Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2326
A. K. Mali, T. Jana, M. Kaushik, S. Thanigaiarasu
This study experimentally evaluated the mixing augmentation of twin tabs mounted along a diameter at the outlet of a convergent-divergent Mach 1.62 circular nozzle. The usefulness of the plain and grooved tabs is examined at various expansion levels prevailing at nozzle outlet. The tab's performance is assessed through pitot pressure distribution measured along and perpendicular to the jet centerline at different nozzle pressure ratios (NPRs). The shadowgraph technique visualized the shocks and expansion fans in uncontrolled and controlled jets. With the introduction of uncorrugated or plain tabs at the nozzle outlet operating under overexpanded conditions corresponding to NPR 4, the supersonic length (SL) was decreased only by 35.4%. On the other hand, the corrugated or grooved tabs under similar conditions decreased the SL substantially. Interestingly, the performance of grooved tabs was best at underexpanded conditions associated with NPR 6, where the SL was reduced by about 88%. The pressure profiles also established the superiority of tabs with grooved edges in mixing augmentation without introducing any significant asymmetry to the flow field. In addition, the Shadowgraph images also confirmed the weakening of shock strength and reduction of shock-cell length in the case of grooved tabs at the nozzle exit compared to the plain
{"title":"Manipulation of Supersonic Jet using Grooved Tabs","authors":"A. K. Mali, T. Jana, M. Kaushik, S. Thanigaiarasu","doi":"10.47176/jafm.17.05.2326","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2326","url":null,"abstract":"This study experimentally evaluated the mixing augmentation of twin tabs mounted along a diameter at the outlet of a convergent-divergent Mach 1.62 circular nozzle. The usefulness of the plain and grooved tabs is examined at various expansion levels prevailing at nozzle outlet. The tab's performance is assessed through pitot pressure distribution measured along and perpendicular to the jet centerline at different nozzle pressure ratios (NPRs). The shadowgraph technique visualized the shocks and expansion fans in uncontrolled and controlled jets. With the introduction of uncorrugated or plain tabs at the nozzle outlet operating under overexpanded conditions corresponding to NPR 4, the supersonic length (SL) was decreased only by 35.4%. On the other hand, the corrugated or grooved tabs under similar conditions decreased the SL substantially. Interestingly, the performance of grooved tabs was best at underexpanded conditions associated with NPR 6, where the SL was reduced by about 88%. The pressure profiles also established the superiority of tabs with grooved edges in mixing augmentation without introducing any significant asymmetry to the flow field. In addition, the Shadowgraph images also confirmed the weakening of shock strength and reduction of shock-cell length in the case of grooved tabs at the nozzle exit compared to the plain","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141038247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2347
†. A.R.Davari, S. Hadavand
Acoustic measurements were performed using microphone downstream of a 2-D wind turbine blade section in wind tunnel. The experiments have been carried out in both static and oscillatory pitching cases. The latter is usually experienced by the blades in actual circumstances. The microphone was 1.5 chords downstream of the airfoil and the measurements were conducted at three transverse positions, i.e. behind the trailing edge, midway between the trailing edge and the ground and very close to the ground. A CFD simulation of the flowfield has also been conducted using Fluent to correlate the acoustic behavior to the phenomena observed in the flowfield around the blade. The results show that the acoustic noise heard by a listener located on the ground is higher and stronger than that positioned downstream of the trailing edge, showing the ground effect on acoustic noise reverberation. The aerodynamic noise heard by the listener, changes from a treble to bass sound as the angle of attack increases. Beyond stall, the flow is dominated by the vortices shed into wake and the acoustic noises would be at very low frequencies which would result in a bass sound accompanied by structural vibration. In high angle of attack range, such noises can hardly be heard by a normal person but have a very destructive role on blade structure.
{"title":"Acoustic Noise Measurement Downstream of an Oscillating Wind Turbine Blade Section","authors":"†. A.R.Davari, S. Hadavand","doi":"10.47176/jafm.17.05.2347","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2347","url":null,"abstract":"Acoustic measurements were performed using microphone downstream of a 2-D wind turbine blade section in wind tunnel. The experiments have been carried out in both static and oscillatory pitching cases. The latter is usually experienced by the blades in actual circumstances. The microphone was 1.5 chords downstream of the airfoil and the measurements were conducted at three transverse positions, i.e. behind the trailing edge, midway between the trailing edge and the ground and very close to the ground. A CFD simulation of the flowfield has also been conducted using Fluent to correlate the acoustic behavior to the phenomena observed in the flowfield around the blade. The results show that the acoustic noise heard by a listener located on the ground is higher and stronger than that positioned downstream of the trailing edge, showing the ground effect on acoustic noise reverberation. The aerodynamic noise heard by the listener, changes from a treble to bass sound as the angle of attack increases. Beyond stall, the flow is dominated by the vortices shed into wake and the acoustic noises would be at very low frequencies which would result in a bass sound accompanied by structural vibration. In high angle of attack range, such noises can hardly be heard by a normal person but have a very destructive role on blade structure.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141039764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2231
J. Wang, X. Shi, Q. Zhang, J. Chang
In this manuscript, the vortex generated by the main frequency excitation of the shedding vortex at various attack angles is investigated by employing the synthetic jet control technique. We also analyzed the impact of the vortex structure on the fled flow around the wing and the spectral characteristics corresponding to the vortex. The dominant frequency and harmonic frequency corresponding to the wave rule of the shedding vortex at various attack angles without the absence of a synthetic jet are selected as the synthetic jet excitation frequency. The results indicate that under the excitation of fixed frequency synthetic jet, the shape of the shedding vortex in the flow field turns correspondingly. Compared with the flow field without jet excitation, it is found that the field with the jet at most attack angles is stable in 2S (Single) mode, and the flow field at a small attack angle is stable in a chaotic state. The angle of attack with a chaotic state is delayed by adding a jet, which makes the curves and corresponding spectral characteristics more orderly. At a defined attack angle, the combined frequency synthetic jet will cause the lift coefficient to fluctuate regularly. At this time, the multiple small-scale vortex structures lead to lift reduction.
{"title":"Effect of Synthetic Jet on NACA0012 Airfoil Vortex Structure and Aerodynamic Characteristics","authors":"J. Wang, X. Shi, Q. Zhang, J. Chang","doi":"10.47176/jafm.17.05.2231","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2231","url":null,"abstract":"In this manuscript, the vortex generated by the main frequency excitation of the shedding vortex at various attack angles is investigated by employing the synthetic jet control technique. We also analyzed the impact of the vortex structure on the fled flow around the wing and the spectral characteristics corresponding to the vortex. The dominant frequency and harmonic frequency corresponding to the wave rule of the shedding vortex at various attack angles without the absence of a synthetic jet are selected as the synthetic jet excitation frequency. The results indicate that under the excitation of fixed frequency synthetic jet, the shape of the shedding vortex in the flow field turns correspondingly. Compared with the flow field without jet excitation, it is found that the field with the jet at most attack angles is stable in 2S (Single) mode, and the flow field at a small attack angle is stable in a chaotic state. The angle of attack with a chaotic state is delayed by adding a jet, which makes the curves and corresponding spectral characteristics more orderly. At a defined attack angle, the combined frequency synthetic jet will cause the lift coefficient to fluctuate regularly. At this time, the multiple small-scale vortex structures lead to lift reduction.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141038394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2169
Z. Wang, Y. Zhu, Q. Yuan, W. B. Gu, X. B. Xie
Regarding the airfoil optimization design of multi-rotor unmanned aerial vehicles, this paper proposes an integral airfoil design method based on upper airfoil contour optimization. Firstly, by designing concave descent input curves with 0-1 distribution, the upper arc of different optimized airfoils is obtained using the Tangent circles method. Secondly, an integral airfoil generation method is developed after establishing the middle arc. As the upper and lower arcs of different shapes are randomly combined, various airfoil profiles are obtained by random assortment. Finally, the effectiveness and accuracy of the designed airfoil are validated through Python programming. The airfoil is generated by the XFOIL program, and the optimal airfoil is output with a lift-to-drag ratio as the target. Meanwhile, an accurate Fluent analysis model is established, and a comparison verification is conducted on the data with the attack angle falling within [-8.02, 12.04] and lift-to-drag ratio falling within [- 50, 100]. After Fluent modeling of the designed airfoil, the Euclidean distance between the calculated angle-lift-drag ratio data curve and the data curve tested by the wind tunnel is 0.0331, while the Euclidean distance between the simulated data in the literature and the wind tunnel data is 0.0408. It indicates that our precise model achieves 18.9% higher accuracy than the literature model. Testing and verification results indicate that our designed airfoil based on upper arc optimization and its corresponding airfoil library can meet the design requirements for the aerodynamic performance of airfoils in practical applications. It provides a valuable reference for the development of airfoil design, optimization, and generation methods.
{"title":"Integral Airfoil Generation of Multi-rotor Aircraft Based on Optimization of Upper Wing Contour and CFD Simulation","authors":"Z. Wang, Y. Zhu, Q. Yuan, W. B. Gu, X. B. Xie","doi":"10.47176/jafm.17.05.2169","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2169","url":null,"abstract":"Regarding the airfoil optimization design of multi-rotor unmanned aerial vehicles, this paper proposes an integral airfoil design method based on upper airfoil contour optimization. Firstly, by designing concave descent input curves with 0-1 distribution, the upper arc of different optimized airfoils is obtained using the Tangent circles method. Secondly, an integral airfoil generation method is developed after establishing the middle arc. As the upper and lower arcs of different shapes are randomly combined, various airfoil profiles are obtained by random assortment. Finally, the effectiveness and accuracy of the designed airfoil are validated through Python programming. The airfoil is generated by the XFOIL program, and the optimal airfoil is output with a lift-to-drag ratio as the target. Meanwhile, an accurate Fluent analysis model is established, and a comparison verification is conducted on the data with the attack angle falling within [-8.02, 12.04] and lift-to-drag ratio falling within [- 50, 100]. After Fluent modeling of the designed airfoil, the Euclidean distance between the calculated angle-lift-drag ratio data curve and the data curve tested by the wind tunnel is 0.0331, while the Euclidean distance between the simulated data in the literature and the wind tunnel data is 0.0408. It indicates that our precise model achieves 18.9% higher accuracy than the literature model. Testing and verification results indicate that our designed airfoil based on upper arc optimization and its corresponding airfoil library can meet the design requirements for the aerodynamic performance of airfoils in practical applications. It provides a valuable reference for the development of airfoil design, optimization, and generation methods.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141055240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2287
M. Zhao, †. D.Liu, J. Hou, X. Zhang, S. Li
As an important control element in steam heating piping systems, the safety and stability of inverted bucket steam valves determine the reliable operation of the system. Therefore, it is necessary to investigate the acoustic mechanism of inverted bucket steam valves. Aiming at the difficulty of numerical simulation in accurately predicting the aerodynamic noise of inverted bucket steam valves, this paper proposes a new method for simulating the aerodynamic noise of inverted bucket steam valves based on multiband analysis (LES). The flow field of the inverted bucket steam valve is numerically simulated using the LES method to obtain wall pressure pulsation information and fluid velocity pulsation information, which are used as excitation sources for acoustic simulation. The characteristics of dipole and quadrupole sound sources were obtained by applying the FW-H method and experimentally verified. The results show that a new multifrequency band analysis method for inverted bucket steam valves is effective by comparing the numerical simulation results, in which the dipole source dominates in the low-frequency band, in the medium frequency range, the quadrupole source outperforms the dipole source, but in the high frequency range, the quadrupole source is dominant. The experimental results are in good agreement with the simulation results, and the correctness of the numerical simulation is confirmed by the fact that there is less than a 3% difference between the findings of the numerical simulation and the experimental data.
作为蒸汽加热管道系统中的重要控制元件，倒吊桶式蒸汽阀门的安全性和稳定性决定了系统的可靠运行。因此，有必要对倒吊桶式蒸汽阀门的声学机理进行研究。针对数值模拟难以准确预测倒吊桶式蒸汽阀门气动噪声的问题，本文提出了一种基于多频带分析（LES）的倒吊桶式蒸汽阀门气动噪声模拟新方法。利用 LES 方法对倒吊桶式蒸汽阀的流场进行数值模拟，获得壁面压力脉动信息和流体速度脉动信息，并将其作为声学模拟的激励源。应用 FW-H 方法获得了偶极子和四极子声源的特性，并进行了实验验证。结果表明，通过比较数值模拟结果，一种新的倒斗蒸汽阀门多频带分析方法是有效的，其中偶极声源在低频段占主导地位，在中频范围内，四极声源优于偶极声源，但在高频范围内，四极声源占主导地位。实验结果与模拟结果十分吻合，数值模拟结果与实验数据的差异小于 3%，这证实了数值模拟的正确性。
{"title":"Numerical Simulation of Inverted Bucket Steam Valve Noise based on Multiband Analysis","authors":"M. Zhao, †. D.Liu, J. Hou, X. Zhang, S. Li","doi":"10.47176/jafm.17.05.2287","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2287","url":null,"abstract":"As an important control element in steam heating piping systems, the safety and stability of inverted bucket steam valves determine the reliable operation of the system. Therefore, it is necessary to investigate the acoustic mechanism of inverted bucket steam valves. Aiming at the difficulty of numerical simulation in accurately predicting the aerodynamic noise of inverted bucket steam valves, this paper proposes a new method for simulating the aerodynamic noise of inverted bucket steam valves based on multiband analysis (LES). The flow field of the inverted bucket steam valve is numerically simulated using the LES method to obtain wall pressure pulsation information and fluid velocity pulsation information, which are used as excitation sources for acoustic simulation. The characteristics of dipole and quadrupole sound sources were obtained by applying the FW-H method and experimentally verified. The results show that a new multifrequency band analysis method for inverted bucket steam valves is effective by comparing the numerical simulation results, in which the dipole source dominates in the low-frequency band, in the medium frequency range, the quadrupole source outperforms the dipole source, but in the high frequency range, the quadrupole source is dominant. The experimental results are in good agreement with the simulation results, and the correctness of the numerical simulation is confirmed by the fact that there is less than a 3% difference between the findings of the numerical simulation and the experimental data.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141053421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2270
Z. Y. Li, †. Y.G.Yu, A. Chen
Modular charging is an advanced technique designed to meet the requirements of auto-loading artillery, whereby granular propellants are stored within modular cartridges that are loaded into the gun chamber. This study employed an extended coupled computational fluid dynamics-discrete element method (CFD-DEM) approach to investigate the gas-particle flow within modular charges. After model validation, we analyzed the distribution characteristics, velocity, coordination number, and orientation of cylindrical pellets in a simulator chamber. Four different loading positions for modular cartridges were examined to assess their impact on particle distribution. Numerical simulations revealed a combination of gentle, horizontal, and steep slopes in the particle distribution. The maximum particle velocity experienced a rapid increase during the initial phase, followed by a zigzag decline after reaching its peak. High-coordination number particles tended to accumulate primarily in the middle layer of steep accumulation. Additionally, the particles exhibited an inverted V-shape orientation range from 0° to 180°, suggesting their tendency to assume upright positions. This established model significantly enhanced our understanding of particle distribution following module cartridge rupture and provided valuable guidance for optimizing the design of large-caliber artillery charges.
模块化装药是为满足自动装填火炮的要求而设计的一种先进技术，它将颗粒状推进剂储存在模块化弹药筒内，然后装入炮膛。本研究采用了一种扩展的计算流体动力学-离散元法（CFD-DEM）耦合方法来研究模块化装药内的气体-颗粒流动。经过模型验证后，我们分析了圆柱形弹丸在模拟室内的分布特征、速度、配位数和方向。我们研究了模块化装药的四个不同装药位置，以评估它们对颗粒分布的影响。数值模拟显示，颗粒分布中既有平缓的斜坡，也有水平的斜坡，还有陡峭的斜坡。颗粒的最大速度在初始阶段迅速增加，达到峰值后呈之字形下降。高配位数粒子往往主要聚集在陡峭聚集的中间层。此外，颗粒呈现出从 0° 到 180° 的倒 V 形取向范围，表明它们倾向于采取直立姿势。这一已建立的模型极大地增强了我们对模块弹破裂后颗粒分布的理解，并为优化大口径火炮装药的设计提供了宝贵的指导。
{"title":"Investigation of Distribution Characteristics of Cylindrical Particles after the Rupture of Modular Cartridges in a Simulator Chamber","authors":"Z. Y. Li, †. Y.G.Yu, A. Chen","doi":"10.47176/jafm.17.05.2270","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2270","url":null,"abstract":"Modular charging is an advanced technique designed to meet the requirements of auto-loading artillery, whereby granular propellants are stored within modular cartridges that are loaded into the gun chamber. This study employed an extended coupled computational fluid dynamics-discrete element method (CFD-DEM) approach to investigate the gas-particle flow within modular charges. After model validation, we analyzed the distribution characteristics, velocity, coordination number, and orientation of cylindrical pellets in a simulator chamber. Four different loading positions for modular cartridges were examined to assess their impact on particle distribution. Numerical simulations revealed a combination of gentle, horizontal, and steep slopes in the particle distribution. The maximum particle velocity experienced a rapid increase during the initial phase, followed by a zigzag decline after reaching its peak. High-coordination number particles tended to accumulate primarily in the middle layer of steep accumulation. Additionally, the particles exhibited an inverted V-shape orientation range from 0° to 180°, suggesting their tendency to assume upright positions. This established model significantly enhanced our understanding of particle distribution following module cartridge rupture and provided valuable guidance for optimizing the design of large-caliber artillery charges.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141047746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2217
S. Venkatramanan, S. Thanigaiarasu, M. Kaushik
Mixing characteristics of jet emerging from a subsonic nozzle exit has been experimented and the results are compared with uncontrolled jet and controlled jet configurations. The mixing enhancement was achieved using a passive method of jet control in which tandem tabs arrangement with rectangular cross section are fixed at the nozzle exit. Two Tab configurations, the Tandem tab (TT) and Stepped Tandem Tab (STT) are used to enhance the mixing characteristics of the jet, the aspect ratio (length /width) of the tabs was 1.67 offering a blockage ratio of 9.55% to the nozzle exit. The blockage ratio of TT and STT configurations are maintained to be equal so that the mixing characteristics can be compared. The axial and radial jet spread are compared for nozzle exit Mach numbers of 0.6, 0.8 and 1.0. The TT controlled jet offered a potential core reduction of 63%, 78% and 82% for Mach numbers 0.6, 0.8 and 1.0 respectively. The STT controlled jet offered a potential core reduction of 89%, 90% and 85% for Mach numbers 0.6, 0.8 and 1.0 respectively. The radial spread of uncontrolled jet, controlled jet with TT and STT are plotted at several X/D locations and found that the controlled jets have more jet spread in both radial directions. A simulation is conducted for jets with exit Mach number 0.8 and the results are validated with the experimental findings. Based on the preliminary experimentation and computation, the STT controlled jet achieved better jet mixing through more potential core reduction and radial spread characteristics as compared to the TT configuration and base nozzle.
{"title":"Enhancement of Jet Mixing using Stepped Tandem Tabs","authors":"S. Venkatramanan, S. Thanigaiarasu, M. Kaushik","doi":"10.47176/jafm.17.05.2217","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2217","url":null,"abstract":"Mixing characteristics of jet emerging from a subsonic nozzle exit has been experimented and the results are compared with uncontrolled jet and controlled jet configurations. The mixing enhancement was achieved using a passive method of jet control in which tandem tabs arrangement with rectangular cross section are fixed at the nozzle exit. Two Tab configurations, the Tandem tab (TT) and Stepped Tandem Tab (STT) are used to enhance the mixing characteristics of the jet, the aspect ratio (length /width) of the tabs was 1.67 offering a blockage ratio of 9.55% to the nozzle exit. The blockage ratio of TT and STT configurations are maintained to be equal so that the mixing characteristics can be compared. The axial and radial jet spread are compared for nozzle exit Mach numbers of 0.6, 0.8 and 1.0. The TT controlled jet offered a potential core reduction of 63%, 78% and 82% for Mach numbers 0.6, 0.8 and 1.0 respectively. The STT controlled jet offered a potential core reduction of 89%, 90% and 85% for Mach numbers 0.6, 0.8 and 1.0 respectively. The radial spread of uncontrolled jet, controlled jet with TT and STT are plotted at several X/D locations and found that the controlled jets have more jet spread in both radial directions. A simulation is conducted for jets with exit Mach number 0.8 and the results are validated with the experimental findings. Based on the preliminary experimentation and computation, the STT controlled jet achieved better jet mixing through more potential core reduction and radial spread characteristics as compared to the TT configuration and base nozzle.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141048402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2302
F. Yazici, M. A. Karadag, P. Gokluberk, A. Kibar
Flow distribution uniformity in manifolds is important in various engineering applications. In this study, the effect of manifold design on flow distribution is examined using both experimental and numerical methods. A comparison was made between a straight manifold and a gradually decreasing cross-sectional design considering two different inlet diameters. In addition, the staggered manifold case with the most homogeneous outlet was compared with the conical manifold under the same conditions. The results demonstrate that the gradually decreasing manifold design significantly improves the flow rate uniformity compared with the straight manifold. This improvement is achieved by reducing the flow rate differences between the distribution branches, leading to a more balanced fluid distribution. The gradual reduction in the cross-sectional area allows the fluid to traverse at lower velocities in regions with higher resistance, effectively minimizing flow rate discrepancies and pressure drops. In addition, the effect of varying the inlet diameter on flow rate uniformity was investigated, revealing that larger inlet diameters contribute to improved flow distribution. The outlet uniformity of the staggered manifold matches the effective performance of the conical manifold, demonstrating similar performance at a lower cost. The results highlight the importance of designing an appropriate manifold, considering factors such as inlet diameter, channel geometry, and staggered ratio, to achieve efficient and uniform fluid distribution.
{"title":"Examining the Uniformity of Flow Distribution in Manifolds","authors":"F. Yazici, M. A. Karadag, P. Gokluberk, A. Kibar","doi":"10.47176/jafm.17.05.2302","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2302","url":null,"abstract":"Flow distribution uniformity in manifolds is important in various engineering applications. In this study, the effect of manifold design on flow distribution is examined using both experimental and numerical methods. A comparison was made between a straight manifold and a gradually decreasing cross-sectional design considering two different inlet diameters. In addition, the staggered manifold case with the most homogeneous outlet was compared with the conical manifold under the same conditions. The results demonstrate that the gradually decreasing manifold design significantly improves the flow rate uniformity compared with the straight manifold. This improvement is achieved by reducing the flow rate differences between the distribution branches, leading to a more balanced fluid distribution. The gradual reduction in the cross-sectional area allows the fluid to traverse at lower velocities in regions with higher resistance, effectively minimizing flow rate discrepancies and pressure drops. In addition, the effect of varying the inlet diameter on flow rate uniformity was investigated, revealing that larger inlet diameters contribute to improved flow distribution. The outlet uniformity of the staggered manifold matches the effective performance of the conical manifold, demonstrating similar performance at a lower cost. The results highlight the importance of designing an appropriate manifold, considering factors such as inlet diameter, channel geometry, and staggered ratio, to achieve efficient and uniform fluid distribution.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141055253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2340
A. Benavides-Moran, S. Lain
Modeling efforts on turbulent gas-solid flows have mainly focused on studying particle-laden flows in channels and pipes. Despite its significance for industrial applications, the study of gas-solid flows in sudden or gradual expansions is less common in the literature. This paper challenges current two-phase flow models to compute the dilute turbulent gas-solid flow in a vertically oriented 12° conical diffuser. The solids phase is modeled in two ways: the Two-Fluid Model approach that incorporates closure relations derived from the kinetic theory of granular flow, and the Euler-Lagrange particle tracking model with two-way coupling. In both cases, turbulence in the gas phase is estimated by the Reynolds stress model with additional modulation terms that account for the effect of the particles on the gas-phase turbulence. Simulation results are validated versus experimental benchmark data not only for gas axial velocity but also for streamwise and radial turbulence intensity, as comparison with such turbulent variables has not been detailed in previous studies. Nevertheless, due to the lack of experimental data for validation, profiles of solids axial velocity are only compared numerically. Contours of turbulence kinetic energy and granular temperature in the diffuser region reveal a high shear area responsible for the production of turbulence in both phases. Moreover, results obtained from the Euler-Lagrange model show an intense particle fluctuating velocity in the streamwise direction downstream of the diffuser.
{"title":"Numerical Simulations of Turbulent Gas-solid Flow in a Gradual Expansion","authors":"A. Benavides-Moran, S. Lain","doi":"10.47176/jafm.17.05.2340","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2340","url":null,"abstract":"Modeling efforts on turbulent gas-solid flows have mainly focused on studying particle-laden flows in channels and pipes. Despite its significance for industrial applications, the study of gas-solid flows in sudden or gradual expansions is less common in the literature. This paper challenges current two-phase flow models to compute the dilute turbulent gas-solid flow in a vertically oriented 12° conical diffuser. The solids phase is modeled in two ways: the Two-Fluid Model approach that incorporates closure relations derived from the kinetic theory of granular flow, and the Euler-Lagrange particle tracking model with two-way coupling. In both cases, turbulence in the gas phase is estimated by the Reynolds stress model with additional modulation terms that account for the effect of the particles on the gas-phase turbulence. Simulation results are validated versus experimental benchmark data not only for gas axial velocity but also for streamwise and radial turbulence intensity, as comparison with such turbulent variables has not been detailed in previous studies. Nevertheless, due to the lack of experimental data for validation, profiles of solids axial velocity are only compared numerically. Contours of turbulence kinetic energy and granular temperature in the diffuser region reveal a high shear area responsible for the production of turbulence in both phases. Moreover, results obtained from the Euler-Lagrange model show an intense particle fluctuating velocity in the streamwise direction downstream of the diffuser.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141048090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-01DOI: 10.47176/jafm.17.05.2121
M. Shahriyari, †. H.Khaleghi
Time-accurate numerical calculations are performed to investigate the effect of air recirculation on NASA Rotor 37. An annular casing-mounted recirculation passageway is designed and located over the blades. Because the investigated rotor does not have any stator, the bleed air has a high circumferential velocity component (in the same direction of the rotor). Therefore, the injected air would have a high swirl component, reducing the injection's effectiveness. As a result, anti-swirl blades have been installed within the recirculation duct, to reduce flow swirl and improve injector effectiveness. Different anti-swirl vanes have been simulated in order to determine the best vanes in terms of minimum pressure loss and zero injection yaw angle (axial injection). Results show that these vanes can effectively turn the circulated fluid to the axial direction and provide a high velocity axial injection upstream of the rotor blades. As a result of the effective injection, the leakage flow moves downstream, improving stability by shifting the stalling point to lower mass flow rates. Because the injection port is close to the blade, the interaction of the passage shock and the injection port causes unsteadiness in the injection mass flow, which is discussed in the paper.
为研究空气再循环对 NASA 37 号转子的影响，进行了精确的时间数值计算。设计了一个安装在叶片上方的环形套管再循环通道。由于所研究的转子没有定子，排出的空气具有较高的圆周速度分量（与转子方向相同）。因此，注入的空气会有较高的漩涡分量，从而降低喷射效果。因此，在再循环管道内安装了防漩涡叶片，以减少气流漩涡，提高喷射效果。对不同的防漩涡叶片进行了模拟，以确定压力损失最小、喷射偏航角为零（轴向喷射）的最佳叶片。结果表明，这些叶片能有效地将循环流体转向轴向，并在转子叶片上游提供高速轴向喷射。有效喷射的结果是，泄漏流向下游移动，通过将停滞点转移到较低的质量流量来提高稳定性。由于喷射口靠近叶片，通道冲击和喷射口的相互作用会导致喷射质量流的不稳定性，本文对此进行了讨论。
{"title":"URANS Simulation of Self-Recirculation Casing Treatment in a Transonic Compressor","authors":"M. Shahriyari, †. H.Khaleghi","doi":"10.47176/jafm.17.05.2121","DOIUrl":"https://doi.org/10.47176/jafm.17.05.2121","url":null,"abstract":"Time-accurate numerical calculations are performed to investigate the effect of air recirculation on NASA Rotor 37. An annular casing-mounted recirculation passageway is designed and located over the blades. Because the investigated rotor does not have any stator, the bleed air has a high circumferential velocity component (in the same direction of the rotor). Therefore, the injected air would have a high swirl component, reducing the injection's effectiveness. As a result, anti-swirl blades have been installed within the recirculation duct, to reduce flow swirl and improve injector effectiveness. Different anti-swirl vanes have been simulated in order to determine the best vanes in terms of minimum pressure loss and zero injection yaw angle (axial injection). Results show that these vanes can effectively turn the circulated fluid to the axial direction and provide a high velocity axial injection upstream of the rotor blades. As a result of the effective injection, the leakage flow moves downstream, improving stability by shifting the stalling point to lower mass flow rates. Because the injection port is close to the blade, the interaction of the passage shock and the injection port causes unsteadiness in the injection mass flow, which is discussed in the paper.","PeriodicalId":49041,"journal":{"name":"Journal of Applied Fluid Mechanics","volume":null,"pages":null},"PeriodicalIF":1.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141043167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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