Search Results (90)

Special orthogonal lateral-intake pumping stations on coastal plains face severe lateral deflection and recirculation in the approach channel and forebay. Their underlying evolutionary mechanisms remain unclear, and conventional rectification methods cause substantial hydraulic losses. Using numerical simulations and hydraulic model experiments, this study investigates these unfavorable flow patterns and proposes an original Combined Arc-Frame Flow Straightening Structure (CAFS). This newly proposed CAFS differs from existing structures, achieving effective flow pattern improvement with reduced hydraulic loss. Results reveal three typical flow regimes—S-shaped mainstream, branching flow, and recirculation—and the flow field is partitioned into four hydrodynamic zones: the Mainstream Incident Zone, Mainstream Impact Zone, Mainstream Reflection Zone, and Low-Velocity Recirculation Zone. Axial velocity uniformity and flow angle are strongly influenced by lateral velocity, while turbulent kinetic energy exhibits intrinsic correlations with vertical vorticity. Lateral velocity, recirculation intensity, and hydraulic losses all increase positively with the Froude number. The CAFS effectively suppresses the low-velocity recirculation zone. Quantitative data show an improvement of 46.40 percentage points in uniformity of axial velocity distribution, a reduction of 0.157 rad (9°) in velocity-weighted average angle, 60.98% less turbulent dissipation, and 38.85% less total hydraulic loss. This study clarifies lateral-intake defect mechanisms and provides a valuable engineering reference. Full article

The present work introduces a fully resolved three-dimensional thermal Lattice Boltzmann framework developed to investigate the impact of freely moving, finite-size spherical particles on natural convection within a cubic enclosure. The fluid-phase momentum and energy fields are resolved using coupled double-distribution function kinetic approach, while the solid phase is governed by explicitly coupled linear, angular, and thermal conservation equations. To accurately map the moving spherical surfaces onto the Eulerian lattice grid, a second-order linear interpolated bounce-back scheme is implemented. The conjugate heat transfer between the phases is simplified via a lumped capacitance model, assuming negligible internal thermal resistance within the solid spheres. Short-range particle–particle and particle–wall interactions are handled using Glowinski’s repulsive force model. The spatial accuracy of the framework is validated using a circular Taylor–Couette flow benchmark—demonstrating second-order spatial convergence and a differentially heated natural convection in a cubic cavity benchmark, yielding bulk Nusselt numbers within $1\%$ of established literature data. This validated tool is subsequently used to analyze the complex interplay between particulate motion and bulk thermal transport efficiency. Analysis of the temperature fields reveals that the overall thermal structure is governed primarily by the Rayleigh number, while the low particle concentration produces only minor modifications to the convective heat transfer. In contrast, the particle distribution exhibits a strong dependence on the flow intensity. Full article

Horizontal annular channels are widely encountered in fluid mechanics. Extensive research has explored how wall roughness alters total pressure loss in circular pipe flows. Meanwhile, existing literature has thoroughly discussed artificially enhanced rough structures (e.g., ribs, helical strips, and axial corrugations) for turbulence control and modulation. By contrast, relevant research on the inner cylinder roughness of annular channels remains insufficient. In practical engineering like petroleum drilling, inner pipes are usually treated as hydraulically smooth in theoretical and numerical models. However, machining inevitably generates tiny surface asperities on inner walls. Though this manufacturing micro-roughness is minimal in size, its true impact on flow characteristics is still unclear and requires a systematic numerical study. This study numerically explores the effects of practical inner-wall roughness on the hydrodynamic performance of annular flow. The simulation results reveal that compared with a fully smooth inner wall, surface roughness significantly rearranges the spatial distribution of major turbulent parameters (e.g., flow velocity, turbulence intensity, turbulent kinetic energy and Reynolds stress), and changes both the magnitude and position of their peak values. When the inner wall roughness is 0.4 mm, the near-wall Reynolds stress increases by 153.5%, the turbulence intensity increases by 52.4%, and the turbulent kinetic energy increases by 133.0%; the velocity peak shifts to the outer ring side, and the critical roughness is 0.06 mm. The findings confirm that considering inner tube roughness is critical for improving the prediction accuracy of both microscale turbulent behaviors and macro flow parameters in practical annular flow engineering. This work distinguishes itself from existing studies by systematically quantifying the response of full first- and second-order turbulent statistics to pipeline manufacturing micro-roughness, revealing the symmetry-breaking turbulent transport mechanism of annular flow, and quantitatively determining the critical inner-wall roughness that shifts the velocity peak to the annular geometric midpoint, which provides a targeted quantitative database for the correction of annular flow numerical simulations that ignore native micro-roughness. Full article

This study investigates the impact of internal muffler geometry on flow-related dissipation characteristics potentially relevant to acoustic behavior using steady-state Computational Fluid Dynamics (CFD) simulations. Four variants were analyzed: an empty tube, considered to be a baseline model, a three-chamber baffle system, a single spiral channel, and a complex multi-channel insert manufacturable only via advanced additive technologies. Simulations were conducted in SimScale using a compressible flow model with the k-ω SST turbulence formulation. Key outputs included static pressure distribution and turbulent kinetic energy (TKE), both of which were evaluated as qualitative surrogate indicators associated with flow-induced energy dissipation phenomena. The results indicate that geometries incorporating spiral features modify flow redistribution patterns, pressure gradients and localized turbulence intensity, suggesting potential applicability for future acoustic optimization studies. The study highlights how additive manufacturing enables the integration of geometrically complex internal structures otherwise unattainable through conventional methods. By comparing pressure drop and TKE patterns with internal design features, the research offers a preliminary CFD-based framework for geometry screening and conceptual evaluation of muffler insert designs for automotive exhaust systems. This approach provides computational support for rapid comparative assessment prior to experimental validation and detailed acoustic analysis. Full article

Erosive wear in pipe elbows subjected to liquid–solid two-phase flow is a major cause of material degradation and service failure in industrial piping systems. In this study, erosion characteristics of pipe elbows were investigated through erosion mapping experiments and numerical simulations. The effects of flow velocity and particle diameter on erosion location and intensity were analyzed. Erosion was found to be mainly concentrated on the outer wall of the elbow within the angular range of 10° to 90°, and both erosion intensity and affected area increased with increasing particle diameter and flow velocity. Dean vortices were shown to play an important role in particle transport and erosion distribution, especially for small particles. Inspired by the ribbed morphology of shells, a biomimetic elbow was further designed and evaluated through an orthogonal numerical study considering flow velocity, particle diameter, rib number, and rib diameter. The results indicate that the ribbed structure can effectively improve erosion resistance by altering particle trajectories, reducing particle impact probability, and dissipating kinetic energy through low-velocity rotating flow between adjacent ribs. This finding provides useful inspiration for addressing erosive wear problems in engineering applications. Full article

This study investigated the correlation between mechanical strengthening and electrochemical corrosion behavior in 18Ni300 maraging steel fabricated via laser powder bed fusion (LPBF). To evaluate the impact of post-processing, specimens were analyzed under four conditions: solution treated (S), solution peened (SP), solution aged (SA), and solution aged peened (SAP). The aging treatment (490 °C for 6 h) effectively enhanced the corrosion resistance by homogenizing the martensitic matrix and promoting the formation of a stable passive film, resulting in the lowest corrosion current density ($i_{corr}$ of 1.716 × 10⁻⁶ A/cm²). In contrast, the application of shot peening after aging (SAP) significantly degraded the corrosion resistance, characterized by the most negative corrosion potential ($E_{corr}$ of −0.374 V and a 2.4 times increase in $i_{corr}$ compared to the SA condition. Quantitative analysis revealed that the 1250 MPa of compressive residual stress induced by peening increased the thermodynamic instability of the surface through extreme lattice distortion, thereby lowering the activation energy for anodic dissolution. Furthermore, the increased surface roughness (60.68 µm) expanded the effective electrochemical reaction area, acting as a kinetic accelerator for corrosion. The results demonstrate that while the SA process provides an optimal balance between microstructural stability and corrosion resistance, additional shot peening (SAP) imposes a significant corrosion penalty despite its mechanical benefits. This study concludes that for 18Ni300 maraging steel, the trade-off between mechanical reinforcement and electrochemical stability must be carefully managed, emphasizing the need for surface stabilization when high-intensity peening is applied in corrosive environments. Full article

Mediterranean tropical-like cyclones (MTLCs), commonly referred to as Medicanes, are high-impact weather systems characterized by complex interactions between baroclinic forcing and tropical-like processes. Despite growing interest, their vertical structures and dynamical regimes remain incompletely understood. In this study, high-resolution Weather Research and Forecasting (WRF) simulations at 1 km resolution are used to investigate the structure and evolution of two dynamically contrasting MTLCs: Ianos (2020) and Qendresa (2014). The analysis focuses on the temporal evolution of kinetic energy and turbulent dissipation as well as on the three-dimensional organization of wind and temperature fields during representative phases of the cyclone life cycle. The results reveal pronounced differences between the two events, with Ianos exhibiting a compact, vertically coherent, convection-dominated structure and Qendresa showing a wider, more asymmetric, and less stationary organization influenced by baroclinic processes. A comparative framework with the ERA5 reanalysis is employed to contextualize cyclone intensity, with ERA5 used as a dynamically consistent large-scale reference rather than as an observational benchmark. Overall, the study highlights the importance of vertical structure and boundary-layer processes in shaping Mediterranean tropical-like cyclones and demonstrates the added value of high-resolution numerical simulations for distinguishing between different dynamical regimes. Full article

This study investigated the impact of the pretreatment of pea plants (Pisum sativum L. Ran 1) for five days by three times higher light intensity (360 μmol m⁻² s⁻¹) than the intensity for their cultivation (120 μmol m⁻² s⁻¹) on the photosynthetic apparatus’s ability to withstand moderately high temperatures. Photosystem II (PSII) performance was assessed by pulse amplitude-modulated (PAM) fluorometry—evaluation of F_v/F_m, Chl fluorescence decrease ratio—R_Fd, excitation pressure on PSII (1 − qP), non-photochemical quenching (NPQ) analysis, and PsbA (D1) abundance. The redox state of P700 was used to examine photosystem I (PSI), and the redox kinetics of P700 was evaluated as an estimate of cyclic electron flow (CEF). The energy distribution and interaction between the two photosystems were assessed by 77 K chlorophyll fluorescence. Diphenylhexatriene (DPH) fluorescence polarization and PsbS accumulation were followed to estimate alterations in thylakoid membrane characteristics. Our data show that pea plants pretreated with a higher level of light intensity showed higher resistance to temperature increase, maintaining R_Fd values similar to control plants, and the effect of high temperature on PSII excitation pressure (1 − qP) was mitigated. A significant difference between the two groups of plants was observed in terms of quantum yields in both types of non-photochemical quenching, with light pretreated plants showing no change in the energy partitioning ratio while the exposure of non-high light pretreated plants to elevated temperatures led to a more significant increase in quantum yield of constitutive non-photochemical quenching. When plants were exposed to higher temperature, the accumulation of PsbS, induced by high light treatment, was accelerated, and stabilization of thylakoid membrane also occurred. A complex mechanism behind the enhanced tolerance to higher temperature includes the reorganization of membrane pigment–protein complexes, which is regulated by the buildup of PsbS and the accompanying redistribution of excitation energy. Full article

While twisted tape inserts are widely used for heat transfer enhancement, the specific impact of tape thickness remains under-explored. This study provides a systematic numerical investigation into the thermo-hydraulic performance of a double-pipe heat exchanger equipped with twisted perforated tape (TPT) inserts of varying thicknesses (1, 1.5, and 2 mm). Using a validated 3D SST k−ω model across Re = 1000–12,000, the research establishes a mechanistic distinction between flow regimes. The results indicate that the 2 mm TPT yields the highest enhancement, achieving a 78.6% increase in the average Nusselt number (Nu_avg) and a 67.8% improvement in the overall heat transfer coefficient at Re = 12,000. Quantitative analysis of secondary flow intensity and turbulence kinetic energy confirms a transition from geometry-induced swirl at low Re to turbulence-driven shear at high Re. Despite a pressure drop penalty of up to 3.26 times the plain tube, the thermal performance factor remained above unity for all cases, peaking at 1.17 at Re ≈ 4000. These findings establish tape thickness as a first-order design variable for optimizing high-performance thermal systems. Full article

Studying the slumping disintegration, movement speed, impact intensity, accumulation characteristics, and energy conversion laws of tower-column unstable rock masses (TCURM) is crucial for high-altitude rockfall hazard risk evaluation. Existing PFC-based rockfall simulations rarely target the unique “top-hard-bottom-weak” structural characteristics of TCURM and lack in-depth integration of on-site monitoring videos to verify dynamic evolution processes. Taking the large-scale collapse of W12^# unstable rock mass at Zengziyan, Jinfo Mountain in Chongqing as an example, a combination method of orthogonal test and PFC^3D discrete element simulation is used. Mesoscopic parameters are calibrated via comparison with on-site video and investigation data, accurately reproducing the entire slumping disintegration process and revealing its dynamic characteristics. Results confirm the simulation is basically consistent with field data, verifying the model and parameter rationality. The total duration from instability to stagnation is 121 s (15 s to impact the secondary steep cliff base, 106 s for debris accumulation). Movement speed time-histories of deteriorated and non-deteriorated zones are generally consistent, both exhibiting a “double-peak” feature. Rockfall impact force first increases, stabilizes in the middle, and declines to stability afterward, with a maximum of 2.1 × 10⁹ N. The kinetic energy curve also shows a “double-peak” distribution, closely related to the on-site two-level steep cliff morphology. The findings provide important references for analyzing the dynamic evolution of such rockfalls and designing disaster prevention/mitigation engineering. Full article

Rhenium is one of the rarest and most strategically important metals, indispensable in high-temperature superalloys and platinum–rhenium catalysts used across the aerospace and petrochemical industries. Owing to its limited primary reserves, recovering rhenium from secondary sources, such as spent catalysts, superalloy residues, and metallurgical dusts, has become vital to ensuring supply security. This review examines technological developments between 1998 and 2025, focusing on how operational parameters, including temperature, leaching time, reagent concentration, and solid-to-liquid ratio, govern dissolution kinetics and overall process efficiency. Comparative evaluation of hydrometallurgical, alkaline, and hybrid processes indicates that modern systems can achieve recovery rates exceeding 98% through selective oxidation, alkaline activation, or combined pyro and hydrometallurgical mechanisms. Acid–chlorine leaching facilitates rapid, low-temperature dissolution; alkaline sintering stabilises rhenium as soluble perrhenates; and hybrid smelting routes enable the concurrent separation of rhenium and osmium. Sustainable aqueous systems employing nitric and ammonium media have also demonstrated near-complete recovery at ambient temperature under closed-loop recycling conditions. Collectively, these findings highlight a technological transition from energy-intensive, acid-based pathways towards low-impact, recyclable, and digitally optimised hydrometallurgical processes. The integration of selective oxidants, phase engineering, circular reagent management, and artificial intelligence-assisted modelling is defining the next generation of rhenium recovery, combining high extraction yields with reduced environmental impact and alignment with global sustainability goals. Full article

In this study, a comprehensive numerical investigation of amplitude-driven flow dynamics in shocked heavy-fluid layers is presented to focus on the evolution of the Richtmyer–Meshkov instability (RMI). A high-order mixed local discontinuous Galerkin scheme is employed to resolve the complex interactions between shock waves and perturbed interfaces within a compressible viscous flow framework. Impacts of the initial interface amplitudes are systematically examined through a series of single-mode configurations with amplitude–wavelength ratios ranging from $a_0/\lambda =0.025$ to $0.4$. The simulations capture the complete transition from early linear growth to nonlinear roll-up and subsequent mixing. This investigation illustrates that increasing the initial perturbation amplitude enhances baroclinic vorticity generation, intensifies interfacial deformation, and accelerates the onset of secondary instabilities. Low-amplitude interfaces maintain nearly symmetric deformation with delayed nonlinear transition, whereas high-amplitude cases exhibit pronounced spike–bubble asymmetry, stronger curvature, and rapid Kelvin–Helmholtz roll-ups. Quantitative diagnostics of the circulation, enstrophy, and kinetic energy demonstrate that both baroclinic torque and mixing intensity scale directly with the initial perturbation amplitude. This study offers new physical insight into amplitude-dependent shock–interface interactions and elucidates the mechanisms governing vorticity amplification and energy redistribution in RMI flows. Full article

In this study, thermogravimetric analysis (TGA) was coupled with Fourier-transform infrared (FTIR) spectroscopy to systematically investigate the pyrolysis characteristics and mechanisms of cement fiberboard across varying heating rates. Experimental findings demonstrated that the thermal degradation process occurs in four distinct phases. Overlapping decomposition peaks in DTG curves were successfully resolved using a double-Gaussian deconvolution algorithm. A comprehensive kinetic analysis was conducted by integrating model-free iso-conversional methods (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose analysis) with a model-fitting technique (Coats–Redfern approximation) to determine the activation energies for each degradation stage. A subsequent FTIR spectroscopic analysis revealed that the evolution of gaseous products follows the sequence CO₂ > H₂O > CH₄. The CO₂ release was found to originate from multiple pathways, including the decomposition of organic components and high-temperature inorganic reactions. Notably, while the heating rate had a negligible impact on product speciation, it exhibited a statistically significant influence on CO₂ emission intensities. Finally, mechanistic interpretations integrating Arrhenius parameters with time-resolved infrared spectral features were proposed for each thermal decomposition stage. Full article

This study investigates the wave-induced vertical mixing mechanism and systematically compares the application of two non-breaking wave parameterization schemes (Bv and Pw) in oceanic numerical simulations of the South China Sea, according to two key physical variables: sea surface temperature (SST) and the vertical mixing coefficient. The goal is to explore the effects of different parameterization methods on the upper-ocean temperature distribution in the South China Sea. The results indicate that although both schemes enhance vertical mixing in the upper ocean, they do so through different mechanisms. The Bv scheme directly increases the vertical mixing coefficient, demonstrating significantly stronger mixing intensity, while the Pw scheme impacts mixing indirectly by modulating turbulent kinetic energy generation, resulting in comparatively weaker mixing. SST simulation results show that the Bv scheme is more effective in reducing SST in both winter and summer, with broader spatial improvements. Further analysis of the mixing coefficient confirms that, compared to the Pw scheme, the Bv scheme not only strengthens surface mixing but also penetrates deeper into the water column. Full article

Mesoscale coastal eddies are key components of ocean circulation, mediating the transport of heat, nutrients, and marine debris. The Surface Water and Ocean Topography (SWOT) mission provides high-resolution sea surface height data, offering a novel opportunity to improve the observation and characterization of these features, especially in coastal regions where conventional altimetry is limited. In this study, we investigate a mesoscale anticyclonic coastal eddy observed southwest of Mallorca Island, in the Balearic Sea, to assess the impact of SWOT-enhanced altimetry in resolving its structure and dynamics. Initial eddy identification is performed using satellite ocean color imagery, followed by a qualitative and quantitative comparison of multiple altimetric datasets, ranging from conventional nadir altimetry to wide-swath products derived from SWOT. We analyze multiple altimetric variables—Sea Level Anomaly, Absolute Dynamic Topography, Velocity Magnitude, Eddy Kinetic Energy, and Relative Vorticity—highlighting substantial differences in spatial detail and intensity. Our results show that SWOT-enhanced observations significantly improve the spatial characterization and dynamical depiction of the eddy. Furthermore, Lagrangian transport simulations reveal how altimetric resolution influences modeled transport pathways and retention patterns. These findings underline the critical role of SWOT in advancing the monitoring of coastal mesoscale processes and improving our ability to model oceanic transport mechanisms. Full article