Ali Shirinzad, Khodr Jaber, Kecheng Xu, Pierre E. Sullivan
Particle Image Velocimetry (PIV) is a widely used experimental technique for measuring flow. In recent years, open-source PIV software has become more popular as it offers researchers and practitioners enhanced computational capabilities. Software development for graphical processing unit (GPU) architectures requires careful algorithm design and data structure selection for optimal performance. PIV software, optimized for central processing units (CPUs), offer an alternative to specialized GPU software. In the present work, an improved algorithm for the OpenPIV–Python software (Version 0.25.1, OpenPIV, Tel Aviv-Yafo, Israel) is presented and implemented under a traditional CPU framework. The Python language was selected due to its versatility and widespread adoption. The algorithm was also tested on a supercomputing cluster, a workstation, and Google Colaboratory during the development phase. Using a known velocity field, the algorithm precisely captured the time-average flow, momentary velocity fields, and vortices.
粒子图像测速(PIV)是一种应用广泛的流量测量实验技术。近年来，开源PIV软件变得越来越流行，因为它为研究人员和从业者提供了增强的计算能力。图形处理单元(GPU)架构的软件开发需要仔细的算法设计和数据结构选择以获得最佳性能。PIV软件针对中央处理器(cpu)进行了优化，为专用GPU软件提供了另一种选择。本文提出了一种针对OpenPIV - python软件(Version 0.25.1, OpenPIV, Tel Aviv-Yafo, Israel)的改进算法，并在传统的CPU框架下实现。选择Python语言是因为它的多功能性和广泛的采用。在开发阶段，该算法还在超级计算集群、工作站和Google协作实验室上进行了测试。利用已知的速度场，该算法精确地捕获了时间平均流量、瞬时速度场和旋涡。
{"title":"An Enhanced Python-Based Open-Source Particle Image Velocimetry Software for Use with Central Processing Units","authors":"Ali Shirinzad, Khodr Jaber, Kecheng Xu, Pierre E. Sullivan","doi":"10.3390/fluids8110285","DOIUrl":"https://doi.org/10.3390/fluids8110285","url":null,"abstract":"Particle Image Velocimetry (PIV) is a widely used experimental technique for measuring flow. In recent years, open-source PIV software has become more popular as it offers researchers and practitioners enhanced computational capabilities. Software development for graphical processing unit (GPU) architectures requires careful algorithm design and data structure selection for optimal performance. PIV software, optimized for central processing units (CPUs), offer an alternative to specialized GPU software. In the present work, an improved algorithm for the OpenPIV–Python software (Version 0.25.1, OpenPIV, Tel Aviv-Yafo, Israel) is presented and implemented under a traditional CPU framework. The Python language was selected due to its versatility and widespread adoption. The algorithm was also tested on a supercomputing cluster, a workstation, and Google Colaboratory during the development phase. Using a known velocity field, the algorithm precisely captured the time-average flow, momentary velocity fields, and vortices.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"10 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136234472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Maxwell equations governing electromagnetic effects are being shown to be equivalent to the compressible inviscid Navier–Stokes equations applicable in fluid dynamics and representing conservation of mass and linear momentum. The latter applies subject to a generalized Beltrami condition to be satisfied by the magnetic field. This equivalence indicates that the compressible inviscid Navier–Stokes equations are Lorentz invariant as they derive directly from the Lorentz-invariant Maxwell equations subject to the same Beltrami condition, provided the pressure wave propagates at the speed of light, i.e., vo=co. In addition, the derivation and results provide support for the claim that electromagnetic potentials have physical significance as demonstrated by Aharonov–Bohm effect, and are not only a convenient mathematical formulation.
{"title":"Rendering Maxwell Equations into the Compressible Inviscid Fluid Dynamics Form","authors":"Peter Vadasz","doi":"10.3390/fluids8110284","DOIUrl":"https://doi.org/10.3390/fluids8110284","url":null,"abstract":"Maxwell equations governing electromagnetic effects are being shown to be equivalent to the compressible inviscid Navier–Stokes equations applicable in fluid dynamics and representing conservation of mass and linear momentum. The latter applies subject to a generalized Beltrami condition to be satisfied by the magnetic field. This equivalence indicates that the compressible inviscid Navier–Stokes equations are Lorentz invariant as they derive directly from the Lorentz-invariant Maxwell equations subject to the same Beltrami condition, provided the pressure wave propagates at the speed of light, i.e., vo=co. In addition, the derivation and results provide support for the claim that electromagnetic potentials have physical significance as demonstrated by Aharonov–Bohm effect, and are not only a convenient mathematical formulation.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"17 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134905992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The flash smelting furnace has previously been simulated using computational fluid dynamics (CFD). A new approach is to combine CFD and the discrete element method (DEM) for more detailed simulations of the different phenomena that occur as copper matte droplets settle through a slag layer. One of the most important phenomena found is the formation of a channeling flow which carries matte droplets faster through the slag. However, such phenomena cannot be directly observed in the flash smelting furnace settler due to the extreme temperatures of the opaque molten slag inside the furnace, therefore alternative methods are required for validating the phenomenon. In this work, the simulated channeling flow is validated with a sphere–oil model. The phenomenon was similar in all of the studied cases, although in the experimental setup the spheres settled faster in the oil model than in the simulations. The differences were most likely caused by the cohesion of the spheres and slight differences in the properties provided by the manufacturer and real properties for the oil and the spheres, and by the fact that simulation ignores surface tension and changing air–oil and water–oil interfaces.
{"title":"Settling Flow Details in the Flash Smelting Furnace—A CFD-DEM Simulation Study","authors":"Jani-Petteri Jylhä, Ari Jokilaakso","doi":"10.3390/fluids8100283","DOIUrl":"https://doi.org/10.3390/fluids8100283","url":null,"abstract":"The flash smelting furnace has previously been simulated using computational fluid dynamics (CFD). A new approach is to combine CFD and the discrete element method (DEM) for more detailed simulations of the different phenomena that occur as copper matte droplets settle through a slag layer. One of the most important phenomena found is the formation of a channeling flow which carries matte droplets faster through the slag. However, such phenomena cannot be directly observed in the flash smelting furnace settler due to the extreme temperatures of the opaque molten slag inside the furnace, therefore alternative methods are required for validating the phenomenon. In this work, the simulated channeling flow is validated with a sphere–oil model. The phenomenon was similar in all of the studied cases, although in the experimental setup the spheres settled faster in the oil model than in the simulations. The differences were most likely caused by the cohesion of the spheres and slight differences in the properties provided by the manufacturer and real properties for the oil and the spheres, and by the fact that simulation ignores surface tension and changing air–oil and water–oil interfaces.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"338 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135366752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wheels contribute significantly to the aerodynamic performance of ground vehicles. Many studies have focused on investigating a single wheel either in isolation or in a wheelhouse. However, there has been less focus on the flow field around a rear wheel, especially when considering varying proximity to the front wheel, despite its importance on aerodynamic forces. In this study, a generic reference body is modified and fitted with a rear wheel within a wheelhouse and analysed while the wheel spacing varies. Reynolds-Averaged Navier–Stokes (RANS) modelling was employed to allow for multiple variations to be considered and the model produced results in good agreement with experimental results. The results confirm that two upper rear wheelhouse outflow vortices are only present when the wheel spacing is short. It was found that the drag values were minimal for the wheel spacing at a critical distance of 1.5 wheel diameters. At this wheel spacing, the formation of the outboard jetting vortex is prevented at the rear wheel, and hence, the rear wheel drag is reduced by more than 10%. Any further reduction in the spacing does not provide any drag benefits. Also, the outflow from the front wheelhouse is projected further away from the body, drawing flow from the rear wheelhouse into the outboard jetting vortex.
车轮对地面车辆的空气动力学性能起着重要的作用。许多研究都集中在单独或驾驶室中的单个车轮上。然而，对后轮周围流场的关注较少，尤其是考虑到与前轮的距离变化时，尽管它对空气动力很重要。在本研究中，修改了一个通用参考体，并在驾驶室内安装了一个后轮，并分析了车轮间距的变化。采用reynolds - average Navier-Stokes (RANS)模型考虑了多种变化，模型得出的结果与实验结果吻合良好。结果表明，只有在轮距较小时才会出现两个上后轮室外流涡。结果表明，当轮距为1.5轮径时，阻力值最小。在此轮距下，可防止后轮形成外侧射流涡，从而使后轮阻力减小10%以上。进一步减小间距不会带来任何阻力优势。此外，从前轮室流出的气流被投射到离车身更远的地方，将后轮室的气流吸引到舷外射流漩涡中。
{"title":"A Detailed Numerical Study on Aerodynamic Interactions of Tandem Wheels on a Generic Vehicle","authors":"Radoje Radovic, Fatemeh Salehi, Sammy Diasinos","doi":"10.3390/fluids8100281","DOIUrl":"https://doi.org/10.3390/fluids8100281","url":null,"abstract":"Wheels contribute significantly to the aerodynamic performance of ground vehicles. Many studies have focused on investigating a single wheel either in isolation or in a wheelhouse. However, there has been less focus on the flow field around a rear wheel, especially when considering varying proximity to the front wheel, despite its importance on aerodynamic forces. In this study, a generic reference body is modified and fitted with a rear wheel within a wheelhouse and analysed while the wheel spacing varies. Reynolds-Averaged Navier–Stokes (RANS) modelling was employed to allow for multiple variations to be considered and the model produced results in good agreement with experimental results. The results confirm that two upper rear wheelhouse outflow vortices are only present when the wheel spacing is short. It was found that the drag values were minimal for the wheel spacing at a critical distance of 1.5 wheel diameters. At this wheel spacing, the formation of the outboard jetting vortex is prevented at the rear wheel, and hence, the rear wheel drag is reduced by more than 10%. Any further reduction in the spacing does not provide any drag benefits. Also, the outflow from the front wheelhouse is projected further away from the body, drawing flow from the rear wheelhouse into the outboard jetting vortex.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135569201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aikaterini C. Stamou, Jovana Radulovic, James M. Buick
Blood is a shear-thinning non-Newtonian fluid in which the viscosity reduces with the shear rate. When simulating arterial flow, it is well established that the non-Newtonian nature is important in the smallest vessels; however, there is no consistent view as to whether it is required in larger arteries, such as the carotid. Here, we investigate the importance of incorporating a non-Newtonian model when applying a plaque deposition model which is based on near-wall local haemodynamic markers: the time-averaged near wall velocity and the ratio of the oscillatory shear index to the wall shear stress. In both cases the plaque deposition was similar between the Newtonian and non-Newtonian simulations, with the observed differences being no more significant than the differences between the selected markers. More significant differences were observed in the haemodynamic properties in the stenosed region, the most significant being that lower levels of near-wall reverse flow were observed for a non-Newtonian fluid.
{"title":"A Comparison of Newtonian and Non-Newtonian Models for Simulating Stenosis Development at the Bifurcation of the Carotid Artery","authors":"Aikaterini C. Stamou, Jovana Radulovic, James M. Buick","doi":"10.3390/fluids8100282","DOIUrl":"https://doi.org/10.3390/fluids8100282","url":null,"abstract":"Blood is a shear-thinning non-Newtonian fluid in which the viscosity reduces with the shear rate. When simulating arterial flow, it is well established that the non-Newtonian nature is important in the smallest vessels; however, there is no consistent view as to whether it is required in larger arteries, such as the carotid. Here, we investigate the importance of incorporating a non-Newtonian model when applying a plaque deposition model which is based on near-wall local haemodynamic markers: the time-averaged near wall velocity and the ratio of the oscillatory shear index to the wall shear stress. In both cases the plaque deposition was similar between the Newtonian and non-Newtonian simulations, with the observed differences being no more significant than the differences between the selected markers. More significant differences were observed in the haemodynamic properties in the stenosed region, the most significant being that lower levels of near-wall reverse flow were observed for a non-Newtonian fluid.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135569566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A fully developed turbulent flow in a concentric annulus, Re =10,000, ri/ro=0.5, with an inner rotating cylinder in the velocity range N=Uω/Ub=0÷4, is studied via a large-eddy simulation. Also, for comparison, simulations by steady-state, unstatiounary RANS k-ω SST (URANS), and Elliptic Blending Model (EBM) were made. The main focus of this study is on the effect of high rotation on the mean flow, turbulence statistics, and vortex structure. Distribution of the tangential velocity and the Reynolds stress tensor change their behaviour at N>0.5∼1. With rotation increases, the production of tangential fluctuation becomes dominant over axial ones and the position of turbulent kinetic energy maximum shifts towards the wall into the buffer zone. URANS and EBM approaches show good agreement with LES in mean flow, turbulent statistics, and integral parameters. The difference in pressure loss prediction between LES and URANS does not exceed 20%, but the average difference is about 11%. The EBM approach underestimates pressure losses up to 9% and on average not more than 5%. Vortex structures are described well by URANS.
{"title":"Numerical Simulation of Taylor—Couette—Poiseuille Flow at Re = 10,000","authors":"Andrey Gavrilov, Yaroslav Ignatenko","doi":"10.3390/fluids8100280","DOIUrl":"https://doi.org/10.3390/fluids8100280","url":null,"abstract":"A fully developed turbulent flow in a concentric annulus, Re =10,000, ri/ro=0.5, with an inner rotating cylinder in the velocity range N=Uω/Ub=0÷4, is studied via a large-eddy simulation. Also, for comparison, simulations by steady-state, unstatiounary RANS k-ω SST (URANS), and Elliptic Blending Model (EBM) were made. The main focus of this study is on the effect of high rotation on the mean flow, turbulence statistics, and vortex structure. Distribution of the tangential velocity and the Reynolds stress tensor change their behaviour at N>0.5∼1. With rotation increases, the production of tangential fluctuation becomes dominant over axial ones and the position of turbulent kinetic energy maximum shifts towards the wall into the buffer zone. URANS and EBM approaches show good agreement with LES in mean flow, turbulent statistics, and integral parameters. The difference in pressure loss prediction between LES and URANS does not exceed 20%, but the average difference is about 11%. The EBM approach underestimates pressure losses up to 9% and on average not more than 5%. Vortex structures are described well by URANS.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135730445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Boundary layer processes play a crucial role in establishing the circulation patterns of the oceans and atmosphere, significantly affecting both regional and global climate, as well as the distributions of heat, nutrients, species, pollutants and more [...]
{"title":"Editorial Summary: Boundary Layer Processes in Geophysical/Environmental Flows","authors":"Joseph Kuehl","doi":"10.3390/fluids8100279","DOIUrl":"https://doi.org/10.3390/fluids8100279","url":null,"abstract":"Boundary layer processes play a crucial role in establishing the circulation patterns of the oceans and atmosphere, significantly affecting both regional and global climate, as well as the distributions of heat, nutrients, species, pollutants and more [...]","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135730368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kevin Ignatowicz, François Morency, Héloïse Beaugendre
Experimental and numerical fluid dynamics studies highlight a change of flow structure in the presence of surface roughness. The changes involve both wall heat transfer and skin friction, and are mainly restricted to the inner region of the boundary layer. Aircraft in-flight icing is a typical application where rough surfaces play an important role in the airflow structure and the subsequent ice growth. The objective of this work is to investigate how surface roughness is tackled in RANS with wall resolved boundary layers for aeronautics applications, with a focus on ice-induced roughness. The literature review shows that semi-empirical correlations were calibrated on experimental data to model flow changes in the presence of roughness. The correlations for RANS do not explicitly resolve the individual roughness. They principally involve turbulence model modifications to account for changes in the velocity and temperature profiles in the near-wall region. The equivalent sand grain roughness (ESGR) approach emerges as a popular metric to characterize roughness and is employed as a length scale for the RANS model. For in-flight icing, correlations were developed, accounting for both surface geometry and atmospheric conditions. Despite these research efforts, uncertainties are present in some specific conditions, where space and time roughness variations make the simulations difficult to calibrate. Research that addresses this gap could help improve ice accretion predictions.
{"title":"Surface Roughness in RANS Applied to Aircraft Ice Accretion Simulation: A Review","authors":"Kevin Ignatowicz, François Morency, Héloïse Beaugendre","doi":"10.3390/fluids8100278","DOIUrl":"https://doi.org/10.3390/fluids8100278","url":null,"abstract":"Experimental and numerical fluid dynamics studies highlight a change of flow structure in the presence of surface roughness. The changes involve both wall heat transfer and skin friction, and are mainly restricted to the inner region of the boundary layer. Aircraft in-flight icing is a typical application where rough surfaces play an important role in the airflow structure and the subsequent ice growth. The objective of this work is to investigate how surface roughness is tackled in RANS with wall resolved boundary layers for aeronautics applications, with a focus on ice-induced roughness. The literature review shows that semi-empirical correlations were calibrated on experimental data to model flow changes in the presence of roughness. The correlations for RANS do not explicitly resolve the individual roughness. They principally involve turbulence model modifications to account for changes in the velocity and temperature profiles in the near-wall region. The equivalent sand grain roughness (ESGR) approach emerges as a popular metric to characterize roughness and is employed as a length scale for the RANS model. For in-flight icing, correlations were developed, accounting for both surface geometry and atmospheric conditions. Despite these research efforts, uncertainties are present in some specific conditions, where space and time roughness variations make the simulations difficult to calibrate. Research that addresses this gap could help improve ice accretion predictions.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136185075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A wide range of commercial powdered products are manufactured by spray drying emulsions. Some product properties are dependent on the oil droplet size, which can be affected by fluid mechanics inside the spray nozzle. However, most of the key flow parameters inside the nozzles are difficult to measure experimentally, and theoretical estimations present deviations at high shear rates and viscosities. Therefore, the purpose of this study was to develop a computational model that could represent the multiphase flow in pressure swirl nozzles and could determine the deformation stresses and residence times that oil droplets experience. The multiphase flow was modelled using the Volume-of-Fluid method under a laminar regime. The model was validated with experimental data using the operating conditions and the spray angle. The numerically calculated shear stresses were found to provide a better prediction of the final oil droplet size than previous theoretical estimations. A two-step breakup mechanism inside of the nozzle was also proposed. Additionally, some of the assumptions used in the theoretical estimations could not be confirmed for the nozzles investigated: No complete air core developed inside of the nozzle during atomization, and the shear stress at the nozzle outlet is not the only stress that can affect oil droplet size. Elongation stresses cannot be neglected in all cases.
{"title":"Using Computation Fluid Dynamics to Determine Oil Droplet Breakup Parameters during Emulsion Atomization with Pressure Swirl Nozzles","authors":"Miguel Ángel Ballesteros Martínez, Volker Gaukel","doi":"10.3390/fluids8100277","DOIUrl":"https://doi.org/10.3390/fluids8100277","url":null,"abstract":"A wide range of commercial powdered products are manufactured by spray drying emulsions. Some product properties are dependent on the oil droplet size, which can be affected by fluid mechanics inside the spray nozzle. However, most of the key flow parameters inside the nozzles are difficult to measure experimentally, and theoretical estimations present deviations at high shear rates and viscosities. Therefore, the purpose of this study was to develop a computational model that could represent the multiphase flow in pressure swirl nozzles and could determine the deformation stresses and residence times that oil droplets experience. The multiphase flow was modelled using the Volume-of-Fluid method under a laminar regime. The model was validated with experimental data using the operating conditions and the spray angle. The numerically calculated shear stresses were found to provide a better prediction of the final oil droplet size than previous theoretical estimations. A two-step breakup mechanism inside of the nozzle was also proposed. Additionally, some of the assumptions used in the theoretical estimations could not be confirmed for the nozzles investigated: No complete air core developed inside of the nozzle during atomization, and the shear stress at the nozzle outlet is not the only stress that can affect oil droplet size. Elongation stresses cannot be neglected in all cases.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135804380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Utkina, Andrey Kozelkov, Roman Zhuchkov, Dmitry Strelets
The paper reports the results of a study concerned with the influence of the size of the leading edge laminar bubble on the aerodynamic characteristics of the HGR01 airfoil. The completely turbulent and transient flows are considered. The mechanism of the appearance and interaction of laminar and turbulent flow separation near the leading and trailing edges of the airfoil is studied in detail. In the paper, the dependence of aerodynamic forces on the critical Reynolds number for the HGR01 airfoil is discussed. It has been established that the separation bubble at the leading edge can only be obtained using the laminar–turbulent transition model. Fully turbulent models are not able to show this feature of the airfoil flow. Graphs of the lift coefficient as a function of the critical Reynolds number, as well as the pressure distribution as a function of the size of the laminar bubble, are shown.
{"title":"Numerical Study of the Influence of the Critical Reynolds Number on the Aerodynamic Characteristics of the Wing Airfoil","authors":"Anna Utkina, Andrey Kozelkov, Roman Zhuchkov, Dmitry Strelets","doi":"10.3390/fluids8100276","DOIUrl":"https://doi.org/10.3390/fluids8100276","url":null,"abstract":"The paper reports the results of a study concerned with the influence of the size of the leading edge laminar bubble on the aerodynamic characteristics of the HGR01 airfoil. The completely turbulent and transient flows are considered. The mechanism of the appearance and interaction of laminar and turbulent flow separation near the leading and trailing edges of the airfoil is studied in detail. In the paper, the dependence of aerodynamic forces on the critical Reynolds number for the HGR01 airfoil is discussed. It has been established that the separation bubble at the leading edge can only be obtained using the laminar–turbulent transition model. Fully turbulent models are not able to show this feature of the airfoil flow. Graphs of the lift coefficient as a function of the critical Reynolds number, as well as the pressure distribution as a function of the size of the laminar bubble, are shown.","PeriodicalId":12397,"journal":{"name":"Fluids","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135858824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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