Search Results (43)

Pumped-storage hydropower requires pump-turbines to operate safely and efficiently under off-design conditions, where stall-induced unsteady flows can redistribute hydraulic losses and reduce operational stability. Unlike previous analyses focused mainly on spatial correlations, this study develops a spatiotemporal framework to clarify how hydraulic loss (HL) and vortex evolution (VE) co-vary under different stall states at the valley point of the pump-mode hump region in a low-specific-speed, ultra-high-head pump-turbine. Detached eddy simulations (DES) were performed for an original-runner scheme (ORI) and an optimized-runner scheme (OPT), with identical stationary components, boundary conditions, and numerical settings. The comparative cases cover four representative flow states: non-stall, fixed stall, rotating stall, and mixed stall. The local hydraulic-loss rate (LHLR) was decomposed into dissipation (DIS) and transport (TRANS) terms, and Liutex-based vorticity decomposition was used to distinguish shear- and rigid-rotation-related vortex quantities. Pearson correlation analysis was then applied in both space and time. The results show that DIS is consistently associated with shear enstrophy ${\Omega }_{\mathrm{S}}$, whereas the spatiotemporal correlation associated with TRANS and VE parameters exhibits stronger regional and stall-state dependence. These findings provide a quantitative basis for identifying loss-sensitive vortex features and support flow-control and runner-optimization strategies for improving pump-turbine efficiency and stability. Full article

The quality of meteorological data from a certain type of commercial aircraft flying between Hong Kong and Shanghai is investigated in this study with a special focus on wind-related parameters, including the horizontal wind speed, horizontal wind direction, and eddy dissipation rate (EDR). The novelty of the study is the analysis of flight data on a new route between Hong Kong and Shanghai. The method for calculating the EDR from Quick Access Recorder (QAR) data of the studied aircraft type is first described. Then, we analyze seven flights operating between Hong Kong and Shanghai in 2025, when Hong Kong was affected by two typhoons, Wipha and Ragasa. Both low-level and enroute wind data are considered. The quality of QAR-based wind data is established through comparison with (a) QAR data from other airline flights separated by 10 min and by one runway from the studied aircraft; (b) headwind and EDR observations from Doppler Light Detection and Ranging (LIDAR) systems at Hong Kong International Airport (HKIA); and (c) reanalysis data of a global numerical weather prediction (NWP) model for the enroute phase of the studied aircraft type. The QAR-based wind data is found to have sufficient quality for the study of low-level windshear and turbulence as well as meteorological applications such as upper-air wind monitoring and data assimilation into NWP models. The wind data collected in the enroute phase is studied further by considering an extended period of July and September 2025 with 151 sets of valid QAR data. The horizontal wind speed and wind direction from the QAR are in general agreement with the model reanalysis data, noting the different nature of the matched data (e.g., averaging period, model grid resolution). Full article

To address the insufficient damping and instability tendency of metal coil spring isolators subjected to intense impact loading, a multi-stage vibration isolation configuration integrating polyurethane, springs, and eddy current dampers is proposed. Dynamic models for both single-stage and multi-stage isolation systems are formulated, and a corresponding simulation model is developed in MATLAB R2023b/Simulink to investigate the peak suppression and attenuation characteristics of the multi-stage isolation under impact. To characterize the nonlinear finite deformation and time-dependent response of polyurethane, a hyperelastic-viscoelastic constitutive model is established by coupling the Ogden hyperelastic model with a generalized Maxwell viscoelastic model, with model parameters identified through quasi-static compression and stress relaxation tests. Drop impact experiments are performed to compare the displacement response, top- and bottom-plate peak accelerations, and vibration isolation rate between a polyurethane-spring-eddy-current multi-stage isolator and a spring-spring-eddy-current multi-stage isolator. The results demonstrate that the multi-stage structure enables staged dissipation of the impact energy, substantially reducing both the peak acceleration and the displacement stroke of the isolated mass. Under all drop test conditions, the polyurethane-based multi-stage isolator yields lower top-plate output peak acceleration and higher isolation rate than its all-spring counterpart, confirming its superior isolation performance. Envelope fitting of the simulation-based output acceleration with experimental inputs reveals that the all-spring multi-stage isolator exhibits a higher attenuation rate and equivalent damping ratio, whereas the polyurethane-based isolator achieves more effective suppression of the output peak level under severe impact conditions. Full article

This study presents a combined computational fluid dynamics (CFD) and experimental evaluation of an adjustable direct-injection reciprocating (IDR) metallurgical furnace fueled by a multicomponent residual oil–solvent mixture. An axisymmetric CFD model, incorporating k–ω SST turbulence modeling, Eddy Dissipation Concept (EDC) combustion, and Discrete Ordinates radiation, was validated against infrared thermography and Process Analytical Technology (PAT) measurements obtained under actual operational conditions. The residual mixture operated in a turbulence-controlled regime (Da < 1), reaching maximum internal temperatures of 1199 °C and achieving a thermal efficiency of 84.6% (based on LHV). Numerical predictions agreed with thermographic data to within 5% across the stabilized operational window. Under comparable process parameters, the alternative fuel reduced cycle time and operational costs compared with diesel and natural gas whilst maintaining stable combustion. Methodological clarifications encompass a consolidated, dimensionally consistent set of equations, a QoI-based mesh-independence study, and a concise summary of the experimental configuration to enhance reproducibility. Full article

Three-dimensional computational fluid dynamics (CFD) simulation was performed using the eddy-dissipation concept coupled with detailed hydrogen oxidation kinetics and a reduced two-step methane mechanism for a newly proposed W-shaped radiant tube burner (RTB). The effects of the hydrogen volume fraction (0–100%) and excess air ratio (0%, 10%, 20%) on the flame morphology, temperature distribution, and NO_X emissions are systematically analyzed. The results deliver three main points. First, a flame-shape transformation was identified in which the near-injector flame changes from a triangular attached mode to a splitting mode as the mixture reactivity increases with the transition occurring at a characteristic laminar flame speed window of about 0.33 to 0.36 m/s. Second, NO_X shows non-monotonic behavior with dilution, and 10% excess air can produce higher NO_X than 0% or 20% because OH radical enhancement locally promotes thermal NO pathways despite partial cooling. Third, a multi-parameter coupling strategy was established showing that hydrogen enrichment raises the maximum gas temperature by roughly 100 to 200 K from 0% to 100% H₂, while higher excess air improves axial temperature uniformity and can suppress NO_X if over-dilution is avoided. These findings provide a quantitative operating map for balancing stability, uniform heating, and NO_X–CO trade-offs in hydrogen-enriched industrial RTBs. Full article

In modern industrial systems, twin-shaft mixers are key units for efficient mixing and reactions; their performance directly affects product quality, production cycle, and energy consumption across the chemical, pharmaceutical, food, and lithium-battery-slurry sectors. Systematic elucidation of the mixing mechanisms is hindered by strongly three-dimensional, unsteady, and nonlinear flow fields induced by the complex motions of the two shafts. To address these issues, an advanced coupled numerical model combining the lattice Boltzmann method (LBM) and large-eddy simulation (LES) in an integrated LBM–LES framework is developed, incorporating the Smagorinsky subgrid-scale model to capture small-scale turbulent dissipation under high-Reynolds-number conditions with fidelity. The model enables systematic simulations across configurations with varying blade counts, quantitatively revealing how blade count governs flow structures and mixing performance. The results show that blade count is a key design parameter for performance tuning. A four-blade configuration generates moderately strong, well-distributed turbulence and vortical structures in both the main-shaft and side-shaft regions. The generated turbulence and vortical structures, in turn, promote effective global blending and mass transfer while avoiding localized energy over concentration, unnecessary power loss, and overheating risk, thereby achieving an optimal balance among mixing efficiency, energy consumption, and operational stability. These findings provide a solid theoretical basis and a reliable numerical paradigm for the refined design and performance optimization of industrial mixing equipment. Full article

ANSYS-Fluent was applied to simulate diffusion combustion flame in a two-dimensional (2D) industrial burner to determine the contours of the mass fraction of gas emissions, velocity, and combustion temperature. The effects of the boundary conditions, including momentum, thermal, and species (inlet air, inlet fuel, and outlet pressure) on combustion temperature and mass fraction (gas emissions) were analyzed in the designed burner. The present study focused on using and analyzing the volumetric reaction and the turbulence-chemistry interaction of the eddy dissipation model for the diffusion flame model. The simulation used the discrete ordinate model and p1 for radiation and the k-ε model for turbulence with enhanced wall treatment. Based on the results, the magnitude velocities of air and fuel, inlet temperature, and mass fractions of oxygen and inert gas can influence the parameters of flame temperature and gas emissions in the industrial burner. The flame shape for all the cases of inlet velocity was predominantly symmetric about the x = 0 mm for all the axial distances towards the outlet. The radial velocity contour at 0.01 m/s (300 K) gave better results with an area of 1.31 m/s to 4.08 m/s, which was wider than that of the case at 0.01 m/s (700 K). By varying the inlet temperature and oxygen mass fraction, the flame configurations on temperature, CO₂, and H₂O formed a symmetric flame structure. The temperature distribution resulted in the centerline being hotter than other radial positions for all of the inlet temperatures. The emissions of CO₂ and H₂O generally increased with the addition of the oxygen mass fraction. Full article

Under extreme operating conditions, the internal lubricating flow field of high-speed gear transmission systems exhibits a transient oil–gas multiphase flow, predominantly governed by cavitation-induced phase transitions and turbulent shear. This phenomenon involves complex mechanisms of nonlinear multi-physical coupling and energy dissipation. Traditional lubrication theories and single-phase flow simplified models show significant limitations in capturing microsecond-scale flow features, dynamic interface evolution, and turbulence modulation mechanisms. To address these challenges, this study developed a cross-scale coupled numerical framework based on the Lattice Boltzmann method and large eddy simulation (LBM-LES). By incorporating an adaptive time relaxation algorithm, the framework effectively enhances the computational accuracy and stability for high-speed rotational flow fields, enabling the precise characterization of lubricant splashing, distribution, and its interaction with air. The research systematically reveals the spatiotemporal evolution characteristics of the internal flow field within the gearbox and focuses on analyzing the nonlinear regulatory effect of baffle geometric parameters on the system’s energy transport and dissipation characteristics. Numerical results indicate that the baffle structure significantly influences the spatial distribution of the vorticity field and turbulence intensity by reconstructing the shear layer topology. Low-profile baffles optimize the energy transfer pathway, effectively reducing the flow enthalpy, whereas excessively tall baffles induce strong secondary recirculation flows, exacerbating vortex-induced energy losses. Simultaneously, appropriately increasing the spacing between double baffles helps enhance global lubricant transport efficiency and suppresses unsteady dissipation caused by localized momentum accumulation. Furthermore, the geometrically optimized double-baffle configuration can achieve synergistic improvements in lubrication performance, oil film stability, and system energy efficiency by guiding the main shear flow and mitigating localized high-momentum impacts. This study provides crucial theoretical foundations and design guidelines for developing the next generation of theory-driven, energy-efficient lubrication design strategies for gear transmissions. Full article

The substation grounding grid, as the primary path for fault current dissipation, is crucial for ensuring the safe operation of the power system and requires regular inspection. The pulsed eddy current method, known for its non-destructive and efficient features, is widely used in grounding grid detection. However, during the parameter identification process, it is prone to local minima or no solution. To address this issue, this paper first develops a pulsed eddy current forward response model for the substation grounding grid based on the magnetic dipole superposition principle, with accuracy validation. Then, a variable dimensional Bayesian parameter identification method is introduced, utilizing the Reversible-Jump Markov Chain Monte Carlo (RJMCMC) algorithm. By using nonlinear optimization results as the initial model and introducing a dual-factor control strategy to dynamically adjust the sampling step size, the model enhances coverage of high-probability regions, enabling effective estimation of grounding grid parameter uncertainties. Finally, the proposed method is validated by comparing the forward response model with field test results, showing that the error is within 10%, demonstrating both the accuracy and practical applicability of the proposed parameter identification method. Full article

Screw propulsors have attracted increasing attention for their potential applications in amphibious vehicles and benthic robots, owing to their ability to perform both terrestrial and underwater locomotion. To investigate their hydrodynamic characteristics, a two-stage numerical analysis was carried out. In the first stage, steady-state simulations under various advance coefficients were conducted to evaluate the influence of key geometric parameters on propulsion performance. Based on these results, a representative configuration was then selected for transient analysis to capture unsteady flow features. In the second stage, a Detached Eddy Simulation approach was employed to capture unsteady flow features under three rotational speeds. The flow field information was analyzed, and the mechanisms of vortex generation, instability, and dissipation were comprehensively studied. The results reveal that the propulsion process is dominated by the formation and evolution of tip vortices, root vortices, and cylindrical wake vortices. As rotation speed increases, vortex structures exhibit a transition from ordered spiral wakes to chaotic turbulence, primarily driven by centrifugal instability and nonlinear vortex interactions. Vortex breakdown and energy dissipation are intensified downstream, especially under high-speed conditions, where vortex integrity is rapidly lost due to strong shear and radial expansion. This hydrodynamic behavior highlights the fundamental difference from conventional propellers, and these findings provide theoretical insight into the flow mechanisms of screw propulsion. Full article

Under the trend of lightweight and high-efficiency development in industrial equipment, precise regulation of lubrication in gear reducers is a key breakthrough for enhancing transmission system efficiency and reliability. This study establishes a three-dimensional numerical model for high-speed gear jet lubrication using computational fluid dynamics (CFD) and dynamic mesh technology. By implementing the volume of fluid (VOF) multiphase flow model and the standard k-ω turbulence model, the study simulates the dynamic distribution of lubricant in gear meshing zones and analyzes critical parameters such as the oil volume fraction, eddy viscosity, and turbulent kinetic energy. The results show that reducing the oil injection distance significantly enhances lubricant coverage and continuity: as the injection distance increases from 4.8 mm to 24 mm, the lubricant shifts from discrete droplets to a dense wedge-shaped film, mitigating lubrication failure risks from secondary atomization and energy loss. The optimized injection distance also improves the spatial stability of eddy viscosity and suppresses excessive dissipation of turbulent kinetic energy, enhancing both the shear-load capacity and thermal management. Dynamic data from monitoring point P show that reducing the injection distance stabilizes lubricant velocity and promotes more consistent oil film formation and heat transfer. Through multiphysics simulations and parametric analysis, this study elucidates the interaction between geometric parameters and hydrodynamic behaviors in jet lubrication systems. The findings provide quantitative evaluation methods for structural optimization and energy control in gear lubrication systems, offering theoretical insights for thermal management and reliability enhancement in high-speed transmission. These results contribute to the lightweight design and sustainable development of industrial equipment. Full article

This study proposes an intelligent prediction framework integrating native sparse attention (NSA) with the Chen-Guan (CHG) algorithm to optimize tunnel boring machine (TBM) operations in heterogeneous geological environments. The framework resolves critical limitations of conventional experience-driven approaches that inadequately address the nonlinear coupling between the spatial heterogeneity of rock mass parameters and mechanical system responses. Three principal innovations are introduced: (1) a hardware-compatible sparse attention architecture achieving O(n) computational complexity while preserving high-fidelity geological feature extraction capabilities; (2) an adaptive kernel function optimization mechanism that reduces confidence interval width by 41.3% through synergistic integration of boundary likelihood-driven kernel selection with Chebyshev inequality-based posterior estimation; and (3) a physics-enhanced modelling methodology combining non-Hertzian contact mechanics with eddy field evolution equations. Validation experiments employing field data from the Pujiang Town Plot 125-2 Tunnel Project demonstrated superior performance metrics, including 92.4% ± 1.8% warning accuracy for fractured zones, ≤28 ms optimization response time, and ≤4.7% relative error in energy dissipation analysis. Comparative analysis revealed a 32.7% reduction in root mean square error (p < 0.01) and 4.8-fold inference speed acceleration relative to conventional methods, establishing a novel data–physics fusion paradigm for TBM control with substantial implications for intelligent tunnelling in complex geological formations. Full article

Theoretical and experimental investigations were conducted to predict permeate flux in direct contact membrane distillation (DCMD) modules equipped with turbulence promoters. These DCMD modules operate at moderate temperatures (45 °C to 60 °C) using a hot saline feed stream while maintaining a constant temperature for the cold inlet stream. The temperature difference between the two streams creates a gradient across the membrane surfaces, leading to thermal energy dissipation due to temperature polarization effects. To address this challenge, 3D-printed turbulence promoters were incorporated into the DCMD modules. Acting as eddy promoters, these structures aim to reduce the temperature polarization effect, thereby enhancing permeate flux and improving pure water productivity. Various designs of promoter-filled channels—with differing array configurations and geometric shapes—were implemented to optimize flow characteristics and further mitigate polarization effects. Theoretical predictions were validated against experimental results across a range of process parameters, including inlet temperatures, volumetric flow rates, hydraulic diameters, and flow configurations, with deviations within 10%. The DCMD module with the inserted 3D-printed turbulence promoters in the flow channel could provide a relative permeate flux enhancement up to 91.73% under the descending diamond-type module in comparison with the module of using the no-promoter-filled channel. The modeling equations demonstrated technical feasibility, particularly with the use of both descending and ascending hydraulic diameters of 3D-printed turbulence promoters inserted into the saline feed stream, as compared to a module using an empty channel. Full article

The eddy dissipation rate (EDR, or turbulence dissipation rate) is a crucial parameter in the study of the atmospheric boundary layer (ABL). However, the existing Doppler lidar-based estimates of EDR seldom offer long-term comparisons that span the entire ABL. Building upon prior research utilizing Doppler lidar wind-field data, we optimized the EDR retrieval algorithm using a genetic adaptive approach. The newly developed algorithm demonstrates enhanced accuracy in EDR estimation. The daily evolution of EDR reveals a distinct diurnal pattern in its variation. A detailed four consecutive days study of turbulence generated via low-level jets (LLJs) indicated that EDR driven by heat flux (~10⁻² m²/s³) is significantly stronger than that produced through wind shear (~10⁻³ m²/s³). Subsequently, we examined seasonal variations in EDR at different mixing layer heights (MLH, Zi): elevated EDR values in summer (~7 × 10⁻³ m²/s³ at 0.1Zi) contrasted with reduced levels in winter (~6 × 10⁻⁴ m²/s³ at 0.1Zi). In the early morning, EDR decreases with height for 1 magnitude, while in later stages, it remains relatively stable within 0.1 order of magnitude across 0.1Zi to 0.9Zi. Notably, the EDR during DJF exceeds that of MAM and SON in the afternoon. This suggests that ML turbulence is not solely dependent on surface fluxes (SHF + LHF) but may also be influenced by MLH. A lower MLH (smaller volume), even with reduced surface fluxes, could potentially result in a stronger EDR. Finally, we compared the evolution of the EDR and MLH in the boundary layer using Doppler lidar data from ARM sites and the PBL (Planetary Boundary Layer) Moving Active Profiling System (PBLMAPS) Airborne Doppler Lidar (ADL). The results show that the vertical wind data exhibit strong consistency (R = 0.96) when the ADL is positioned near ARM Southern Great Plains (SGP) sites C1 or E37. The ADL’s mobility and flexibility provide significant advantages for future field experiments, particularly in challenging environments such as mountainous or complex terrains. This study not only highlights the potential of utilizing Doppler lidar alone for EDR calculations but also extensively explores the development patterns of EDR within the ABL. Full article

The magnetic acceleration noise (MAN) that stems from the eddy current dissipation of a test mass (TM) serves as an important source of noise for space inertial sensors. Given the problem that the eddy current dissipation magnetic acceleration noise (ECDMAN) of a cubic TM defies analytical solutions, an analytical model of ECDMAN for a spherical TM, which has the same volume as the cubic TM, is systematically derived on the basis of the principles of electromagnetism and the fluctuation-dissipation theorem, and this model can be used as an approximate analytical model for the evaluation of this noise term. Based on the approximate analytical model, with the TM of the LISA Pathfinder (LPF) as the research object, this paper obtains a modification coefficient using the approach of combining the analytical method with the finite element method (FEM), and establishes a semi-analytical model of ECDMAN for the cubic TM. Using the parameters of the LPF’s TM, the calculation error of the semi-analytical model is reduced by about 4.64% compared with the approximate analytical model. Finally, a generalized modeling approach for the semi-analytical model of ECDMAN is put forward, which is applicable to TMs with different parameters and can realize the real-time and rapid evaluation of ECDMAN during in-orbit experiments. Full article