Sign in to use this feature.

Years

Between: -

Subjects

remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline
remove_circle_outline

Journals

remove_circle_outline
remove_circle_outline
remove_circle_outline

Article Types

Countries / Regions

Search Results (156)

Search Parameters:
Keywords = distribution of extreme velocity

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
25 pages, 9138 KB  
Article
Numerical Investigations of Snowdrift Characteristics on Roofs with Consideration of Snow Crystal Morphological Features
by Guolong Zhang, Qingwen Zhang, Huamei Mo, Yueyue Zhao, Xudong Zhi and Feng Fan
Buildings 2025, 15(19), 3606; https://doi.org/10.3390/buildings15193606 - 8 Oct 2025
Viewed by 42
Abstract
Under extreme snowfall conditions, wind-induced snow drifting can lead to the redistribution of snow accumulation on roofs, resulting in localized overloads that pose a serious threat to building structural safety. Notably, morphological differences in snow particles significantly alter their aerodynamic characteristics, causing variations [...] Read more.
Under extreme snowfall conditions, wind-induced snow drifting can lead to the redistribution of snow accumulation on roofs, resulting in localized overloads that pose a serious threat to building structural safety. Notably, morphological differences in snow particles significantly alter their aerodynamic characteristics, causing variations in their motion trajectories and increasing the uncertainty in determining roof snow loads. Therefore, this study develops a numerical simulation method that accounts for snow morphologies based on the drag coefficients of typical snow crystals, and further investigates the accumulation characteristics of differently shaped snow particles on typical roofs. Analysis results demonstrate that the observed variations in snow particle motion characteristics primarily originate from differences in their respective drag coefficients. The drag coefficient exerts a direct influence on particle settling velocity, which subsequently governs spatial distribution patterns of snow concentration and final accumulation patterns. Under identical inflow snow concentration conditions, particles with higher drag coefficients exhibit reduced depositional accumulation on roof surfaces. Notably, this shape-dependent effect diminishes with increasing roof span and slope. Full article
(This article belongs to the Section Building Structures)
Show Figures

Figure 1

24 pages, 4192 KB  
Article
Investigation on Dynamic Thermal Transfer Characteristics of Electromagnetic Rail Spray Cooling in Transient Processes
by Shuo Ma and Hongting Ma
Energies 2025, 18(19), 5254; https://doi.org/10.3390/en18195254 - 3 Oct 2025
Viewed by 204
Abstract
Electromagnetic Railguns Face Severe Ablation and Melting Risks Due to Extremely High Transient Thermal Loads During High-Speed Launching, Directly Impacting Launch Reliability and Service Life. To address this thermal management challenge, this study proposes and validates the effectiveness of spray cooling technology. Leveraging [...] Read more.
Electromagnetic Railguns Face Severe Ablation and Melting Risks Due to Extremely High Transient Thermal Loads During High-Speed Launching, Directly Impacting Launch Reliability and Service Life. To address this thermal management challenge, this study proposes and validates the effectiveness of spray cooling technology. Leveraging its high heat transfer coefficient, exceptional critical heat flux (CHF) carrying capacity, and strong transient cooling characteristics, it is particularly suitable for the unsteady thermal control during the initial launch phase. An experimental platform was established, and a three-dimensional numerical model was developed to systematically analyze the dynamic influence mechanisms of nozzle inlet pressure, flow rate, spray angle, and spray distance on cooling performance. Experimental results indicate that the system achieves maximum critical heat flux (CHF) and rail temperature drop at an inlet pressure of 0.5 MPa and a spray angle of 0°. Numerical simulations further reveal that a 45° spray cone angle simultaneously achieves the maximum temperature drop and optimal wall temperature uniformity. Key parameter sensitivity analysis demonstrates that while increasing spray distance leads to larger droplet diameters, the minimal droplet velocity decay combined with a significant increase in overall momentum markedly enhances convective heat transfer efficiency. Concurrently, increasing spray distance effectively improves rail surface temperature uniformity by optimizing the spatial distribution of droplet size and velocity. Full article
(This article belongs to the Section J: Thermal Management)
Show Figures

Figure 1

21 pages, 3628 KB  
Article
Uncertainty Propagation for Power-Law, Bingham, and Casson Fluids: A Comparative Stochastic Analysis of a Class of Non-Newtonian Fluids in Rectangular Ducts
by Eman Alruwaili and Osama Hussein Galal
Mathematics 2025, 13(18), 3030; https://doi.org/10.3390/math13183030 - 19 Sep 2025
Viewed by 237
Abstract
This study presents a novel framework for uncertainty propagation in power-law, Bingham, and Casson fluids through rectangular ducts under stochastic viscosity (Case I) and pressure gradient conditions (Case II). Using the computationally efficient Stochastic Finite Difference Method with Homogeneous Chaos (SFDHC), validated via [...] Read more.
This study presents a novel framework for uncertainty propagation in power-law, Bingham, and Casson fluids through rectangular ducts under stochastic viscosity (Case I) and pressure gradient conditions (Case II). Using the computationally efficient Stochastic Finite Difference Method with Homogeneous Chaos (SFDHC), validated via comparison with quasi-Monte Carlo simulations, we demonstrate significantly lower computational costs across varying Coefficients of Variation (COVs). For viscosity uncertainty (Case I), results show a 0.54–2.8% increase in mean maximum velocity with standard deviations reaching 75.3–82.5% of the COV, where the power-law model exhibits the greatest sensitivity (velocity variations spanning 71.2–177.3% of the mean at COV = 20%). Pressure gradient uncertainty (Case II) preserves mean velocities but produces narrower and symmetric distributions. We systematically evaluate the effects of aspect ratio, yield stress, and flow behavior index on the stochastic velocity response of each fluid. Moreover, our analysis pioneers a performance hierarchy: Herschel–Bulkley fluids show the highest mean and standard deviation of maximum velocity, followed by power-law, Robertson–Stiff, Bingham, and Casson models. A key finding is the extreme fluctuation of the Robertson–Stiff model, which exhibits the most drastic deviations, reaching up to 177% of the average velocity. The significance of fluid-specific stochastic analysis in duct system design is underscored by these results. This is especially critical for non-Newtonian flows, where system performance and reliability are greatly impacted by uncertainties in viscosity and pressure gradient, which reflect actual operational variations. Full article
(This article belongs to the Section E: Applied Mathematics)
Show Figures

Figure 1

25 pages, 6532 KB  
Article
Representing Small Shallow Water Estuary Hydrodynamics to Uncover Litter Transport Patterns
by Lubna Benchama Ahnouch, Frans Buschman, Helene Boisgontier, Ana Bio, Luis R. Vieira, Sara C. Antunes, Gary F. Kett, Isabel Sousa-Pinto and Isabel Iglesias
Water 2025, 17(18), 2698; https://doi.org/10.3390/w17182698 - 12 Sep 2025
Viewed by 872
Abstract
Plastic pollution is an increasing global concern, with estuaries being especially vulnerable as transition zones between freshwater and marine systems. These ecosystems often accumulate large amounts of waste, affecting wildlife and water quality. This study focuses on analysing the circulation patterns of the [...] Read more.
Plastic pollution is an increasing global concern, with estuaries being especially vulnerable as transition zones between freshwater and marine systems. These ecosystems often accumulate large amounts of waste, affecting wildlife and water quality. This study focuses on analysing the circulation patterns of the Ave Estuary, a small, shallow system on Portugal’s north-western coast, and their influence on litter transport and distribution. This site was selected for installing an aquatic litter removal technology under the EU-funded MAELSTROM project. A 2DH hydrodynamic model using Delft3D FM, coupled with the Wflow hydrological model, was implemented and validated. Various scenarios were simulated to assess estuarine dynamics and pinpoint zones prone to litter accumulation and flood risk. The results show that tidal action and river discharge mainly drive the estuary’s behaviour. Under low discharge, floating litter should be mostly transported toward the ocean, while high discharge conditions should result in litter movement at all depths due to stronger currents. High water levels and flooding occur mainly upstream and in specific low-lying areas near the mouth. Low-velocity zones, which can favour litter accumulation, were found around the main channel and on the western margin near the estuary’s mouth, even during high flows. These findings highlight persistent accumulation zones, even under extreme event conditions. Full article
(This article belongs to the Special Issue Marine Plastic Pollution: Recent Advances and Future Challenges)
Show Figures

Figure 1

22 pages, 4003 KB  
Article
Numerical Modelling of Rock Fragmentation in Landslide Propagation: A Test Case
by Claudia Zito, Massimo Mangifesta, Mirko Francioni, Luigi Guerriero, Diego Di Martire, Domenico Calcaterra, Corrado Cencetti, Antonio Pasculli and Nicola Sciarra
Geosciences 2025, 15(9), 354; https://doi.org/10.3390/geosciences15090354 - 7 Sep 2025
Viewed by 489
Abstract
Landslides and rockfalls can negatively impact human activities and cause radical changes to the surrounding environment. For example, they can destroy entire buildings and roadway infrastructure, block waterways and create sudden dams, resulting in upstream flooding and increased flood risk downstream. In extreme [...] Read more.
Landslides and rockfalls can negatively impact human activities and cause radical changes to the surrounding environment. For example, they can destroy entire buildings and roadway infrastructure, block waterways and create sudden dams, resulting in upstream flooding and increased flood risk downstream. In extreme cases, they can even cause loss of life. External factors such as weathering, vegetation and mechanical stress alterations play a decisive role in their evolution. These actions can reduce strength, which can have an adverse impact on the slope’s ability to withstand failure. For rockfalls, this process also affects fragmentation, creating variations in the size, shape and volume of detached blocks, which influences propagation and impact on the slope. In this context, the Morino-Rendinara landslide is a clear example of rockfall propagation influenced by fragmentation. In this case, fragmentation results from tectonic stresses acting on the materials as well as specific climatic conditions affecting rock mass properties. This study explores how different fragmentation scales influence both velocity and landslide propagation along the slope. Using numerical models, based on lumped mass approach and stochastic analyses, various scenarios of rock material fracturing were examined and their impact on runout was assessed. Different scenarios were defined, varying only the fragmentation degree and different random seed sets at the beginning of simulations, carried out using the Rock-GIS tool. The results suggest that rock masses with high fracturing show reduced cohesion along joints and cracks, which significantly lowers their shear strength and makes them more prone to failure. Increased fragmentation further decreases the bonding between rock blocks, thereby accelerating landslide propagation. Conversely, less fragmented rocks retain higher resistance, which limits the extent of movement. These processes are influenced by uncertainties related to the distribution and impact of different alteration grades, resulting from variable tectonic stresses and/or atmospheric weathering. Therefore, a stochastic distribution model was developed to integrate the results of all simulations and to reconstruct both the landslide propagation and the evolution of its deposits. This study emphasizes the critical role of fragmentation and the volume involved in rockfalls and their runout behaviour. Furthermore, the method provides a framework for enhancing risk assessment in complex geological environments and for developing mitigation strategies, particularly regarding runout distance and block size. Full article
(This article belongs to the Section Natural Hazards)
Show Figures

Figure 1

24 pages, 3141 KB  
Article
Research on Transmission Line Icing Prediction for Power System Based on Improved Snake Optimization Algorithm-Optimized Deep Hybrid Kernel Extreme Learning Machine
by Guanhua Li, Haoran Chen, Shicong Sun, Tie Guo and Luyu Yang
Energies 2025, 18(17), 4646; https://doi.org/10.3390/en18174646 - 1 Sep 2025
Viewed by 428
Abstract
As extreme weather events become more frequent, the icing of transmission lines in winter has become more common, causing significant economic losses to power systems and drawing increasing attention. However, owing to the complexity of the conductor icing process, establishing high-precision ice thickness [...] Read more.
As extreme weather events become more frequent, the icing of transmission lines in winter has become more common, causing significant economic losses to power systems and drawing increasing attention. However, owing to the complexity of the conductor icing process, establishing high-precision ice thickness prediction models is vital for ensuring the safe and stable operation of power grids. Therefore, this paper proposes a hybrid model combining an improved snake optimization (ISO) algorithm, deep extreme learning machine (DELM), and hybrid kernel extreme learning machine (HKELM). Firstly, based on the analysis of the factors that influence the icing, the temperature, the humidity, the wind velocity, the wind direction, and the precipitation are selected as the weather parameters for the prediction model of the transmission line icing. Secondly, the HKELM is introduced into the regression layer of DELM to obtain the deep hybrid kernel extreme learning machine (DHKELM) model for ice thickness prediction. The SO algorithm is then augmented by incorporating the Latin hypercube sampling technique, t-distribution mutation strategy, and Cauchy mutation, enhancing its convergence. Finally, the ISO-DHKELM model is applied to the icing data of transmission lines in Sichuan Province for experiments. The simulation results indicate that this model not only performs well, but also enhances the accuracy of ice thickness predictions. Full article
Show Figures

Figure 1

17 pages, 4123 KB  
Article
Crystallographic Effect of TiAl Alloy Under High-Speed Shock Deformation
by Jiayu Liu, Huailin Liu and Zhengping Zhang
Appl. Sci. 2025, 15(16), 8837; https://doi.org/10.3390/app15168837 - 11 Aug 2025
Viewed by 381
Abstract
In this paper, the molecular dynamics simulation method was adopted to systematically study the microstructure evolution behavior of TiAl alloys under impact compression under three typical crystal orientations ([001], [110], [111]). By analyzing the characteristics of structural phase transition, defect type evolution, dislocation [...] Read more.
In this paper, the molecular dynamics simulation method was adopted to systematically study the microstructure evolution behavior of TiAl alloys under impact compression under three typical crystal orientations ([001], [110], [111]). By analyzing the characteristics of structural phase transition, defect type evolution, dislocation expansion, and radial distribution function, the anisotropic response mechanism under the joint regulation of crystal orientation and impact velocity was revealed. The results show that the [111] crystal orientation is most prone to local amorphous transformation at high strain rates, and its structural collapse is due to the rapid accumulation and limited reconstruction of dislocations/faults. The [001] crystal orientation is prone to forming staggered stacking of layers and local HCP phase transformation, presenting as a medium-strength structural disorder. Under the strain regulation mechanism dominated by twinning, the [110] orientation exhibits superior structural stability and anti-disorder ability. With increases in the impact velocity, the defect type gradually changes from isolated dislocations to large-scale HCP regions and amorphous bands, and there are significant differences in the critical velocities of amorphous transformation corresponding to different crystal orientations. Further analysis indicates that the HCP structure and the formation of layering faults are important precursor states of amorphous transformation. The evolution of the g(r) function verifies the stepwise disintegration process of medium and long-range ordered structures under shock induction. It provides a new theoretical basis and microscopic perspective for the microstructure regulation, damage tolerance improvement, and impact resistance design of TiAl alloys under extreme stress conditions. Full article
Show Figures

Figure 1

35 pages, 8516 KB  
Article
Study on Stress Monitoring and Risk Early Warning of Flexible Mattress Deployment in Deep-Water Sharp Bend Reaches
by Chu Zhang, Ping Li, Zebang Cui, Kai Wu, Tianyu Chen, Zhenjia Tian, Jianxin Hao and Sudong Xu
Water 2025, 17(15), 2333; https://doi.org/10.3390/w17152333 - 6 Aug 2025
Viewed by 497
Abstract
This study addresses the complex challenges associated with flexible mattress (soft mattress) installation in the sharply curved and deep-water sections of the Yangtze River, particularly in the Yaozui revetment reconstruction project. Under extreme hydrodynamic conditions—water depths exceeding 30 m and velocities over 2.5 [...] Read more.
This study addresses the complex challenges associated with flexible mattress (soft mattress) installation in the sharply curved and deep-water sections of the Yangtze River, particularly in the Yaozui revetment reconstruction project. Under extreme hydrodynamic conditions—water depths exceeding 30 m and velocities over 2.5 m/s—the risk of structural failures such as displacement, flipping, or tearing of the mattress becomes significant. To improve construction safety and stability, the study integrates numerical modeling and on-site strain monitoring to analyze the mechanical response of flexible mattresses during deployment. A three-dimensional finite element model based on the catenary theory was developed to simulate stress distributions under varying flow velocities and angles, revealing stress concentrations at the mattress’s upper edge and reinforcement junctions. Concurrently, a real-time monitoring system using high-precision strain sensors was deployed on critical shipboard components, with collected data analyzed through a remote IoT platform. The results demonstrate strong correlations between mattress strain, flow velocity, and water depth, enabling the identification of high-risk operational thresholds. The proposed monitoring and early-warning framework offers a practical solution for managing construction risks in extreme riverine environments and contributes to the advancement of intelligent construction management for underwater revetment works. Full article
(This article belongs to the Section Oceans and Coastal Zones)
Show Figures

Figure 1

17 pages, 1653 KB  
Article
Corner Case Dataset for Autonomous Vehicle Testing Based on Naturalistic Driving Data
by Jian Zhao, Wenxu Li, Bing Zhu, Peixing Zhang, Zhaozheng Hu and Jie Meng
Smart Cities 2025, 8(4), 129; https://doi.org/10.3390/smartcities8040129 - 5 Aug 2025
Viewed by 1213
Abstract
The safe and reliable operation of autonomous vehicles is contingent on comprehensive testing. However, the operational scenarios are inexhaustible. Corner cases, which critically influence autonomous vehicle safety, occur at an extremely low probability and follow a long-tail distribution. Corner cases can be defined [...] Read more.
The safe and reliable operation of autonomous vehicles is contingent on comprehensive testing. However, the operational scenarios are inexhaustible. Corner cases, which critically influence autonomous vehicle safety, occur at an extremely low probability and follow a long-tail distribution. Corner cases can be defined as combinations of driving task and scenario elements. These scenarios are characterized by low probability, high risk, and a tendency to reveal functional limitations inherent to autonomous driving systems, triggering anomalous behavior. This study constructs a novel corner case dataset using naturalistic driving data, specifically tailored for autonomous vehicle testing. A scenario marginality quantification method is designed to analyze multi-source naturalistic driving data, enabling efficient extraction of corner cases. Heterogeneous scenarios are systematically transformed, resulting in a dataset characterized by diverse interaction behaviors and standardized formatting. The results indicate that the scenario marginality of the dataset constructed in this study is 2.78 times that of mainstream naturalistic driving datasets, and the scenarios exhibit considerable diversity. The trajectory and velocity fluctuations, quantified at 0.013 m and 0.021 m/s, respectively, are consistent with the kinematic characteristics of real-world driving scenarios. These results collectively demonstrate the dataset’s high marginality, diversity, and applicability. Full article
Show Figures

Figure 1

16 pages, 1859 KB  
Article
Simulation of Effect on Charge Accumulation Distribution in Laminar Oil Flow with Bubbles in Oil Passage of Converter Transformer
by Wen Si, Haibo Li, Hongshun Liu and Xiaotian Gu
Energies 2025, 18(15), 3992; https://doi.org/10.3390/en18153992 - 26 Jul 2025
Viewed by 402
Abstract
The converter transformer is subjected to AC/DC composite voltage during operation, and the sealed and time-varying internal state makes its electric field distribution and charge accumulation unable to be monitored in real-time experiments. In this paper, aiming at the influence of bubbles in [...] Read more.
The converter transformer is subjected to AC/DC composite voltage during operation, and the sealed and time-varying internal state makes its electric field distribution and charge accumulation unable to be monitored in real-time experiments. In this paper, aiming at the influence of bubbles in the oil passage of the converter transformer on charge accumulation before discharge, a simulation model in a laminar flow environment is established, and four different calculation conditions are set to simulate the charge accumulation in 1 s. It is found that under laminar flow conditions, the trapped bubbles on the insulation paper wall play an obvious role in intensifying the charge accumulation in transformer oil, and the extreme range of charge density will increase by about 104 times. Bubbles aggravate the electric field distortion, and the insulation strength of bubbles is lower, which becomes the weak link of insulation. In the laminar flow environment, the oil flow will take away part of the accumulated charge in the oil, but in the case of trapped bubbles, the charge accumulation in the insulating paper will increase from the order of 10−2 to 10−1. In the case of no bubbles, the transformer oil layer flow will increase the charge accumulation in the insulation paper by 4–5 orders of magnitude. Therefore, it can be seen that the flow of transformer oil will increase the deterioration level of insulation paper. And when the transformer oil is already in the laminar flow state, the influence of laminar flow velocity on charge accumulation is not obvious. The research results in this paper provide a time-varying simulation reference state for the charge accumulation problem that cannot be measured experimentally under normal charged operation conditions, and we obtain quantitative numerical results, which can provide a valuable reference for the study of transformer operation and insulation discharge characteristics. Full article
Show Figures

Figure 1

22 pages, 5131 KB  
Article
Multi-Region OpenFOAM Solver Development for Compact Toroid Transport in Drift Tube
by Kun Bao, Feng Wang, Chengming Qu, Defeng Kong and Jian Song
Appl. Sci. 2025, 15(13), 7569; https://doi.org/10.3390/app15137569 - 5 Jul 2025
Viewed by 547
Abstract
Compact toroid (CT) injection, with its characteristics of high plasma density and extremely high injection velocity, is considered a highly promising method for core fueling in fusion reactors. Previous studies have lacked investigation into the transport process of CT within drift tubes. To [...] Read more.
Compact toroid (CT) injection, with its characteristics of high plasma density and extremely high injection velocity, is considered a highly promising method for core fueling in fusion reactors. Previous studies have lacked investigation into the transport process of CT within drift tubes. To investigate the dynamic processes of CT in drift tubes, this study developed a compressible magnetohydrodynamics (MHD) solver and a magnetic diffusion solver based on the OpenFOAM platform. They were integrated into a multi-region coupling framework to create a multi-region coupled MHD solver, mhdMRF, for simulating the dynamic behavior of CT in drift tubes and its interaction with finite-resistivity walls. The solver demonstrated excellent performance in simulations of the Orszag–Tang MHD vortex problem, the Brio–Wu shock tube problem, analytical verification of magnetic diffusion, and validation of internal coupling boundary conditions. Additionally, this work innovatively explored the effects of the geometric structure at the end of the inner electrode and finite-resistivity walls on the transport processes of CT. The results indicate that optimizing the geometric structure at the end of the inner electrode can significantly enhance the confinement performance and stability of CT transport. The resistivity of the wall profoundly influences the magnetic field structure and density distribution of CT. Full article
(This article belongs to the Special Issue Plasma Physics: Theory, Methods and Applications)
Show Figures

Figure 1

23 pages, 43685 KB  
Article
Rapid Computation of Seismic Loss Curves for Canadian Buildings Using Tail Approximation Method
by Payam Momeni, Katsuichiro Goda, Navid Sirous and Sheri Molnar
GeoHazards 2025, 6(2), 26; https://doi.org/10.3390/geohazards6020026 - 1 Jun 2025
Cited by 1 | Viewed by 1121
Abstract
Traditional seismic risk assessments often require specialized expertise and extensive computational time, making probabilistic seismic risk evaluations less accessible to practitioners and decision-makers. To reduce the barriers related to applications of quantitative seismic risk analysis, this paper develops a Quick Loss Estimation Tool [...] Read more.
Traditional seismic risk assessments often require specialized expertise and extensive computational time, making probabilistic seismic risk evaluations less accessible to practitioners and decision-makers. To reduce the barriers related to applications of quantitative seismic risk analysis, this paper develops a Quick Loss Estimation Tool (QLET) designed for rapid seismic risk assessment of Canadian buildings. By approximating the upper tail of a seismic hazard curve using an extreme value distribution and by integrating it with building exposure-vulnerability models, the QLET enables efficient computation of seismic loss curves for individual sites. The tool generates seismic loss exceedance probability curves and financial risk metrics based on Monte Carlo simulations, offering customizable risk assessments for various building types. The QLET also incorporates regional site proxy models based on average shear-wave velocity in the uppermost 30 m to enhance site-specific hazard characterization, addressing key limitations of global site proxy models and enabling risk-based seismic microzonation. The QLET streamlines hazard, exposure, and vulnerability assessments into a user-friendly tool, facilitating regional-scale risk evaluations within practical timeframes, making it particularly applicable to emergency preparedness, urban planning, and insurance analysis. Full article
Show Figures

Figure 1

18 pages, 583 KB  
Article
An Analytical Model for the Prediction of Emptying Processes in Single Water Pipelines
by Carlos R. Payares Guevara, Alberto Patiño-Vanegas, Enrique Pereira-Batista, Oscar E. Coronado-Hernández and Vicente S. Fuertes-Miquel
Appl. Sci. 2025, 15(11), 6000; https://doi.org/10.3390/app15116000 - 26 May 2025
Cited by 1 | Viewed by 563
Abstract
Air pockets in water distribution networks can cause various operational issues, as their expansion during drainage operations leads to sub-atmospheric conditions that may result in pipeline collapse depending on soil conditions and pipe stiffness. This study presents an analytical solution for calculating air [...] Read more.
Air pockets in water distribution networks can cause various operational issues, as their expansion during drainage operations leads to sub-atmospheric conditions that may result in pipeline collapse depending on soil conditions and pipe stiffness. This study presents an analytical solution for calculating air pocket pressure, water column length, and water velocity during drainage operations in a pipeline with an entrapped air pocket and a closed upstream end. The existing system of three differential equations is reduced to two first-order nonlinear differential equations, enabling a rigorous analysis of the existence and uniqueness of solutions. The system is then further reduced to a single secondorder nonlinear ordinary differential equation (ODE), providing an intuitive framework for examining the physical behaviour of the hydraulic and thermodynamic variables. Furthermore, through a change of variables, the second-order ODE is transformed into a first-order linear ODE, facilitating the derivation of an analytical solution. The analytical solution is validated by comparing it with a numerical solution. Additionally, a practical application demonstrates the effectiveness of the developed tool in predicting the extreme pressure values in the air pocket during the water drainage process in a pipe, within a controlled environment. Full article
(This article belongs to the Special Issue Advances in Fluid Mechanics Analysis)
Show Figures

Figure 1

16 pages, 5781 KB  
Article
Hydrodynamic Performance and Vortex Structure Analysis of a Toroidal Propeller
by Jie Bai, Yunhai Li, Xiaohui Liu, Hongliang Zhang and Liuzhen Ren
J. Mar. Sci. Eng. 2025, 13(6), 1046; https://doi.org/10.3390/jmse13061046 - 26 May 2025
Cited by 1 | Viewed by 1392
Abstract
Because of their distinctive toroidal blade configuration, toroidal propellers can improve propulsion efficiency, reduce underwater noise, and enhance blade stability and strength. In recent years, they have emerged as an extremely promising novel underwater propulsion technology. To investigate their working mechanism, a geometric [...] Read more.
Because of their distinctive toroidal blade configuration, toroidal propellers can improve propulsion efficiency, reduce underwater noise, and enhance blade stability and strength. In recent years, they have emerged as an extremely promising novel underwater propulsion technology. To investigate their working mechanism, a geometric model of the toroidal propeller was initially established, and an unsteady numerical calculation model was constructed based on the sliding mesh technique. Subsequently, with the E779A conventional propeller as the research subject, the numerical model was verified, and a grid independence test was accomplished. Thereafter, the hydrodynamic performance of the toroidal propeller under diverse advance coefficients was analyzed based on the numerical model, and open water characteristic curves were established. Eventually, the surface pressure distribution, velocity field, and vorticity field of the toroidal propeller under various working conditions were studied. The outcomes demonstrate that the toroidal propeller attains the maximum propulsion efficiency at high advance coefficients, possesses a broad range of working condition adaptability, and is more applicable to high-speed vessels. At low advance coefficients, the toroidal propeller exhibits a relatively strong thrust performance, with the thrust generated by the front propeller being greater than that generated by the rear propeller, and the pressure peak emerges at the leading edge of the transition section of the front blade. The analysis of the velocity field indicates that its acceleration effect is superior to that of the conventional propeller. The analysis of the vorticity field reveals that the trailing vortices shed from the leading edge of the transition section of the front propeller merge and develop with the tip vortices, resulting in a more complex vortex structure. This research clarifies the working mechanism of the toroidal propeller through numerical simulation methods, providing an important basis for its performance optimization. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

31 pages, 10580 KB  
Article
An Exploratory Assessment of a Submarine Topographic Characteristic Index for Predicting Extreme Flow Velocities: A Case Study of Typhoon In−Fa in the Zhoushan Sea Area
by Fanjun Chen, Wankang Yang, Long Xiao, Xiaoliang Xia, Kaixuan Ding and Zhilin Sun
J. Mar. Sci. Eng. 2025, 13(5), 864; https://doi.org/10.3390/jmse13050864 - 25 Apr 2025
Viewed by 513
Abstract
This study analyzes the 96 h flow velocity time series data from the Zhoushan Sea during Typhoon In−fa to investigate the conditions for extreme flow velocities. Through force analysis of the unit fluid and statistical analysis of topographic features, we identified the critical [...] Read more.
This study analyzes the 96 h flow velocity time series data from the Zhoushan Sea during Typhoon In−fa to investigate the conditions for extreme flow velocities. Through force analysis of the unit fluid and statistical analysis of topographic features, we identified the critical water depth, slope, and sea surface width for extreme flow velocities under ideal conditions as 15 m, 4.5°, and 2000 m, respectively. The Submarine Topographic Characteristic Index (STCI) is introduced for the first time in this study, revealing its significant impact on extreme flow velocities. Three types of “extreme velocity points”—associated with constant storm surge, astronomical tide, and typhoon storm surge—were defined, occurring over 85% of the time during typhoon events. These extreme velocity points were analyzed in relation to their topographic characteristics, including water depth, slope, and sea surface width. Simulations of Typhoon In−fa in the Zhoushan Sea area were used to construct the STCI model, resulting in the following weightings: water depth = 0.96, slope = 0.39, and sea surface width = 0.49. Typhoon In−fa occurred in 2021, exhibited a maximum wind speed of approximately 35 m/s, and played a key role in the hydrodynamic processes investigated in this study. Validation with Typhoons Muifa (2021) and Bebinca (2413) confirmed the model’s high consistency. The STCI model provides insight into the occurrence of extreme velocities, categorizing them according to tidal phase and typhoon influence. Preliminary findings indicate the model’s applicability under varying typhoon intensities, offering a robust tool for predicting extreme seabed flow velocities during typhoon events. Full article
(This article belongs to the Section Coastal Engineering)
Show Figures

Figure 1

Back to TopTop