Pub Date : 2024-11-23DOI: 10.1016/j.euromechflu.2024.11.009
Mahadev Prabhu, C.M. Hariprasad, R. Ajith Kumar
Air-core vortexing phenomenon during draining of liquids from cylindrical vessels is of major interest because this phenomenon has significant impact in multiple engineering systems. The adverse effects created by vortex formation via air-core ingestion in the field of aerospace engineering, metal casting and hydraulic engineering demanded the need for air-core vortex suppression. From past few decades, researchers have come up with unique strategies to suppress vortexing phenomenon. As the first ever initiative, the current review classifies all the strategies reported in the literature and addresses the advantages and adverse effects of each strategy. Based on this classification, this review identifies vortex suppression strategies suitable for various engineering applications. The present review also investigates the contradictions and misinterpretations observed in the published results. Research gaps and major outcomes identified in this review are novel and are expected to give a fresh impetus for further research delivering new insights on the phenomenon of air core vortex formation aiding to develop new suppression strategies.
{"title":"Suppression of rankine vortex formation in liquid draining tanks: A critical review","authors":"Mahadev Prabhu, C.M. Hariprasad, R. Ajith Kumar","doi":"10.1016/j.euromechflu.2024.11.009","DOIUrl":"10.1016/j.euromechflu.2024.11.009","url":null,"abstract":"<div><div>Air-core vortexing phenomenon during draining of liquids from cylindrical vessels is of major interest because this phenomenon has significant impact in multiple engineering systems. The adverse effects created by vortex formation via air-core ingestion in the field of aerospace engineering, metal casting and hydraulic engineering demanded the need for air-core vortex suppression. From past few decades, researchers have come up with unique strategies to suppress vortexing phenomenon. As the first ever initiative, the current review classifies all the strategies reported in the literature and addresses the advantages and adverse effects of each strategy. Based on this classification, this review identifies vortex suppression strategies suitable for various engineering applications. The present review also investigates the contradictions and misinterpretations observed in the published results. Research gaps and major outcomes identified in this review are novel and are expected to give a fresh impetus for further research delivering new insights on the phenomenon of air core vortex formation aiding to develop new suppression strategies.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"110 ","pages":"Pages 34-64"},"PeriodicalIF":2.5,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.euromechflu.2024.11.008
Nang X. Ho, Vinh T. Nguyen, Hoe D. Nguyen, Truong V. Vu
In this work, we numerically analyze the breakup process of a two-dimensional compound droplet as it moves through a microchannel and encounters an obstacle embedded in it. Initially, the droplet is circular and concentric, and positioned near the inlet of the main channel. Under the influence of the inflow, the droplet moves toward the head of the obstacle, which has a semicircular shape. At a certain moment, the droplet and the obstacle interact with each other. With this interaction, simple daughter droplets and compound daughter droplets can be generated from the original droplet due to changes in the obstacle size, the inner droplet size, and especially the variation in surface tension described by the Weber number. The results reveal that with larger Weber numbers and smaller radii of the inner droplet and the obstacle, the compound droplet is completely separated. Based on the influence of these parameters, a phase diagram for the problem is constructed.
{"title":"Dynamics of a compound droplet in a microchannel containing a long obstacle","authors":"Nang X. Ho, Vinh T. Nguyen, Hoe D. Nguyen, Truong V. Vu","doi":"10.1016/j.euromechflu.2024.11.008","DOIUrl":"10.1016/j.euromechflu.2024.11.008","url":null,"abstract":"<div><div>In this work, we numerically analyze the breakup process of a two-dimensional compound droplet as it moves through a microchannel and encounters an obstacle embedded in it. Initially, the droplet is circular and concentric, and positioned near the inlet of the main channel. Under the influence of the inflow, the droplet moves toward the head of the obstacle, which has a semicircular shape. At a certain moment, the droplet and the obstacle interact with each other. With this interaction, simple daughter droplets and compound daughter droplets can be generated from the original droplet due to changes in the obstacle size, the inner droplet size, and especially the variation in surface tension described by the Weber number. The results reveal that with larger Weber numbers and smaller radii of the inner droplet and the obstacle, the compound droplet is completely separated. Based on the influence of these parameters, a phase diagram for the problem is constructed.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"110 ","pages":"Pages 25-33"},"PeriodicalIF":2.5,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.euromechflu.2024.11.007
David M. Salazar, Tianshu Liu
This work provides direct experimental evidence supporting the generation of the airfoil circulation associated with a starting vortex as a viscous-flow process based on global velocity measurements near the trailing edge (TE) of a NACA0012 airfoil at the angle of attack of 6° in a low-speed wind tunnel. The evolving flow topology near the TE exhibits the apparent inviscid flow pattern in a very short initial period, the sequential formation and growth of the starting vortex as a result of near-wall viscous flow development, and the final establishment of the Kutta condition as the starting vortex travels downstream. The evolving flow field in the starting flow over the airfoil is topologically consistent.
{"title":"Birth of starting vortex and establishment of Kutta condition","authors":"David M. Salazar, Tianshu Liu","doi":"10.1016/j.euromechflu.2024.11.007","DOIUrl":"10.1016/j.euromechflu.2024.11.007","url":null,"abstract":"<div><div>This work provides direct experimental evidence supporting the generation of the airfoil circulation associated with a starting vortex as a viscous-flow process based on global velocity measurements near the trailing edge (TE) of a NACA0012 airfoil at the angle of attack of 6° in a low-speed wind tunnel. The evolving flow topology near the TE exhibits the apparent inviscid flow pattern in a very short initial period, the sequential formation and growth of the starting vortex as a result of near-wall viscous flow development, and the final establishment of the Kutta condition as the starting vortex travels downstream. The evolving flow field in the starting flow over the airfoil is topologically consistent.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"110 ","pages":"Pages 19-24"},"PeriodicalIF":2.5,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.euromechflu.2024.11.004
Sreeja Sadasivan , Grzegorz Litak , Mohd Furquan , Bibin John , Michał Jan Gęca
Numerical computations were conducted to investigate the vortex-induced oscillations of two adjacent circular cylinders, which are elastically supported by linear springs. The calculations were performed across a range of Reynolds numbers, spanning from 4200 to 42000. The cylinders were allowed to oscillate only in the transverse direction. The study aims to examine the influence of the spacing between two cylinders on their vibrations within the flow. The center-to-center spacing between the cylinders is varied between 1.2 and 4. The observed flow pattern exhibits different wake modes, accompanied by gap flow patterns. At a spacing ratio of 3, the response amplitude for both cylinders during lock-in is larger than that of a single cylinder. The characteristics of fluid forces, vortex patterns, output power as well as vibrational responses are extensively investigated in three different spacing configurations.
{"title":"Computational investigation of vortex-induced oscillation of two side-by-side cylinders at high Reynolds numbers","authors":"Sreeja Sadasivan , Grzegorz Litak , Mohd Furquan , Bibin John , Michał Jan Gęca","doi":"10.1016/j.euromechflu.2024.11.004","DOIUrl":"10.1016/j.euromechflu.2024.11.004","url":null,"abstract":"<div><div>Numerical computations were conducted to investigate the vortex-induced oscillations of two adjacent circular cylinders, which are elastically supported by linear springs. The calculations were performed across a range of Reynolds numbers, spanning from 4200 to 42000. The cylinders were allowed to oscillate only in the transverse direction. The study aims to examine the influence of the spacing between two cylinders on their vibrations within the flow. The center-to-center spacing between the cylinders is varied between 1.2 and 4. The observed flow pattern exhibits different wake modes, accompanied by gap flow patterns. At a spacing ratio of 3, the response amplitude for both cylinders during lock-in is larger than that of a single cylinder. The characteristics of fluid forces, vortex patterns, output power as well as vibrational responses are extensively investigated in three different spacing configurations.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"110 ","pages":"Pages 1-18"},"PeriodicalIF":2.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.euromechflu.2024.11.006
Chentao Huang , Yinhua Ma , Yuye Wang , Li Liu , Ao Mei
The accurate simulation of sand-laden turbulence under different stratification stabilities remains a critical challenge in turbulence research. This study presents an innovative approach to reconstructing streamwise turbulence in an unstable atmospheric surface layer (ASL) using a multi-layer perceptron (MLP) neural network architecture. Leveraging high-resolution measurements of three-dimensional wind velocity and temperature from multiple observational sites, the study develops prediction models for streamwise wind velocity at varying heights in the unstable ASL. The predictive model integrates large-scale motions (LSMs) generated by the MLP, small-scale motions (SSMs) derived from the Kaimal spectrum, and mean wind velocity, providing a comprehensive representation of turbulence. The impact of sand content and stratification stability on model performance is analyzed, with discussion highlighting the model's strengths and limitations under weak instability conditions. Validation is conducted through cross-site comparison, statistical analysis, and power spectrum assessment, demonstrating the model's ability to capture the temporal and spectral characteristics of wind velocity in sand-laden, unstable ASL conditions. The study also reveals that, under weak instability, shear forces dominate the formation of coherent structures, while buoyancy effects enhance vertical mixing as instability increases. Compared to existing models, the proposed prediction model is applicable over a broader range of conditions, offering a valuable data source for the study of atmospheric sand-laden turbulence and serving as a reference for practical sand control projects.
如何准确模拟不同分层稳定性下的含沙湍流仍然是湍流研究中的一个关键挑战。本研究提出了一种利用多层感知器（MLP）神经网络结构重建不稳定大气表层（ASL）流向湍流的创新方法。该研究利用来自多个观测站点的三维风速和温度的高分辨率测量数据，建立了不稳定大气表层不同高度的流向风速预测模型。该预测模型综合了由 MLP 生成的大尺度运动（LSM）、由 Kaimal 频谱得出的小尺度运动（SSM）和平均风速，提供了湍流的综合表征。分析了含沙量和分层稳定性对模型性能的影响，重点讨论了弱不稳定性条件下模型的优势和局限性。通过跨站点比较、统计分析和功率谱评估进行了验证，证明该模型能够捕捉到含沙、不稳定 ASL 条件下风速的时间和频谱特征。研究还发现，在弱不稳定性条件下，剪切力主导着相干结构的形成，而浮力效应则会随着不稳定性的增加而加强垂直混合。与现有模型相比，所提出的预测模型适用于更广泛的条件，为研究大气含沙湍流提供了宝贵的数据来源，也为实际的防沙治沙工程提供了参考。
{"title":"Reconstruction of unstable atmospheric surface layer streamwise turbulence based on multi-layer perceptron neural network architecture","authors":"Chentao Huang , Yinhua Ma , Yuye Wang , Li Liu , Ao Mei","doi":"10.1016/j.euromechflu.2024.11.006","DOIUrl":"10.1016/j.euromechflu.2024.11.006","url":null,"abstract":"<div><div>The accurate simulation of sand-laden turbulence under different stratification stabilities remains a critical challenge in turbulence research. This study presents an innovative approach to reconstructing streamwise turbulence in an unstable atmospheric surface layer (ASL) using a multi-layer perceptron (MLP) neural network architecture. Leveraging high-resolution measurements of three-dimensional wind velocity and temperature from multiple observational sites, the study develops prediction models for streamwise wind velocity at varying heights in the unstable ASL. The predictive model integrates large-scale motions (LSMs) generated by the MLP, small-scale motions (SSMs) derived from the Kaimal spectrum, and mean wind velocity, providing a comprehensive representation of turbulence. The impact of sand content and stratification stability on model performance is analyzed, with discussion highlighting the model's strengths and limitations under weak instability conditions. Validation is conducted through cross-site comparison, statistical analysis, and power spectrum assessment, demonstrating the model's ability to capture the temporal and spectral characteristics of wind velocity in sand-laden, unstable ASL conditions. The study also reveals that, under weak instability, shear forces dominate the formation of coherent structures, while buoyancy effects enhance vertical mixing as instability increases. Compared to existing models, the proposed prediction model is applicable over a broader range of conditions, offering a valuable data source for the study of atmospheric sand-laden turbulence and serving as a reference for practical sand control projects.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 392-413"},"PeriodicalIF":2.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.euromechflu.2024.11.003
Shuai Wang , Zhen Ouyang , Qiang Yang , Zijing Ding
This paper investigates the stability in a heated fluid-porous system. Darcy’s law is used for the flow in the porous medium. Previous studies indicate that the classical Rayleigh–Bénard instability in this flow is independent of the mutual positions of the fluid layer and porous layer. This paper demonstrates that the instability depends on the mutual positions of the fluid layer and porous layer when the liquid density is nonlinearly dependent on temperature. When porous medium is located at the bottom of the system, onset of convection may occur in lower porous layer (pure-porous mode), upper water layer (pure-water mode) or across both layers (porous-water mode). However, onset of convection cannot take place only in the upper porous layer when porous medium is placed at the top of the system. The influence of depth ratio and the density inversion parameter on instability of bilayer system are investigated in detail and dependence of critical modes on parameters are summarized in phase diagrams. In addition, direct numerical simulation is used to analyse the instability mechanism and identify subcritical or supercritical instability for bilayer systems.
{"title":"Instability in heated water-porous system","authors":"Shuai Wang , Zhen Ouyang , Qiang Yang , Zijing Ding","doi":"10.1016/j.euromechflu.2024.11.003","DOIUrl":"10.1016/j.euromechflu.2024.11.003","url":null,"abstract":"<div><div>This paper investigates the stability in a heated fluid-porous system. Darcy’s law is used for the flow in the porous medium. Previous studies indicate that the classical Rayleigh–Bénard instability in this flow is independent of the mutual positions of the fluid layer and porous layer. This paper demonstrates that the instability depends on the mutual positions of the fluid layer and porous layer when the liquid density is nonlinearly dependent on temperature. When porous medium is located at the bottom of the system, onset of convection may occur in lower porous layer (pure-porous mode), upper water layer (pure-water mode) or across both layers (porous-water mode). However, onset of convection cannot take place only in the upper porous layer when porous medium is placed at the top of the system. The influence of depth ratio <span><math><mover><mrow><mi>d</mi></mrow><mrow><mo>ˆ</mo></mrow></mover></math></span> and the density inversion parameter <span><math><msub><mrow><mi>θ</mi></mrow><mrow><mi>M</mi></mrow></msub></math></span> on instability of bilayer system are investigated in detail and dependence of critical modes on parameters are summarized in phase diagrams. In addition, direct numerical simulation is used to analyse the instability mechanism and identify subcritical or supercritical instability for bilayer systems.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 428-439"},"PeriodicalIF":2.5,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1016/j.euromechflu.2024.11.005
Menghan Zhang , Lu Jiang , Zewen Gu , Chicheng Ma , Yuting Wu , Jianlin Liu
Viscous fingering is a common instability event that occurs during the process of water-drive oil for oil recovery, significantly limiting the efficiency of oil extraction. In this study, we propose a film flow model that accounts for the variation in height at the water-oil two phase interface, enabling the calculation and analysis of the triggering mechanism and flow evolution process of this unstable phenomenon. We theoretically derive the equation of water film flow, which can be used to explore the flow evolution of the two-phase interface in the process of oil displacement. By numerically solving the two-dimensional flow equation, we obtain the traveling wave profile and find that the morphology of the two-phase interface is significantly affected by the plane’s inclined angle, capillary number and density ratio of the two-phase liquid. Furthermore, we perform linear stability analysis and finite element numerical simulation considering small initial disturbances to explore the triggering conditions of viscous fingering phenomenon and the full time from gentle displacement to unstable flow. The results reveal that the moving contact line of the driven liquid front is more stable when the viscosity of the oil is less different from the driven liquid and has a smaller density, thereby improving of the driving efficiency in the water-driven oil process. These insights have significant implications for guiding efforts to enhance oil recovery efficiency, and we provide concrete engineering suggestions to achieve this aim.
{"title":"Viscous fingering analysis for water-drive oil in the inclined plane","authors":"Menghan Zhang , Lu Jiang , Zewen Gu , Chicheng Ma , Yuting Wu , Jianlin Liu","doi":"10.1016/j.euromechflu.2024.11.005","DOIUrl":"10.1016/j.euromechflu.2024.11.005","url":null,"abstract":"<div><div>Viscous fingering is a common instability event that occurs during the process of water-drive oil for oil recovery, significantly limiting the efficiency of oil extraction. In this study, we propose a film flow model that accounts for the variation in height at the water-oil two phase interface, enabling the calculation and analysis of the triggering mechanism and flow evolution process of this unstable phenomenon. We theoretically derive the equation of water film flow, which can be used to explore the flow evolution of the two-phase interface in the process of oil displacement. By numerically solving the two-dimensional flow equation, we obtain the traveling wave profile and find that the morphology of the two-phase interface is significantly affected by the plane’s inclined angle, capillary number and density ratio of the two-phase liquid. Furthermore, we perform linear stability analysis and finite element numerical simulation considering small initial disturbances to explore the triggering conditions of viscous fingering phenomenon and the full time from gentle displacement to unstable flow. The results reveal that the moving contact line of the driven liquid front is more stable when the viscosity of the oil is less different from the driven liquid and has a smaller density, thereby improving of the driving efficiency in the water-driven oil process. These insights have significant implications for guiding efforts to enhance oil recovery efficiency, and we provide concrete engineering suggestions to achieve this aim.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 414-427"},"PeriodicalIF":2.5,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-09DOI: 10.1016/j.euromechflu.2024.11.002
Wenhui Zhai , Yuxin Fan
The fluid oscillator, relying on the Coanda effect, is a flow control device that can alter the direction or velocity of a jet both spatially and temporally. The fuel injection device based on a fluid oscillator significantly enhances atomization and spatial dispersion performance compared to a direct-spray nozzle. However, when used in high heat load afterburners with aviation kerosene as the working medium, oxidative coking issues may arise. To address this, it is recommended to use premixed rich fuel-vapor as the working fluid in order to reduce the residence time of fuel in the oscillator. This study investigates the flow rate and frequency variation of ideal air (simulated gas phase fuel) as it moves through a double feedback channel fluid oscillator with varying thicknesses and outlet throat widths. Experimental and numerical simulation methods are employed. And the influence mechanism is analyzed through an examination of the flow field structure within the cavity of the fluid oscillator. The results indicate that increasing the thickness of the fluid oscillator leads to a higher outlet tangential velocity and deflection angle, while simultaneously decreasing the oscillation frequency. Conversely, widening the fluid oscillator throat results in a decrease in tangential velocity, deflection angle, and oscillation frequency. The performance of the fluid oscillator reaches a critical threshold when the outlet throat is square. As thickness increases, the rate of decrease in oscillation frequency and the rate of increase in tangential velocity both slow down. Furthermore, the maximum deflection angle of the airflow at the oscillator outlet reaches a critical value at a thickness of 3.375 mm, beyond which the trend of increasing deflection angle also slows. When the thickness of the oscillator is less than 3.375 mm, mass flow is the predominant driving factor for airflow deflection in the mixing chamber. In contrast, when the thickness is greater than or equal to 3.375 mm, pressure becomes the primary driving factor for this deflection.
{"title":"Influence of structural parameters on the performance of fluid oscillators","authors":"Wenhui Zhai , Yuxin Fan","doi":"10.1016/j.euromechflu.2024.11.002","DOIUrl":"10.1016/j.euromechflu.2024.11.002","url":null,"abstract":"<div><div>The fluid oscillator, relying on the Coanda effect, is a flow control device that can alter the direction or velocity of a jet both spatially and temporally. The fuel injection device based on a fluid oscillator significantly enhances atomization and spatial dispersion performance compared to a direct-spray nozzle. However, when used in high heat load afterburners with aviation kerosene as the working medium, oxidative coking issues may arise. To address this, it is recommended to use premixed rich fuel-vapor as the working fluid in order to reduce the residence time of fuel in the oscillator. This study investigates the flow rate and frequency variation of ideal air (simulated gas phase fuel) as it moves through a double feedback channel fluid oscillator with varying thicknesses and outlet throat widths. Experimental and numerical simulation methods are employed. And the influence mechanism is analyzed through an examination of the flow field structure within the cavity of the fluid oscillator. The results indicate that increasing the thickness of the fluid oscillator leads to a higher outlet tangential velocity and deflection angle, while simultaneously decreasing the oscillation frequency. Conversely, widening the fluid oscillator throat results in a decrease in tangential velocity, deflection angle, and oscillation frequency. The performance of the fluid oscillator reaches a critical threshold when the outlet throat is square. As thickness increases, the rate of decrease in oscillation frequency and the rate of increase in tangential velocity both slow down. Furthermore, the maximum deflection angle of the airflow at the oscillator outlet reaches a critical value at a thickness of 3.375 mm, beyond which the trend of increasing deflection angle also slows. When the thickness of the oscillator is less than 3.375 mm, mass flow is the predominant driving factor for airflow deflection in the mixing chamber. In contrast, when the thickness is greater than or equal to 3.375 mm, pressure becomes the primary driving factor for this deflection.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 367-377"},"PeriodicalIF":2.5,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.euromechflu.2024.10.008
A. Hadane , V. Laurent , J.A. Redford , M. Gueguin , F. Hafid , J.-M. Ghidaglia
Quantification of the wind loading is critical in lattice tower structure engineering. In this study, we use Computational Fluid Dynamics (CFD) to investigate the aerodynamic loading on two angle members of a lattice tower structure. The presence of two bluff bodies means that one of the angle members may be masked by the other and will thus undergo less wind loading, which is called the mask effect. In the current work, we were specifically interested in investigating this effect with respect to the angles of attack of the two angle members along with the inline and normal separation distance. The four parameters yield a large parameter space which is best tackled using a sophisticated sampling method such as Latin hypercube sampling. First, we validated our RANS simulation results against experiments and Large Eddy Simulation (LES). Then, we performed two-dimensional simulations on a large range of configurations to underline the impact of the input parameters on the output variables, which are the drag and lift coefficients. To produce a tool that can be applied by a structural engineer, the database created using the time-consuming CFD simulations was used to create a correlation between the input parameters and output variables. The functions used in the correlations were designed to respect the symmetries and limiting behavior in the problem. We then investigated the performance of four different cross-validated regression models to predict the drag and lift coefficients. Once created, the regression models produce a method that does not require CFD simulations to be run. The models’ accuracy represents a significant improvement in predicting wind loads on lattice towers. While further refinement is possible, the current results provide a solid basis for engineering design purposes.
{"title":"Prediction of wind loading on masked angle members in lattice tower structures","authors":"A. Hadane , V. Laurent , J.A. Redford , M. Gueguin , F. Hafid , J.-M. Ghidaglia","doi":"10.1016/j.euromechflu.2024.10.008","DOIUrl":"10.1016/j.euromechflu.2024.10.008","url":null,"abstract":"<div><div>Quantification of the wind loading is critical in lattice tower structure engineering. In this study, we use Computational Fluid Dynamics (CFD) to investigate the aerodynamic loading on two angle members of a lattice tower structure. The presence of two bluff bodies means that one of the angle members may be masked by the other and will thus undergo less wind loading, which is called the mask effect. In the current work, we were specifically interested in investigating this effect with respect to the angles of attack of the two angle members along with the inline and normal separation distance. The four parameters yield a large parameter space which is best tackled using a sophisticated sampling method such as Latin hypercube sampling. First, we validated our RANS simulation results against experiments and Large Eddy Simulation (LES). Then, we performed two-dimensional simulations on a large range of configurations to underline the impact of the input parameters on the output variables, which are the drag and lift coefficients. To produce a tool that can be applied by a structural engineer, the database created using the time-consuming CFD simulations was used to create a correlation between the input parameters and output variables. The functions used in the correlations were designed to respect the symmetries and limiting behavior in the problem. We then investigated the performance of four different cross-validated regression models to predict the drag and lift coefficients. Once created, the regression models produce a method that does not require CFD simulations to be run. The models’ accuracy represents a significant improvement in predicting wind loads on lattice towers. While further refinement is possible, the current results provide a solid basis for engineering design purposes.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"109 ","pages":"Pages 378-391"},"PeriodicalIF":2.5,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.euromechflu.2024.10.016
Yaroslav Ignatenko , Andrey Gavrilov , Oleg B. Bocharov , Roger Aragall
Transient three-dimensional numerical simulations of power-law fluid flow in an annular channel with a diameter ratio of 1/2 were performed. The outcomes of the simulations using the URANS approach were contrasted with the results of the RANS and LES approaches for Newtonian and power-law fluids. It was demonstrated that comparable outcomes to those obtained through LES can be achieved through URANS with a reduced computational cost. It was determined that the RANS approach tends to underestimate turbulent kinetic energy and pressure losses. Parametric studies were conducted using the URANS approach, encompassing a range of Reynolds numbers () between 100 and 10,000, dimensionless rotation rates () values between 0.2 and 5, and power-law indices () between 0.4 and 1. The following flow regimes were identified: (1) flow without vortices; (2) Taylor-type toroidal vortices; (3) Görtler-type continuous spiral vortices swirling around the inner cylinder; and (4) small-scale Görtler-type vortices near both channel walls. The numerical experiments demonstrated that the rotation of the inner cylinder resulted in three notable effects: a reduction in the apparent viscosity within the vicinity of the rotating cylinder, a decline in viscous shear stresses, and the development of Görtler-type vortex structures, which contributed to an increase in energy losses. Additionally, at Reynolds numbers below 300, high rotation led to the formation of Taylor-type vortices and a reduction in pressure losses. The power law fluid requires increased rotation of the inner cylinder to form vortices and transition the flow to turbulent. When the Reynolds number is less than 300, the first mechanism is the dominant factor, resulting in a reduction in pressure loss. At Reynolds numbers of approximately 300, the first two mechanisms are in competition, with the pressure loss dependent on the power law index, . Finally, at Reynolds numbers greater than 300, secondary vortex structures, such as Görtler vortices, become the dominant factor, leading to an increase in pressure loss with rotation.
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