Pub Date : 2026-01-17DOI: 10.1016/j.jfluidstructs.2026.104516
Wenshan Shan , Qingshan Yang , Yong Chul Kim , Chao Li , Chen Li , Shuai Huang
Tall slender structures, including high-rise buildings and towers, exhibit significant sensitivity to wind-induced vibrations owing to their flexibility and minimal intrinsic damping. While extensive studies have focused on across-wind aeroelastic effects, recent findings suggest that coupling between along-wind and across-wind responses could happen under certain conditions. However, this phenomenon remains insufficiently explored. This study examines the coupling of wind-induced responses in two structural principal orientations of a tall square tower with an aspect ratio of 16, utilizing aeroelastic model tests performed in a large-scale boundary layer wind tunnel. The influence of the wind direction, structural damping ratio, and wind velocity on coupled responses is systematically examined. The observations demonstrate that at wind direction θ = 0°, the across-wind response exhibits significant aeroelastic behavior, with a strong correlation but negligible coupling with the along-wind response. Moreover, at oblique wind directions, pronounced coupling effects of displacements in X and Y orientations emerge, particularly around the vortex shedding frequency, as confirmed by coherence function analysis. These findings provide valuable perspectives into the aeroelastic behavior of slender structures subjected to varying wind conditions and highlight the necessity of considering multi-directional coupling effects in wind-resistant design.
{"title":"Experimental study of along-/across-wind aeroelastic response coupling in a tall square tower","authors":"Wenshan Shan , Qingshan Yang , Yong Chul Kim , Chao Li , Chen Li , Shuai Huang","doi":"10.1016/j.jfluidstructs.2026.104516","DOIUrl":"10.1016/j.jfluidstructs.2026.104516","url":null,"abstract":"<div><div>Tall slender structures, including high-rise buildings and towers, exhibit significant sensitivity to wind-induced vibrations owing to their flexibility and minimal intrinsic damping. While extensive studies have focused on across-wind aeroelastic effects, recent findings suggest that coupling between along-wind and across-wind responses could happen under certain conditions. However, this phenomenon remains insufficiently explored. This study examines the coupling of wind-induced responses in two structural principal orientations of a tall square tower with an aspect ratio of 16, utilizing aeroelastic model tests performed in a large-scale boundary layer wind tunnel. The influence of the wind direction, structural damping ratio, and wind velocity on coupled responses is systematically examined. The observations demonstrate that at wind direction <em>θ</em> = 0°, the across-wind response exhibits significant aeroelastic behavior, with a strong correlation but negligible coupling with the along-wind response. Moreover, at oblique wind directions, pronounced coupling effects of displacements in X and Y orientations emerge, particularly around the vortex shedding frequency, as confirmed by coherence function analysis. These findings provide valuable perspectives into the aeroelastic behavior of slender structures subjected to varying wind conditions and highlight the necessity of considering multi-directional coupling effects in wind-resistant design.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104516"},"PeriodicalIF":3.5,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980245","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}
Pub Date : 2026-01-16DOI: 10.1016/j.jfluidstructs.2026.104509
Toushik Roy , Sourav Gupta , Soumen De , R. Gayen
In the quest for sustainable and renewable energy sources, use of piezoelectric wave energy converters for harnessing ocean wave energy is becoming increasingly important. However, mathematical modeling of the related problems is somewhat difficult. Thus, in this study we have endeavoured to solve the problem of wave interaction with two unequal vertically submerged piezoelectric plates present in water of uniform finite depth. The piezoelectric nature of the plates gives rise to boundary conditions involving fourth order derivatives with complex coefficients. We have developed a semi-analytical method where this boundary condition is tackled by employing Green’s function technique and the boundary value problem is transformed into a coupled system of integral equations employing a mixed Fourier transform. The integral equations are solved using a Galerkin method to find the reflection and transmission coefficients and the power absorption efficiency of the piezoelectric system. The influence of structural parameters, such as length asymmetry, depth of submergence, spacing and boundary conditions on the scattering coefficients and the efficiency of the plates is systematically examined. Results demonstrate that geometric asymmetry between the plates can significantly enhance energy conversion performance. The findings provide valuable insights for the efficient design and deployment of submerged piezoelectric wave energy converters in real-world marine environments.
{"title":"Hydrodynamic behaviour of two asymmetrically submerged piezoelectric plates","authors":"Toushik Roy , Sourav Gupta , Soumen De , R. Gayen","doi":"10.1016/j.jfluidstructs.2026.104509","DOIUrl":"10.1016/j.jfluidstructs.2026.104509","url":null,"abstract":"<div><div>In the quest for sustainable and renewable energy sources, use of piezoelectric wave energy converters for harnessing ocean wave energy is becoming increasingly important. However, mathematical modeling of the related problems is somewhat difficult. Thus, in this study we have endeavoured to solve the problem of wave interaction with two unequal vertically submerged piezoelectric plates present in water of uniform finite depth. The piezoelectric nature of the plates gives rise to boundary conditions involving fourth order derivatives with complex coefficients. We have developed a semi-analytical method where this boundary condition is tackled by employing Green’s function technique and the boundary value problem is transformed into a coupled system of integral equations employing a mixed Fourier transform. The integral equations are solved using a Galerkin method to find the reflection and transmission coefficients and the power absorption efficiency of the piezoelectric system. The influence of structural parameters, such as length asymmetry, depth of submergence, spacing and boundary conditions on the scattering coefficients and the efficiency of the plates is systematically examined. Results demonstrate that geometric asymmetry between the plates can significantly enhance energy conversion performance. The findings provide valuable insights for the efficient design and deployment of submerged piezoelectric wave energy converters in real-world marine environments.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104509"},"PeriodicalIF":3.5,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980250","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}
Pub Date : 2026-01-15DOI: 10.1016/j.jfluidstructs.2026.104518
Minghao Zhou , Ming Luo , Zhigang Wu , Chao Yang
Body and caudal fin propulsion is the primary mode of swimming for most fish species. Although the associated hydrodynamics have garnered increasing attention in recent years, previous studies have considered the fish body to be fixed or part of the travelling wave motion, neglecting the effect of passive recoil motion. In this paper, an efficient fluid-structure interaction analysis method is employed to investigate a three-dimensional flying fish model featuring a rigid head, prescribed-motion tail, and flexible caudal fin. A strongly coupled analysis framework, integrating flexible multi-body dynamics and the vortex particle method, is utilized. By permitting free yaw rotation of the fish body, this study investigates the impact of multiple kinematic parameters and caudal fin flexibility on the yaw stability and propulsion performance when incorporating recoil motion into the simulations. The results indicate that although increasing either the frequency or amplitude of the oscillation enhances the thrust force, a rise in frequency notably improves stability, whereas an increase in amplitude reduces it. Moreover, the moderately flexible caudal fin effectively mitigates recoil motion and enhances propulsion performance, but reduces yaw stability during extended cruising.
{"title":"Fluid-structure interaction analysis for yaw stability and propulsion of the biomimetic fish considering recoil motion","authors":"Minghao Zhou , Ming Luo , Zhigang Wu , Chao Yang","doi":"10.1016/j.jfluidstructs.2026.104518","DOIUrl":"10.1016/j.jfluidstructs.2026.104518","url":null,"abstract":"<div><div>Body and caudal fin propulsion is the primary mode of swimming for most fish species. Although the associated hydrodynamics have garnered increasing attention in recent years, previous studies have considered the fish body to be fixed or part of the travelling wave motion, neglecting the effect of passive recoil motion. In this paper, an efficient fluid-structure interaction analysis method is employed to investigate a three-dimensional flying fish model featuring a rigid head, prescribed-motion tail, and flexible caudal fin. A strongly coupled analysis framework, integrating flexible multi-body dynamics and the vortex particle method, is utilized. By permitting free yaw rotation of the fish body, this study investigates the impact of multiple kinematic parameters and caudal fin flexibility on the yaw stability and propulsion performance when incorporating recoil motion into the simulations. The results indicate that although increasing either the frequency or amplitude of the oscillation enhances the thrust force, a rise in frequency notably improves stability, whereas an increase in amplitude reduces it. Moreover, the moderately flexible caudal fin effectively mitigates recoil motion and enhances propulsion performance, but reduces yaw stability during extended cruising.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104518"},"PeriodicalIF":3.5,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980247","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}
Pub Date : 2026-01-15DOI: 10.1016/j.jfluidstructs.2026.104514
Shuai Huang , Qingshan Yang , Zhanfang Liu , Haohong Li , Wenshan Shan , Chen Li
Tall slender structures are prone to aeroelastic instability, such as vortex resonance and galloping, in which the along-wind response is often neglected in conventional analyses. Recent experimental studies, however, have shown that near the wind speed corresponding to across-wind resonance, the along-wind vibration becomes coupled with the across-wind vibration, resulting in a significant amplification of the along-wind response and a reduction of the across-wind response. The underlying nonlinear self-excited forces driving this coupled behavior remain insufficiently understood. This study proposes a method for identifying the self-excited forces of tall slender structures accounting for along- and across-wind coupling. Displacement responses in both directions were measured through wind tunnel tests using a pivot model, followed by complex modal parameter identification. It was found that the mode with a frequency close to the across-wind natural frequency predominantly governs the structural response. A mathematical model was then established to predict coupled vibrations and to identify nonlinear self-excited forces. A generalized Van der Pol-type damping model was employed to capture the amplitude dependence of the first-mode damping ratio. Finally, the prediction model and the self-excited force identification method were validated against experimental results. The proposed approach provides a theoretical framework for analyzing aeroelastic instability of tall slender structures with along- and across-wind coupling effects.
细长高架结构容易发生涡共振和驰动等气动弹性失稳，而在这些失稳中，沿风响应在传统分析中往往被忽略。然而，最近的实验研究表明，在横风共振对应的风速附近，顺风振动与横风振动耦合，导致顺风响应明显放大，横风响应减弱。驱动这种耦合行为的潜在非线性自激力仍然没有得到充分的了解。本文提出了一种考虑顺风和横风耦合的高细长结构自激力识别方法。采用主轴模型进行风洞试验，测量了两个方向的位移响应，然后进行了复杂模态参数辨识。研究发现，接近横风固有频率的模态主导结构响应。然后建立数学模型来预测耦合振动和识别非线性自激力。采用广义Van der pol型阻尼模型来捕捉第一模态阻尼比的幅值依赖性。最后，根据实验结果对预测模型和自激力识别方法进行了验证。该方法为分析具有顺风和横风耦合效应的高细长结构的气动弹性失稳提供了理论框架。
{"title":"Mathematical modeling of nonlinear coupled along- and across-wind aeroelastic responses in tall slender structures with square section","authors":"Shuai Huang , Qingshan Yang , Zhanfang Liu , Haohong Li , Wenshan Shan , Chen Li","doi":"10.1016/j.jfluidstructs.2026.104514","DOIUrl":"10.1016/j.jfluidstructs.2026.104514","url":null,"abstract":"<div><div>Tall slender structures are prone to aeroelastic instability, such as vortex resonance and galloping, in which the along-wind response is often neglected in conventional analyses. Recent experimental studies, however, have shown that near the wind speed corresponding to across-wind resonance, the along-wind vibration becomes coupled with the across-wind vibration, resulting in a significant amplification of the along-wind response and a reduction of the across-wind response. The underlying nonlinear self-excited forces driving this coupled behavior remain insufficiently understood. This study proposes a method for identifying the self-excited forces of tall slender structures accounting for along- and across-wind coupling. Displacement responses in both directions were measured through wind tunnel tests using a pivot model, followed by complex modal parameter identification. It was found that the mode with a frequency close to the across-wind natural frequency predominantly governs the structural response. A mathematical model was then established to predict coupled vibrations and to identify nonlinear self-excited forces. A generalized Van der Pol-type damping model was employed to capture the amplitude dependence of the first-mode damping ratio. Finally, the prediction model and the self-excited force identification method were validated against experimental results. The proposed approach provides a theoretical framework for analyzing aeroelastic instability of tall slender structures with along- and across-wind coupling effects.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104514"},"PeriodicalIF":3.5,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980246","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}
Pub Date : 2026-01-13DOI: 10.1016/j.jfluidstructs.2025.104497
James L. Fields , Anshul Suri , Caleb J. Barnes , Jack J. McNamara , Datta V. Gaitonde
This paper investigates the interplay between the Kelvin-Helmholtz (K-H) instability, aeroelastic flutter, and laminar shock-boundary layer interactions. The coupled system is studied by performing modal-based analyses over distinct phases of the aeroelastic response. The initial response is comparable to classical panel flutter and is dominated by first- and second-mode panel deflections. Over time, a frequency lock-in occurs between K-H waves in the flow and high-order modes in the panel, resulting in mutual growth. The growth of the K-H instability leads to a period of cascading frequency and modal content in which energy is channeled into several discrete oscillating panel modes. It is shown through a bispectral mode decomposition that the frequency cascade is driven by nonlinear interactions between panel modes. The asymptotic state of the aeroelastic system is classified as a multi-mode limit cycle oscillation and exhibits a traveling wave flutter. The time-mean flow field exhibits reductions in both the separation bubble volume and downstream boundary layer thickness in the presence of the fluttering panel, supporting the notion of fluid-structure interaction as a means for passive flow control of SBLIs.
{"title":"Interplay between shock-induced panel flutter and the Kelvin-Helmholtz instability in laminar flow","authors":"James L. Fields , Anshul Suri , Caleb J. Barnes , Jack J. McNamara , Datta V. Gaitonde","doi":"10.1016/j.jfluidstructs.2025.104497","DOIUrl":"10.1016/j.jfluidstructs.2025.104497","url":null,"abstract":"<div><div>This paper investigates the interplay between the Kelvin-Helmholtz (K-H) instability, aeroelastic flutter, and laminar shock-boundary layer interactions. The coupled system is studied by performing modal-based analyses over distinct phases of the aeroelastic response. The initial response is comparable to classical panel flutter and is dominated by first- and second-mode panel deflections. Over time, a frequency lock-in occurs between K-H waves in the flow and high-order modes in the panel, resulting in mutual growth. The growth of the K-H instability leads to a period of cascading frequency and modal content in which energy is channeled into several discrete oscillating panel modes. It is shown through a bispectral mode decomposition that the frequency cascade is driven by nonlinear interactions between panel modes. The asymptotic state of the aeroelastic system is classified as a multi-mode limit cycle oscillation and exhibits a traveling wave flutter. The time-mean flow field exhibits reductions in both the separation bubble volume and downstream boundary layer thickness in the presence of the fluttering panel, supporting the notion of fluid-structure interaction as a means for passive flow control of SBLIs.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104497"},"PeriodicalIF":3.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980249","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}
Pub Date : 2026-01-12DOI: 10.1016/j.jfluidstructs.2026.104512
Ming Lei , Qingyuan Gai , Tongfu Zou , Dan Xia
To enhance the surface operation capabilities of traditional bionic underwater vehicles (BUVs) in, this study explored the feasibility of dolphins performing cross-medium standing-and-turning (SAT) behavior on the water surface from a hydrodynamics perspective. A physical model and computational model of the robotic dolphin’s surface SAT behavior were established. After numerous attempts, the surface SAT behavior of the robotic dolphin was successfully replicated through coordinated movements of the body, caudal fin, and pectoral fins, and the quantitative relationship between controllable parameters and hydrodynamic performance was investigated. By combining data analysis and flow field distribution patterns, the underlying physical mechanisms of the robotic dolphin’s surface SAT behavior were revealed. The results indicate that the turning trajectory of SAT behavior exhibits a circular characteristic, and the turning radius can be adjusted by modifying the kinematic parameters. Additionally, when the movement parameters of the body and caudal fin are fixed, and the phase difference between the two pectoral fins is T/2, the robotic dolphin achieves optimal turning maneuverability, with a maximum turning speed of 1.69 rad/s and a turning efficiency of up to 45.5%. Notably, by optimizing kinematic parameters, the robotic dolphin achieves cross-medium in-situ turning with exceptionally high maneuverability, which is indeed a very valuable discovery. The findings provide a cross-medium fluid dynamics explanation for the development of BUVs with dual underwater/surface operating capabilities.
{"title":"Hydrodynamic study of a novel surface standing-and-turning behavior of robotic dolphins","authors":"Ming Lei , Qingyuan Gai , Tongfu Zou , Dan Xia","doi":"10.1016/j.jfluidstructs.2026.104512","DOIUrl":"10.1016/j.jfluidstructs.2026.104512","url":null,"abstract":"<div><div>To enhance the surface operation capabilities of traditional bionic underwater vehicles (BUVs) in, this study explored the feasibility of dolphins performing cross-medium standing-and-turning (SAT) behavior on the water surface from a hydrodynamics perspective. A physical model and computational model of the robotic dolphin’s surface SAT behavior were established. After numerous attempts, the surface SAT behavior of the robotic dolphin was successfully replicated through coordinated movements of the body, caudal fin, and pectoral fins, and the quantitative relationship between controllable parameters and hydrodynamic performance was investigated. By combining data analysis and flow field distribution patterns, the underlying physical mechanisms of the robotic dolphin’s surface SAT behavior were revealed. The results indicate that the turning trajectory of SAT behavior exhibits a circular characteristic, and the turning radius can be adjusted by modifying the kinematic parameters. Additionally, when the movement parameters of the body and caudal fin are fixed, and the phase difference between the two pectoral fins is <em>T</em>/2, the robotic dolphin achieves optimal turning maneuverability, with a maximum turning speed of 1.69 rad/s and a turning efficiency of up to 45.5%. Notably, by optimizing kinematic parameters, the robotic dolphin achieves cross-medium <em>in-situ</em> turning with exceptionally high maneuverability, which is indeed a very valuable discovery. The findings provide a cross-medium fluid dynamics explanation for the development of BUVs with dual underwater/surface operating capabilities.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104512"},"PeriodicalIF":3.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980244","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}
Pub Date : 2026-01-12DOI: 10.1016/j.jfluidstructs.2026.104513
Hao Liu , Shaowei Wang , Moli Zhao , Peiyuan Wang , Shuai Liu , Yegao Qu
The vortex-induced vibration (VIV) dynamics of a flexible splitter beam interacting with the laminar wake flow of a circular cylinder in shear-thinning and shear-thickening fluids are investigated using a partitioned nonlinear fluid-structure interaction simulation. The flow field is modeled within an Arbitrary Lagrangian-Eulerian (ALE) framework based on the finite volume method. To capture the beam's large deformations, Reddy's higher-order shear deformation theory is employed in conjunction with von Kármán strain formulations. After validating the present method, a comprehensive analysis is conducted to investigate the effects of the following parameters, including beam characteristic length (L/H = 10 and 15), inflow velocity (0.5 m/s ≤ Ur ≤ 3 m/s), power-law index (0.6 ≤ n ≤ 1.4) and time constant (0.2 s ≤ ≤ 4 s) on the VIV characteristics (including limit-cycle oscillation, vortex shedding pattern and viscosity distribution) are discussed. Several distinct deformation regimes of elastic beams are observed: first or second mode-like vibration regimes; standing or traveling wave deflection vibration regimes; the large amplitude traveling wave symmetry vibration regimes; and periodic or quasi-periodic dual-frequency vibration regimes. These different regimes result in variations in the wake vortex modes, specifically the '2S' (two single vortices of opposite sign) and '2P' (two pairs of vortices) modes. Key findings indicate that shear-thinning fluids lowers the onset point of VIV in comparison with Newtonian fluids, while shear-thickening fluids elevates it, suggesting a viscous damping effect. Additionally, shear-thinning fluids amplify vorticity intensity and contract the wake region, while shear-thickening fluids suppress vorticity generation and significantly elongate the wake. Moreover, a higher time constant in shear-thinning fluids amplifies vibrations by enhancing vorticity persistence and energy transfer. In shear-thickening fluids, however, it suppresses VIV by promoting viscosity-dominated damping.
{"title":"Vortex-induced vibration dynamics of a splitter beam behind a cylinder in shear-thinning or shear-thickening non-Newtonian fluids","authors":"Hao Liu , Shaowei Wang , Moli Zhao , Peiyuan Wang , Shuai Liu , Yegao Qu","doi":"10.1016/j.jfluidstructs.2026.104513","DOIUrl":"10.1016/j.jfluidstructs.2026.104513","url":null,"abstract":"<div><div>The vortex-induced vibration (VIV) dynamics of a flexible splitter beam interacting with the laminar wake flow of a circular cylinder in shear-thinning and shear-thickening fluids are investigated using a partitioned nonlinear fluid-structure interaction simulation. The flow field is modeled within an Arbitrary Lagrangian-Eulerian (ALE) framework based on the finite volume method. To capture the beam's large deformations, Reddy's higher-order shear deformation theory is employed in conjunction with von Kármán strain formulations. After validating the present method, a comprehensive analysis is conducted to investigate the effects of the following parameters, including beam characteristic length (<em>L</em>/<em>H</em> = 10 and 15), inflow velocity (0.5 m/s ≤ <em>U<sub>r</sub></em> ≤ 3 m/s), power-law index (0.6 ≤ <em>n</em> ≤ 1.4) and time constant (0.2 s ≤ <span><math><mi>λ</mi></math></span> ≤ 4 s) on the VIV characteristics (including limit-cycle oscillation, vortex shedding pattern and viscosity distribution) are discussed. Several distinct deformation regimes of elastic beams are observed: first or second mode-like vibration regimes; standing or traveling wave deflection vibration regimes; the large amplitude traveling wave symmetry vibration regimes; and periodic or quasi-periodic dual-frequency vibration regimes. These different regimes result in variations in the wake vortex modes, specifically the '2S' (two single vortices of opposite sign) and '2P' (two pairs of vortices) modes. Key findings indicate that shear-thinning fluids lowers the onset point of VIV in comparison with Newtonian fluids, while shear-thickening fluids elevates it, suggesting a viscous damping effect. Additionally, shear-thinning fluids amplify vorticity intensity and contract the wake region, while shear-thickening fluids suppress vorticity generation and significantly elongate the wake. Moreover, a higher time constant in shear-thinning fluids amplifies vibrations by enhancing vorticity persistence and energy transfer. In shear-thickening fluids, however, it suppresses VIV by promoting viscosity-dominated damping.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104513"},"PeriodicalIF":3.5,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980248","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}
Pub Date : 2026-01-11DOI: 10.1016/j.jfluidstructs.2025.104498
Masoud Hayatdavoodi , Shuijin Li
The interaction of combined waves and current with floating bodies is studied by conducting laboratory experiments and by developing theoretical models. The laboratory experiments are conducted in a wave-current tank using two floating cylinders with circular and square waterplane areas. Both freely floating and moored conditions are considered. Two theoretical models are developed to study wave-body and wave-current-body interactions: one based on the computational fluid dynamics and the other following the linear wave-current diffraction theory using the Green function method. Results from these models are compared with laboratory measurements for a range of wave and wave-current conditions. The study analyses the effect of ambient current on the wave-induced motions of floating bodies and evaluates how well the models capture the wave-current-body interactions. Additionally, the effect of the square cylinder’s sharp edges on wave-current-body interactions is analysed in comparison to the circular cylinder, along with the models’ capability to capture these effects. It is observed that the presence of the current not only causes significant drift of the freely floating cylinders, but also affects their surge and pitch oscillations, while having no notable effect on heave motion. For the conditions considered, the linear theory based on the Green function method provides overall good predictions of the floating bodies’ responses at a significantly lower computational cost compared to the computational fluid dynamics model.
{"title":"Wave-current-floating body interactions: Experiments and modelling","authors":"Masoud Hayatdavoodi , Shuijin Li","doi":"10.1016/j.jfluidstructs.2025.104498","DOIUrl":"10.1016/j.jfluidstructs.2025.104498","url":null,"abstract":"<div><div>The interaction of combined waves and current with floating bodies is studied by conducting laboratory experiments and by developing theoretical models. The laboratory experiments are conducted in a wave-current tank using two floating cylinders with circular and square waterplane areas. Both freely floating and moored conditions are considered. Two theoretical models are developed to study wave-body and wave-current-body interactions: one based on the computational fluid dynamics and the other following the linear wave-current diffraction theory using the Green function method. Results from these models are compared with laboratory measurements for a range of wave and wave-current conditions. The study analyses the effect of ambient current on the wave-induced motions of floating bodies and evaluates how well the models capture the wave-current-body interactions. Additionally, the effect of the square cylinder’s sharp edges on wave-current-body interactions is analysed in comparison to the circular cylinder, along with the models’ capability to capture these effects. It is observed that the presence of the current not only causes significant drift of the freely floating cylinders, but also affects their surge and pitch oscillations, while having no notable effect on heave motion. For the conditions considered, the linear theory based on the Green function method provides overall good predictions of the floating bodies’ responses at a significantly lower computational cost compared to the computational fluid dynamics model.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104498"},"PeriodicalIF":3.5,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980337","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}
Pub Date : 2026-01-09DOI: 10.1016/j.jfluidstructs.2025.104499
Yuxiang Ying, Geng Guan, Tongxiao Jiang, Amin Ullah, JianZhong Lin
Microswimmers exhibit remarkable dynamic properties in fluid environments, making them important for advancing the fields of fluid mechanics and biophysics. In this study, we extended the classical squirmer model to an ellipsoidal geometry and investigated its swimming behavior in a three-dimensional square-tube flow. The results were compared with those of a spherical microswimmer. By systematically varying key parameters, including the self-propulsion strength (α), swimming type factor (β), chirality factor (χ), and flow field Reynolds number (Rem), we identified five distinct swimming modes: near-wall helical motion, near-center helical motion, steady linear motion, zigzag motion, and near-wall double-helical motion, in which the microswimmer exhibited two different swimming directions (upstream and downstream). The results show that chirality and geometric anisotropy significantly influenced the swimming behavior of the microswimmer. The formation of swimming modes is also related to the pressure distribution between the microswimmer and the wall. In addition, the swimming velocity and helical frequency of the microswimmer increased with increasing α or Rem; however, the increase in the Reynolds number did not change the swimming mode of the microswimmer. Our research is expected to promote the understanding of the motion characteristics of active matter in dynamic flows and provide valuable insights into the design of efficient and controllable artificial microswimmers for biomedical and environmental applications.
{"title":"Dynamics of elongated microswimmers in a square-tube flow","authors":"Yuxiang Ying, Geng Guan, Tongxiao Jiang, Amin Ullah, JianZhong Lin","doi":"10.1016/j.jfluidstructs.2025.104499","DOIUrl":"10.1016/j.jfluidstructs.2025.104499","url":null,"abstract":"<div><div>Microswimmers exhibit remarkable dynamic properties in fluid environments, making them important for advancing the fields of fluid mechanics and biophysics. In this study, we extended the classical squirmer model to an ellipsoidal geometry and investigated its swimming behavior in a three-dimensional square-tube flow. The results were compared with those of a spherical microswimmer. By systematically varying key parameters, including the self-propulsion strength (<em>α</em>), swimming type factor (<em>β</em>), chirality factor (<em>χ</em>), and flow field Reynolds number (<em>Re<sub>m</sub></em>), we identified five distinct swimming modes: near-wall helical motion, near-center helical motion, steady linear motion, zigzag motion, and near-wall double-helical motion, in which the microswimmer exhibited two different swimming directions (upstream and downstream). The results show that chirality and geometric anisotropy significantly influenced the swimming behavior of the microswimmer. The formation of swimming modes is also related to the pressure distribution between the microswimmer and the wall. In addition, the swimming velocity and helical frequency of the microswimmer increased with increasing <em>α</em> or <em>Re<sub>m</sub></em>; however, the increase in the Reynolds number did not change the swimming mode of the microswimmer. Our research is expected to promote the understanding of the motion characteristics of active matter in dynamic flows and provide valuable insights into the design of efficient and controllable artificial microswimmers for biomedical and environmental applications.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104499"},"PeriodicalIF":3.5,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929241","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}
Pub Date : 2026-01-08DOI: 10.1016/j.jfluidstructs.2025.104500
Cristiano Biagioli, Francesco Serraino, Valerio Belardi, Francesco Vivio
This study investigates liquid sloshing in a rectangular tank equipped with horizontal flexible baffles to understand their influence on sloshing mitigation and intricate fluid-structure interaction (FSI) phenomena. A two-way coupled FSI model was developed using the Finite Element Method (FEM) for structural analysis and Finite Volume Method (FVM) with the Volume Of Fluid (VOF) formulation for fluid dynamics, employing a partitioned coupling strategy. Numerical decay tests explored dynamic behavior by varying baffle Young’s modulus and submergence levels. Enstrophy evolution was investigated as a robust indicator for quantifying energy dissipation associated with vortex dynamics, and a reduced-order acoustic-structural model was benchmarked as a tool for predicting fundamental frequency shifts. The FSI simulation methodology was validated against experimental results from previous literature, showing close agreement.
Key outcomes reveal that baffle stiffness critically governs system response, with appropriate flexibility significantly enhancing damping performance. For submerged baffles, increasing flexibility led to optimal damping driven by maximal vortex-induced energy loss. Conversely, shallow baffles showed superior damping with rigid configurations, primarily due to pressure drag rather than vortex dynamics. While initial conditions introduced transient nonlinearities with flexible baffles, overall trends for damping and frequency remained consistent. The simplified frequency-prediction model was reliable for practical flexibility ranges, but less accurate for extreme flexibility. Overall, this work deepens understanding of how baffle characteristics influence slosh mitigation, offering valuable guidance for anti-sloshing device engineering.
{"title":"Impact of baffle flexibility on sloshing mitigation: A parametric study using partitioned two-way fluid-structure interaction","authors":"Cristiano Biagioli, Francesco Serraino, Valerio Belardi, Francesco Vivio","doi":"10.1016/j.jfluidstructs.2025.104500","DOIUrl":"10.1016/j.jfluidstructs.2025.104500","url":null,"abstract":"<div><div>This study investigates liquid sloshing in a rectangular tank equipped with horizontal flexible baffles to understand their influence on sloshing mitigation and intricate fluid-structure interaction (FSI) phenomena. A two-way coupled FSI model was developed using the Finite Element Method (FEM) for structural analysis and Finite Volume Method (FVM) with the Volume Of Fluid (VOF) formulation for fluid dynamics, employing a partitioned coupling strategy. Numerical decay tests explored dynamic behavior by varying baffle Young’s modulus and submergence levels. Enstrophy evolution was investigated as a robust indicator for quantifying energy dissipation associated with vortex dynamics, and a reduced-order acoustic-structural model was benchmarked as a tool for predicting fundamental frequency shifts. The FSI simulation methodology was validated against experimental results from previous literature, showing close agreement.</div><div>Key outcomes reveal that baffle stiffness critically governs system response, with appropriate flexibility significantly enhancing damping performance. For submerged baffles, increasing flexibility led to optimal damping driven by maximal vortex-induced energy loss. Conversely, shallow baffles showed superior damping with rigid configurations, primarily due to pressure drag rather than vortex dynamics. While initial conditions introduced transient nonlinearities with flexible baffles, overall trends for damping and frequency remained consistent. The simplified frequency-prediction model was reliable for practical flexibility ranges, but less accurate for extreme flexibility. Overall, this work deepens understanding of how baffle characteristics influence slosh mitigation, offering valuable guidance for anti-sloshing device engineering.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"142 ","pages":"Article 104500"},"PeriodicalIF":3.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929240","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}
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