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Search Results (569)

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Keywords = Reynolds-Averaged Navier-Stokes (RANS)

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19 pages, 26478 KiB  
Article
Three-Dimensional Numerical Simulation of Flow Around a Spur Dike in a Meandering Channel Bend
by Yan Xing, Congfang Ai, Hailong Cui and Zhangling Xiao
Fluids 2025, 10(8), 198; https://doi.org/10.3390/fluids10080198 - 29 Jul 2025
Viewed by 227
Abstract
This paper presents a three-dimensional (3D) free surface model to predict incompressible flow around a spur dike in a meandering channel bend, which is highly 3D due to the presence of curvature effects. The model solves the Reynolds-averaged Navier–Stokes (RANS) equations using an [...] Read more.
This paper presents a three-dimensional (3D) free surface model to predict incompressible flow around a spur dike in a meandering channel bend, which is highly 3D due to the presence of curvature effects. The model solves the Reynolds-averaged Navier–Stokes (RANS) equations using an explicit projection method. The 3D grid system is built from a two-dimensional grid by adding dozens of horizontal layers in the vertical direction. Numerical simulations consider four test cases with different spur dike locations in the same meandering channel bend with the same Froude numbers as 0.22. Four turbulence models, the standard k-ε model, the k-ω model, the RNG k-ε model and a nonlinear k-ε model, are implemented in our three-dimensional free surface model. The performance of these turbulence models within the RANS framework is assessed. Comparisons between the model results and experimental data show that the nonlinear k-ε model behaves better than the three other models in general. Based on the results obtained by the nonlinear k-ε model, the highly 3D flow field downstream of the spur dike was revealed by presenting velocity vectors at representative cross-sections and streamlines at the surface and bottom layers. Meanwhile, the 3D characteristics of the downstream separation zone were also investigated. In addition, to highlight the advantage of the nonlinear turbulence model, comparisons of velocity vectors at representative cross-sections between the results obtained by the linear and nonlinear k-ε models are also presented. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics Applied to Transport Phenomena)
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12 pages, 2015 KiB  
Article
Low-Order Modelling of Extinction of Hydrogen Non-Premixed Swirl Flames
by Hazem S. A. M. Awad, Savvas Gkantonas and Epaminondas Mastorakos
Aerospace 2025, 12(8), 676; https://doi.org/10.3390/aerospace12080676 - 29 Jul 2025
Viewed by 185
Abstract
Predicting the blow-off (BO) is critical for characterising the operability limits of gas turbine engines. In this study, the applicability of a low-order extinction prediction modelling, which is based on a stochastic variant of the Imperfectly Stirred Reactor (ISR) approach, to predict the [...] Read more.
Predicting the blow-off (BO) is critical for characterising the operability limits of gas turbine engines. In this study, the applicability of a low-order extinction prediction modelling, which is based on a stochastic variant of the Imperfectly Stirred Reactor (ISR) approach, to predict the lean blow-off (LBO) curve and the extinction conditions in a hydrogen Rich-Quench-Lean (RQL)-like swirl combustor is investigated. The model predicts the blow-off scalar dissipation rate (SDR), which is then extrapolated using Reynolds-Averaged Navier–Stokes (RANS) cold-flow simulations and simple scaling laws, to determine the critical blow-off conditions. It has been found that the sISR modelling framework can predict the BO flow split ratio at different global equivalence ratios, showing a reasonable agreement with the experimental data. This further validates sISR as an efficient low-order modelling flame extinction tool, which can significantly contribute to the development of robust hydrogen RQL combustors by enabling the rapid exploration of combustor operability during the preliminary design phases. Full article
(This article belongs to the Special Issue Scientific and Technological Advances in Hydrogen Combustion Aircraft)
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15 pages, 7636 KiB  
Article
Rapid Prediction of High-Resolution 3D Ship Airwake in the Glide Path Based on CFD, BP Neural Network, and DWL
by Qingsong Liu, Gan Ren, Dingfu Zhou, Bo Liu and Zida Li
Appl. Sci. 2025, 15(15), 8336; https://doi.org/10.3390/app15158336 - 26 Jul 2025
Viewed by 228
Abstract
To meet the requirements of the high spatiotemporal three-dimensional (3D) airflow field within the glide path corridor during carrier-based aircraft/unmanned aerial vehicles (UAVs) landings, this paper proposes a prediction method for high spatiotemporal resolution 3D ship airwake along the glide path by integrating [...] Read more.
To meet the requirements of the high spatiotemporal three-dimensional (3D) airflow field within the glide path corridor during carrier-based aircraft/unmanned aerial vehicles (UAVs) landings, this paper proposes a prediction method for high spatiotemporal resolution 3D ship airwake along the glide path by integrating computational fluid dynamics (CFD), backpropagation (BP) neural network, and Doppler wind lidar (DWL). Firstly, taking the conceptual design aircraft carrier model as the research object, CFD numerical simulations of the ship airwake within the glide path region are carried out using the Poly-Hexcore grid and the detached eddy simulation (DES)/the Reynolds-averaged Navier–Stokes (RANS) turbulence models. Then, using the high spatial resolution ship airwake along the glide path obtained from steady RANS computations under different inflow conditions as a sample dataset, the BP neural network prediction models were trained and optimized. Along the ideal glide path within 200 m behind the stern, the correlation coefficients between the predicted results of the BP neural network and the headwind, crosswind, and vertical wind of the testing samples exceeded 0.95, 0.91, and 0.82, respectively. Finally, using the inflow speed and direction with high temporal resolution from the bow direction obtained by the shipborne DWL as input, the BP prediction models can achieve accurate prediction of the 3D ship airwake along the glide path with high spatiotemporal resolution (3 m, 3 Hz). Full article
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26 pages, 11770 KiB  
Article
Flow Dynamics and Local Scour Around Seabed-Mounted Artificial Reefs: A Case Study from Torbay, UK
by Amir Bordbar, Jakub Knir, Vasilios Kelefouras, Samuel John Stephen Hickling, Harrison Short and Yeaw Chu Lee
J. Mar. Sci. Eng. 2025, 13(8), 1425; https://doi.org/10.3390/jmse13081425 - 26 Jul 2025
Viewed by 298
Abstract
This study investigates the flow dynamics and local scour around a Reef Cube® artificial reef deployed in Torbay, UK, using computational fluid dynamics. The flow is modelled using Reynolds-Averaged Navier–Stokes (RANS) equations with a k-ω SST turbulence model. A novel hydro-morphodynamic model [...] Read more.
This study investigates the flow dynamics and local scour around a Reef Cube® artificial reef deployed in Torbay, UK, using computational fluid dynamics. The flow is modelled using Reynolds-Averaged Navier–Stokes (RANS) equations with a k-ω SST turbulence model. A novel hydro-morphodynamic model employing the generalized internal boundary method in HELYX (OpenFOAM-based) is used to simulate scour development. Model performance was validated against experimental data for flow fields, bed shear stress, and local scour. Flow simulations across various scenarios demonstrated that parameters such as the orientation angle and arrangement of Reef Cubes significantly influence flow patterns, bed shear stress, and habitat suitability. The hydro-morphodynamic model was used to simulate scouring around a reef cube in the Torbay marine environment. Results indicate that typical tidal flow velocity flow in the region is barely sufficient to initiate sediment motion, whereas extreme flow events, represented by doubling the mean flow velocity, significantly accelerate scour development, producing holes up to ten times deeper. These findings underscore the importance of considering extreme flow conditions in scour analyses due to their potential impact on the stability and failure risk of AR projects. Full article
(This article belongs to the Section Ocean Engineering)
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23 pages, 9064 KiB  
Article
A Computational Thermo-Fluid Dynamics Simulation of Slot Jet Impingement Using a Generalized Two-Equation Turbulence Model
by Antonio Mezzacapo, Rossella D’Addio and Giuliano De Stefano
Energies 2025, 18(14), 3862; https://doi.org/10.3390/en18143862 - 20 Jul 2025
Viewed by 1021
Abstract
In this study, a computational thermo-fluid dynamics simulation of a wide-slot jet impingement heating process is performed. The present configuration consists of a turbulent incompressible air jet impinging orthogonally on an isothermal cold plate at a Reynolds number of around 11,000. The two-dimensional [...] Read more.
In this study, a computational thermo-fluid dynamics simulation of a wide-slot jet impingement heating process is performed. The present configuration consists of a turbulent incompressible air jet impinging orthogonally on an isothermal cold plate at a Reynolds number of around 11,000. The two-dimensional mean turbulent flow field is numerically predicted by solving Reynolds-averaged Navier–Stokes (RANS) equations, where the two-equation eddy viscosity k-ω model is utilized for turbulence closure. As the commonly used shear stress transport variant overpredicts heat transfer at the plate due to excessive turbulent diffusion, the recently developed generalized k-ω (GEKO) model is considered for the present analysis, where the primary model coefficients are suitably tuned. Through a comparative analysis of the various solutions against one another, in addition to reference experimental and numerical data, the effectiveness of the generalized procedure in predicting both the jet flow characteristics and the heat transfer at the plate is thoroughly evaluated, while determining the optimal set of model parameters. By improving accuracy within the RANS framework, the importance of model adaptability and parameter tuning for this specific fluid engineering application is demonstrated. This study offers valuable insights for improving predictive capability in turbulent jet simulations with broad engineering implications, particularly for industrial heating or cooling systems relying on wide-slot jet impingement. Full article
(This article belongs to the Special Issue Computational Fluids Dynamics in Energy Conversion and Heat Transfer)
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31 pages, 5988 KiB  
Article
Influence of the Upstream Channel of a Ship Lift on the Hydrodynamic Performance of a Fleet Entry Chamber and Design of Traction Scheme
by Haichao Chang, Qiang Zheng, Zuyuan Liu, Yu Yao, Xide Cheng, Baiwei Feng and Chengsheng Zhan
J. Mar. Sci. Eng. 2025, 13(7), 1375; https://doi.org/10.3390/jmse13071375 - 18 Jul 2025
Viewed by 319
Abstract
This study investigates the hydrodynamic performance of ships entering a ship lift compartment that is under the influence of upstream channel geometry and proposes a mechanical traction scheme to enhance operational safety and efficiency. Utilizing a Reynolds-averaged Navier–Stokes (RANS)-based computational fluid dynamics (CFD) [...] Read more.
This study investigates the hydrodynamic performance of ships entering a ship lift compartment that is under the influence of upstream channel geometry and proposes a mechanical traction scheme to enhance operational safety and efficiency. Utilizing a Reynolds-averaged Navier–Stokes (RANS)-based computational fluid dynamics (CFD) approach with overlapping grid technology, numerical simulations were conducted for both single and grouped ships navigating through varying water depths, speeds, and shore distances. The results revealed significant transverse force oscillations near the floating navigation wall due to unilateral shore effects, posing risks of deviation. The cargo ship experienced drastic resistance fluctuations in shallow-to-very-shallow-water transitions, while tugboats were notably affected by hydrodynamic interactions during group entry. A mechanical traction system with a four-link robotic arm was designed and analyzed kinematically and statically, demonstrating structural feasibility under converted real-ship traction forces (55.1 kN). The key findings emphasize the need for collision avoidance measures in wall sections and validate the proposed traction scheme for safe and efficient ship entry/exit. This research provides critical insights for optimizing ship lift operations in restricted waters. Full article
(This article belongs to the Section Ocean Engineering)
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21 pages, 5135 KiB  
Article
Assessing the Heat Transfer Modeling Capabilities of CFD Software for Involute-Shaped Plate Research Reactors
by Cezary Bojanowski, Ronja Schönecker, Katarzyna Borowiec, Kaltrina Shehu, Julius Mercz, Frederic Thomas, Yoann Calzavara, Aurelien Bergeron, Prashant Jain, Christian Reiter and Jeremy Licht
Energies 2025, 18(14), 3692; https://doi.org/10.3390/en18143692 - 12 Jul 2025
Viewed by 348
Abstract
The ongoing efforts to convert High-Performance Research Reactors (HPRRs) using Highly Enriched Uranium (HEU) to Low-Enriched Uranium (LEU) fuel require reliable thermal–hydraulic assessments of modified core designs. The involute-shaped fuel plates used in several major HPRRs present unique modeling challenges due to their [...] Read more.
The ongoing efforts to convert High-Performance Research Reactors (HPRRs) using Highly Enriched Uranium (HEU) to Low-Enriched Uranium (LEU) fuel require reliable thermal–hydraulic assessments of modified core designs. The involute-shaped fuel plates used in several major HPRRs present unique modeling challenges due to their compact core geometries and high heat flux conditions. This study evaluates the capability of three commercial CFD tools, STAR-CCM+, COMSOL, and ANSYS CFX, to predict cladding-to-coolant heat transfer using Reynolds-Averaged Navier–Stokes (RANS) methods within the thermal–hydraulic regimes of involute-shaped plate reactors. Broad sensitivity analysis was conducted across a range of reactor-relevant parameters using two turbulence models (kϵ and kω SST) and different near-wall treatment strategies. The results were benchmarked against the Sieder–Tate correlation and experimental data from historic studies. The codes produced consistent results, showing good agreement with the empirical correlation of Sieder–Tate and the experimental measurements. The findings support the use of these commercial CFD codes as effective tools for assessing the thermal–hydraulic performance of involute-shaped plate HPRRs and guide future LEU core development. Full article
(This article belongs to the Section B4: Nuclear Energy)
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22 pages, 8767 KiB  
Article
Towards Efficiency and Endurance: Energy–Aerodynamic Co-Optimization for Solar-Powered Micro Air Vehicles
by Weicheng Di, Xin Dong, Zixing Wei, Haoji Liu, Zhan Tu, Daochun Li and Jinwu Xiang
Drones 2025, 9(7), 493; https://doi.org/10.3390/drones9070493 - 11 Jul 2025
Viewed by 348
Abstract
Despite decades of development, micro air vehicles (MAVs) still face challenges related to endurance. While solar power has been successfully implemented in larger aircraft as a clean and renewable source of energy, its adaptation to MAVs presents unique challenges due to payload constraints [...] Read more.
Despite decades of development, micro air vehicles (MAVs) still face challenges related to endurance. While solar power has been successfully implemented in larger aircraft as a clean and renewable source of energy, its adaptation to MAVs presents unique challenges due to payload constraints and complex surface geometries. To address this, this work proposes an automated algorithm for optimal solar panel arrangement on complex upper surfaces of the MAV. In addition to that, the aerodynamic performance is evaluated through computational fluid dynamics (CFD) simulations based on the Reynolds-Averaged Navier–Stokes (RANS) method. A multi-objective optimization approach simultaneously considers photovoltaic energy generation and aerodynamic efficiency. Wind tunnel validation and stability analysis of flight dynamics confirm the advantages of our optimized design. To our knowledge, this represents the first systematic framework for the energy–aerodynamic co-optimization of solar-powered MAVs (SMAVs). Flight tests of a 500mm-span tailless prototype demonstrate the practical feasibility of our approach with maximum solar cell deployment. Full article
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19 pages, 2560 KiB  
Article
Aerodynamic Instability Mechanisms of Iced Eight-Bundled Conductors: Frequency-Domain Analysis and Stability Assessment via Wind Tunnel–CFD Synergy
by Bolin Zhong, Minghao Qiao, Mengqi Cai and Maoming Hu
Sensors 2025, 25(13), 4120; https://doi.org/10.3390/s25134120 - 1 Jul 2025
Viewed by 337
Abstract
Icing on transmission lines in cold regions can cause asymmetry in the conductor cross-section. This asymmetry can lead to low-frequency, large-amplitude oscillations, posing a serious threat to the stability and safety of power transmission systems. In this study, the aerodynamic characteristics of crescent-shaped [...] Read more.
Icing on transmission lines in cold regions can cause asymmetry in the conductor cross-section. This asymmetry can lead to low-frequency, large-amplitude oscillations, posing a serious threat to the stability and safety of power transmission systems. In this study, the aerodynamic characteristics of crescent-shaped and sector-shaped iced eight-bundled conductors were systematically investigated over an angle of attack range from 0° to 180°. A combined approach involving wind tunnel tests and high-precision computational fluid dynamics (CFD) simulations was adopted. In the wind tunnel tests, static aerodynamic coefficients and dynamic time series data were obtained using a high-precision aerodynamic balance and a turbulence grid. In the CFD simulations, transient flow structures and vortex shedding mechanisms were analyzed based on the Reynolds-averaged Navier–Stokes (RANS) equations with the SST k-ω turbulence model. A comprehensive comparison between the two ice accretion geometries was conducted. The results revealed distinct aerodynamic instability mechanisms and frequency-domain characteristics. The analysis was supported by Fourier’s fourth-order harmonic decomposition and energy spectrum analysis. It was found that crescent-shaped ice, due to its streamlined leading edge, induced a dominant single vortex shedding. In this case, the first-order harmonic accounted for 67.7% of the total energy. In contrast, the prismatic shape of sector-shaped ice caused migration of the separation point and introduced broadband energy input. Stability thresholds were determined using the Den Hartog criterion. Sector-shaped iced conductors exhibited significant negative aerodynamic damping under ten distinct operating conditions. Compared to the crescent-shaped case, the instability risk range increased by 60%. The strong agreement between simulation and experimental results validated the reliability of the numerical approach. This study establishes a multiscale analytical framework for understanding galloping mechanisms of iced conductors. It also identifies early warning indicators in the frequency domain and provides essential guidance for the design of more effective anti-galloping control strategies in resilient power transmission systems. Full article
(This article belongs to the Section Electronic Sensors)
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25 pages, 2703 KiB  
Article
Strategy Analysis of Seamlessly Resolving Turbulent Flow Simulations
by Stefan Heinz
Aerospace 2025, 12(7), 597; https://doi.org/10.3390/aerospace12070597 - 30 Jun 2025
Viewed by 233
Abstract
Modeling of wall-bounded turbulent flows, in particular the hybridization of the Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) methods, has faced serious questions for decades. Specifically, there is continuous research of how usually applied methods such as detached eddy simulation (DES) and [...] Read more.
Modeling of wall-bounded turbulent flows, in particular the hybridization of the Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) methods, has faced serious questions for decades. Specifically, there is continuous research of how usually applied methods such as detached eddy simulation (DES) and wall-modeled LES (WMLES) can be made more successful in regard to complex, high-Reynolds-number (Re) flow simulations. The simple question is how it is possible to enable reliable and cost-efficient predictions of high-Re wall-bounded turbulent flows in particular under conditions where data for validation are unavailable. This paper presents a strict analysis of strategies for the design of seamlessly resolving turbulent flow simulations for a wide class of turbulence models. The essential conclusions obtained are the following ones: First, by construction, usually applied methods like DES are incapable of systematically spanning the range from modeled to resolved flow simulations, which implies significant disadvantages. Second, a strict solution for this problem is given by novel continuous eddy simulation (CES) methods, which perform very well. Third, the design of a computational simplification of CES that still outperforms DES appears to be very promising. Full article
(This article belongs to the Section Aeronautics)
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14 pages, 3860 KiB  
Article
Large Eddy Simulations on the Diffusion Features of the Cold-Vented Natural Gas Containing Sulfur
by Xu Sun, Meijiao Song, Sen Dong, Dongying Wang, Yibao Guo, Jinpei Wang and Jingjing Yu
Processes 2025, 13(6), 1940; https://doi.org/10.3390/pr13061940 - 19 Jun 2025
Viewed by 335
Abstract
For cold venting processes frequently employed in oil and gas fields, precisely predicting the instantaneous diffusion process of the vented explosive and/or toxic gases is of great importance, which cannot be captured by the Reynolds-averaged Navier–Stokes (RANS) method. In this paper, the large [...] Read more.
For cold venting processes frequently employed in oil and gas fields, precisely predicting the instantaneous diffusion process of the vented explosive and/or toxic gases is of great importance, which cannot be captured by the Reynolds-averaged Navier–Stokes (RANS) method. In this paper, the large eddy simulation (LES) method is introduced for gas diffusion in an open space, and the diffusion characteristics of the sulfur-containing natural gas in the cold venting process is analyzed numerically. Firstly, a LES solution procedure of compressible gas diffusion is proposed based on the ANSYS Fluent 2022, and the numerical solution is verified using benchmark experiments. Subsequently, a computational model of the sulfur-containing natural gas diffusion process under the influence of a wind field is established, and the effects of wind speed, sulfur content, the venting rate and a downstream obstacle on the natural gas diffusion process are analyzed in detail. The results show that the proposed LES with the DSM sub-grid model is able to capture the transient diffusion process of heavy and light gases released in turbulent wind flow; the ratio between the venting rate and wind speed has a decisive influence on the gas diffusion process: a large venting rate increases the vertical diffusion distance and makes the gas cloud fluctuate more, while a large wind speed decreases the vertical width and stabilizes the gas cloud; for an obstacle located closely downstream, the venting pipe makes the vented gas gather on the windward side and move toward the ground, increasing the risk of ignition and poisoning near the ground. The LES solution procedure provides a more powerful tool for simulating the cold venting process of natural gas, and the results obtained could provide a theoretical basis for the safety evaluation and process optimization of sulfur-containing natural gas venting. Full article
(This article belongs to the Section Energy Systems)
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22 pages, 5581 KiB  
Article
Film Cooling Performance and Superposition Method of an Actual Turbine Vane at High Freestream Turbulence
by Peng Chu, Yongfeng Sui, Bin Dai, Jibing Lan, Wenyang Shao, Binbin Xue, Xiliang Xu and Zhenping Feng
Aerospace 2025, 12(6), 533; https://doi.org/10.3390/aerospace12060533 - 12 Jun 2025
Viewed by 422
Abstract
This study aims to enhance the understanding of film cooling performance in an actual turbine vane by investigating influencing factors and developing more precise numerical prediction methods. Pressure sensitive paint (PSP) testing and Reynolds-Averaged Navier–Stokes (RANS) simulations were conducted. The findings indicate that [...] Read more.
This study aims to enhance the understanding of film cooling performance in an actual turbine vane by investigating influencing factors and developing more precise numerical prediction methods. Pressure sensitive paint (PSP) testing and Reynolds-Averaged Navier–Stokes (RANS) simulations were conducted. The findings indicate that the current design blowing ratio of S1 holes (0.89) is too high, resulting in poor film cooling effectiveness. However, the blowing ratios of P3 (0.78) and P4 (0.69) holes are relatively low, suggesting that increasing the coolant flow could improve the film cooling effectiveness. It is not recommended to design an excessively low blowing ratio on the suction surface, as this can lead to poor wall adherence downstream of the film holes. A slight increase in turbulence intensity enhances the film covering effect, particularly on the suction surface. Additionally, a novel superposition method for multirow fan-shaped film cooling holes on an actual turbine vane is proposed, exhibiting better agreement with experimental data. Compared with experimental results, the numerical predictions tend to underestimate the film cooling effectiveness with the examined k-ε-based viscosity turbulence models and Reynolds stress turbulence models, while the SST demonstrates relatively higher accuracy owing to its hybrid k-ω/k-ε formulation that better resolves near-wall physics and separation flows characteristic of turbine cooling configurations. This study contributes to the advancement of turbine vane thermal analysis and design in engineering applications. Full article
(This article belongs to the Section Aeronautics)
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17 pages, 3263 KiB  
Article
Computational Fluid Dynamics Analysis into the Comparison of Resistance Characteristics Between DARPA Suboff and Modified U209 Types of Submarines
by Ahmad Nasirudin, Sutiyo, Ardi Nugroho Yulianto, Eko Julianto, I Ketut Aria Pria Utama and Martin Renilson
Sci 2025, 7(2), 82; https://doi.org/10.3390/sci7020082 - 6 Jun 2025
Viewed by 562
Abstract
Submarines are required to have good performance, which is influenced by their type of hull, hull conditions, and operational conditions. This study compares the resistance between a Modified-U209 (U209) submarine and the DARPA Suboff. The former is an older hull geometry with both [...] Read more.
Submarines are required to have good performance, which is influenced by their type of hull, hull conditions, and operational conditions. This study compares the resistance between a Modified-U209 (U209) submarine and the DARPA Suboff. The former is an older hull geometry with both surface and submerged operation considered, whereas the latter represents a modern nuclear-powered submarine designed for submerged operations only. The two geometries were scaled to give the same usable volume, and all results were non-dimensionalized using this to ensure consistency. A Computational Fluid Dynamics (CFD) method was utilized to predict resistance by employing the Reynolds-averaged Navier–Stokes (RANS) equations. The results show that the total resistance coefficient for the U209 bare hull is approximately 6% higher than the Suboff bare hull. When a casing was added to the U209 geometry the increase in total resistance coefficient was approximately 8%. The addition of the sail resulted in an increase in total resistance coefficient ranging from approximately 4% (Suboff sail added to U209) to approximately 14% (U209 sail added to U209). An existing empirical prediction technique was used to predict the resistance, with the total resistance coefficient predicted being consistently about 5% lower than the values obtained using CFD. Full article
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24 pages, 3126 KiB  
Article
Two-Phase Multi-Point Design Exploration of Submerged Nacelles for Marine Propulsive Pump Installation
by Filippo Avanzi, Andrea Magrini and Francesco De Vanna
J. Mar. Sci. Eng. 2025, 13(6), 1110; https://doi.org/10.3390/jmse13061110 - 2 Jun 2025
Viewed by 419
Abstract
Outboard Dynamic-inlet Waterjets (ODW) are axisymmetric units, powered by a self-contained pump, that, by processing a uniform undisturbed streamtube, can operate more efficiently than conventional marine propulsors. This feature also provides methodological convenience, enabling accurate numerical investigations of the system alone using 2D [...] Read more.
Outboard Dynamic-inlet Waterjets (ODW) are axisymmetric units, powered by a self-contained pump, that, by processing a uniform undisturbed streamtube, can operate more efficiently than conventional marine propulsors. This feature also provides methodological convenience, enabling accurate numerical investigations of the system alone using 2D axisymmetric models. Leveraging this property, the present study bridges the gap on the design principles required to tailor ODW geometries across multiple operating conditions. Reynolds-Averaged Navier Stokes (RANS) equations are solved, including turbulence and cavitation models, to draw the propulsor’s characteristic maps and identify two relevant operating points, set by the combination of a specified pump rotational regime with an advancing velocity. Simulations for these in- and off-design conditions are systematically performed over a database of 512 randomly sampled geometric variants. The corresponding results show that optimised shapes improving the inlet Pressure Recovery (PR) and nacelle drag at cruise conditions result in beneficial outcomes also at take-off operations, where lip cavitation may occur. Thus, analysing together the off-design PR and the cruise net force underscores their conflicting behaviour. In fact, while nacelles shortened by 12% can reduce overall drag and enhance nominal net thrust by 2%, designs featuring a 34% wider capture area improve off-design PR by over 1.5%, albeit at the cost of compromised propulsive efficiency under any operating range. Full article
(This article belongs to the Special Issue Novelties in Marine Propulsion)
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49 pages, 5500 KiB  
Review
Heat Transfer Enhancement in Heat Exchangers by Longitudinal Vortex Generators: A Review of Numerical and Experimental Approaches
by Yidie Luo, Gongli Li, Nick S. Bennett, Zhen Luo, Adnan Munir and Mohammad S. Islam
Energies 2025, 18(11), 2896; https://doi.org/10.3390/en18112896 - 31 May 2025
Viewed by 1345
Abstract
Heat exchangers are critical components in various industrial applications, requiring efficient thermal management to enhance thermal performance and energy efficiency. Longitudinal vortex generators (LVGs) have emerged as a potent mechanism to enhance heat transfer within these devices. A precise knowledge of the thermal [...] Read more.
Heat exchangers are critical components in various industrial applications, requiring efficient thermal management to enhance thermal performance and energy efficiency. Longitudinal vortex generators (LVGs) have emerged as a potent mechanism to enhance heat transfer within these devices. A precise knowledge of the thermal performance enhancement of HE through LVGs is missing in the literature. Therefore, this study aims to provide a critical review of both numerical simulations and experimental studies focusing on the enhancement of heat transfer through LVGs to further enhance the knowledge of the field. It begins with elucidating the fundamental principles behind LVGs and delineating their role in manipulating flow patterns to augment heat transfer. This is followed by an exploration of the various numerical methods employed in the field, including computational fluid dynamics techniques such as Reynolds-Averaged Navier–Stokes (RANS) models, Large Eddy Simulation (LES), and Direct Numerical Simulation (DNS). Various experimental methods are then summarised, including differential pressure measuring instruments, temperature measurements, velocity measurements, heat transfer coefficient measurements, and flow visualisation techniques. The effectiveness of these methods in capturing the complex fluid dynamics and thermal characteristics induced by LVGs is critically assessed. The review covers a wide range of LVG configurations, including their geometry, placements, and orientations, and their effects on the thermal performance of heat exchangers. Different from previous reviews that mainly focus on classical configurations and historical studies, this review also emphasizes recent developments in computational fluid dynamics and progress in interdisciplinary fields such as innovative materials, additive manufacturing, surface finishing, and machine learning. By bridging the gap between fluid dynamics, thermal enhancement, and emerging manufacturing technologies, this paper provides a forward-looking, comprehensive analysis that is valuable for both academic and industrial innovations. Full article
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