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Search Results (1,953)

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22 pages, 5182 KB  
Article
A Novel TMR Cantilever-Based Bi-Directional Flow Sensor for Agricultural and Domestic Applications
by Anwar Ulla Khan and Ateyah Alzahrani
Sensors 2025, 25(18), 5915; https://doi.org/10.3390/s25185915 - 22 Sep 2025
Viewed by 202
Abstract
This article introduces a novel, cost-effective, noninvasive sensing mechanism for measuring water flow rate. It employs two tunneling magnetoresistance (TMR) sensors (analog and bi-polar), a magnet, and a stainless-steel cantilever. The TMR sensors are installed outside the insulating water pipe. A magnet is [...] Read more.
This article introduces a novel, cost-effective, noninvasive sensing mechanism for measuring water flow rate. It employs two tunneling magnetoresistance (TMR) sensors (analog and bi-polar), a magnet, and a stainless-steel cantilever. The TMR sensors are installed outside the insulating water pipe. A magnet is fixed at the free end of the cantilever and integrated into the pipe system. The cantilever’s deflection corresponds to the flow rate, with an analog TMR sensor measuring the bending angle. This bending angle, in either direction of the cantilever’s deflection, is captured through the analog voltage from the TMR sensor. The output from the analog TMR sensor is an analog voltage that directly reflects the strength of the magnetic field. An ESP32 microcontroller records the voltage from the analog TMR sensor, converts it to flow rates, and utilizes the bi-polar TMR sensor to ascertain the flow direction. A prototype sensor was developed and tested in a laboratory-scale setup to validate the effectiveness of the sensing mechanism. This prototype demonstrated a worst-case accuracy of 1.0% across flow rates of 0 to 1.5 m3/h for both the forward and reverse flow directions. The response and recovery times of the sensor are approximately 470 ms and 592 ms for forward and 487 ms and 625 ms for reverse direction flow. Also, hysteresis errors of 1.84% and 2.06% have been calculated for both flow directions. Notably, the sensing element does not contain any rotating components or require electrical connections to the cantilever for measurement. These attributes potentially lead to lower maintenance requirements and a longer lifespan for the sensor. Full article
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14 pages, 3326 KB  
Article
Experimental Study on the Flow Regime Evolution of Stiff Shotcrete Materials in Pneumatic Conveying
by Zhi Zhou, Zhiwei Shi and Zhenjiao Sun
Buildings 2025, 15(18), 3389; https://doi.org/10.3390/buildings15183389 - 18 Sep 2025
Viewed by 224
Abstract
Pneumatic conveying of stiff shotcrete material plays a crucial role in mine support; however, the flow regime evolution mechanism of its complex multi-scale particle system during conveying remains insufficiently studied. This study establishes a customized pneumatic conveying experimental platform, integrating a high-speed camera [...] Read more.
Pneumatic conveying of stiff shotcrete material plays a crucial role in mine support; however, the flow regime evolution mechanism of its complex multi-scale particle system during conveying remains insufficiently studied. This study establishes a customized pneumatic conveying experimental platform, integrating a high-speed camera and pressure sensors to systematically investigate the flow regime evolution and characteristics of stiff shotcrete material under different operating parameters. Experimental results indicate that air velocity and water–cement ratio significantly influence flow regime evolution: at low air velocities, the material primarily exhibits dune flow and stratified flow. As the air velocity increases to 475 m3/h, the flow regime gradually transitions to suspended flow. An increase in the water–cement ratio significantly enhances liquid bridge forces between particles, intensifying particle agglomeration and making the bottom-layer flow characteristics more pronounced. Additionally, pipe diameter plays a crucial role in flow regime distribution, with suspended flow dominating in smaller pipes and bottom-layer flow becoming more prominent in larger pipes. In the downstream section of the elbow, the abrupt decrease in airflow velocity causes the flow regime to degrade from suspended flow to bottom-layer flow, leading to significant particle deposition. This study reveals the flow regime evolution patterns of stiff shotcrete material in pneumatic conveying, providing essential experimental evidence and theoretical support for optimizing long-distance pneumatic conveying systems in mine support applications. Full article
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23 pages, 1282 KB  
Article
An Integrated Water Resources Solution for a Wide Arid to Semi-Arid Urbanized Coastal Tropical Region with Several Topographic Challenges—A Case Study
by António Freire Diogo and António Luís Oliveira
Water 2025, 17(18), 2750; https://doi.org/10.3390/w17182750 - 17 Sep 2025
Viewed by 437
Abstract
Pressure on fresh water resources has been aggravated in recent decades, basically due to population growth, rapid urbanization, and global warming. Integrated engineering solutions and the circular economy, considering the urban water cycle as a whole, are becoming fundamental, particularly in arid and [...] Read more.
Pressure on fresh water resources has been aggravated in recent decades, basically due to population growth, rapid urbanization, and global warming. Integrated engineering solutions and the circular economy, considering the urban water cycle as a whole, are becoming fundamental, particularly in arid and semi-arid regions under permanent or recurrent hydric deficit. This study aims to develop and present an integrated engineering solution for water supply, wastewater collection, and treated wastewater reuse for landscape irrigation in a large, topographically complex, and arid to semi-arid coastal urban region at the south of Santiago Island, Cape Verde. The region is one of the driest and most arid of the Island, with a current average annual precipitation between about 100 and 200 mm, and has very limited underground water resources. The main study area, with about 600 ha, has altitudes ranging from values close to sea level up to about 115 m and has several topographic difficulties, including several relatively rugged zones. The devised water supply system considers four altimetric distribution levels, three main reservoirs connected to each other by a serial system of pipelines with successive pumping, a fourth downstream reservoir for pressure balance in one of the levels, and desalinated water as the source. The sanitary sewer pipes of the urbanizations drain to an interceptor system that operates predominantly in open channel flow in a closed pipe. The long interceptor crosses laterally along the coast several very dug valleys in the path to the Praia Wastewater Treatment Plant in the east, and requires several conduits working under pressure for the crossings, either lifting or governed by gravity. The under-pressure pipeline system of recycled water is partially forced and partially ruled by gravity and transports the treated wastewater from the plant in the opposite direction of the interceptor to a natural reservoir or lake located in the region of urbanizations and the main green spaces to be irrigated. The conceived design of the interceptor and recycled water pipeline minimizes the construction and operation costs, maximizing their hydraulic performance. Full article
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19 pages, 4586 KB  
Article
Heat Losses in the Exhaust Manifold of a 4-Stoke DI Diesel Engine Subjected to Pulsating Flow
by Grigorios Spyrounakos and Georgios Mavropoulos
Computation 2025, 13(9), 223; https://doi.org/10.3390/computation13090223 - 15 Sep 2025
Viewed by 302
Abstract
This paper presents a study aiming to provide insight into the complex flow and heat transfer processes in the exhaust manifold of a four-stroke, compression ignition engine. An experimental system has been constructed capable of capturing temperature and heat flux high-frequency signals as [...] Read more.
This paper presents a study aiming to provide insight into the complex flow and heat transfer processes in the exhaust manifold of a four-stroke, compression ignition engine. An experimental system has been constructed capable of capturing temperature and heat flux high-frequency signals as they develop in the exhaust pipe wall during the engine cycle, under its steady-state operation. The values of the Heat Transfer Coefficient obtained by applying the classic convection relations have been correlated in the form of a Nusselt–Reynolds number relationship for local and spatially averaged steady-state heat transfer and compared with available experimental data obtained at the same position of the exhaust manifold. It has been shown that the use of conventional steady-state heat transfer relationships for fully developed steady-state turbulent flow in pipes underpredicts heat transfer rates when compared with those experimentally observed. Periodic flow of high frequency and geometrical effects at the exhaust entrance are expected to affect the validity of the application of the classic steady-state correlations for the exhaust manifold. To overcome this problem it is developed and presented a new correlation for the time-averaged heat transfer rates. To verify the heat transfer mechanism, the thermal field of the whole engine cylinder head, including the intake and exhaust manifolds, was analyzed using FEA (Finite Element Analysis), and the results are compared and verified with available experimental data. Full article
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40 pages, 9182 KB  
Article
Optimal Design of Combined Weir–Orifice Tail Escape Structures Using Graphical Methods and the TAILOPT Tool
by Ahmed M. Tawfik and Mohamed H. Elgamal
Water 2025, 17(18), 2724; https://doi.org/10.3390/w17182724 - 14 Sep 2025
Viewed by 479
Abstract
Dual-inlet tail escapes, combining an orifice and a weir, are key hydraulic structures that evacuate excess water from canal termini during maintenance and protect berms by discharging surplus irrigation flows. Conventional sizing methods typically depend on trial and error, which is time-consuming and [...] Read more.
Dual-inlet tail escapes, combining an orifice and a weir, are key hydraulic structures that evacuate excess water from canal termini during maintenance and protect berms by discharging surplus irrigation flows. Conventional sizing methods typically depend on trial and error, which is time-consuming and may yield suboptimal design. This study introduces a graphical design approach and a MATLAB-based tool, TAILOPT, developed to streamline tail escape design. The tool incorporates both the Fanning and Darcy–Weisbach friction formulations for head loss estimation and can automatically generate an “.inp” file for EPA-SWMM, enabling direct unsteady-state hydraulic assessment. This integration reduces design effort and supports evaluation of alternative hydraulic and drainage scenarios within a single workflow. Two applications illustrate the framework. The first shows that overly steep drainage slopes (Sp > 2%) are impractical, while vertical drops may require larger pipe diameters. The second application applies TAILOPT to a distributary canal, determining the optimal pipe size and verifying its performance in EPA-SWMM under emergency surplus flow and routine dewatering conditions. The results demonstrate that the method yields economical, robust, and practitioner-friendly designs; however, modeling simplifications, such as assuming continuously submerged orifice flow, can introduce minor deviations in the predicted channel emptying times. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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23 pages, 8230 KB  
Article
3D Compressible Flow Analysis of an Ultra-High-Head Pumped Storage Unit with Water Conveyance System at Maximum Pumping Head
by Zhixing Li, Xinbo Li, Xingxing Huang, Tao Li, Meng Liu and Zhengwei Wang
Energies 2025, 18(18), 4864; https://doi.org/10.3390/en18184864 - 12 Sep 2025
Viewed by 242
Abstract
Severe pressure pulsations caused by complex flow fields in pumped-storage power stations significantly threaten operational safety and stability. With advances in computational technology, fully three-dimensional simulations coupling pipelines and pump-turbine units have become feasible. In this study, a fully three-dimensional analysis model was [...] Read more.
Severe pressure pulsations caused by complex flow fields in pumped-storage power stations significantly threaten operational safety and stability. With advances in computational technology, fully three-dimensional simulations coupling pipelines and pump-turbine units have become feasible. In this study, a fully three-dimensional analysis model was developed, coupling the water conveyance system and a finely modeled prototype-scale pump-turbine with splitter blades, to numerically simulate the compressible flow field under the maximum head pump mode. The study reveals a strong bidirectional coupling between the flow in the long outlet pipe and the internal flow within the pump-turbine unit. Influenced by structural features such as bifurcations and flow impingement at the T-junction, complex three-dimensional vortices arise and cannot be neglected. Based on the flow field, the study further investigates the time-domain, frequency-domain, and spatial characteristics of pressure pulsations at various downstream hydraulic components, ranging from the vaneless space to the outlet of the long outlet pipe. The pressure pulsation frequencies are shown to be affected by both rotor–stator interactions and the complex vortical structures in the flow. These findings clearly demonstrate the necessity of fully three-dimensional simulations that incorporate both the water conveyance system and the pump-turbine unit. Full article
(This article belongs to the Section A: Sustainable Energy)
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23 pages, 5246 KB  
Article
Numerical Simulation of Sedimentation Behavior of Densely Arranged Particles in a Vertical Pipe Using Coupled SPH-DEM
by Peng Ji, Zhiyuan Wang, Weigang Du, Zhenli Pang, Liyong Guan, Yong Liu and Xiangwei Dong
Processes 2025, 13(9), 2911; https://doi.org/10.3390/pr13092911 - 12 Sep 2025
Viewed by 324
Abstract
This study develops a coupled Smoothed Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM) framework to explore the sedimentation behavior of densely arranged particles in vertical pipes. An unresolved SPH-DEM model is proposed, which integrates porosity-dependent fluid governing equations through local averaging [...] Read more.
This study develops a coupled Smoothed Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM) framework to explore the sedimentation behavior of densely arranged particles in vertical pipes. An unresolved SPH-DEM model is proposed, which integrates porosity-dependent fluid governing equations through local averaging techniques to connect pore-scale interactions with macroscopic flow characteristics. Validated against single-particle settling experiments, the model accurately captures transient acceleration, drag equilibrium, and rebound dynamics. Systematic simulations reveal that particle number, arrangement patterns, and fluid domain geometry play critical roles in regulating collective settling: Increasing particle count induces nonlinear terminal velocity reduction. Systems of 16 particles show 50% lower velocity than single-particle cases due to enhanced shielding and energy dissipation. Particle configuration (compact layouts 4 × 8 vs. elongated arrangements 8 × 4) dictates hydrodynamic resistance, compact layouts facilitate faster settling by reducing cross-sectional blockage, while elongated arrangements amplify lateral resistance. The width of the fluid domain exerts threshold effects: narrow boundaries (0.03 m) intensify wall-induced drag and suppress vortices, whereas wider domains promote symmetric vortices that enhance stability. Additionally, critical transitions in multi-row/column systems are identified, where stress-chain redistribution and fluid-permeation thresholds govern particle detachment and velocity stratification. These findings deepen the understanding of granular–fluid interactions in confined spaces and provide a predictive tool for optimizing particle management in industrial processes such as wellbore cleaning and hydraulic fracturing. Full article
(This article belongs to the Section Chemical Processes and Systems)
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21 pages, 2556 KB  
Article
Scour Control in a 90° Bend by Means of an Air Bubble Screen
by Pari Maleki, Javad Ahadiyan, Rui Aleixo, Hossein Azizi Nadian, Zeinab Tamoradi, Seyed Mahmood Kashefipour, Anton J. Schleiss and Manouchehr Fathi Moghadam
Water 2025, 17(18), 2693; https://doi.org/10.3390/w17182693 - 12 Sep 2025
Viewed by 423
Abstract
Scouring is an erosional process driven by the water motion over a sediment bed. Scour can lead to structural safety risks of built structures and to riverbanks’ instabilities and collapse. In particular, scouring in river bends is a known phenomenon caused by secondary [...] Read more.
Scouring is an erosional process driven by the water motion over a sediment bed. Scour can lead to structural safety risks of built structures and to riverbanks’ instabilities and collapse. In particular, scouring in river bends is a known phenomenon caused by secondary flow currents. This scouring can result in negative impacts on the economic and social activities that occur on the riverbanks. On the other hand, the erosion and scouring processes of riverbeds are often addressed by means of heavy civil engineering construction works. Aiming at looking for different solutions for the scour in river bends, this research investigates the use of an air bubble screen system to minimize the scouring in river bends by providing detailed measurements of sedimentation patterns and velocity fields in a mild 90-degree bend where an air screen bubble was installed. The air bubble screen is generated by injecting compressed air through a perforated pipe placed on the bed along the outer bend. Different parameters were tested, including the water flow rate in the channel, the air flow rate, the angle of attack between the air bubble screen and the secondary flow, and flow direction. The air bubble screen opposes the direction of the bend’s induced secondary flows, altering the velocity pattern such that the maximum velocity at cross-sections of 45°, 65°, 80°, and 90° were displaced from the outer wall as much as 53%, 68%, 89%, and 84% of the width, respectively. The air bubble screen system also reduced the secondary flow power in the maximum scour zone by 35%. Hence, the maximum scour depth was reduced by 59% to 79.8% for the maximum flow rate by increasing the air bubbles’ angle of attack relative to the primary flow from 0° to 90°. Finally, the limitations of this study and its applicability to real cases is discussed. Full article
(This article belongs to the Special Issue Numerical Modeling of Hydrodynamics and Sediment Transport)
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33 pages, 2380 KB  
Review
A Comprehensive Review of Symmetrical Multilateral Well (MLW) Applications in Cyclic Solvent Injection (CSI): Advancements, Challenges, and Future Prospects
by Shengyi Wu, Farshid Torabi and Ali Cheperli
Symmetry 2025, 17(9), 1513; https://doi.org/10.3390/sym17091513 - 11 Sep 2025
Viewed by 336
Abstract
This paper presents a comprehensive review and theoretical analysis of integrating Cyclic Solvent Injection (CSI) with multilateral well (MLW) technologies to enhance heavy oil recovery. Given that many MLW configurations inherently exhibit symmetrical geometries, CSI–MLW integration offers structural advantages for fluid distribution. CSI [...] Read more.
This paper presents a comprehensive review and theoretical analysis of integrating Cyclic Solvent Injection (CSI) with multilateral well (MLW) technologies to enhance heavy oil recovery. Given that many MLW configurations inherently exhibit symmetrical geometries, CSI–MLW integration offers structural advantages for fluid distribution. CSI offers a non-thermal mechanism for oil production through viscosity reduction, oil swelling, and foamy oil behaviour, but its application is often limited by poor sweep efficiency and non-uniform solvent distribution in conventional single-well configurations. In contrast, MLW configurations are effective in increasing reservoir contact and improving flow control but lack solvent-based enhancement mechanisms. In particular, symmetrical MLW configurations, such as dual-opposing laterals and evenly spaced fishbone laterals, can facilitate balanced solvent distribution and pressure profiles, thereby improving sweep efficiency and mitigating early breakthrough. By synthesizing experimental findings and theoretical insights from the existing literature, laboratory studies have reported that post-CHOPS CSI using a 28% C3H8–72% CO2 mixture can recover about 50% of the original oil in place after six cycles, while continuous-propagation CSI (CPCSI) has achieved up to ~85% OOIP in 1D physical models. These representative values illustrate the performance spectrum observed across different CSI operational modes, underscoring the importance of operational parameters in governing recovery outcomes. Building on this foundation, this paper synthesizes key operational parameters, including solvent composition, pressure decline rate, and well configuration, that influence CSI performance. While previous studies have extensively reviewed CSI and MLW as separate technologies, systematic analyses of their integration remain limited. This review addresses that gap by providing a structured synthesis of CSI–MLW interactions, supported by representative quantitative evidence from the literature. The potential synergy between CSI and MLW is highlighted as a promising direction to overcome current limitations. By leveraging geometric symmetry in well architecture, the integrated CSI–MLW approach offers unique opportunities for optimizing solvent utilization, enhancing recovery efficiency, and guiding future experimental and field-scale developments. Such symmetry-oriented designs are also central to the experimental framework proposed in this study, in which potential methods, such as the microfluidic visualization of different MLW configurations, spanning small-scale visualization studies, bench-scale experiments on fluid and chemical interactions, and mock field setups with pipe networks, are proposed as future avenues to further explore and validate this integrated strategy. Full article
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14 pages, 2508 KB  
Article
Automated Weld Defect Detection in Radiographic Images Using Normalizing Flows
by Morteza Mahvelatishamsabadi and Sudong Lee
Machines 2025, 13(9), 836; https://doi.org/10.3390/machines13090836 - 9 Sep 2025
Viewed by 443
Abstract
Anomaly detection is a pressing issue, particularly in industrial images. Detecting weld defects in radiographic images is a challenge due to the small signal-to-noise ratio (SNR) and the limited availability of data. In this paper, we propose an automated weld defect detection method [...] Read more.
Anomaly detection is a pressing issue, particularly in industrial images. Detecting weld defects in radiographic images is a challenge due to the small signal-to-noise ratio (SNR) and the limited availability of data. In this paper, we propose an automated weld defect detection method using Normalizing Flows (NFs). We employed various state-of-the-art NF architectures with different feature extractors to detect defects in radiographic images of welds, comprehensively comparing the results with radiographic images of welded steel pipes collected from industrial sites. The results show that the combination of CFlow-AD with a wide residual network-50-2 (WRN-50-2) outperformed the other methods, indicating its effectiveness in anomaly detection. Full article
(This article belongs to the Special Issue Reliability in Mechanical Systems: Innovations and Applications)
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28 pages, 58198 KB  
Article
Numerical Investigation of Ultra-Long Gravity Heat Pipe Systems for Geothermal Power Generation at Mount Meager
by Yutong Chai, Wenwen Cui, Ao Ren, Soheil Asgarpour and Shunde Yin
Mining 2025, 5(3), 55; https://doi.org/10.3390/mining5030055 - 9 Sep 2025
Viewed by 780
Abstract
The Super-long Gravity Heat Pipe (SLGHP) is an efficient geothermal energy utilization technology that can transmit thermal energy by fully utilizing natural temperature differences without external energy input. This study focuses on the high-altitude geothermal environment of Mount Meager, Canada, and employs numerical [...] Read more.
The Super-long Gravity Heat Pipe (SLGHP) is an efficient geothermal energy utilization technology that can transmit thermal energy by fully utilizing natural temperature differences without external energy input. This study focuses on the high-altitude geothermal environment of Mount Meager, Canada, and employs numerical simulations and dynamic thermal analysis to systematically investigate the thermal transport performance of the SLGHP system under both steady-state and dynamic operating conditions. The study also examines the impact of various structural parameters on the system’s performance. Three-dimensional CFD simulations were conducted to analyze the effects of pipe diameter, length, filling ratio, working fluid selection, and pipe material on the heat transfer efficiency and heat flux distribution of the SLGHP. The results indicate that working fluids such as CO2 and NH3 significantly enhance the heat flux density, while increasing pipe diameter may reduce the amount of liquid retained in the condenser section, thereby affecting condensate return and thermal stability. Furthermore, dynamic thermal analysis using a three-node RC network model simulated the effects of diurnal temperature fluctuations and variations in the convective heat transfer coefficient in the condenser section on system thermal stability. The results show that the condenser heat flux can reach a peak of 5246 W/m2 during the day, while maintaining a range of 2200–2600 W/m2 at night, with the system exhibiting good thermal responsiveness and no significant lag or flow interruption. In addition, based on the thermal output of the SLGHP system and the integration with the Organic Rankine Cycle (ORC) system, the power generation potential analysis indicates that the system, with 100 heat pipes, can provide stable power generation of 50–60 kW. In contrast to previous SLGHP studies focused on generalized modeling, this work introduces a site-specific CFD–RC framework, quantifies structural sensitivity via heat flux indices, and bridges numerical performance with economic feasibility, offering actionable insights for high-altitude deployment. This system has promising practical applications, particularly for providing stable renewable power in remote and cold regions. Future research will focus on field experiments and system optimization to further improve system efficiency and economic viability. Full article
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27 pages, 8062 KB  
Article
Comparative Study of RANS Models for Simulating Turbulent Flow and Heat Transfer in Corrugated Pipes
by Ting-Ting Tang, Fang-Qiu Li, Guang-Yao Wang, Jun Yan and Zhao-Kuan Lu
Water 2025, 17(17), 2649; https://doi.org/10.3390/w17172649 - 8 Sep 2025
Viewed by 685
Abstract
Corrugated pipes are extensively used in engineering applications that require flexibility and enhanced heat exchange, such as drainage and compact heat exchangers, and recently as inner layers in cryogenic flexible hoses for offshore liquid ship-to-ship transfer. The great flexibility of these hoses makes [...] Read more.
Corrugated pipes are extensively used in engineering applications that require flexibility and enhanced heat exchange, such as drainage and compact heat exchangers, and recently as inner layers in cryogenic flexible hoses for offshore liquid ship-to-ship transfer. The great flexibility of these hoses makes them well-suited for deployment in dynamic and harsh marine environments. However, the corrugated geometry also induces flow separation, elevated turbulence, and intricate heat transfer behaviors. This study focuses on the flow and heat transfer characteristics in corrugated pipes with various geometries, addressing the current lack of systematic comparative studies on the performance of different Reynolds-Averaged Navier–Stokes (RANS) models in such configurations. Despite their limitations in accuracy compared to high-fidelity methods, RANS models remain the workhorse for engineering analysis due to their computational efficiency. This study employs several RANS models to simulate flow and heat transfer in three corrugated pipe geometries—sinusoidal (Sin), C-type, and U-type—over a Reynolds number range of O(104) to O(105) and assesses their performance against high-fidelity Large Eddy Simulation benchmarks. The results show that prediction accuracy decreases with increasing corrugation depth, with the most significant errors in trough regions where reverse flow dominates, and that the choice of turbulence model has a strong influence on the predicted flow and heat transfer behavior. Among all models, the kϵ models overall provide the most consistent and accurate predictions for friction factor, velocity distribution, and Nusselt number, while the kω models perform the worst. The Reynolds Stress Model improves friction factor prediction accuracy at high Reynolds numbers and provides marginally better accuracy in mean Nusselt number prediction, but its advantages are limited relative to its substantially higher computational cost. The Standard kϵ model with Enhanced Wall Treatment demonstrates robust and balanced performance across geometries and flow regimes, making it a practical choice for engineering use. This work provides engineers and researchers guidance for choosing RANS models that balance accuracy and computational efficiency in simulations of LNG ship-to-ship transfer, compact heat exchangers, and other industrial systems that employ corrugated pipes. Full article
(This article belongs to the Special Issue Ship and Ocean Engineering)
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19 pages, 6638 KB  
Article
High-Temperature Degradation of Throttling Performance in While-Drilling Jars Induced by Thermal Expansion and Fluid Rheology
by Zhaoyang Zhao, Zhanghua Lian, Hao Yu, Wei Sun, Senyan Liu, Zhiyong Wan and Jiachang Nie
Machines 2025, 13(9), 824; https://doi.org/10.3390/machines13090824 - 7 Sep 2025
Viewed by 372
Abstract
During deep and ultra-deep well drilling operations, the throttling performance of the hydraulic-while-drilling jar is significantly affected by the combined influence of temperature-induced differential thermal expansion among components and changes in the rheological properties of hydraulic oil. These effects often lead to unstable [...] Read more.
During deep and ultra-deep well drilling operations, the throttling performance of the hydraulic-while-drilling jar is significantly affected by the combined influence of temperature-induced differential thermal expansion among components and changes in the rheological properties of hydraulic oil. These effects often lead to unstable jarring behavior or even complete failure to trigger jarring during stuck pipe events. Here, we propose a high-temperature degradation evaluation model for the throttling performance of the throttle valve in an HWD jar based on thermal expansion testing of individual components and high-temperature rheological experiments of hydraulic oil. By using the variation characteristics of the throttling passage geometry as a linkage, this model integrates the thermo-mechanical coupling of the valve body with flow field simulation. Numerical results reveal that fluid pressure decreases progressively along the flow path through the throttle valve, while flow velocity increases sharply at the channel entrance and exhibits mild fluctuations within the throttling region. Under fluid compression, the throttling areas of both the upper and lower valves expand to some extent, with their spatial distributions closely following the pressure gradient and decreasing gradually along the flow direction. Compared with ambient conditions, thermal expansion under elevated temperatures causes a more pronounced increase in throttling area. Additionally, as hydraulic oil viscosity decreases with increasing temperature, flow velocities and mass flow rates rise significantly, leading to a marked deterioration in the throttling performance of the drilling jar under high-temperature downhole conditions. Full article
(This article belongs to the Section Machine Design and Theory)
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18 pages, 6260 KB  
Article
Operational Mechanisms and Energy Analysis of Variable-Speed Pumping Stations
by Yan Li, Jilong Lin, Yonggang Lu, Zhiwang Liu, Litao Qu, Fanxiao Jiao, Zhengwei Wang and Qingchang Meng
Water 2025, 17(17), 2620; https://doi.org/10.3390/w17172620 - 4 Sep 2025
Viewed by 879
Abstract
The spatiotemporal uneven distribution of water resources conflicts sharply with human demands, with pumping stations facing efficiency decline due to aging infrastructure and complex hydraulic interactions. This study employs numerical simulation to investigate operational mechanisms in a parallel pump system at the Yanhuanding [...] Read more.
The spatiotemporal uneven distribution of water resources conflicts sharply with human demands, with pumping stations facing efficiency decline due to aging infrastructure and complex hydraulic interactions. This study employs numerical simulation to investigate operational mechanisms in a parallel pump system at the Yanhuanding Yanghuang Cascade Pumping Station. Using ANSYS Fluent 2024 R1 and the SST k-ω turbulence model, we demonstrate that variable-speed control expands the adjustable flow range to 1.17–1.26 m3/s while maintaining system efficiency at 83–84% under head differences of 77.8–79.8 m. Critically, energy losses (δH) at the 90° outlet pipe junction escalate from 3.8% to 18.2% of total energy with increasing flow, while Q-criterion vortex analysis reveals a 63% vortex area reduction at lower speeds. Furthermore, a dual-mode energy dissipation mechanism was identified: at 0.90n0 speed, turbulent kinetic energy surges by 115% with minimal dissipation change, indicating large-scale vortex dominance, whereas at 0.80n0, turbulent dissipation rate increases drastically by 39%, signifying a shift to small-scale viscous dissipation. The novelty of this work lies in the first systematic quantification of junction energy losses and the revelation of turbulent energy transformation mechanisms in parallel pump systems. These findings provide a physics-based foundation for optimizing energy efficiency in high-lift cascade pumping stations. Full article
(This article belongs to the Section Hydraulics and Hydrodynamics)
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21 pages, 8653 KB  
Article
Startup Characteristics and Thermal Instability of a Visual Loop Heat Pipe Under Acceleration Force
by Lijun Chen, Yongqi Xie, Longzhu Han, Huifeng Kang and Hongwei Wu
Aerospace 2025, 12(9), 797; https://doi.org/10.3390/aerospace12090797 - 4 Sep 2025
Viewed by 421
Abstract
Loop heat pipes are efficiently two-phase heat transfer devices in the field of aircraft thermal management. To investigate the startup behavior and thermal instability of loop heat pipes under acceleration force, this study designed a novel loop heat pipe featuring two visual compensation [...] Read more.
Loop heat pipes are efficiently two-phase heat transfer devices in the field of aircraft thermal management. To investigate the startup behavior and thermal instability of loop heat pipes under acceleration force, this study designed a novel loop heat pipe featuring two visual compensation chambers and a visual condenser. Elevated acceleration experiments were conducted across four different heat loads, acceleration magnitudes, and directions. The heat load ranged from 30 W to 150 W, while the acceleration magnitude varied from 1 g to 15 g, with four acceleration directions (A, B, C, and D). The startup behavior, thermal instability, internal flow pattern, and phase distribution were analyzed systematically. The experimental results reveal the following: (i) The startup behaviors vary across the four acceleration directions. In direction A, startup is more difficult due to additional resistance induced by the acceleration force. In direction C, startup time generally decreases with increasing heat load and acceleration up to 7 g. The longest startup time observed is 372 s at 30 W and 11 g. (ii) At high heat load, periodic temperature fluctuations are observed, particularly in directions B and C. Simultaneously, the vapor–liquid phase interface in the condenser exhibits periodic back-and-forth movement. (iii) The visual DCCLHP exhibits a loss of temperature control under the combined influence of high heat loads and acceleration force, often accompanied by working fluid reverse flow, periodic temperature fluctuations, or wick dry-out. Full article
(This article belongs to the Special Issue Aircraft Thermal Management Technologies)
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