Journal of Fluids and Structures最新文献_第10页

Enhanced vortex-induced vibration prediction of marine risers using excitation coefficient databases at high Reynolds numbers 基于高雷诺数激励系数数据库的船用隔水管涡激振动增强预测

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-26 DOI: 10.1016/j.jfluidstructs.2025.104406

Jiawei Shen, Pengqian Deng, Shixiao Fu, Xuepeng Fu, Leijian Song, Yuwang Xu

Current methods for predicting vortex-induced vibration (VIV) of marine risers mainly depend on excitation coefficient databases obtained from forced vibration experiments on a rigid cylinder at a low Reynolds number (Re = 1.0E4). However, investigations at higher Reynolds numbers have revealed notable effects on VIV behaviors, resulting in discrepancies when predictions are based on previous experimental databases. To resolve this, forced vibration experiments were carried out on a rigid cylinder model over a Reynolds number range of 5.0E4 to 3.5E5. The acquired data enabled the development of comprehensive excitation coefficient databases covering both subcritical and critical Re regimes. A non-iterative frequency-domain prediction method integrating the updated excitation coefficient databases was proposed and validated through experiments on a flexible riser model. Subsequently, predictive calculations were conducted to investigate the effects of the Reynolds numbers in the excitation coefficient databases on the prediction outcomes. Comparative analysis shows that method based on a higher subcritical Reynolds number (2.0E5) tend to predict larger vibration amplitudes and amplified fatigue damage, whereas those corresponding to critical Reynolds numbers (3.0E5 and 3.5E5) indicate lower amplitudes and reduced fatigue damage. These findings underscore the importance of using excitation coefficient databases that match the relevant Reynolds number conditions to mitigate the risks of overly optimistic or conservative marine riser designs.

目前海洋隔水管涡激振动的预测方法主要依赖于低雷诺数（Re = 1.0E4）下刚性圆柱强制振动实验得到的激励系数数据库。然而，高雷诺数的研究已经揭示了对VIV行为的显着影响，导致基于先前实验数据库的预测存在差异。为了解决这一问题，在雷诺数为5.0E4 ~ 3.5E5的刚性圆柱模型上进行了强迫振动实验。获得的数据使开发涵盖亚临界和临界Re状态的综合激励系数数据库成为可能。提出了一种集成更新的激励系数数据库的非迭代频域预测方法，并通过柔性立管模型进行了实验验证。随后，进行预测计算，研究激励系数数据库中雷诺数对预测结果的影响。对比分析表明，基于较高亚临界雷诺数（2.0E5）的方法预测的振动幅值较大，疲劳损伤放大，而基于临界雷诺数（3.0E5和3.5E5）的方法预测的振动幅值较小，疲劳损伤减小。这些发现强调了使用与相关雷诺数条件相匹配的激励系数数据库来降低过于乐观或保守的海洋立管设计风险的重要性。

{"title":"Enhanced vortex-induced vibration prediction of marine risers using excitation coefficient databases at high Reynolds numbers","authors":"Jiawei Shen, Pengqian Deng, Shixiao Fu, Xuepeng Fu, Leijian Song, Yuwang Xu","doi":"10.1016/j.jfluidstructs.2025.104406","DOIUrl":"10.1016/j.jfluidstructs.2025.104406","url":null,"abstract":"<div><div>Current methods for predicting vortex-induced vibration (VIV) of marine risers mainly depend on excitation coefficient databases obtained from forced vibration experiments on a rigid cylinder at a low Reynolds number (Re = 1.0E4). However, investigations at higher Reynolds numbers have revealed notable effects on VIV behaviors, resulting in discrepancies when predictions are based on previous experimental databases. To resolve this, forced vibration experiments were carried out on a rigid cylinder model over a Reynolds number range of 5.0E4 to 3.5E5. The acquired data enabled the development of comprehensive excitation coefficient databases covering both subcritical and critical Re regimes. A non-iterative frequency-domain prediction method integrating the updated excitation coefficient databases was proposed and validated through experiments on a flexible riser model. Subsequently, predictive calculations were conducted to investigate the effects of the Reynolds numbers in the excitation coefficient databases on the prediction outcomes. Comparative analysis shows that method based on a higher subcritical Reynolds number (2.0E5) tend to predict larger vibration amplitudes and amplified fatigue damage, whereas those corresponding to critical Reynolds numbers (3.0E5 and 3.5E5) indicate lower amplitudes and reduced fatigue damage. These findings underscore the importance of using excitation coefficient databases that match the relevant Reynolds number conditions to mitigate the risks of overly optimistic or conservative marine riser designs.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104406"},"PeriodicalIF":3.5,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144894905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Geometrically exact mechanics of pipes conveying fluid with an axially sliding downstream end 具有轴向滑动下游端输送流体的管道的几何精确力学

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-25 DOI: 10.1016/j.jfluidstructs.2025.104402

Amir Mehdi Dehrouyeh-Semnani

In this study, the post-buckling patterns and stability characteristics of hanging and standing soft pipes conveying fluid, with an axially sliding downstream end, are investigated using a new nonlinear geometrically exact model. The mathematical formulation in terms of the rotation angle and lateral displacement, is derived by incorporating the lateral constraint at the downstream end into the geometrically exact model of a cantilevered pipe conveying fluid in terms of the rotation angle. Additionally, a linearized mathematical model of the system around its post-buckling path is established to assess the stability characteristics of post-buckled configurations. To determine the post-buckling patterns and their stability behavior, the shooting scheme in conjunction with the Runge-Kutta finite difference method is utilized. The analysis focuses on both hanging and standing systems, where the downstream end is simply supported and the upstream end may be either clamped or simply supported, taking into account the simultaneous influences of flow velocity and gravity. Furthermore, in the case of the standing system with both ends simply supported, the potential for snap-through buckling is examined. Ultimately, the geometrically exact patterns are compared with those obtained by the original and approximate versions of the nonlinear third-order model.

本文采用一种新的非线性几何精确模型，研究了下游端轴向滑动的悬挂式和直立式软管道的后屈曲模式和稳定性特性。通过将下游端的横向约束纳入悬臂管输送流体的旋转角度几何精确模型，推导出了旋转角度和横向位移的数学表达式。此外，建立了系统后屈曲路径的线性化数学模型，以评估后屈曲构型的稳定性特性。为了确定后屈曲模式及其稳定性行为，采用了结合龙格-库塔有限差分法的射击方案。考虑到流速和重力的同时影响，下端采用简支，上端采用夹紧或简支的悬挂式和立式两种系统进行了分析。此外，在两端简单支撑的站立系统的情况下，检查了卡嗒通屈曲的可能性。最后，将几何上精确的图形与非线性三阶模型的原始和近似版本所得到的图形进行了比较。

{"title":"Geometrically exact mechanics of pipes conveying fluid with an axially sliding downstream end","authors":"Amir Mehdi Dehrouyeh-Semnani","doi":"10.1016/j.jfluidstructs.2025.104402","DOIUrl":"10.1016/j.jfluidstructs.2025.104402","url":null,"abstract":"<div><div>In this study, the post-buckling patterns and stability characteristics of hanging and standing soft pipes conveying fluid, with an axially sliding downstream end, are investigated using a new nonlinear geometrically exact model. The mathematical formulation in terms of the rotation angle and lateral displacement, is derived by incorporating the lateral constraint at the downstream end into the geometrically exact model of a cantilevered pipe conveying fluid in terms of the rotation angle. Additionally, a linearized mathematical model of the system around its post-buckling path is established to assess the stability characteristics of post-buckled configurations. To determine the post-buckling patterns and their stability behavior, the shooting scheme in conjunction with the Runge-Kutta finite difference method is utilized. The analysis focuses on both hanging and standing systems, where the downstream end is simply supported and the upstream end may be either clamped or simply supported, taking into account the simultaneous influences of flow velocity and gravity. Furthermore, in the case of the standing system with both ends simply supported, the potential for snap-through buckling is examined. Ultimately, the geometrically exact patterns are compared with those obtained by the original and approximate versions of the nonlinear third-order model.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104402"},"PeriodicalIF":3.5,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Corrigendum to "Flow-induced vibration of an underwater lazy wave cable in unidirectional current" Journal of Fluids and Structures 137 (2025) 104385/YJFLS 104385 https://doi.org/10.1016/j.jfluidstructs.2025.104385 “单向电流下水下懒波电缆的流致振动”《流体与结构学报》137 (2025)104385/YJFLS 104385 https://doi.org/10.1016/j.jfluidstructs.2025.104385的勘误表

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-25 DOI: 10.1016/j.jfluidstructs.2025.104401

R. Moideen , V. Venugopal , J.R. Chaplin , A.G.L. Borthwick

引用次数: 0

Experimental parametric study of a flap-NES passive absorber for post-flutter control 后颤振控制中扑翼- nes被动吸收器的实验参数研究

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-24 DOI: 10.1016/j.jfluidstructs.2025.104405

Jesús García Pérez , Leonardo Sanches , Amin Ghadami , Bogdan I. Epureanu , Guilhem Michon

Aeroelastic instabilities present significant challenges in aircraft design, particularly for novel designs leveraging high aspect ratios and flexible wings to enhance aerodynamic efficiency. These advancements, seen in both high-altitude, high-endurance aircraft and commercial airliners, introduce complexities such as low resonant frequencies and increased susceptibility to aeroelastic instabilities, particularly flutter, which can lead to structural failure. The current certification process requires aircraft to be free from flutter within the operational flight envelope and beyond it, typically with a safety margin of 15% Various strategies have been explored to mitigate flutter and expand the flight envelope. In this work, passive vibration mitigation is applied to an experimental aeroelastic system exhibiting complex aeroelastic instabilities in a wind tunnel. The system consists of a rigid wing mounted on elastic supports with a flap that spans one-third of the wingspan and acts as an innovative nonlinear passive absorber. The setup includes pitch stiffness nonlinearity, which contributes to complex aeroelastic responses such as subcritical flutter and limit cycle oscillations. This solution benefits from aerodynamic damping and adds a very small amount of mass to the system. The main focus of this paper is to assess the influence of flap-NES parameters on aeroelastic behavior and to explore its potential impact on different wing configurations. Results show a delay in the onset of instability up to 34% in airspeed, a suppression of large amplitude vibrations due to stall flutter, and a removal of subcritical behavior.

气动弹性不稳定性对飞机设计提出了重大挑战，特别是对于利用高展弦比和柔性机翼来提高气动效率的新型设计。在高空、高耐力飞机和商用客机上都可以看到这些进步，但这些进步带来了复杂性，如低谐振频率和对气动弹性不稳定性（特别是颤振）的敏感性增加，这可能导致结构失效。目前的认证过程要求飞机在运行飞行包线内外无颤振，通常安全裕度为15%，已经探索了各种策略来减轻颤振和扩大飞行包线。在这项工作中，被动减振应用于一个具有复杂气动弹性不稳定性的风洞实验气动弹性系统。该系统由一个刚性机翼和一个翼展三分之一的襟翼组成，作为一个创新的非线性被动吸收器。该设置包含俯仰刚度非线性，导致复杂的气动弹性响应，如亚临界颤振和极限环振荡。这种解决方案得益于空气动力阻尼，并为系统增加了非常小的质量。本文的主要重点是评估襟翼- nes参数对气动弹性性能的影响，并探讨其对不同机翼构型的潜在影响。结果表明，在空速下，不稳定性的发作延迟高达34%，由于失速颤振引起的大振幅振动得到抑制，并且消除了亚临界行为。

{"title":"Experimental parametric study of a flap-NES passive absorber for post-flutter control","authors":"Jesús García Pérez , Leonardo Sanches , Amin Ghadami , Bogdan I. Epureanu , Guilhem Michon","doi":"10.1016/j.jfluidstructs.2025.104405","DOIUrl":"10.1016/j.jfluidstructs.2025.104405","url":null,"abstract":"<div><div>Aeroelastic instabilities present significant challenges in aircraft design, particularly for novel designs leveraging high aspect ratios and flexible wings to enhance aerodynamic efficiency. These advancements, seen in both high-altitude, high-endurance aircraft and commercial airliners, introduce complexities such as low resonant frequencies and increased susceptibility to aeroelastic instabilities, particularly flutter, which can lead to structural failure. The current certification process requires aircraft to be free from flutter within the operational flight envelope and beyond it, typically with a safety margin of 15% Various strategies have been explored to mitigate flutter and expand the flight envelope. In this work, passive vibration mitigation is applied to an experimental aeroelastic system exhibiting complex aeroelastic instabilities in a wind tunnel. The system consists of a rigid wing mounted on elastic supports with a flap that spans one-third of the wingspan and acts as an innovative nonlinear passive absorber. The setup includes pitch stiffness nonlinearity, which contributes to complex aeroelastic responses such as subcritical flutter and limit cycle oscillations. This solution benefits from aerodynamic damping and adds a very small amount of mass to the system. The main focus of this paper is to assess the influence of flap-NES parameters on aeroelastic behavior and to explore its potential impact on different wing configurations. Results show a delay in the onset of instability up to 34% in airspeed, a suppression of large amplitude vibrations due to stall flutter, and a removal of subcritical behavior.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104405"},"PeriodicalIF":3.5,"publicationDate":"2025-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Corrigendum to “FSI simulations of wind gusts impacting an air-inflated flexible membrane at Re = 100,000” [J. Fluids Struct. 109 (2022) 103462] “Re = 100,000时阵风冲击充气柔性膜的FSI模拟”的更正[J]。流体结构。109 (2022)103462 [j]

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-23 DOI: 10.1016/j.jfluidstructs.2025.104384

G. De Nayer, M. Breuer, K. Boulbrachene

引用次数: 0

Snap-through oscillations of an elastic sheet for enhanced heat transfer in dual-channel systems 双通道系统中用于增强传热的弹性片的弹跳振荡

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-21 DOI: 10.1016/j.jfluidstructs.2025.104407

Jingyu Cui , Yansong Li , Yuzhen Jin , Xianghui Su , Zhaokun Wang

This study explores the use of the snap-through behavior of an elastic sheet as a vortex generator (VG) to enhance heat transfer in a dual-channel system. By leveraging snap-through oscillations, a single sheet clamped at the common wall of the dual channels can simultaneously enhance heat transfer in both channels with a reduced pressure drop. The thermohydraulic performance is analyzed using the immersed boundary-lattice Boltzmann method across varying system parameters. The results demonstrate that for a given Reynolds number (Re), the sheet can operate in either a snap-through mode or dormant mode, depending on its buckled length and bending stiffness (EI*). The snap-through mode achieves superior heat transfer performance, especially at lower bending stiffness, with a thermal efficiency factor (η) of 1.3 at EI* = 0.002, outperforming the wall-clamped flag configuration by 5% and the rigid VG by 14.5%. Comparative analysis reveals that, while the wall-clamped flag configuration is more effective at higher bending stiffness, the proposed VG excels at lower bending stiffness, making these configurations complementary across different applications. The performance of the VG can be further adjusted by modifying the buckled distance of the sheet, with η decreasing as the buckled length increases. Additionally, as Re rises, oscillation-induced flow separation intensifies, further enhancing convective heat transfer. At Re = 1000, η exceeds 1.4, demonstrating robust performance in high-Re regimes. These findings highlight the VG’s potential for tunable and efficient heat transfer enhancement in dual-channel applications.

本研究探讨了利用弹性薄片作为涡流发生器（VG）来增强双通道系统中的传热。通过利用卡通振荡，夹紧在双通道共同壁上的单片材料可以同时增强两个通道的传热，同时降低压降。采用浸入式边界格玻尔兹曼方法分析了不同系统参数下的热工性能。结果表明，在给定雷诺数（Re）下，根据屈曲长度和弯曲刚度（EI*）的不同，薄板可以在卡通模式或休眠模式下工作。卡通模式具有优越的传热性能，特别是在较低的弯曲刚度下，在EI* = 0.002时，热效率系数（η）为1.3，比壁面夹紧的旗杆结构高5%，比刚性的VG结构高14.5%。对比分析表明，虽然壁面夹紧标志结构在较高的弯曲刚度下更有效，但所提出的VG在较低的弯曲刚度下表现出色，使这些结构在不同的应用中互补。通过改变板材的屈曲距离，可以进一步调节卷材的性能，η随屈曲长度的增加而减小。此外，随着Re的升高，振荡引起的流动分离加剧，进一步增强了对流换热。在Re = 1000时，η值超过1.4，在高Re状态下表现出稳健的性能。这些发现突出了VG在双通道应用中可调和高效传热增强的潜力。

{"title":"Snap-through oscillations of an elastic sheet for enhanced heat transfer in dual-channel systems","authors":"Jingyu Cui , Yansong Li , Yuzhen Jin , Xianghui Su , Zhaokun Wang","doi":"10.1016/j.jfluidstructs.2025.104407","DOIUrl":"10.1016/j.jfluidstructs.2025.104407","url":null,"abstract":"<div><div>This study explores the use of the snap-through behavior of an elastic sheet as a vortex generator (VG) to enhance heat transfer in a dual-channel system. By leveraging snap-through oscillations, a single sheet clamped at the common wall of the dual channels can simultaneously enhance heat transfer in both channels with a reduced pressure drop. The thermohydraulic performance is analyzed using the immersed boundary-lattice Boltzmann method across varying system parameters. The results demonstrate that for a given Reynolds number (<em>Re</em>), the sheet can operate in either a snap-through mode or dormant mode, depending on its buckled length and bending stiffness (<em>EI*</em>). The snap-through mode achieves superior heat transfer performance, especially at lower bending stiffness, with a thermal efficiency factor (<em>η</em>) of 1.3 at <em>EI*</em> = 0.002, outperforming the wall-clamped flag configuration by 5% and the rigid VG by 14.5%. Comparative analysis reveals that, while the wall-clamped flag configuration is more effective at higher bending stiffness, the proposed VG excels at lower bending stiffness, making these configurations complementary across different applications. The performance of the VG can be further adjusted by modifying the buckled distance of the sheet, with <em>η</em> decreasing as the buckled length increases. Additionally, as <em>Re</em> rises, oscillation-induced flow separation intensifies, further enhancing convective heat transfer. At <em>Re</em> = 1000, <em>η</em> exceeds 1.4, demonstrating robust performance in high-<em>Re</em> regimes. These findings highlight the VG’s potential for tunable and efficient heat transfer enhancement in dual-channel applications.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104407"},"PeriodicalIF":3.5,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mitigating unsteady loads at low Reynolds numbers using a passive trailing-edge flap 利用被动尾缘襟翼减轻低雷诺数下的非定常载荷

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-21 DOI: 10.1016/j.jfluidstructs.2025.104392

C. Martínez-Muriel , I.M. Viola , M. García-Villalba , O. Flores

The load mitigation potential of a passive pitching trailing edge flap for NACA0012 airfoils at a Reynolds number of 1000 subjected to oscillations in the angle of attack is analyzed. For this purpose, direct numerical simulations of the two-dimensional, incompressible flow have been conducted to examine the effectiveness of the flap in reducing aerodynamic load fluctuations across a range of oscillation amplitudes and flap-to-chord ratios. The validity of a quasi-steady model to predict the load mitigation using passive pitching flaps, previously proposed in the literature and predicting a load mitigation proportional to the flap-to-chord length ratio,

a / c

, is here investigated for large amplitude oscillations. The results show that the increment in the reduction in fluctuations is generally proportional to the increment in

a / c

. This closely aligns with the predictions of the quasi-steady theory, even for the cases with the largest oscillation amplitudes, where non-linear aerodynamic effects are present, although some variation is observed. Notably, we explored the interaction between vortical structures and the flap dynamics, and its relevance on the flow patterns around the airfoil and ultimately on load mitigation. This interaction, alongside flap inertia, provides insight into the timing and magnitude of load reduction, demonstrating the potential of tailored passive pitching mechanisms for unsteady flow conditions. These findings offer valuable insights for the design and development of passive unsteady load mechanisms for small aerial and underwater vehicles, as well as microscale energy harvesters, by highlighting the relevance of considering non-linear effects in their optimization.

分析了NACA0012型被动俯仰后缘襟翼在雷诺数为1000时受迎角振荡影响的减载潜力。为此，对二维不可压缩流动进行了直接数值模拟，以检验襟翼在振荡幅度和襟翼弦比范围内减少气动载荷波动的有效性。本文研究了准稳态模型的有效性，该模型用于预测使用被动俯仰襟翼的负载缓解，该模型先前在文献中提出，并预测了与襟翼与弦长比（a/c）成比例的负载缓解，用于大振幅振荡。结果表明，波动减少的增量一般与a/c的增量成正比。这与准稳定理论的预测密切一致，即使在振荡幅度最大的情况下，非线性气动效应也存在，尽管观察到一些变化。值得注意的是，我们探索了涡旋结构和襟翼动力学之间的相互作用，以及它与翼型周围流动模式的相关性，并最终与负载缓解有关。这种相互作用与襟翼惯性一起，提供了对载荷减少时间和幅度的深入了解，展示了针对非定常流动条件量身定制的被动俯仰机制的潜力。这些发现通过强调在优化中考虑非线性效应的相关性，为小型空中和水下航行器以及微型能量采集器的被动非定常负载机制的设计和开发提供了有价值的见解。

{"title":"Mitigating unsteady loads at low Reynolds numbers using a passive trailing-edge flap","authors":"C. Martínez-Muriel , I.M. Viola , M. García-Villalba , O. Flores","doi":"10.1016/j.jfluidstructs.2025.104392","DOIUrl":"10.1016/j.jfluidstructs.2025.104392","url":null,"abstract":"<div><div>The load mitigation potential of a passive pitching trailing edge flap for NACA0012 airfoils at a Reynolds number of 1000 subjected to oscillations in the angle of attack is analyzed. For this purpose, direct numerical simulations of the two-dimensional, incompressible flow have been conducted to examine the effectiveness of the flap in reducing aerodynamic load fluctuations across a range of oscillation amplitudes and flap-to-chord ratios. The validity of a quasi-steady model to predict the load mitigation using passive pitching flaps, previously proposed in the literature and predicting a load mitigation proportional to the flap-to-chord length ratio, <span><math><mrow><mi>a</mi><mo>/</mo><mi>c</mi></mrow></math></span>, is here investigated for large amplitude oscillations. The results show that the increment in the reduction in fluctuations is generally proportional to the increment in <span><math><mrow><mi>a</mi><mo>/</mo><mi>c</mi></mrow></math></span>. This closely aligns with the predictions of the quasi-steady theory, even for the cases with the largest oscillation amplitudes, where non-linear aerodynamic effects are present, although some variation is observed. Notably, we explored the interaction between vortical structures and the flap dynamics, and its relevance on the flow patterns around the airfoil and ultimately on load mitigation. This interaction, alongside flap inertia, provides insight into the timing and magnitude of load reduction, demonstrating the potential of tailored passive pitching mechanisms for unsteady flow conditions. These findings offer valuable insights for the design and development of passive unsteady load mechanisms for small aerial and underwater vehicles, as well as microscale energy harvesters, by highlighting the relevance of considering non-linear effects in their optimization.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104392"},"PeriodicalIF":3.5,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental identification of blade-level forces, torque, and pitching moment for cross-flow turbines 横流涡轮叶片水平力、扭矩和俯仰力矩的实验识别

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-20 DOI: 10.1016/j.jfluidstructs.2025.104403

Abigale Snortland , Katherine Van Ness , Jennifer A. Franck , Ari Athair , Owen Williams , Brian Polagye

Cross-flow turbine power is a net sum of power generation from rotating blades and power loss from rotating support structures. While the aggregate forces and torques at the turbine level are important for end use, these can inhibit a deeper understanding of fluid–structure interactions. Identification of blade-level forces and torques allows for specific investigations into how the fluid forcing on the blade drives rotation and can aid blade structural design. Here, we present a physics-based methodology for extracting blade-level forces and torques from experimental measurements at the axis of rotation of a cross-flow turbine, and demonstrate strong agreement with equivalent blade-only simulations. In doing so, we highlight the often-overlooked pitching moment, which offsets continuous increases in power generation from the tangential force and leads to net-zero power generation at freewheel.

横流涡轮功率是旋转叶片产生的功率和旋转支撑结构产生的功率损失的总和。虽然涡轮级的总力和扭矩对最终用途很重要，但它们可能会阻碍对流固相互作用的更深入理解。确定叶片水平的力和扭矩，可以对叶片上的流体力如何驱动旋转进行具体研究，并有助于叶片结构设计。在这里，我们提出了一种基于物理的方法，从横流涡轮旋转轴的实验测量中提取叶片水平的力和扭矩，并证明了与等效的仅叶片模拟的强烈一致性。在此过程中，我们强调了经常被忽视的俯仰力矩，它抵消了切向力产生的持续增加的发电量，并导致自由轮的净零发电量。

引用次数: 0

Nonlinear parameter identification via bifurcation-guided multiscale analysis: Decoding vortex-induced dynamics of grooved/ribbed cylinders 基于分岔引导的多尺度分析的非线性参数辨识：槽形/肋形圆柱体涡致动力学解码

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-16 DOI: 10.1016/j.jfluidstructs.2025.104386

Shuguang Yang , Dongmei Huang , Guangyun Min , Zhaokun Zhu

This study establishes a parameter identification model for two-degree-of-freedom vortex-induced vibrations (VIV) in smooth, grooved, and ribbed cylinders under locked-in conditions. Wind tunnel experiments on elastically mounted models captured cross-flow and in-flow VIV responses, analyzed via Fast Fourier Transform (FFT) spectral methods. Using the multiple-scale method, we derived approximate solutions for nonlinear(forced/dual-forced) self-excited force models (NSFM/NFSFM/NDFSFM), analyzing primary resonance characteristics. Key discoveries reveal: (1) in-flow beat vibrations transitioning to periodic motion under lock-in conditions, (2) stabilized frequency-doubling components in grooved cylinder responses, and (3) second/third harmonic-induced trajectory asymmetry and equilibrium drift in ribbed cylinders. To address these phenomena, we developed a novel nonlinear time-varying forced-self-excited model (NTFSFM) that effectively identifies decaying cross/in-flow responses. Integration of analytical solutions (NFSFM/NDFSFM) with parameter bifurcation diagrams enabled precise characterization of multi-harmonic components in grooved cylinders and displacement anomalies in ribbed configurations. The final fluid-structure coupling equations governing two-degree-of-freedom vibrations in both flow directions provide fundamental references for engineering design and nonlinear vibration theory.

本研究建立了锁紧条件下光滑、沟槽和带肋圆柱两自由度涡激振动（VIV）的参数识别模型。在弹性安装模型上进行风洞实验，通过快速傅里叶变换（FFT）光谱方法分析了横流和内流的涡激振动响应。采用多尺度方法，推导了非线性（强迫/双强迫）自激力模型（NSFM/NFSFM/NDFSFM）的近似解，分析了主共振特性。主要发现包括：(1)在锁紧条件下流动节拍振动转变为周期运动；(2)槽形圆柱体响应中的稳定倍频分量；(3)肋形圆柱体中第二/第三次谐波诱导的轨迹不对称和平衡漂移。为了解决这些现象，我们开发了一种新的非线性时变强迫自激模型（NTFSFM），该模型可以有效识别衰减的横向/流内响应。将解析解（NFSFM/NDFSFM）与参数分岔图集成在一起，可以精确表征槽形气缸中的多谐分量和肋形结构中的位移异常。最终得到的控制两自由度流动方向振动的流固耦合方程为工程设计和非线性振动理论提供了基础参考。

{"title":"Nonlinear parameter identification via bifurcation-guided multiscale analysis: Decoding vortex-induced dynamics of grooved/ribbed cylinders","authors":"Shuguang Yang , Dongmei Huang , Guangyun Min , Zhaokun Zhu","doi":"10.1016/j.jfluidstructs.2025.104386","DOIUrl":"10.1016/j.jfluidstructs.2025.104386","url":null,"abstract":"<div><div>This study establishes a parameter identification model for two-degree-of-freedom vortex-induced vibrations (VIV) in smooth, grooved, and ribbed cylinders under locked-in conditions. Wind tunnel experiments on elastically mounted models captured cross-flow and in-flow VIV responses, analyzed via Fast Fourier Transform (FFT) spectral methods. Using the multiple-scale method, we derived approximate solutions for nonlinear(forced/dual-forced) self-excited force models (NSFM/NFSFM/NDFSFM), analyzing primary resonance characteristics. Key discoveries reveal: (1) in-flow beat vibrations transitioning to periodic motion under lock-in conditions, (2) stabilized frequency-doubling components in grooved cylinder responses, and (3) second/third harmonic-induced trajectory asymmetry and equilibrium drift in ribbed cylinders. To address these phenomena, we developed a novel nonlinear time-varying forced-self-excited model (NTFSFM) that effectively identifies decaying cross/in-flow responses. Integration of analytical solutions (NFSFM/NDFSFM) with parameter bifurcation diagrams enabled precise characterization of multi-harmonic components in grooved cylinders and displacement anomalies in ribbed configurations. The final fluid-structure coupling equations governing two-degree-of-freedom vibrations in both flow directions provide fundamental references for engineering design and nonlinear vibration theory.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104386"},"PeriodicalIF":3.5,"publicationDate":"2025-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144851794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Lift mechanism and strategies of a variable-area flapping wing 变面积扑翼升力机理及策略

IF 3.5 2区工程技术 Q1 ENGINEERING, MECHANICAL

Journal of Fluids and Structures

Pub Date : 2025-08-15 DOI: 10.1016/j.jfluidstructs.2025.104388

Ruiyong Mou , Zhe Li , Xingrong Huang , Weixi Huang , Le Fang

In biological world and human sports, changing windward area of flapping wing in a flapping period is a common method to gain high lift. However, studies on the underlying mechanism are still rare. In the present paper, we select the multibody dynamics model proposed by Toomey & Eldredge as a basic model for flexible flapping wing, and add retractable plates between the lead and trailing bodies to enable the change of windward area. First, an intermittent strategy designed to increase the lift of the flapping wings is proposed and thoroughly examined. Results show that this intermittent strategy can increase the lift for narrower gaps, but leads to a reduction for wider gaps due to collisions between the trailing body and newly generated vortices. Then a modified intermittent strategy is further introduced to solve this problem. In this strategy, the gaps are closed earlier to promote the earlier formation of vortices, thus preventing the collision between the trailing body and the vortex structures. The modified intermittent strategy leads to significant increase of lift, especially for

d = 0.18

and

d = 0.20

(

d

represents the width of the wing gap). For

d = 0.20

, the lift coefficient is increased from 0.57 (the intermittent strategy) to 1.48 (the modified intermittent strategy). Finally, by dividing the lift into three phases, the mechanisms for the lift increase under this strategy are analyzed. The significant increase of lift by changing windward area is expected to inspire and encourage future investigations of variable-area flexible flapping wing.

在生物界和人类运动中，改变扑翼的迎风面积是获得高升力的常用方法。然而，对其潜在机制的研究仍然很少。在本文中，我们选择了Toomey &；以Eldredge作为柔性扑翼的基本模型，并在前后体之间增加可伸缩板，实现迎风面积的变化。首先，提出了一种旨在增加扑翼升力的间歇策略，并进行了彻底的研究。结果表明，这种间歇策略可以提高窄间隙的升力，但由于尾随体与新产生的涡之间的碰撞，导致较大间隙的升力降低。然后提出了一种改进的间歇策略来解决这一问题。在这种策略中，间隙关闭得越早，旋涡形成得越早，从而避免了尾体与旋涡结构的碰撞。改进后的间歇策略可以显著提高升力，特别是当d=0.18和d=0.20时（d代表翼隙宽度）。当d=0.20时，升力系数从0.57（间歇策略）增加到1.48（改进的间歇策略）。最后，通过将升力划分为三个阶段，分析了该策略下升力增加的机理。通过改变迎风面积而显著提高升力的研究，有望对未来变面积柔性扑翼的研究提供启发和鼓励。

{"title":"Lift mechanism and strategies of a variable-area flapping wing","authors":"Ruiyong Mou , Zhe Li , Xingrong Huang , Weixi Huang , Le Fang","doi":"10.1016/j.jfluidstructs.2025.104388","DOIUrl":"10.1016/j.jfluidstructs.2025.104388","url":null,"abstract":"<div><div>In biological world and human sports, changing windward area of flapping wing in a flapping period is a common method to gain high lift. However, studies on the underlying mechanism are still rare. In the present paper, we select the multibody dynamics model proposed by Toomey & Eldredge as a basic model for flexible flapping wing, and add retractable plates between the lead and trailing bodies to enable the change of windward area. First, an intermittent strategy designed to increase the lift of the flapping wings is proposed and thoroughly examined. Results show that this intermittent strategy can increase the lift for narrower gaps, but leads to a reduction for wider gaps due to collisions between the trailing body and newly generated vortices. Then a modified intermittent strategy is further introduced to solve this problem. In this strategy, the gaps are closed earlier to promote the earlier formation of vortices, thus preventing the collision between the trailing body and the vortex structures. The modified intermittent strategy leads to significant increase of lift, especially for <span><math><mrow><mi>d</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>18</mn></mrow></math></span> and <span><math><mrow><mi>d</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>20</mn></mrow></math></span> (<span><math><mi>d</mi></math></span> represents the width of the wing gap). For <span><math><mrow><mi>d</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>20</mn></mrow></math></span>, the lift coefficient is increased from 0.57 (the intermittent strategy) to 1.48 (the modified intermittent strategy). Finally, by dividing the lift into three phases, the mechanisms for the lift increase under this strategy are analyzed. The significant increase of lift by changing windward area is expected to inspire and encourage future investigations of variable-area flexible flapping wing.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"138 ","pages":"Article 104388"},"PeriodicalIF":3.5,"publicationDate":"2025-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0