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

Article Types

Countries / Regions

Search Results (168)

Search Parameters:
Keywords = RNG and k-ε models

Order results
Result details
Results per page
Select all
Export citation of selected articles as:
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 115
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)
Show Figures

Figure 1

28 pages, 31155 KiB  
Article
Numerical Simulation of Treatment Capacity and Operating Limits of Alkali/Surfactant/Polymer (ASP) Flooding Produced Water Treatment Process in Oilfields
by Jiawei Zhu, Mingxin Wang, Keyu Jing, Jiajun Hong, Fanxi Bu and Zhihua Wang
Energies 2025, 18(13), 3420; https://doi.org/10.3390/en18133420 - 29 Jun 2025
Viewed by 330
Abstract
As an enhanced oil recovery (EOR) technique, alkali/surfactant/polymer (ASP) flooding effectively mitigates production decline in mature oilfields through chemical flooding mechanisms. The breakthrough of ASP chemical agents poses challenges to the green and efficient separation of oilfield produced water. In this paper, sedimentation [...] Read more.
As an enhanced oil recovery (EOR) technique, alkali/surfactant/polymer (ASP) flooding effectively mitigates production decline in mature oilfields through chemical flooding mechanisms. The breakthrough of ASP chemical agents poses challenges to the green and efficient separation of oilfield produced water. In this paper, sedimentation separation of produced water was simulated using the Eulerian method and the RNG k–ε model. In addition, the filtration process was simulated using a discrete phase model (DPM) and a porous media model. The distribution characteristics of oil/suspended solids obtained through simulation, along with the water quality parameters at each treatment node, were systematically extracted, and the influence of operating conditions on treatment capacity was analyzed. Simulations reveal that elevated treatment loads and produced water polymer concentrations synergistically impair ASP flooding produced water treatment efficiency. Fluctuations of operating conditions generate oil/suspended solids content in output water ranges spanning 13–78 mg/L and 19–92 mg/L, respectively. The interpolation method is adopted to determine the critical water quality parameters of each treatment node, ensuring that the treated produced water meets the treatment standards. The operating limits of the ASP flooding produced water treatment process are established. Full article
(This article belongs to the Special Issue Advances in Wastewater Treatment, 2nd Edition)
Show Figures

Figure 1

19 pages, 2838 KiB  
Article
Comparative Analysis of Combustion Characteristics and Emission Formation in Marine Diesel Engines Using Biofuels: Chemical Mechanism Analysis and Computational Fluid Dynamics Simulation
by Kwang-Sik Jo, Kyeong-Ju Kong and Seung-Hun Han
J. Mar. Sci. Eng. 2025, 13(6), 1098; https://doi.org/10.3390/jmse13061098 - 30 May 2025
Viewed by 428
Abstract
This study presents a comprehensive analysis of combustion mechanisms and emission formation in marine diesel engines using biodiesel blends through experimental validation and computational fluid dynamics simulation using Matlab 2024a. Two marine engines were tested—YANMAR 6HAL2-DTN (200 kW, 1200 rpm) and Niigatta Engineering [...] Read more.
This study presents a comprehensive analysis of combustion mechanisms and emission formation in marine diesel engines using biodiesel blends through experimental validation and computational fluid dynamics simulation using Matlab 2024a. Two marine engines were tested—YANMAR 6HAL2-DTN (200 kW, 1200 rpm) and Niigatta Engineering 6L34HX (2471 kW, 600 rpm)—with biodiesel ratios B0, B20, B50, and B100 at loads from 10% to 100%. The methodology combines detailed experimental measurements of exhaust emissions, fuel consumption, and engine performance with three-dimensional CFD simulations employing k-ε RNG turbulence model, Kelvin–Helmholtz–Rayleigh–Taylor droplet breakup model, and extended Zeldovich mechanism for NOx formation modeling. Key findings demonstrate that biodiesel’s oxygen content (10–12% by mass) increases maximum combustion temperature by 25 °C at 50% load, resulting in NOx emissions increase of 5–13% across all loads. Conversely, CO emissions decrease by 7–10% due to enhanced oxidation reactions. CFD analysis reveals that B100 exhibits 12% greater spray penetration depth, 20% larger Sauter Mean Diameter, and 20–25% slower evaporation rate compared to B0. The thermal Zeldovich mechanism dominates NOx formation (>90%), with prompt-NO and fuel-NO contributions increasing from 6.5% and 0.3% for B0 to 7.2% and 1.3% for B100, respectively, at 25% load. Optimal injection timing varies with biodiesel ratio: 13–15° BTDC for B0 reducing to 10–12° BTDC for B100. These quantitative insights enable evidence-based optimization of marine diesel engines for improved environmental performance while maintaining operational efficiency. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

12 pages, 940 KiB  
Article
The Effect of Turbulent Intensity on Friction Coefficient in Boundary-Layer Transitional Flat Plate Flow
by Muhsine Saru, Hıfzı Arda Erşan and Erhan Pulat
Appl. Sci. 2025, 15(11), 5852; https://doi.org/10.3390/app15115852 - 23 May 2025
Viewed by 368
Abstract
In this study, the effect of inlet-turbulence intensity on the friction coefficient for the transitional boundary layer has been investigated computationally. For this purpose, two equation turbulence models of Std. k-ε, RNG k-ε, Std. k-ω, and SST k-ω have been compared with the [...] Read more.
In this study, the effect of inlet-turbulence intensity on the friction coefficient for the transitional boundary layer has been investigated computationally. For this purpose, two equation turbulence models of Std. k-ε, RNG k-ε, Std. k-ω, and SST k-ω have been compared with the Gamma–Theta (GT) transitional model, and it has been found that the Gamma–Theta model is the most consistent model with the experimental values of the ERCOFTAC T3A test case. Then, the effect of inlet-turbulence intensity on the friction coefficient has been computed by using this Gamma–Theta model. The transition from laminar to turbulence is shortened with increasing turbulence intensity by changing it from 1% to 10%. The most suitable inlet-turbulence intensity value with the experimental results of the ERCOFTAC T3A test case is found as Tu = 3.3%. Full article
(This article belongs to the Section Fluid Science and Technology)
Show Figures

Figure 1

13 pages, 4251 KiB  
Article
Numerical Simulation Study on Hydraulic Performance of Diaphragm Valve
by Fengwei Yu, Yuncheng Xu and Haijun Yan
Water 2025, 17(10), 1450; https://doi.org/10.3390/w17101450 - 11 May 2025
Viewed by 557
Abstract
Diaphragm valves play a crucial role in controlling fluid flow in piping systems, and their hydraulic performance directly impacts system efficiency. This study employs numerical simulations using OpenFOAM v8 to investigate the hydraulic characteristics of a diaphragm valve, focusing on the effects of [...] Read more.
Diaphragm valves play a crucial role in controlling fluid flow in piping systems, and their hydraulic performance directly impacts system efficiency. This study employs numerical simulations using OpenFOAM v8 to investigate the hydraulic characteristics of a diaphragm valve, focusing on the effects of inlet boundary conditions and turbulence models on head loss. At the maximum valve opening, two inlet conditions of OpenFOAM, flowRateInletVelocity and timeVaryingMappedFixedValue, were compared. Results show that the flowRateInletVelocity inlet condition yields simulation results in excellent agreement with experimental data, validating its reliability. Five turbulence models (Standard k-ε, Realizable k-ε, RNG k-ε, SST k-ω, and Spalart-Allmaras) were evaluated, revealing that the SST k-ω model offers the highest computational accuracy in capturing flow field details and head loss, while the Spalart-Allmaras model demonstrates significant discrepancies. Further analysis under varying valve openings and flow rates identifies an exponential relationship between head loss and value opening, with the most pronounced changes occurring below 50% opening. These findings provide a theoretical basis for optimizing diaphragm valve designs and enhancing the accuracy of CFD simulations in hydraulic engineering applications. Full article
Show Figures

Figure 1

20 pages, 9009 KiB  
Article
Calibration of RNG k-ε Model Constants Based on Experimental Data Assimilation: A Study on the Flow Characteristics of Air-Lifted Plunger Interstitial Flow
by Jinglong Zhang, Yucheng Song, Yan Xu, Yanli Yang and Jiahuan Wang
Appl. Sci. 2025, 15(8), 4515; https://doi.org/10.3390/app15084515 - 19 Apr 2025
Viewed by 297
Abstract
This study optimized the constants of the RNG k-ε model using the Ensemble Kalman Filter (ENKF) data assimilation method to improve the accuracy of air-lift plunger gap flow predictions. For high Reynolds number turbulent flow, we conducted numerical simulations integrating experimental data with [...] Read more.
This study optimized the constants of the RNG k-ε model using the Ensemble Kalman Filter (ENKF) data assimilation method to improve the accuracy of air-lift plunger gap flow predictions. For high Reynolds number turbulent flow, we conducted numerical simulations integrating experimental data with a library of predicted data generated via optimal Latin hypercube sampling. ENKF was employed to assimilate these data and adjust the model constants, significantly reducing prediction errors and enhancing the accuracy of plunger models. Specifically, mean square errors for rectangular and circular plungers decreased from 60.67 and 61.48 to 7.12 and 7.20, respectively. The study also revealed significant changes in vortex dynamics and flow distribution following data assimilation, providing insights for optimizing plunger design and improving system energy efficiency. These findings underscore the potential of data assimilation in advancing oil and gas production. Full article
Show Figures

Figure 1

18 pages, 7690 KiB  
Article
Experimental Study on the Hydraulic Characteristics and Shape Optimization of Ship Lock Water Conveyance Systems
by Yu Duan, Dianguang Ma, Weidong Gan, Chao Ji and Junwei Zhou
J. Mar. Sci. Eng. 2025, 13(4), 784; https://doi.org/10.3390/jmse13040784 - 15 Apr 2025
Viewed by 420
Abstract
To enhance the passing capacity of the Bailongtan Ship Lock on the Hongshui River, this study focused on the design scheme of its water conveyance system reconstruction and expansion project. A three-dimensional mathematical model meeting the experimental accuracy requirements was established based on [...] Read more.
To enhance the passing capacity of the Bailongtan Ship Lock on the Hongshui River, this study focused on the design scheme of its water conveyance system reconstruction and expansion project. A three-dimensional mathematical model meeting the experimental accuracy requirements was established based on the RNG k-ε turbulence model and the Volume of Fluid (VOF) free-surface tracking method. A 1:30 scale ship lock water conveyance system physical model was built and used the independently developed system for hydraulic test monitoring, acquisition, and control. Experimental research on the hydraulic characteristics and shape optimization of the water conveyance system was carried out. The experimental results show that, under the condition of a maximum head difference of 16.0 m between the upstream and downstream of the ship lock, in the design scheme, the flow in the corridor after the filling valve fails to diffuse adequately, forming a high-velocity zone and a significant pressure difference between the inner and outer sides, which poses an operational risk. By optimizing the shape of the corridor after the valve (deepening the bottom end by 2.0 m and adjusting the turning angle from 75° to 70°), the range of the high-velocity zone can be shortened from 3.0 m to 1.5 m. The pressure difference between the inner and outer sides of the corridor at the horizontal turning section is reduced by 19.2% from 5.35 m to 4.32 m of the pressure head at the moment of maximum flow rate, and the velocity in the horizontal section is less than 15 m/s. Physical model tests confirmed these improvements, with mooring forces within safety limits (longitudinal ≤ 32 kN, transverse ≤ 16 kN). The research findings indicate that integrating numerical simulation with physical model testing can effectively mitigate risks in the original design of the ship lock water conveyance system. This approach notably enhances the reliability and safety of the design scheme, as demonstrated by the significant reduction in high-velocity zones and pressure differentials. Moreover, it offers a robust scientific basis and practical technical reference for in-depth hydraulic research and targeted optimization of ship lock water conveyance systems. Full article
(This article belongs to the Section Ocean Engineering)
Show Figures

Figure 1

24 pages, 41116 KiB  
Article
Study on the Improvement of Coastal Pumping Station Inlet Flow Regime and Evaluation of Transverse Flow Velocity Elimination
by Fusheng Lv, Pingping Li, Bo Zhu, Xilong Guo, Lei Wang and Lei Xu
J. Mar. Sci. Eng. 2025, 13(4), 673; https://doi.org/10.3390/jmse13040673 - 27 Mar 2025
Viewed by 385
Abstract
Pump station engineering is extensively utilized in water supply and drainage, as well as agricultural irrigation. Due to its geographical advantages and significant comprehensive benefits, the construction of pumping stations in coastal areas has gained substantial attention in recent years. Adverse flow conditions [...] Read more.
Pump station engineering is extensively utilized in water supply and drainage, as well as agricultural irrigation. Due to its geographical advantages and significant comprehensive benefits, the construction of pumping stations in coastal areas has gained substantial attention in recent years. Adverse flow conditions caused by various factors negatively affect the inlet flow regime of pumps, becoming a key factor that restricts the operating life and further development of pump station systems. Optimizing the flow regime in the forebay is crucial for enhancing overall engineering quality, minimizing pump performance degradation, and reducing the risks of cavitation and vibration. This study investigates the flow characteristics of the forebay by combining the Navier–Stokes equations and the kε RNG turbulence model. The analysis focuses on the internal flow field, transverse flow before the inlet channel, and the uniformity of flow velocity distribution after the inlet channel. Numerical simulations are validated through physical model tests. We examine the flow characteristics in the forebay, analyze the causes of internal flow disorder, and propose a reasonable and practical rectification scheme for the forebay. Additionally, we elucidate the mechanism of flow state optimization through partition walls. The findings indicate that with the optimal partition wall length, the average elimination rate of transverse flow velocity before the pump station inlet channel reached 48.3%, and the uniformity of flow velocity distribution after the inlet increased by 3.24%. These research findings contribute to mitigating cavitation and vibration in water pump units, providing theoretical support for the safe operation of coastal pumping stations. Full article
(This article belongs to the Section Coastal Engineering)
Show Figures

Figure 1

19 pages, 7046 KiB  
Article
Study on the Influence of Split Blades on the Force Characteristics and Fluid–Structure Coupling Characteristics of Pumps as Turbines
by Fengxia Shi, Xuexue Zong, Guangbiao Zhao, Denghui Zhang, Pengcheng Wang and Haonan Zhan
Energies 2025, 18(7), 1642; https://doi.org/10.3390/en18071642 - 25 Mar 2025
Cited by 1 | Viewed by 347
Abstract
In order to study the influence of split blades on the turbine force characteristics and fluid–structure coupling characteristics of pumps, this paper selected the IS 80-50-315 centrifugal pump, used as a reverse-acting hydraulic turbine, as the research object, optimized the original pump-acting turbine [...] Read more.
In order to study the influence of split blades on the turbine force characteristics and fluid–structure coupling characteristics of pumps, this paper selected the IS 80-50-315 centrifugal pump, used as a reverse-acting hydraulic turbine, as the research object, optimized the original pump-acting turbine impeller, and adopted different combinations of long and short blades. Based on the SIMPLE algorithm and RNG k–ε turbulence model, a complete three-dimensional unsteady numerical simulation was conducted on the internal flow field of the pump-turbine. The results show that the split blades reduce the radial and axial forces. The deformation patterns of rotor components in the two pump types used as turbine models were similar, with deformation gradually decreasing from the inlet to the outlet of the impeller. The equivalent stress distribution law of the rotor components of the two pump turbine models has also been found to be similar, with the maximum stress occurring at the connection between the blades and the front and rear cover plates and the minimum stress occurring at the outlet area of the impeller and the maximum shaft diameter of the pump shaft. The maximum deformation and stress of the rotor components in the split blade impeller model were smaller than those in the original impeller model. Full article
(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
Show Figures

Figure 1

14 pages, 263 KiB  
Article
Renormalization Group Approach as a Symmetry Transformation for an Analysis of Non-Newtonian Elastic Turbulence
by Andriy A. Avramenko, Igor V. Shevchuk, Nataliia P. Dmitrenko and Alina V. Konyk
Fluids 2025, 10(4), 79; https://doi.org/10.3390/fluids10040079 - 24 Mar 2025
Viewed by 312
Abstract
Symmetry transformation methods are widely used in fluid flow problems. One such method is renormalization group analysis. Renormalization group methods are used to develop a macroscopic turbulence model for non-Newtonian fluids (Oldroyd-B type). This model accounts for the large-distance and large-time behavior of [...] Read more.
Symmetry transformation methods are widely used in fluid flow problems. One such method is renormalization group analysis. Renormalization group methods are used to develop a macroscopic turbulence model for non-Newtonian fluids (Oldroyd-B type). This model accounts for the large-distance and large-time behavior of velocity correlations generated by the momentum equation for a randomly stirred, incompressible flow and does not account for empirical constants. The aim of this mathematical study was to develop a k-ε RNG turbulence model for non-Newtonian fluids (Oldroyd-B type). For the first time, using the renormalization procedure, the transport equations for the large-scale modes and expressions for effective transport coefficients are obtained. Expressions for the renormalized turbulent viscosity are also derived. This model explains the phenomenon of the abrupt growth of the irregularity of velocity at low values of the Reynolds number. Full article
(This article belongs to the Special Issue Advances in Computational Mechanics of Non-Newtonian Fluids)
27 pages, 9632 KiB  
Article
Investigating Sedimentation Patterns and Fluid Movement in Drip Irrigation Emitters in the Yellow River Basin
by Mengyang Wang, Mengyun Xue, Hao Sun, Hui Li, Rui Li and Qibiao Han
Water 2025, 17(7), 910; https://doi.org/10.3390/w17070910 - 21 Mar 2025
Cited by 1 | Viewed by 512
Abstract
Developing efficient water-saving irrigation technologies that utilize high sand-laden water is an important approach to alleviating agricultural water scarcity in the Yellow River Basin. This study aims to investigate sedimentation patterns and fluid movement characteristics in drip irrigation emitters under such challenging water [...] Read more.
Developing efficient water-saving irrigation technologies that utilize high sand-laden water is an important approach to alleviating agricultural water scarcity in the Yellow River Basin. This study aims to investigate sedimentation patterns and fluid movement characteristics in drip irrigation emitters under such challenging water conditions. The dynamic changes in Dra and Cu were determined through short-period intermittent clogging tests to evaluate the anti-clogging performance of four different emitter types. The distribution and particle size composition of the deposited sediments inside the emitters were analyzed using a high-resolution electron microscope and a laser particle size analyzer. Additionally, the RNG k-ε turbulence model was used to simulate the fluid movement inside the emitters. The results showed that the B drip irrigation belt had better sediment tolerance and operational stability. The anti-clogging capacity of drip irrigation can be improved by optimizing the combination of emitter channel structure and sediment content. The fluid in the channel was divided into mainstream zone and vortex zone. Sediment particles increased in the backing-water zone and vortex center, where particles of 0.05–0.1 mm were more prone to settling due to reduced transport capacity. Energy dissipation primarily took place at the curvature of the emitter channel, and within each channel unit, gradually decreasing along the vortex flow direction, with the lowest dissipation aligning with sediment deposition zones. These findings provide a theoretical basis for mitigating clogging in high sand-laden water drip irrigation systems, offering valuable insights for improving the effective utilization of water resources in the Yellow River Basin. Full article
(This article belongs to the Special Issue Advances in Agricultural Irrigation Management and Technology)
Show Figures

Figure 1

21 pages, 5048 KiB  
Article
Numerical Methodology for Enhancing Heat Transfer in a Channel with Arc-Vane Baffles
by Piphatpong Thapmanee, Arnut Phila, Khwanchit Wongcharee, Naoki Maruyama, Masafumi Hirota, Varesa Chuwattanakul and Smith Eiamsa-ard
Computation 2025, 13(3), 71; https://doi.org/10.3390/computation13030071 - 12 Mar 2025
Viewed by 686
Abstract
This study numerically investigates flow and heat transfer in a channel with arc-vane baffles at various radius-to-channel high ratios (r/H = 0.125, 0.25, 0.375, and 0.5) for Reynolds numbers between 6000 and 24,000, focusing on solar air-heater applications. The calculations [...] Read more.
This study numerically investigates flow and heat transfer in a channel with arc-vane baffles at various radius-to-channel high ratios (r/H = 0.125, 0.25, 0.375, and 0.5) for Reynolds numbers between 6000 and 24,000, focusing on solar air-heater applications. The calculations utilize the finite volume method, and the SIMPLE algorithm is executed with the QUICK scheme. For the analysis of turbulent flow, the finite volume method with the Renormalization Group (RNG) k-ε turbulence model was used. The results show that arc-vane baffles create double vortices along the axial direction, promoting flow reattachment on the heated surface and enhancing heat transfer. Baffles with smaller r/H ratios strengthen flow reattachment, reduce dead zones, and improve fluid contact with the heat transfer surface. The baffles with the smallest r/H ratio achieve a Nusselt number ratio (Nu/Nus) of 4.91 at Re = 6000. As r/H increases, the friction factor (f) and friction factor ratio (f/fs) rise due to increased baffle curvature and surface area. The highest thermal performance factor (TPF) of 2.28 occurs at r/H = 0.125 and Re = 6000, reflecting an optimal balance of heat transfer and friction losses. Arc-vane baffles with a r/H ratio of 0.125 yield a TPF exceeding unity, indicating potential energy savings. These findings provide valuable insights for optimizing baffle designs to enhance thermal performance in practical applications. Full article
(This article belongs to the Section Computational Engineering)
Show Figures

Figure 1

25 pages, 5486 KiB  
Article
Study on the Dynamic Modeling of Two-Phase Flow and Lubrication Characteristics of Toothless Stirring Oil Pans
by Yiming Huang, Man Ge and Gaoan Zheng
Processes 2025, 13(3), 829; https://doi.org/10.3390/pr13030829 - 12 Mar 2025
Viewed by 606
Abstract
The toothless oil stirring disk is vital in modern transmission technology, particularly in fields like aviation, aerospace, and nuclear power, significantly impacting equipment performance. Oil-stirring lubrication is widely used in internal systems due to its simplicity and high reliability, but oil-stirring losses during [...] Read more.
The toothless oil stirring disk is vital in modern transmission technology, particularly in fields like aviation, aerospace, and nuclear power, significantly impacting equipment performance. Oil-stirring lubrication is widely used in internal systems due to its simplicity and high reliability, but oil-stirring losses during lubrication contribute to increased system temperatures, affecting lifespan and performance. Accurate simulation of the two-phase flow during the lubrication process of high-speed toothless oil stirring disks is crucial for extending the lubrication system service life. This paper proposes a dynamic modeling approach for the lubrication of high-speed toothless oil stirring disks, integrating the volume of fluid (VOF) model and the RNG k-ε turbulence model, alongside spring smoothing and dynamic mesh reconstruction techniques. The model explores fluid flow and oil distribution in high-speed, toothless oil stirring pans, investigating the effects of different stirring pan speeds and oil heights on lubrication performance. Results indicate that stirring pan speed and oil height are key to improving lubrication efficiency. At high speeds, centrifugal force and gravity cause the lubricating oil to detach from the stirring pan surface, continuing to splash due to inertia. At 3200 r/min and an oil level of 20 mm, a stable oil film forms in the gearbox. Higher stirring pan speeds generate greater turbulence, enhancing lubrication effectiveness. The findings offer theoretical insights for dynamic lubrication system modeling and support gearbox design and optimization in aerospace and similar fields. Full article
(This article belongs to the Section AI-Enabled Process Engineering)
Show Figures

Figure 1

14 pages, 4669 KiB  
Article
Numerical Investigation of the Two-Phase Flow Characteristics of an Axisymmetric Bypass Dual-Throat Nozzle
by Xuefeng Xia, Zhensheng Sun, Yu Hu, Hongfu Qiang, Yujie Zhu and Yin Zhang
Aerospace 2025, 12(3), 226; https://doi.org/10.3390/aerospace12030226 - 11 Mar 2025
Viewed by 698
Abstract
The bypass dual-throat nozzle is based on the dual-throat nozzle, which is a fluidic thrust vector nozzle suitable for integration into rocket motors in a symmetrical manner. As the effects of gas–solid two-phase flows are essential for solid rocket motors (SRMs), this study [...] Read more.
The bypass dual-throat nozzle is based on the dual-throat nozzle, which is a fluidic thrust vector nozzle suitable for integration into rocket motors in a symmetrical manner. As the effects of gas–solid two-phase flows are essential for solid rocket motors (SRMs), this study employs the RNG k–ε turbulence model and a particle trajectory model to numerically simulate the three-dimensional flow field inside a fixed-geometry axisymmetric bypass dual-throat nozzle to investigate its two-phase flow characteristics and thrust vectoring performance. Numerical results reveal that the smaller-diameter particles exhibit better flow-following characteristics and have a more significant impact on nozzle performance. As particle size increases, particle trajectories gradually rise within the cavity and converge toward the nozzle axis until a critical value is exceeded, after which the distribution tends to disperse. Particle deposition occurs at the bends of the bypass channel, the upstream converging section of the nozzle, and the converging section of the cavity, underscoring the need for a reinforced geometric design and thermal protection. In addition, the introduction of the particle phase into the flow reduces the thrust-vectoring angle of the nozzle and results in a loss of thrust coefficient. This research has the potential to guide the design of engines according to the incorporation of metal powder in propellants and combustion control. Full article
(This article belongs to the Special Issue Flow and Heat Transfer in Solid Rocket Motors)
Show Figures

Figure 1

21 pages, 12715 KiB  
Article
Effect of Twisted Tapes on Swirling Flow Dynamics in Gas–Solid Two-Phase Flows for Natural Gas Hydrate Transportation
by Yongchao Rao, Zijia Gong, Shuli Wang, Chenglong Zhang, Yunxiao Wang and Chuang Wen
Processes 2025, 13(3), 781; https://doi.org/10.3390/pr13030781 - 7 Mar 2025
Viewed by 889
Abstract
The discrete phase model (DPM) and the RNG k-ε turbulence model were employed to simulate the swirl flow behavior of hydrate transport in pipelines equipped with twisted tapes. The study analyzed the effects of various twisted tape parameters on the velocity [...] Read more.
The discrete phase model (DPM) and the RNG k-ε turbulence model were employed to simulate the swirl flow behavior of hydrate transport in pipelines equipped with twisted tapes. The study analyzed the effects of various twisted tape parameters on the velocity field, turbulent dissipation, turbulent kinetic energy, and pressure distribution of hydrate particles. The results indicate that increasing the placement angle of the twisted tape enhances the tangential velocity near the pipe axis while reducing the axial velocity. Similarly, higher twisted tape configurations result in a further decrease in axial velocity. An increase in the number of twisted tapes leads to reductions in both tangential and axial velocities, and maximum speed increased by 18.2%. Larger placement angles of twisted tapes also intensify turbulence dissipation, with a more pronounced decay in turbulence intensity observed from the pipe wall to the axis. At section 8D, the turbulent kinetic energy increases by 60% with the increase in the height of the twisted tapes. Furthermore, as the number of twisted tapes increases, the disparity in turbulence strength between regions near the twisted tape and the pipe axis diminishes. The inner pipe pressure distribution is 360°/n rotation symmetrical distribution, and the twist tape is more, and the high pressure area is greater on the pipe section. The minimum pressure area is gradually close from the lee plane of the diversion strip to the position of the pipe axis. At section 65D, the pressure drop increases gradually with the increase in the orientation angle, and it increases by 36.8%. Full article
Show Figures

Figure 1

Back to TopTop