The usefulness of the supersonic jet is inhabitable in the Aerospace industry. However, control of the supersonic jet is important for efficient mixing and noise attenuation. Particularly, asymmetric jets are better than axisymmetric jets in rapid mixing. Considering this, the experimental investigation has been carried out for the vortex generators or tab-controlled Mach 1.6 elliptic jet. To compare the impact of the locations of the vortex generators, they are deployed at the diametrically opposite locations of the nozzle outlet along the major or longest axis and the minor or shortest axis, respectively. The investigations have been carried out using the centerline pressure distributions employing the Pitot probe and the Schlieren flow visualizations. A maximum of 66.43% reduction in supersonic length has been observed from the centerline pressure distributions for the vortex generator placed along the shortest axis. In addition, the Schlieren flow visualizations confirm substantial distortions in the shock cell structures when the vortex generators are placed along the shortest axis which results in noise mitigation. The study concluded that the impact of the vortex generator, placed along the shortest axis, is superior in the manipulation of shock cell structure, efficient mixing, and thereby noise mitigation than those placed along the longest axis.
{"title":"Impact of Vortex Generators' Location on Supersonic Asymmetric Jet Control","authors":"T. Paramesh, T. Jana, M. Kaushik","doi":"10.47176/jafm.17.9.2543","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2543","url":null,"abstract":"The usefulness of the supersonic jet is inhabitable in the Aerospace industry. However, control of the supersonic jet is important for efficient mixing and noise attenuation. Particularly, asymmetric jets are better than axisymmetric jets in rapid mixing. Considering this, the experimental investigation has been carried out for the vortex generators or tab-controlled Mach 1.6 elliptic jet. To compare the impact of the locations of the vortex generators, they are deployed at the diametrically opposite locations of the nozzle outlet along the major or longest axis and the minor or shortest axis, respectively. The investigations have been carried out using the centerline pressure distributions employing the Pitot probe and the Schlieren flow visualizations. A maximum of 66.43% reduction in supersonic length has been observed from the centerline pressure distributions for the vortex generator placed along the shortest axis. In addition, the Schlieren flow visualizations confirm substantial distortions in the shock cell structures when the vortex generators are placed along the shortest axis which results in noise mitigation. The study concluded that the impact of the vortex generator, placed along the shortest axis, is superior in the manipulation of shock cell structure, efficient mixing, and thereby noise mitigation than those placed along the longest axis.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141683933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Chen, C. Huang, W. H. Yan, G. P. He, S. X. Zhang
The finite volume method (FVM) is used to numerically investigate the sloshing behaviors of dual liquid tanks with gas inflow in this study. The sloshing process of a single liquid tank is simulated to verify the feasibility of the numerical method. Three different inlet boundary conditions are then discussed in order to obtain a reasonable gas flow rate. The sloshing process of a dual liquid tank with the gas inflow is simulated, and the effects of three different factors on the sloshing behaviors are investigated. The results indicate that the overload, flow rate, and filling ratio can affect the peak value of the impact force acting on the tank wall. The impact force is positively proportional to the overload (1G, 3G, or 5G). An increase in flow rate (50 g/s, 1000 g/s, or 5000 g/s) or a decrease in filling ratio (99.52%, 75.64%, or 63.69%) can increase the size and number of bubbles, leading to intensified sloshing behavior and increased impact force.
{"title":"Numerical Study on the Sloshing Behaviors of Dual Liquid Tanks with Gas Inflow","authors":"Y. Chen, C. Huang, W. H. Yan, G. P. He, S. X. Zhang","doi":"10.47176/jafm.17.9.2595","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2595","url":null,"abstract":"The finite volume method (FVM) is used to numerically investigate the sloshing behaviors of dual liquid tanks with gas inflow in this study. The sloshing process of a single liquid tank is simulated to verify the feasibility of the numerical method. Three different inlet boundary conditions are then discussed in order to obtain a reasonable gas flow rate. The sloshing process of a dual liquid tank with the gas inflow is simulated, and the effects of three different factors on the sloshing behaviors are investigated. The results indicate that the overload, flow rate, and filling ratio can affect the peak value of the impact force acting on the tank wall. The impact force is positively proportional to the overload (1G, 3G, or 5G). An increase in flow rate (50 g/s, 1000 g/s, or 5000 g/s) or a decrease in filling ratio (99.52%, 75.64%, or 63.69%) can increase the size and number of bubbles, leading to intensified sloshing behavior and increased impact force.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141681889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The experimental investigation aimed to determine how the use of biodiesel derived from dill and cresson oil affected the performance of semi-industrial burners. Furthermore, an investigation will be conducted to assess the combustion properties of different blends of biodiesel, specifically B10, B20, B40, and B60. The study looks at biodiesel's chemical makeup, physical properties, and how it works in the system that moves it to the burner and the burner simulator's burning process. Biodiesel exhibits comparable qualities to conventional diesel oil, enabling the possibility of blending it to achieve the desired ratio. The results suggest that increasing the percentage of biodiesel leads to a reduction in flame distance and a rise in flame temperature. Furthermore, the complete combustion of the fuel is responsible for the brilliant and transparent flame. Additionally, using dill and Cresson fuels that come from biodiesel raises the average flame temperature by about 17% and 16.1%, respectively, compared to regular diesel fuel.
{"title":"Study of the Flame Characteristics of Biodiesel Blend Fuel in a Semi-industrial Boiler","authors":"F. A. Saleh, M. K. Allawi","doi":"10.47176/jafm.17.9.2399","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2399","url":null,"abstract":"The experimental investigation aimed to determine how the use of biodiesel derived from dill and cresson oil affected the performance of semi-industrial burners. Furthermore, an investigation will be conducted to assess the combustion properties of different blends of biodiesel, specifically B10, B20, B40, and B60. The study looks at biodiesel's chemical makeup, physical properties, and how it works in the system that moves it to the burner and the burner simulator's burning process. Biodiesel exhibits comparable qualities to conventional diesel oil, enabling the possibility of blending it to achieve the desired ratio. The results suggest that increasing the percentage of biodiesel leads to a reduction in flame distance and a rise in flame temperature. Furthermore, the complete combustion of the fuel is responsible for the brilliant and transparent flame. Additionally, using dill and Cresson fuels that come from biodiesel raises the average flame temperature by about 17% and 16.1%, respectively, compared to regular diesel fuel.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141682407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stepped spillways are specialized hydraulic structures crafted to optimize the effective dissipation of hydraulic energy along stepped chutes. The central objective is to scrutinize and improve the mitigation of flow separation occurring from the ogee crest to the stepped chute, focusing on various profiles within the critical zone (CZ) to understand its flow behavior. The study evaluates the impact of CZ profile alterations on velocity distribution, revealing a reduction in velocity ranging from 10% to 18% for nappe flow and 7% to 15% for skimming flow, with a dissipation rate 5% higher than other tested profiles in the CZ. By combining physical experiments and numerical simulations, the research aims to understand the complex dynamics of CZ flow. A comparative analysis is conducted, comparing turbulence models (specifically RNG) against experimental data for velocity and dissipation rate, considering different numbers of steps (N=16, 22, 56, 60). Moreover, the research seeks to unravel the effects of introducing additional steps within the CZ on crucial hydraulic parameters. The results indicate a significant improvement in flow patterns, velocity fields, and energy dissipation for the modified profile, highlighting the practical applicability of the proposed approaches in effectively sizing the CZ.
{"title":"Influence of a Modified Weir Profile on Velocity Field and Dissipation Rate in Stepped Spillways: A Comparative Study Using Physical Models and Computational Fluid Dynamics","authors":"†. H.Souli, J. Ahattab, S. Bensallam","doi":"10.47176/jafm.17.9.2572","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2572","url":null,"abstract":"Stepped spillways are specialized hydraulic structures crafted to optimize the effective dissipation of hydraulic energy along stepped chutes. The central objective is to scrutinize and improve the mitigation of flow separation occurring from the ogee crest to the stepped chute, focusing on various profiles within the critical zone (CZ) to understand its flow behavior. The study evaluates the impact of CZ profile alterations on velocity distribution, revealing a reduction in velocity ranging from 10% to 18% for nappe flow and 7% to 15% for skimming flow, with a dissipation rate 5% higher than other tested profiles in the CZ. By combining physical experiments and numerical simulations, the research aims to understand the complex dynamics of CZ flow. A comparative analysis is conducted, comparing turbulence models (specifically RNG) against experimental data for velocity and dissipation rate, considering different numbers of steps (N=16, 22, 56, 60). Moreover, the research seeks to unravel the effects of introducing additional steps within the CZ on crucial hydraulic parameters. The results indicate a significant improvement in flow patterns, velocity fields, and energy dissipation for the modified profile, highlighting the practical applicability of the proposed approaches in effectively sizing the CZ.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141680713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Wu, J. Gao, Y. Han, B. Ai, X. Shao, B. Guo, B. Hao
This study investigated the effect of a mixed obstacle layout on the deflagration mechanism of propane–air premixed gases. Most previous studies focused on a single type of obstacle, changing the shape and number of the obstacles to observe the effect on the flame deflagration characteristics. However, in real explosion accident sites, obstacles are often a mixture of different types. Little literature exists on the deflagration characteristics of hybrid barriers in semi-confined spaces. In this paper, the deflagration characteristics of propane-air premixed gas with a mixed structure of hurdles and square obstacles was studied. First, the effectiveness of numerical simulations was demonstrated by comparing experimental and large eddy simulation (LES) results for the flame dynamics with a single flat plate obstacle. Based on this, the flame behavior for different layouts of square obstacles in a mixed obstacle configuration was further simulated using the large eddy simulation method, focusing on the flame behavior, overpressure characteristics, and flow field structure in the vicinity of the obstacle. The results showed that a mixed obstacle promoted flame evolution more than a single obstacle when the square obstacle was within a critical distance from the ignition source location at the same moment in time. When the flame front crossed the first hurdle-type obstacle, the flame pattern spread in a “cat’s paw” pattern to the unburned portion of the tube. In addition, the increased distance of the square obstacle from the ignition source did not allow the peak overpressure and the peak rate of overpressure rise to show a positive feedback mechanism. Finally, the strength of the vorticity in the flow field was positively correlated with the distance of the square obstacle from the ignition source. The results of study provide theoretical for the prevention of explosions.
{"title":"Experimental and LES Studies of Propane–air Premixed Gases in Pipelines Containing Mixed Obstacles","authors":"Y. Wu, J. Gao, Y. Han, B. Ai, X. Shao, B. Guo, B. Hao","doi":"10.47176/jafm.17.9.2550","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2550","url":null,"abstract":"This study investigated the effect of a mixed obstacle layout on the deflagration mechanism of propane–air premixed gases. Most previous studies focused on a single type of obstacle, changing the shape and number of the obstacles to observe the effect on the flame deflagration characteristics. However, in real explosion accident sites, obstacles are often a mixture of different types. Little literature exists on the deflagration characteristics of hybrid barriers in semi-confined spaces. In this paper, the deflagration characteristics of propane-air premixed gas with a mixed structure of hurdles and square obstacles was studied. First, the effectiveness of numerical simulations was demonstrated by comparing experimental and large eddy simulation (LES) results for the flame dynamics with a single flat plate obstacle. Based on this, the flame behavior for different layouts of square obstacles in a mixed obstacle configuration was further simulated using the large eddy simulation method, focusing on the flame behavior, overpressure characteristics, and flow field structure in the vicinity of the obstacle. The results showed that a mixed obstacle promoted flame evolution more than a single obstacle when the square obstacle was within a critical distance from the ignition source location at the same moment in time. When the flame front crossed the first hurdle-type obstacle, the flame pattern spread in a “cat’s paw” pattern to the unburned portion of the tube. In addition, the increased distance of the square obstacle from the ignition source did not allow the peak overpressure and the peak rate of overpressure rise to show a positive feedback mechanism. Finally, the strength of the vorticity in the flow field was positively correlated with the distance of the square obstacle from the ignition source. The results of study provide theoretical for the prevention of explosions.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141680390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wind turbines can freeze due to exposure to cold air. Ice formation on the rotor blades of a wind turbine reduces their performance. In the present work, the effects of ice formation on rotor blades of straight-blade vertical-axis wind turbines (SBVAWT) with a three-blade rotor and a NACA 0021 airfoil are numerically evaluated under two-dimensional transient settings by solving the continuity, momentum and turbulence equations become in ANSYS FLUENT. Grid and time step independence was investigated. For validation, the numerical model was compared with experimental data. An experimental ice model from the literature was then used to numerically simulate the iced rotor in two-dimensional transition settings. The numerical simulation of the icy rotor was compared with an ice-free rotor. It was found that ice formation on the rotor blades changed the velocity and pressure fields around the rotor blades at angles of 180—360°, changing the streamlines and increasing the vortices. Furthermore, the maximum and minimum reductions in moment coefficient during blade icing occurred at angles of 225—315° and 45—135°, respectively. Due to ice formation on the rotor blades, the power coefficient of the rotor blades at angles 180—360° decreased drastically, and the power coefficient of the iced rotor was smaller than that of an ice-free rotor. It was concluded that ice formation on the blades of the SBVAWT reduced the average power coefficient of the blades and rotor power coefficient by 94.2% and 95%, respectively.
{"title":"A Numerical Study on Effects of Ice Formation on Vertical-axis Wind Turbine Performance and Flow Field at Optimal Tip Speed Ratio","authors":"S. Abbasi, A. Mahmoodi, A. Joodaki","doi":"10.47176/jafm.17.9.2525","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2525","url":null,"abstract":"Wind turbines can freeze due to exposure to cold air. Ice formation on the rotor blades of a wind turbine reduces their performance. In the present work, the effects of ice formation on rotor blades of straight-blade vertical-axis wind turbines (SBVAWT) with a three-blade rotor and a NACA 0021 airfoil are numerically evaluated under two-dimensional transient settings by solving the continuity, momentum and turbulence equations become in ANSYS FLUENT. Grid and time step independence was investigated. For validation, the numerical model was compared with experimental data. An experimental ice model from the literature was then used to numerically simulate the iced rotor in two-dimensional transition settings. The numerical simulation of the icy rotor was compared with an ice-free rotor. It was found that ice formation on the rotor blades changed the velocity and pressure fields around the rotor blades at angles of 180—360°, changing the streamlines and increasing the vortices. Furthermore, the maximum and minimum reductions in moment coefficient during blade icing occurred at angles of 225—315° and 45—135°, respectively. Due to ice formation on the rotor blades, the power coefficient of the rotor blades at angles 180—360° decreased drastically, and the power coefficient of the iced rotor was smaller than that of an ice-free rotor. It was concluded that ice formation on the blades of the SBVAWT reduced the average power coefficient of the blades and rotor power coefficient by 94.2% and 95%, respectively.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141683355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Jin, H. Xiang, M. Wang, R. Wen, X. Liu, C. Wang
High-pressure black water angle valves are essential equipment of black water flash treatment systems in the coal gasification process, and they usually suffer from a high risk of erosion wear failure. In this study, computational fluid dynamics (CFD), combined with the discrete particle method (DPM) and the volume of fluid (VOF) method, was used to study the flow characteristics and erosion wear phenomenon in high-pressure black water angle valves under different valve cavity radii and opening angles. In particular, a new parameter, the drift index, was introduced to analyze the bias flow phenomenon in the throttling zone. With the increase in valve cavity radius, the drift index first decreases and then increases, and the influence of the valve cavity radius gradually weakens with the increase in the valve opening. It was found that, with the increase in valve cavity radius, the average erosion wear rate of the valve body decreases first and then increases. When the valve cavity radius was 132 mm, the average erosion wear rate of the valve body was the smallest. Therefore, the optimization of the valve cavity radius selection value can reduce the erosion wear damage of the high-pressure black water angle valve and increase its operational dependability.
高压黑水角阀是煤气化过程中黑水闪蒸处理系统的重要设备，通常具有很高的冲蚀磨损失效风险。本研究采用计算流体动力学（CFD）方法，结合离散粒子法（DPM）和流体体积法（VOF），研究了高压黑水角阀在不同阀腔半径和开启角度下的流动特性和冲蚀磨损现象。其中，引入了一个新参数--漂移指数，用于分析节流区的偏流现象。随着阀腔半径的增大，漂移指数先减小后增大，并且随着阀门开度的增大，阀腔半径的影响逐渐减弱。研究发现，随着阀腔半径的增大，阀体的平均冲蚀磨损率先减小后增大。当阀腔半径为 132 mm 时，阀体的平均冲蚀磨损率最小。因此，优化阀腔半径选择值可以减少高压黑水角阀的冲蚀磨损破坏，提高其运行可靠性。
{"title":"Numerical Study of Erosion Wear Characteristics in a High-pressure Black Water Angle Valve by Using CFD-VOF-DPM Method","authors":"H. Jin, H. Xiang, M. Wang, R. Wen, X. Liu, C. Wang","doi":"10.47176/jafm.17.9.2456","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2456","url":null,"abstract":"High-pressure black water angle valves are essential equipment of black water flash treatment systems in the coal gasification process, and they usually suffer from a high risk of erosion wear failure. In this study, computational fluid dynamics (CFD), combined with the discrete particle method (DPM) and the volume of fluid (VOF) method, was used to study the flow characteristics and erosion wear phenomenon in high-pressure black water angle valves under different valve cavity radii and opening angles. In particular, a new parameter, the drift index, was introduced to analyze the bias flow phenomenon in the throttling zone. With the increase in valve cavity radius, the drift index first decreases and then increases, and the influence of the valve cavity radius gradually weakens with the increase in the valve opening. It was found that, with the increase in valve cavity radius, the average erosion wear rate of the valve body decreases first and then increases. When the valve cavity radius was 132 mm, the average erosion wear rate of the valve body was the smallest. Therefore, the optimization of the valve cavity radius selection value can reduce the erosion wear damage of the high-pressure black water angle valve and increase its operational dependability.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141683245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A stable upwind finite-difference method for unsteady gas-liquid two-phase flows is proposed and applied to shock tube flows. The artificial dissipation terms in the flux difference splitting upwinding scheme are derived using a preconditioned matrix to enhance the stability and convergence of the numerical calculation of mixed compressible and incompressible flows with arbitrary void fractions. A homogeneous gas-liquid two-phase flow model is used. A stable four-stage Runge-Kutta method and the flux difference splitting upwind scheme combined with a third-order MUSCL TVD scheme are employed. Using the proposed method, we compute gas-liquid mixture shock tube problems and compare their results with the exact solution to check the reliability of the proposed method. Shock and expansion wave propagations through the gas-liquid two-phase media are observed in detail. The effect of the preconditioned artificial dissipation on the numerical stability and convergence rate are investigated. We confirm that the proposed method is stable and effective for computations of unsteady two-phase complex flows with arbitrary Mach numbers.
{"title":"Upwind Scheme Using Preconditioned Artificial Dissipation for Unsteady Gas-liquid Two-phase Flow and Its Application to Shock Tube Flow","authors":"T. Zhao, B. R. Shin","doi":"10.47176/jafm.17.9.2556","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2556","url":null,"abstract":"A stable upwind finite-difference method for unsteady gas-liquid two-phase flows is proposed and applied to shock tube flows. The artificial dissipation terms in the flux difference splitting upwinding scheme are derived using a preconditioned matrix to enhance the stability and convergence of the numerical calculation of mixed compressible and incompressible flows with arbitrary void fractions. A homogeneous gas-liquid two-phase flow model is used. A stable four-stage Runge-Kutta method and the flux difference splitting upwind scheme combined with a third-order MUSCL TVD scheme are employed. Using the proposed method, we compute gas-liquid mixture shock tube problems and compare their results with the exact solution to check the reliability of the proposed method. Shock and expansion wave propagations through the gas-liquid two-phase media are observed in detail. The effect of the preconditioned artificial dissipation on the numerical stability and convergence rate are investigated. We confirm that the proposed method is stable and effective for computations of unsteady two-phase complex flows with arbitrary Mach numbers.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141682812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Modern underwater warfare necessitates the development of high-speed supercavitating torpedoes. Achieving supercavitation involves integrating a cavitator at the torpedo's front, making cavitator design a critical research area. The present study simulated supercavity formation by cavitators of various shapes attached to a heavyweight torpedo. The study involves simulations of thirteen cavitator designs with various geometrical configurations at different cavitation numbers. The simulations employ the VOF multiphase model along with the Schnerr and Sauer cavitation model to analyze supercavitation hydrodynamics. The study examines the supercavity geometry and drag characteristics for individual cavitator designs. The results reveal a significant reduction in skin friction drag by a majority of cavitators. Notably, a disc cavitator at a cavitation number of 0.09 demonstrates a remarkable 92% reduction in the coefficient of skin friction drag. However, the overall drag reduces when incorporating a cavitator, but it introduces additional pressure drag. The study found that the cavitators generating larger supercavities also yield higher pressure drag. Therefore, the supercavity should just envelop the entire torpedo, as excessively small supercavities amplify skin friction drag, while overly large ones elevate pressure drag. Ultimately, the study concludes that selecting the ideal cavitator entails a comprehensive evaluation of factors such as supercavity and torpedo geometry, reductions in skin friction drag and increments in pressure drag.
{"title":"A Comparative Assessment of Various Cavitator Shapes for High-speed Supercavitating Torpedoes: Geometry, Flow-physics and Drag Considerations","authors":"K. Gaurav, N. Venkatesh, †. A.Karn","doi":"10.47176/jafm.17.9.2631","DOIUrl":"https://doi.org/10.47176/jafm.17.9.2631","url":null,"abstract":"Modern underwater warfare necessitates the development of high-speed supercavitating torpedoes. Achieving supercavitation involves integrating a cavitator at the torpedo's front, making cavitator design a critical research area. The present study simulated supercavity formation by cavitators of various shapes attached to a heavyweight torpedo. The study involves simulations of thirteen cavitator designs with various geometrical configurations at different cavitation numbers. The simulations employ the VOF multiphase model along with the Schnerr and Sauer cavitation model to analyze supercavitation hydrodynamics. The study examines the supercavity geometry and drag characteristics for individual cavitator designs. The results reveal a significant reduction in skin friction drag by a majority of cavitators. Notably, a disc cavitator at a cavitation number of 0.09 demonstrates a remarkable 92% reduction in the coefficient of skin friction drag. However, the overall drag reduces when incorporating a cavitator, but it introduces additional pressure drag. The study found that the cavitators generating larger supercavities also yield higher pressure drag. Therefore, the supercavity should just envelop the entire torpedo, as excessively small supercavities amplify skin friction drag, while overly large ones elevate pressure drag. Ultimately, the study concludes that selecting the ideal cavitator entails a comprehensive evaluation of factors such as supercavity and torpedo geometry, reductions in skin friction drag and increments in pressure drag.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141682449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Abid, N. Yasin, M. Saqlain, S. Ul-Islam, S. Ahmad
Flow past bluff bodies like square cylinders is important in engineering applications, but flow patterns behind staggered cylinder arrangements remain poorly understood. Existing studies have focused on tandem or side-by-side configurations, while offset orientations have received less attention. The aim of this paper is to numerically investigate flow dynamics and force characteristics behind two offset square cylinders using the single relaxation time lattice Boltzmann method. The effects of changing both the Reynolds number (Re = 1-150) and gap spacing ratio (g* = 0.5-5) between the cylinders are analyzed. Instantaneous vorticity contours, time histories of drag and lift coefficients, power spectra of lift, and force statistics are used to characterize the flow. Different flow regimes have been identified in various ranges of Re and g* - including steady, chaotic, flip-flopping, single-bluff body, and fully developed flows. Larger spacings led to more regular vortex dynamics and force statistics. Smaller spacings promoted complex interactions and modulated forces. Offset cylinder orientation and spacing significantly influence flow features in staggered arrangements. The findings provide new modalities for controlling
在工程应用中，流经方形气缸等崖壁体的流动非常重要，但交错气缸布置背后的流动模式却鲜为人知。现有的研究主要集中在串联或并排配置上，而偏移方向的研究则较少受到关注。本文旨在使用单弛豫时间晶格玻尔兹曼方法对两个偏置方形圆柱体后的流动动力学和力特性进行数值研究。本文分析了改变雷诺数（Re = 1-150）和圆柱体间隙间距比（g* = 0.5-5）的影响。瞬时涡度等值线、阻力和升力系数的时间历程、升力的功率谱以及力统计用于描述流动特征。在不同的 Re 和 g* 范围内，确定了不同的流态--包括稳定流、混沌流、翻转流、单漂移体流和完全发展流。间距越大，涡旋动力学和力统计越有规律。较小的间距可促进复杂的相互作用和调节力。偏置圆柱体的方向和间距对交错排列的流动特征有很大影响。这些发现为控制
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