail height > rail thickness. (3) The mean absolute error of the BP neural network prediction is 0.70%; after optimization by PSO, the mean absolute error is reduced to 0.28% and the mean relative accuracy is improved from 0.9774 to 0.9910, which indicates the feasibility of the PSO-BP neural network for the prediction of the launcher efficiency of an electromagnetic launcher. [ABSTRACT FROM AUTHOR]

Semi-local scales have been widely used in compressible wall-bounded turbulence, but it is still unclear whether they are applicable to the scaling of coherent structures, especially under conditions of high Mach number and cold wall temperature. By scrutinizing the direct numerical simulation dataset at different Mach numbers and wall temperatures, this paper demonstrates that the coherent structures normalized by semi-local scales are universal in size. In addition to this, we find that the ratios of Kolmogorov scales to semi-local scales are independent of Mach number and wall temperature. Thus, Kolmogorov scales can achieve the same scaling effect as the semi-local scales. The velocity spectra are also compared to verify the current scaling method quantitatively. A method to determine the threshold for the vortex identification criterion is proposed, allowing the same threshold for different cases to obtain vortices of similar size. The scaling of other statistics including turbulent kinetic energy, streamwise Reynolds normal stress, and root mean square of fluctuating vorticity is also investigated. A new velocity scale is proposed based on the total-stress-based transformation for mean streamwise velocity, which can collapse the profiles of these statistics more accurately than the semi-local velocity scale. The present paper demonstrates that through appropriate normalization, the structures and statistics of compressible turbulence become universal, reaffirming the validity of Morkovin's hypothesis even for the present high Mach number and cold wall cases. [ABSTRACT FROM AUTHOR]

In this paper, a heat generator with fluid agitation is developed and experimentally studied. This heat generator can convert kinetic energy from a wind turbine directly to thermal energy through the process of viscous dissipation—a process achieved through the agitation of the working fluid inside a container. In the experimental study, an electric motor (instead of a wind turbine) was used to provide the kinetic energy input to the heat generator. The torque, rotational speed, and temperature rise in the fluid were measured. Using the measured quantities, the efficiency of kinetic energy to sensible heat conversion was calculated. Experiments were conducted to investigate the effects of different impellers, rotational speeds, and working fluids, including distilled water, ethylene glycol (EG), and their respective nanofluids, with A l 2 O 3 nanoparticles at different concentrations. The study also found that the temperature rise in fluids due to viscous dissipation was influenced by the specific heat of the fluid, suggesting that the heat generator can be optimized for energy storage with high-specific-heat fluids, such as water, or for achieving a higher temperature rise with low-specific-heat fluids, such as ethylene glycol. The experimental results indicated that the heat generator was up to 90% efficient in converting kinetic energy to thermal energy. The study revealed that, for constant power input, the heat dissipation rate depends solely on the vessel's geometry, not the fluid properties. Optimizing the impeller design and baffles within the vessel is crucial for maximizing power input. For applications, a wind turbine can power this heat generator to provide heat to a house or a commercial building. [ABSTRACT FROM AUTHOR]

The paper describes a theoretical research approach that performs a dynamic study upon a complex gear transmission. The transmission errors of the gears from the considered complex gear drive are considered when kinematics is analyzed and presented. The cutting forces from a gear hobbing process, possibly driven by such a complex gear transmission, are considered when parameters of the dynamic model are mathematically evaluated and presented. The proposed model development includes the obtaining of the differential equation for kinetic energy. Some discussions are also made regarding the studied complex mechanism. Practically, mathematical models for the influence of transmission errors and hobbing forces upon the considered complex gear drive are proposed as deliverable results of the study. Final conclusions are also included in the paper. The aspects discussed in the paper are presenting utility for the design of such mechanisms or for calculating the parameters of some gear hobbing processes. [ABSTRACT FROM AUTHOR]

In this paper, the impact resistance of a cylindrical structure with a buffer ring and an energy-absorbing ring under double impact loads is studied. Based on ABAQUS 2023 finite element software, a simulation model of a buffer ring structure with three different sibs was established, and the specimens were subjected to double impact loading. The results show that the impact resistance of the structure decreases with the increase in curvature radius. The increase in the thickness of the panel can effectively reduce the deformation difference between the center point of the panel and the maximum displacement point. The buffer ring composed of cell structure with negative Poisson's ratio effect has better shock resistance under explosion load, while the buffer ring with hexagonal cellular structure has excellent kinetic energy shock resistance. [ABSTRACT FROM AUTHOR]

In this paper, according to the actual size of gas turbine blade interior space, eight vortex cooling models with different cross-sectional shapes of coolant chambers are established. Rectangular, Circle, Trapezoidal up, Trapezoidal down, Ellipse up, Ellipse down, Sine up and Sine down are the eight coolant chamber shapes. Functions of variable coolant chamber structures on vortex cooling flow and heat exchange characteristics are numerically analyzed by verifying the Standard k - ω turbulence model and conducting grid independence analysis. Research results show that the heat exchange ability of Sine up coolant chamber is the best compared with the other coolant chambers. The cool air enters the vortex chamber at a faster speed and impacts on the target surface to form a high-pressure area and a low-temperature swirl. The more the cool air moves downstream, the greater the turbulent kinetic energy becomes, which is more conducive to the heat transfer. Therefore, Sine up coolant chambers have the highest thermal performance factor. Due to the low drag coefficient and high target surface average Nusselt number of Ellipse up, its thermal exchange performance is second only to that of Sine up. Circle coolant chamber will not bring favorable factors to engineering application because of the slowest flow speed and the worst heat exchange capacity. For Trapezoidal up and Trapezoidal down, the flow velocity, pressure distribution, turbulent kinetic energy intensity and heat transfer uniformity are almost the same as Rectangle coolant chamber. The models of Ellipse down and Sine down coolant chambers exhibit less turbulent kinetic energy strength to heat transfer and higher temperature in the vortex chamber, and it is not suggested for cooling system optimal design. [ABSTRACT FROM AUTHOR]

The supersaturation equation for a vertically moving adiabatic cloud parcel is analyzed. The effects of turbulent updrafts are incorporated in the shape of a stochastic Lagrangian model, with spatial and time correlations expressed in terms of turbulent kinetic energy. Using the Fokker–Planck equation, the steady-state probability distributions of supersaturation are analytically computed for a number of approximations involving the time-scale separation between updraft fluctuations and phase relaxation, and droplet or ice particle size fluctuations. While the analytical results are presented in general for single-phase clouds, the calculated distributions are used to compute mixed-phase cloud properties—mixed fraction and mean liquid water content in an initially icy cloud—and are argued to be useful for generalizing and constructing new parameterization schemes. Significance Statement: Supersaturation is the fuel for the development of clouds in the atmosphere. In this paper, our goal is to better understand the supersaturation budget of clouds embedded in a turbulent environment by analyzing the basic equations of cloud microphysics. It is found that the turbulent characteristics of an air parcel substantially affect the cloud's supersaturation budget and hence its life cycle. This is also shown in the context of mixed-phase clouds where, depending on the turbulent regime, different liquid-to-ice ratios are found. Consequently, the theoretical approach of this paper is crucial to develop tools to parameterize small-scale atmospheric features, like clouds, into global circulation models to improve climate projections for the future. [ABSTRACT FROM AUTHOR]

Purpose: In the post-capture stage, the tumbling target rotates the combined spacecraft system, and the detumbling operation performed by the space robot is required. To save the costly onboard fuel of the space robot, this paper aims to present a novel post-capture detumbling strategy. Design/methodology/approach: Actuated by the joint rotations of the manipulator, the combined system is driven from three-axis tumbling state to uniaxial rotation about its maximum principal axis. Only unidirectional thrust perpendicular to the axis is needed to slow down the uniaxial rotation, thus saving the thruster fuel. The optimization problem of the collision-free detumbling trajectory of the space robot is described, and it is optimized by the particle swarm optimization algorithm. Findings: The numerical simulation results show that along the trajectory planned by the detumbling strategy, the maneuver of the manipulator can precisely drive the combined system to rotate around its maximum principal axis, and the final kinetic energy of the combined system is smaller than the initial. The unidirectional thrust and the lower kinetic energy can ensure the fuel-saving in the subsequent detumbling stage. Originality/value: This paper presents a post-capture detumbling strategy to drive the combined system from three-axis tumbling state to uniaxial rotation about its maximum principal axis by redistributing the angular momentum of the parts of the combined system. The strategy reduces the thrust torque for detumbling to effectively save the thruster fuel. [ABSTRACT FROM AUTHOR]

This paper aims on evaluating the terminal effects and outcomes related to the use of some improvised non-lethal ammunition consisting of regular 12-gauge shot ammunition for which the shots were replaced with a certain amount of rubber spheres that equip the HDS airsoft shotgun variants. Since the rubber spheres are available for online acquisition and they come in three different gauges (.40, .50 and .68 inches), trials were conducted with three different configurations for the 12-gauge non-lethal cartridge. Experimental testing environments were represented by a force wall and a ballistic gelatin rig, in coherence with the STANREC 4744 procedures. Furthermore, a numerical evaluation was made in order to identify the behavior of the rubber sphere - gelatin interface. Even though the making of such non-lethal cartridges is relatively simple and does not require special purpose equipment, the results confirm that this improvised approach does not lead to a safe and reliable non-lethal kinetic ammunition and its terminal effects might inflict severe damage to the persons engaged from a short distance. [ABSTRACT FROM AUTHOR]

Incorporating a guide vane-type spiral flow generator can effectively resolve particle deposition issues during long-distance pipeline conveyance. Combining model experiments and computational fluid dynamics (CFD) results under different guide vane height conditions, the paper investigated the structure of the circumferential velocity and the generated rotational effects of the guide vane-type spiral flow generator. Due to the combined effects of the guide vane constraint and water inertia, an envelope surface with a zero circumferential velocity exists along the inner edge of the guide vanes and in the direction of water flow. The envelope surface divides the circumferential flow velocity distribution into internal negative and external positive velocity zones. This paper discovered that the distribution of the envelope surface in the radial and axial directions is affected by both the height of the guide vanes and the Reynolds number. The rotational intensity of the fluid particles around the axis was characterized by the circumferential moment of momentum. When the relative height of the guide vane was 0.35, the highest percentage of circumferential flow velocity in the flow field was reached, while the rotational kinetic energy conversion efficiency was maximum. [ABSTRACT FROM AUTHOR]