Efficient and compact axial compressors are currently undergoing rapid development for use in micro-cooling systems and small-scale vehicles. Limited experimental work concentrates on the inner flow field of the compressors working at such low Reynolds numbers (Re ~ 104). This study examines the vortical structures and the resulting turbulence production in the transitional flow over a C4 compressor blade at a Reynolds number Re of 24000, with a specific focus on the impact of tip clearance. The particle image velocimetry measurements reveal the tip flow structures in detail, including the tip leakage vortex (TLV) and its induced complex vortical structures. The tip secondary flow at the low Reynolds number can be divided as the tip leakage flow/vortex and transitional boundary layer both at the end walls and the blade surfaces. The TLV propagates at the highest spanwise positions and farthest pitchwise positions at the middle tip gap size (τ/C = 3%) for the three tip gap sizes investigated. The tip flow fluctuations decrease from τ/C = 5% to τ/C = 3% and then increase from τ/C = 3% to τ/C = 1%. The spatial distribution, streamwise evolution, and individual Reynolds normal stress components contributing to the turbulent kinetic energy (TKE) are discussed. The primary contributors to the turbulence generation are examined to elucidate the flow mechanism leading to the distinct anisotropic turbulence structure in the tip region with various tip gap sizes.
{"title":"Effect of Tip Gap Size On the Tip Flow Structure and Turbulence Generation in a Low Reynolds Number Compressor Cascade","authors":"Lei Shi, Hongwei Ma, Huajie Wang, Tianyou Wang","doi":"10.1115/1.4065295","DOIUrl":"https://doi.org/10.1115/1.4065295","url":null,"abstract":"\u0000 Efficient and compact axial compressors are currently undergoing rapid development for use in micro-cooling systems and small-scale vehicles. Limited experimental work concentrates on the inner flow field of the compressors working at such low Reynolds numbers (Re ~ 104). This study examines the vortical structures and the resulting turbulence production in the transitional flow over a C4 compressor blade at a Reynolds number Re of 24000, with a specific focus on the impact of tip clearance. The particle image velocimetry measurements reveal the tip flow structures in detail, including the tip leakage vortex (TLV) and its induced complex vortical structures. The tip secondary flow at the low Reynolds number can be divided as the tip leakage flow/vortex and transitional boundary layer both at the end walls and the blade surfaces. The TLV propagates at the highest spanwise positions and farthest pitchwise positions at the middle tip gap size (τ/C = 3%) for the three tip gap sizes investigated. The tip flow fluctuations decrease from τ/C = 5% to τ/C = 3% and then increase from τ/C = 3% to τ/C = 1%. The spatial distribution, streamwise evolution, and individual Reynolds normal stress components contributing to the turbulent kinetic energy (TKE) are discussed. The primary contributors to the turbulence generation are examined to elucidate the flow mechanism leading to the distinct anisotropic turbulence structure in the tip region with various tip gap sizes.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"48 S1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140715909","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}
Analysis on eddy motion is the essential method for understanding viscous flows. Compared with the current methods to identify the vortex, the study presents a method to investigate vortex structures based on topological analysis and nonlinear dynamics, and establishes a connection between the direction of the vortex and the real eigenvalue of the velocity gradient tensor. The study highlights the significance of the real and imaginary parts of complex eigenvalues in vortex development, wherein the real part indicates topological stability, and the imaginary part represents swirling strength, contributing to get the characters of the viscous flows.
{"title":"Vortex Identification Method Based On Topological Analysis and Velocity Gradient Invariance","authors":"Xiaoyun Qu, Rong He, Tong Wang","doi":"10.1115/1.4065293","DOIUrl":"https://doi.org/10.1115/1.4065293","url":null,"abstract":"\u0000 Analysis on eddy motion is the essential method for understanding viscous flows. Compared with the current methods to identify the vortex, the study presents a method to investigate vortex structures based on topological analysis and nonlinear dynamics, and establishes a connection between the direction of the vortex and the real eigenvalue of the velocity gradient tensor. The study highlights the significance of the real and imaginary parts of complex eigenvalues in vortex development, wherein the real part indicates topological stability, and the imaginary part represents swirling strength, contributing to get the characters of the viscous flows.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"31 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140714555","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}
P. Perali, F. Hauville, A. Leroyer, J. Astolfi, Michel Visonneau
The hydroelastic response of a flexible NACA 0015 hydrofoil is investigated for both wetted and cavitating flow conditions. Computational Fluid Dynamics (CFD) analysis are performed using a fully implicit coupling between the ISIS-CFD solver (developed by the METHRIC team at Ecole Centrale de Nantes) and a modal approach for the structure. The RANS (Reynolds Averaged Navier-Stokes) solver is first validated for wetted and cavitating flow conditions around a similar rigid hydrofoil, with experimental results carried out at the hydrodynamic tunnel of the French Naval Academy, including lift and drag measurements and high speed camera images. Then the numerical predictions for the flexible hydrofoil response are compared with experimental bending shapes and vibrations amplitudes, with a focus on cavitating flow conditions. For wetted flow conditions, numerical results show a good agreement with the experiments, for both rigid and flexible hydrofoils. For cavitating flow conditions, the hydroelastic response is dominated by vibrations at the hydrofoil modal frequencies and the re-entrant jet instability frequency. For the lowest values of the cavitation parameter, a large amplitude peak is experimentally observed in the frequency response spectra, due to lock-in between the first modal frequency and the re-entrant jet frequency. Strong harmonics of this dominant peak also appear in the spectra, revealing a non-linear response of the hydrofoil. While the amplitudes of vibrations are well predicted by the computations, the frequency lock-in observed in the experiments is not captured by the numerical model.
{"title":"Experimental and Numerical Study of the Flow Around Rigid and Flexible Hydrofoils for Wetted and Cavitating Flow Conditions","authors":"P. Perali, F. Hauville, A. Leroyer, J. Astolfi, Michel Visonneau","doi":"10.1115/1.4065296","DOIUrl":"https://doi.org/10.1115/1.4065296","url":null,"abstract":"\u0000 The hydroelastic response of a flexible NACA 0015 hydrofoil is investigated for both wetted and cavitating flow conditions. Computational Fluid Dynamics (CFD) analysis are performed using a fully implicit coupling between the ISIS-CFD solver (developed by the METHRIC team at Ecole Centrale de Nantes) and a modal approach for the structure. The RANS (Reynolds Averaged Navier-Stokes) solver is first validated for wetted and cavitating flow conditions around a similar rigid hydrofoil, with experimental results carried out at the hydrodynamic tunnel of the French Naval Academy, including lift and drag measurements and high speed camera images. Then the numerical predictions for the flexible hydrofoil response are compared with experimental bending shapes and vibrations amplitudes, with a focus on cavitating flow conditions. For wetted flow conditions, numerical results show a good agreement with the experiments, for both rigid and flexible hydrofoils. For cavitating flow conditions, the hydroelastic response is dominated by vibrations at the hydrofoil modal frequencies and the re-entrant jet instability frequency. For the lowest values of the cavitation parameter, a large amplitude peak is experimentally observed in the frequency response spectra, due to lock-in between the first modal frequency and the re-entrant jet frequency. Strong harmonics of this dominant peak also appear in the spectra, revealing a non-linear response of the hydrofoil. While the amplitudes of vibrations are well predicted by the computations, the frequency lock-in observed in the experiments is not captured by the numerical model.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"14 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140715603","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}
Yang Chen, E. Avital, John Williams, Srimanta Santra, Avraham Seifert
Aerofoil leading-edge fluid-blowing control is computationally studied to improve aerodynamic efficiency. The fluid injection momentum coefficient Cu (the ratio of injection to incoming square velocities times the slot's width to aerofoil's half chord-length), varies from 0.5% to 5.4%. Both static and dynamic conditions are investigated for a NACA0018 aerofoil at low speed and Reynolds number of 250k based on the aerofoil's chord-length. The aerofoil is dynamically pitched at at a reduced frequency (the pitching tangential speed to the free-stream speed ratio), varying between 0.0078 to 0.2. RANS and Unsteady RANS (URANS) are used in the simulations as based on the Transition SST and Spalart-Allmaras models, generally achieving good agreement with experimental results in lift and drag coefficients and in the pressure coefficient distributions along the aerofoil. It is found that oscillating the aerofoil can delay stall, as expected, in dynamic stall. Leading-edge blowing control can also significantly delay stall both in static and dynamic conditions as long as sufficient momentum is applied to the control. On the other hand, for a small Cu such as 0.5%, the leading-edge control worsens the performance and hastens the appearance of stall in both static and dynamic conditions. The aerofoil's oscillation reduces the differences between pitch-up and pitch-down aerodynamic performances. Detailed analysis of vorticity, pressure, velocity and streamline contours are given to provide plausible explanations and insight to the flow.
{"title":"Effects of Leading-Edge Blowing Control and Reduced Frequency on Aerofoil Aerodynamic Performances","authors":"Yang Chen, E. Avital, John Williams, Srimanta Santra, Avraham Seifert","doi":"10.1115/1.4065294","DOIUrl":"https://doi.org/10.1115/1.4065294","url":null,"abstract":"\u0000 Aerofoil leading-edge fluid-blowing control is computationally studied to improve aerodynamic efficiency. The fluid injection momentum coefficient Cu (the ratio of injection to incoming square velocities times the slot's width to aerofoil's half chord-length), varies from 0.5% to 5.4%. Both static and dynamic conditions are investigated for a NACA0018 aerofoil at low speed and Reynolds number of 250k based on the aerofoil's chord-length. The aerofoil is dynamically pitched at at a reduced frequency (the pitching tangential speed to the free-stream speed ratio), varying between 0.0078 to 0.2. RANS and Unsteady RANS (URANS) are used in the simulations as based on the Transition SST and Spalart-Allmaras models, generally achieving good agreement with experimental results in lift and drag coefficients and in the pressure coefficient distributions along the aerofoil. It is found that oscillating the aerofoil can delay stall, as expected, in dynamic stall. Leading-edge blowing control can also significantly delay stall both in static and dynamic conditions as long as sufficient momentum is applied to the control. On the other hand, for a small Cu such as 0.5%, the leading-edge control worsens the performance and hastens the appearance of stall in both static and dynamic conditions. The aerofoil's oscillation reduces the differences between pitch-up and pitch-down aerodynamic performances. Detailed analysis of vorticity, pressure, velocity and streamline contours are given to provide plausible explanations and insight to the flow.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"16 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140712912","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 circular synthetic jet (SJ) for different dimensionless stroke lengths and at Reynolds number Re=5000 was investigated in this paper. Particle image velocimetry was used. The flow was measured at a distance of 240 mm from the orifice and this area was divided into two fields of view (FOV). The parameter fields were created by the injunction of these two FOVs. The time-averaged velocity, turbulent kinetic energy (TKE), turbulence intensity, vorticity field, centreline, and profiles of SJ were presented and discussed. Additionally, the jet half-width of SJ was investigated. The data discontinuity at a line of the FOVs was discussed. The impact of the dimensionless stroke lengths on the parameters of SJ at Re=5000 was discussed.
{"title":"Time-Averaged Parameters of the Circular Synthetic Jet for Different Dimensionless Stroke Length","authors":"Emil Smyk, P. Gil, Joanna Wilk","doi":"10.1115/1.4065228","DOIUrl":"https://doi.org/10.1115/1.4065228","url":null,"abstract":"\u0000 The circular synthetic jet (SJ) for different dimensionless stroke lengths and at Reynolds number Re=5000 was investigated in this paper. Particle image velocimetry was used. The flow was measured at a distance of 240 mm from the orifice and this area was divided into two fields of view (FOV). The parameter fields were created by the injunction of these two FOVs. The time-averaged velocity, turbulent kinetic energy (TKE), turbulence intensity, vorticity field, centreline, and profiles of SJ were presented and discussed. Additionally, the jet half-width of SJ was investigated. The data discontinuity at a line of the FOVs was discussed. The impact of the dimensionless stroke lengths on the parameters of SJ at Re=5000 was discussed.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"702 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140749162","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}
Efforts are made to elucidate a comprehensive analysis of entrainment dynamics triggered by a couple of unequal rotational fluxes within a viscous pool. Cylindrical rollers are employed to establish the rotational field. The top drum is equally submerged in both phases and also it provides a constant rotational inertia. Concomitantly, the bottom roller is completely submerged in the viscous bath, and it provides an unequal rotational strength in reference to top roller. The average rotational strength of both rollers is measured using average Capillary number (Ca)avg. The entrainment phenomenon is strongly influenced by both Caavg and gap between the rollers (W/D). Characterization of entrained filament is elucidated by predicting the horizontal distance (L*), radial distance (r*), temporal vertical displacement (Y*), maximum vertical displacement (Ymax*), width (H*), and location of V-shaped diversion (∅s*). Characterization of liquid tip is performed by measuring the travel rate (Y*) along periphery of drum from receding to advancing junction. Air mass ejection from filament tip is analysed by estimating the 1st bubble ejection time (t1st*), volume of accumulated of ejected gaseous masses (v*), and ejection frequency (f). Furthermore, the effect of gravitational pull (specified by Archimedes number, Ar) and viscous drag (measured by Morton number, Mo) on the pattern of entrained air filament is described. Lastly, an analytical framework is established to determine the width of the V-junction by balancing the important influencing forces, which are strongly affecting the filament. Analytical observations show a satisfactory agreement with numerical findings.
本研究致力于全面分析粘性水池中两个不相等的旋转通量所引发的夹带动力学。圆柱滚筒用于建立旋转场。顶部滚筒同样浸没在两相中，并提供恒定的转动惯量。与此同时，底部滚筒完全浸没在粘液池中，与顶部滚筒相比，底部滚筒的旋转强度不等。两个辊子的平均旋转强度用平均毛细管数 (Ca)avg 来测量，夹带现象受 Caavg 和辊子间隙 (W/D) 的影响很大。通过预测水平距离 (L*)、径向距离 (r*)、时间垂直位移 (Y*)、最大垂直位移 (Ymax*)、宽度 (H*) 和 V 形分流位置 (∅s*)，阐明了夹带细丝的特征。通过测量滚筒外围从后退交界处到前进交界处的移动速度 (Y*)，可以确定液丝尖端的特征。通过估算第一个气泡喷射时间 (t1st*)、喷射气态物质的累积体积 (v*) 和喷射频率 (f)，分析了从丝尖喷射出的气态物质。此外，还描述了引力（以阿基米德数 Ar 表示）和粘性阻力（以莫顿数 Mo 表示）对夹带气丝形态的影响。最后，建立了一个分析框架，通过平衡对气丝有强烈影响的重要影响力来确定 V 形交界处的宽度。分析观测结果与数值研究结果的一致性令人满意。
{"title":"Influence of a Pair of Unequal Rotational Fluxes On Entrained Gaseous Filament","authors":"Santosh Kumar Panda, B. Rana","doi":"10.1115/1.4065263","DOIUrl":"https://doi.org/10.1115/1.4065263","url":null,"abstract":"\u0000 Efforts are made to elucidate a comprehensive analysis of entrainment dynamics triggered by a couple of unequal rotational fluxes within a viscous pool. Cylindrical rollers are employed to establish the rotational field. The top drum is equally submerged in both phases and also it provides a constant rotational inertia. Concomitantly, the bottom roller is completely submerged in the viscous bath, and it provides an unequal rotational strength in reference to top roller. The average rotational strength of both rollers is measured using average Capillary number (Ca)avg. The entrainment phenomenon is strongly influenced by both Caavg and gap between the rollers (W/D). Characterization of entrained filament is elucidated by predicting the horizontal distance (L*), radial distance (r*), temporal vertical displacement (Y*), maximum vertical displacement (Ymax*), width (H*), and location of V-shaped diversion (∅s*). Characterization of liquid tip is performed by measuring the travel rate (Y*) along periphery of drum from receding to advancing junction. Air mass ejection from filament tip is analysed by estimating the 1st bubble ejection time (t1st*), volume of accumulated of ejected gaseous masses (v*), and ejection frequency (f). Furthermore, the effect of gravitational pull (specified by Archimedes number, Ar) and viscous drag (measured by Morton number, Mo) on the pattern of entrained air filament is described. Lastly, an analytical framework is established to determine the width of the V-junction by balancing the important influencing forces, which are strongly affecting the filament. Analytical observations show a satisfactory agreement with numerical findings.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"839 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140749363","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}
This paper investigates the effects of Reynolds number on the wake characteristics of a notchback Ahmed body with effective backlight angle, βe = 17.8°. The Reynolds number based on the body height was varied from 5 × 103 to 5 × 104. Prior to the Reynolds number investigation, a Reynolds-Averaged Navier-Stokes (RANS) model assessment was performed using nine turbulence models consisting of one- and two-equation eddy-viscosity models and second moment closure models. The standard Spalart-Allmaras model was the only model that accurately predicted the asymmetric time-averaged wake topology, as reported in previous studies, for the βe = 17.8° notchback Ahmed body at Re = 5 × 104. The drag coefficient decreased with increasing Reynolds number, while the lift coefficient remained constant for Re = 1 × 104. The wake structure exhibited three regimes: symmetric (Re = 1 × 104), transitionally asymmetric (1 × 104< Re = 3.5 × 104) and fully asymmetric (Re ≤ 3.5 × 104) states. The wake asymmetry was attributed to an imbalance in entrainment from the side and asymmetric separation from the roof and the C-pillars of the body. The tilting and stretching terms in the vorticity transport equation were used to provide insight into the source of asymmetry in the vorticity field around the body.
{"title":"Effects of Reynolds Number On the Wake Characteristics of a Notchback Ahmed Body","authors":"Newton F. Ouedraogo, E. Essel","doi":"10.1115/1.4065225","DOIUrl":"https://doi.org/10.1115/1.4065225","url":null,"abstract":"\u0000 This paper investigates the effects of Reynolds number on the wake characteristics of a notchback Ahmed body with effective backlight angle, βe = 17.8°. The Reynolds number based on the body height was varied from 5 × 103 to 5 × 104. Prior to the Reynolds number investigation, a Reynolds-Averaged Navier-Stokes (RANS) model assessment was performed using nine turbulence models consisting of one- and two-equation eddy-viscosity models and second moment closure models. The standard Spalart-Allmaras model was the only model that accurately predicted the asymmetric time-averaged wake topology, as reported in previous studies, for the βe = 17.8° notchback Ahmed body at Re = 5 × 104. The drag coefficient decreased with increasing Reynolds number, while the lift coefficient remained constant for Re = 1 × 104. The wake structure exhibited three regimes: symmetric (Re = 1 × 104), transitionally asymmetric (1 × 104< Re = 3.5 × 104) and fully asymmetric (Re ≤ 3.5 × 104) states. The wake asymmetry was attributed to an imbalance in entrainment from the side and asymmetric separation from the roof and the C-pillars of the body. The tilting and stretching terms in the vorticity transport equation were used to provide insight into the source of asymmetry in the vorticity field around the body.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"6 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140793623","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}
Chan-Soo Kim, Taehoon Kim, Hwalong You, Minchang Kim, Yong-Shik Han, Byung-Il Choi, Kyuhyung Do
Recently, cryogenic fluids are widely transported via cargo ships as energy sources. The generation of boil-off gas (BOG) is inevitable in a cryogenic container due to the large temperature difference. Therefore, accurately analyzing the boil-off gas over time is essential to increase delivery efficiency and ensure tank safety. However, predicting the boil-off rate is not a simple task, as both experiment and calculation require a significant amount of time. In this study, a simple predictive method is developed for simulating a 1/50 scaled model tank. The method consists of steady and quasi-unsteady calculations. Steady calculations are performed to establish a correlation between LN2 level and inner-wall temperature. Quasi-unsteady calculations simulate BOG over time by changing the inner-wall boundary conditions. This method can help engineers effectively evaluate the insulation performance of a cryogenic container in a short time and provide guidelines for simulating a real scale tank.
{"title":"A Simple Predictive Method for Estimating Bor Over Time in a Cryogenic Container","authors":"Chan-Soo Kim, Taehoon Kim, Hwalong You, Minchang Kim, Yong-Shik Han, Byung-Il Choi, Kyuhyung Do","doi":"10.1115/1.4065220","DOIUrl":"https://doi.org/10.1115/1.4065220","url":null,"abstract":"\u0000 Recently, cryogenic fluids are widely transported via cargo ships as energy sources. The generation of boil-off gas (BOG) is inevitable in a cryogenic container due to the large temperature difference. Therefore, accurately analyzing the boil-off gas over time is essential to increase delivery efficiency and ensure tank safety. However, predicting the boil-off rate is not a simple task, as both experiment and calculation require a significant amount of time. In this study, a simple predictive method is developed for simulating a 1/50 scaled model tank. The method consists of steady and quasi-unsteady calculations. Steady calculations are performed to establish a correlation between LN2 level and inner-wall temperature. Quasi-unsteady calculations simulate BOG over time by changing the inner-wall boundary conditions. This method can help engineers effectively evaluate the insulation performance of a cryogenic container in a short time and provide guidelines for simulating a real scale tank.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":"167 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140785832","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}
This article investigates the laminar flow of power-law fluids through two identical porous square cylinders in a side-by-side configuration within a channel. The effects of three critical parameters, power-law index (n), Darcy number (Da), and gap ratio (g/W) on the flow behavior are explored for ranges of g/W=0.5-5, n=0.4-0.8, and Da=10-6-10-2, respectively. Two flow conditions are considered: first, for a creeping flow (unseparated flow) at Re=1 where only Darcy's law is applicable; second, for a viscous dominant flow at Re=100, where Darcy-Forchheimer extended model is exercised. The flow patterns behind the porous square cylinders are analyzed using streamlines, velocity profiles, pressure distribution curves, and vorticity structural parameters (Г). In low permeability levels, the flow exhibits an irregular non-periodic vortex shedding characterized by a single large vortex street far-off the downstream for g/W=0.5. However, synchronized wake patterns were observed in either anti-phase or in-phase modes for higher gap ratios. The presence of a jet-like flow in the square cylinders' gap section significantly influences unsteady wake patterns. The impact of g/W, power-law index, and permeability on drag is also examined. The study findings provide valuable insights into flow behavior and offer a potential approach for improving the design of fluidic systems that involve porous cylinders.
{"title":"Influence of Permeability and Shear-Thinning Behavior On the Hydrodynamics Flow Features Around Porous Square Cylinders","authors":"S. Jamshed, A. Dhiman","doi":"10.1115/1.4065150","DOIUrl":"https://doi.org/10.1115/1.4065150","url":null,"abstract":"\u0000 This article investigates the laminar flow of power-law fluids through two identical porous square cylinders in a side-by-side configuration within a channel. The effects of three critical parameters, power-law index (n), Darcy number (Da), and gap ratio (g/W) on the flow behavior are explored for ranges of g/W=0.5-5, n=0.4-0.8, and Da=10-6-10-2, respectively. Two flow conditions are considered: first, for a creeping flow (unseparated flow) at Re=1 where only Darcy's law is applicable; second, for a viscous dominant flow at Re=100, where Darcy-Forchheimer extended model is exercised. The flow patterns behind the porous square cylinders are analyzed using streamlines, velocity profiles, pressure distribution curves, and vorticity structural parameters (Г). In low permeability levels, the flow exhibits an irregular non-periodic vortex shedding characterized by a single large vortex street far-off the downstream for g/W=0.5. However, synchronized wake patterns were observed in either anti-phase or in-phase modes for higher gap ratios. The presence of a jet-like flow in the square cylinders' gap section significantly influences unsteady wake patterns. The impact of g/W, power-law index, and permeability on drag is also examined. The study findings provide valuable insights into flow behavior and offer a potential approach for improving the design of fluidic systems that involve porous cylinders.","PeriodicalId":504378,"journal":{"name":"Journal of Fluids Engineering","volume":" 15","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140216009","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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