Field Characteristics Research Articles

Research on Flow Field Characteristics of a Three-Plate Vertical Rotary Gate

Research on Flow Field Characteristics of a Three-Plate Vertical Rotary Gate

Numerical Simulation and Optimization Study on the Flow Field Characteristics of a Double-Slot Spillway

To investigate the flow characteristics of a novel dual-slot overflow channel, a research approach integrating physical experiments and numerical simulations was adopted. A three-dimensional model of the overflow channel was developed, employing the RNG k-ε turbulence model and the VOF two-phase flow model to optimize the numerical simulation of the high-low dual-slot flow field. Physical experiments were conducted to verify and analyze the hydraulic characteristics of the high-low overflow channel, including the longitudinal water surface profile and flow patterns. The numerical simulation results aligned well with the physical model test results. By analyzing the flow field of the dual-slot counterflow spillway, the flow characteristics at both the spillway and outlet sections were identified. This study focused on the water surface profile along the spillway, the pressure distribution, and the counterflow characteristics of the protruding water tongue, and explored optimization strategies for the WES surface and spillway design. Physical model tests were conducted on the final optimized design, yielding good agreement between the theoretical predictions and experimental results, thereby confirming the feasibility of the energy dissipation methods for both high and low spillways. The research outcomes offer valuable references for related engineering applications.

Multi-slotted airfoil design for enhanced aerodynamic performance and economic efficiency.

Recently, slotted airfoils have been introduced as a passive flow control approach. The slotted airfoil method resulted in stall delay and enhanced the lift coefficient. The single-slot airfoil is unable to delay stall if the flow is injected downstream of the separation point at the stall angle of attack. A multi-slot airfoil ensures air is injected along the airfoil suction side, delaying stalls over a large range of AOA. The current study focuses on enhancing wind turbine blades' efficiency by utilizing a novel multi-slot NACA23012C airfoil design as a passive control approach. A numerical study of the optimal grid number was carried out, followed by validating the numerical model with previous experimental results in the literature. The numerical study is followed by a study of the effect of the number of airfoil slots: one, two, three, four, five, and six. The characteristics of the flow field were analyzed to explain the benefit of applying multi-slotted on the aerodynamic performance of an airfoil with a high AOA at Reynolds number 2.74 × 105. The findings showed a significant improvement in the lift coefficient values and the delayed stall AOA for multi-slot airfoils compared to the clean and single-slot airfoils. Increasing the slots number is effective up to four slots. The four-slot airfoil improved lift by 15.8%, and the two slots achieved a 22.31% CL/CD increase. Future work could optimize slot geometry, validate findings experimentally, and study dynamic and 3D effects.

Study on Sound Field Properties of Parametric Array Under the Influence of Underwater Waveguide Interface Scattering Based on Non-Paraxial Model—Theory and Experiment

This paper theoretically and experimentally studies the effect of underwater waveguide interface scattering on the nonlinear sound field characteristics of parametric array (PA) radiation. Based on the image source method, the components of the sound field in the waveguide are first analyzed. Then, a non-paraxial model is developed to account for the influence of interface scattering. This model enables accurate calculation of the wide-angle sound field. The impact of the sound source depth and the interface reflection coefficient on the distribution of the difference-frequency wave (DFW) sound field in the waveguide is studied. The interface alters the phase distribution of the DFW’s virtual source density function, thereby affecting the sound field accumulation process. Waveguide interfaces with different absorption coefficients influence the amplitude oscillation caused by interface reflection and change the sidelobe size of the DFW beam. The DFW sound field distribution is measured at three typical frequencies. Simulation and experimental results show that the attenuation of the DFW’s axial sound pressure level in the waveguide oscillates, and the DFW’s beamwidth gradually widens as the frequency decreases. The calculated results from the proposed model agree well with the measured data, with average errors along the sound axis and depth being less than 3 dB and 6 dB, respectively. This demonstrates the model’s superior applicability compared to the existing free-field model.

Multiphase flow simulations and experiments on electrochemical jet machining of rough surfaces of high-speed additive manufactured titanium alloys

ABSTRACT The application of titanium alloy parts manufactured by high-speed additive manufacturing in industry is currently constrained by the low surface accuracy. This severely constrains the potential of high-speed additive manufacturing for processing aerospace titanium alloy components. To address this issue, it is crucial to address the high-speed additive manufactured rough surface in order to enhance surface accuracy. As a highly flexible non-contact machining method, electrochemical jet machining is well-suited for surface post-treatment of additive manufactured titanium alloy parts due to its distinctive advantages, including the absence of tool loss, no cutting force, and no thermal effects. This paper examines the electrochemical jet machining of rough low-precision surfaces produced by high-speed additive manufacturing. The distribution characteristics of the machining electric field and machining flow field on extremely rough additive manufactured surfaces were investigated through simulation. A series of experiments were conducted to verify the effectiveness of the simulation. The research findings indicated that the cut-in electrochemical jet machining method effectively circumvented the adverse effects of rough surfaces on electrolyte flow, thereby allowing for high-quality machining. The surface roughness of titanium alloy samples produced by high-speed additive manufacturing was reduced from Ra 21.179–1.838 um, representing a 90% reduction.

First-principles, magnetothermal and magnetocaloric calculations on Gd1-xCexMn2Ge2 ([formula omitted])

In this research, we study the two compounds, Gd0.5Ce0.5Mn2Ge2 and Gd0.33Ce0.67Mn2Ge2, employing the molecular field theory and the first-principles calculations. The electronic and elastic characteristics are determined through the use of Density Functional Theory (DFT) calculations. Super-cell DFT computations are utilized to calculate the overall density of states (DOS), elastic stiffness constants Cij, and various elastic properties e.g. bulk and shear moduli. The primary objective is to investigate important physical properties such as magnetization, magnetic heat capacity, and key aspects of the magnetocaloric effect including both isothermal magnetic entropy change ΔSm and adiabatic temperature change ΔTad., relative cooling power (RCP), and magnetic phase transition. We investigate these characteristics in magnetic fields up to 6 T and at temperatures up to 400 K. The two compounds show a Curie temperature TC around 340 K. We also studied the effect of high magnetic fields on the nature of the phase transition.

Influences and variations of wave impedance of electromagnetic fields generated by lightning return strokes

The domains of lightning electromagnetic pulse (LEMP) fields are classified as “near-field,” “intermediate-field,” and “far-field” based on qualitative descriptions. However, the systematic quantitative classification of LEMP fields is yet to be reported. This study characterized the wave impedance of lightning electromagnetic pulse (WILEMP) to solve this problem. The components and field domain distribution ranges of LEMP were analyzed by varying the WILEMP and the distance between the observation point and radiation source (r). The changes in the WILEMP with r under the influence of different factors were calculated using the finite-difference time-domain (FDTD) method. The results indicated that the LEMP field has high impedance. the WILEMP decreased rapidly with the increase in r when r ≤ 10 km, consistent with the characteristics of the electrostatic and induction fields (near field). The WILEMP gradually decreased and stabilized with the increase in r when r ≥ 20 km, and the value was roughly the same as the impedance of free space (377 Ω) when r = 100 km, consistent with the characteristics of radiation field (far field). The decay rate of the WILEMP was lower than that when r ≤ 10 km but higher than that when r ≥ 20 km. Finally, when 10 km < r < 20 km, the apparent transitivity was consistent with intermediate-field characteristics.

Research and evaluation of turbulent jet ignition mode for improving combustion performance of ethanol rotary engine

Improving the combustion performance of ethanol rotary engine (ERE) is crucial for enhancing energy efficiency and reducing emissions, particularly in the context of global emission reduction efforts. Although the application of ethanol as a clean alternative fuel is growing, research on optimizing its combustion in rotary engines remains limited. The novelty of this work lies in the comparison of two ignition modes: the conventional spark plug ignition mode (CSPIM) and the turbulent jet ignition mode (TJIM). Experimental validation and numerical simulation methods were employed to evaluate the effects of these two ignition modes on in-cylinder flow field and combustion characteristics. The results indicate that, compared to the CSPIM, the use of the TJIM significantly improves turbulence intensity, increases peak pressure, reduces combustion duration, and expands the flame propagation area, leading to an average increase of 0.42 kW in the power output of the ERE. Furthermore, the use of the TJIM leads to a 130 % average increase in NO mass produced in the cylinder, while CO emissions are reduced by 40 % on average. These findings demonstrate that the TJIM has significant potential to improve the combustion performance of ERE, offering considerable advantages in both efficiency and emissions control.

Large eddy simulation of the flow field characteristics around a jacket foundation under unidirectional flow actions

Large eddy simulation of the flow field characteristics around a jacket foundation under unidirectional flow actions

Fully automated CFD simulation system research based on design scheme tree

Compared with the remarkable achievements of computer-aided drug discovery systems for drug discovery, the role of computational fluid dynamics (CFD) in flow channel design requires further development. While CFD has undergone rapid evolution, the absence of integrated geometry and mesh processing hinders the potential development of advanced applications of this technology. To overcome this limitation, in this paper, the JIACFD toolset is presented, and a fully automated CFD simulation system is established. The simulation system is also constructed on a design scheme tree, which is more in accordance with engineering logic. The control parameter trend analysis method is introduced to select appropriate candidates from the design scheme tree. Additionally, the control parameter trend assumption, which is proven via the Spearman method, is proposed to improve the efficiency of the system. During the verification process for the study case, two independent control parameters exhibit correlating trends, and one control parameter converges when the number of meshes increases, indicating a lack of trend sensitivity. The design scheme tree and trend curve are subsequently utilized to effectively analyze the flow field characteristics of different schemes. Finally, the control parameter trend analysis method is employed to rank the design scheme tree and verify that the ranking of candidates is not dependent on the number of meshes. This paper investigates and verifies the presented system, method, and assumption and explores the possibility of an established system playing a more critical role in performance design work.

Mechanism analysis of high-order harmonics acting on transonic shock buffeting

Periodic oscillations of shock waves in transonic flow fields create very unstable aerodynamic loads that have a big effect on how safe an aircraft is and how well it handles. To elucidate the mechanism of transonic shock buffeting, a jet disturbance method is introduced and used to analyze the evolution of the flow field characteristics. First, the basic characteristics of buffeting are obtained through wind tunnel experiments. Numerical simulations are then conducted using the unsteady Reynolds-averaged Navier–Stokes equation based on the Reynolds stress model. The response of the global flow field to a jet disturbance enables the effects of the jet intervention time, jet withdrawal, and jet intensity to be studied. When the flow field is disturbed, the oscillations of the shock wave on the upper surface slow, and the buffeting load is reduced. An increase in jet strength suppresses the buffeting by preventing the factors that cause this phenomenon from exerting any influence. When the jet intensity exceeds a critical value, a complex multi-vortex structure and high-frequency pressure fluctuations appear at the trailing edge. In the presence of the jet disturbance, special high-order harmonics appear in the frequency spectrum, and high-frequency pressure waves occur in the global flow field. The fluctuating pressure generates high-order harmonics, and the trailing edge is the core position of transonic shock buffeting. The resulting high-frequency pressure waves are transmitted upstream, strengthening the shock wave–boundary layer interaction and causing shock oscillations.

Enhanced underwater three-dimensional imaging using acoustic orbital angular momentum waves and mode matching beamforming.

Improving the underwater three-dimensional imaging resolution of a sonar system is of great significance to achieving high-precision ocean exploration results. Actually, improving the resolution can be considered from the perspective of information acquisition. The acoustic orbital angular momentum (AOAM) wave has a modal dimension and can carry more target information. However, there are few studies on the application of AOAM waves for underwater three-dimensional imaging. This paper establishes the related signal models of the AOAM wave in underwater imaging and examines the sound field characteristics from both simulation and underwater real test data. A method called mode matching beamforming (MMBF) is proposed, and a composite structure of uniform circular array (UCA) plus spiral array is combined to study the imaging performance of AOAM waves and plane waves. The simulation results indicate that, compared with the plane wave, the sidelobe in the AOAM wave imaging beam pattern reaches -22.43 and -29.10 dB in the azimuth and elevation angles, respectively, and the mainlobe widths are reduced by 1.70° and 0.40° in both directions. Finally, this paper uses the MMBF method to process the echo data of underwater real object and realizes the imaging of the corner reflector.

Experimental and numerical investigation of flow field characteristics and local scour around trapezoidal artificial reefs

Experimental and numerical investigation of flow field characteristics and local scour around trapezoidal artificial reefs

Study on Fluctuating Wind Characteristics and Non-Stationarity at U-Shaped Canyon Bridge Site

To investigate the non-stationary characteristics of the wind field at the U-shaped canyon bridge site and its impact on fluctuating wind characteristics, a wind observation tower was installed near a cable-stayed bridge. The Augmented Dickey–Fuller (ADF) test was employed to assess the stationarity of wind speed series, while the discrete wavelet transform (DWT) was applied to reconstruct the time-varying mean wind and analyze its effect on fluctuating wind characteristics. Results indicate that wind speeds in this region exhibit bimodal distribution characteristics, with the Weibull-Gamma mixed distribution model providing the best fit. The proportion of non-stationary samples increases with height. Autocorrelation function (ACF), partial autocorrelation function (PACF) tests, and power spectral density (PSD) analysis determined the optimal wavelet decomposition level for wind speed in this region. Analysis of non-stationary samples using db10 wavelet reconstruction reveals that the stationary wind speed model overestimates turbulence intensity but underestimates the turbulence integral scale. The downwind spectrum deviates from the Kaimal spectrum in both low- and high-frequency bands, whereas the vertical spectrum aligns well with the Panofsky spectrum. The findings demonstrate that the wavelet reconstruction method more accurately captures fluctuating wind characteristics under the complex terrain conditions of this canyon area.

Experimental Study on Noise-Reduced Propagation Characteristics of the Parametric Acoustic Array Field in a Neck Phantom

The electrolarynx (EL) is a common device for voice reconstruction in laryngectomy patients, but its mechanical sound source generates significant radiation noise, affecting the naturalness and acceptability of the speech. The parametric acoustic array (PAA), which produces directionally propagated difference-frequency sound waves, presents a promising alternative for creating a more natural glottal-like voice source in the trachea while reducing radiation noise. In this study, we developed a tissue-mimicking phantom to simulate human neck tissue and used a single-transducer-based PAA platform to generate modulated ultrasound signals with glottal waveform characteristics. Ultrasonic microphones captured sound signals fromthe trachea and surrounding air, and signal processing was used to isolate the difference-frequency signals. The results demonstrated that difference-frequency signals were successfully detected in the phantom’s trachea, with time-domain waveforms and frequency spectra closely resembling the designed glottal waveform (Pearson correlation coefficient = 0.9438). Additionally, radiation noise produced by the PAA was significantly lower (23 dB, p < 0.0001) compared to the traditional EL. These findings demonstrate the potential of PAA for voice source reconstruction in laryngectomy patients and suggest its capacity to enhance speech rehabilitation outcomes. Further research is required to refine the frequency range and evaluate clinical applicability.

Influence of creep–slip fracture length on the local deformation field and fracture characteristics of rock-like models

Influence of creep–slip fracture length on the local deformation field and fracture characteristics of rock-like models

Modelling and optimization of small - scale soft magnetic robots for enhanced locomotion

Small-scale soft robots are vital in medical scenarios requiring access to confined spaces. This study explores motion optimization for such robots, emphasizing magnetically responsive materials that enable shape changes through controlled magnetic fields. These materials provide robots with versatile and agile locomotion capabilities. Using genetic algorithms, we present a novel approach to optimize magnetic field parameters and robot dimensions. In magnetic field optimization, the results validate prior experimental observations while providing new insights into determining optimal magnetic field characteristics for walking motions. Deviations from optimal magnetic field magnitudes directly affect walking velocity, revealing a non-linear relationship between magnetic fields and locomotion speed, diverging from linear modeling results. Furthermore, we find that both excessively low and high robot heights hinder walking speed lower heights reduce surface friction, while higher heights compromise agility. This comprehensive optimization strategy advances the capabilities of small-scale soft magnetic robots. Our work in motion modeling and optimization enhances the understanding of these robots' dynamics and unlocks new possibilities for deployment in complex environments. These findings reaffirm the significance of soft robots in medical and confined-space applications, offering a robust foundation for further innovations in this evolving field.

Investigating the spatiotemporal characteristics of motion fields using three‐dimensional radar echoes to construct an ensemble nowcasting system

AbstractIn this study, a spatial and temporal analysis of three‐dimensional motion fields was conducted to formulate an ensemble nowcasting scheme. These motion fields were derived from radar data covering the entire volume and were analyzed across space and time for five different weather phenomena in Taiwan, namely, autumn precipitation, Meiyu front, squall line, afternoon thunderstorm and typhoon. Subsequently, perturbations will be introduced into the two‐dimensional motion field to develop an ensemble nowcasting framework. The magnitude of the perturbations will be adjusted based on the spatiotemporal analysis of the three‐dimensional motion fields. The effectiveness of the ensemble nowcasting in forecasting radar echoes and accumulated rainfall will be examined using a variety of verification scores. An evaluation of this ensemble nowcasting method demonstrated its efficacy in accurately predicting precipitation occurrences, with a reliability extending nearly three hours for five afore‐mentioned weather events. Furthermore, the forecasted accumulation of rainfall closely mirrored observed patterns, indicating the scheme's ability to capture precipitation distribution accurately. In summary, the ensemble nowcasting scheme mitigates uncertainties associated with motion field and exhibits superior forecasting capabilities compared with the original extrapolation method.

Behavioral and neurophysiological effects of electrical stunning on zebrafish larvae

Two methods dominate the way that zebrafish larvae are euthanized after experimental procedures: anesthetic overdose and rapid cooling. Although MS-222 is easy to apply, this anesthetic takes about a minute to act and fish show aversive reactions and interindividual differences, limiting its reliability. Rapid cooling kills larvae after several hours and is not listed as an approved method in the relevant European Union directive. Electrical stunning is a promising alternative euthanasia method for zebrafish but has not yet been fully established. Here we characterize both behavioral and neurophysiological effects of electrical stunning in 4-day-old zebrafish larvae. We identified the electric field characteristics and stimulus duration (50 V/cm alternating current for 32 s) that reliably euthanizes free-swimming larvae and agarose-embedded larvae with an easy-to-implement protocol. Behavioral analysis and calcium neurophysiology show that larvae lose consciousness and stop responding to touch and visual stimuli very quickly (<1 s). Electrically stunned larvae no longer show coordinated brain activity. Their brains instead undergo a series of concerted whole-brain calcium waves over the course of many minutes before the cessation of all brain signals. Consistent with the need to implement the 3R at all stages of animal experimentation, the rapid and reliable euthanasia achieved by electrical stunning has potential for refinement of the welfare of more than 5 million zebrafish used annually in biomedical research worldwide.

Influence of heat input and heat exchange coefficient on temperature and stress field of a X80 steel pipeline repair-weld root pass of a type-B sleeve

Abstract The formation of the type-B sleeve repaisring root pass seriously affects the quality of in-service repair of B-type sleeve. Therefore, it is necessary to systematically study the temperature field, stress field, and deformation field of type-B sleeve repairing root pass. In this paper, a double ellipsoid heat source model is developed to investigate the weld temperature, residual stress, and deformation field characteristics in the type-B sleeve repairing root pass. The results show that the heat exchange coefficient of the inner wall of the pipeline has a relatively small impact on the penetration depth, residual stress, and deformation of type-B sleeve repairing root pass, and the weld heat input has a significant impact on the penetration depth, residual stress, and deformation of type-B sleeve repairing root pass. In a whole, when the heat input of the repairing root pass is around 0.9 KJ mm−1, a well-formed repairing root pass with moderate residual stress and minimal deformation can be obtained.