Pub Date : 2025-11-05DOI: 10.1016/j.jfluidstructs.2025.104446
Divyaprakash, Amitabh Bhattacharya
Passive biological cilia function as sensory organelles in various animal cells and microorganisms. In this computational study, we demonstrate that tip and base perturbations in an array of flexible passive artificial cilia may be used to detect the size and aspect ratio of ellipse-shaped particles immersed in an oscillatory Couette flow setup. Two-dimensional numerical simulations of the system are carried out for varying particle shape and size, and the immersed boundary method is used to couple the fluid and structure solvers. Kirchhoff rod theory and finite element method are used to evolve the elastic forces in cilia and particle, respectively. A machine learning model, comprising a Long Short-Term Memory (LSTM) network coupled with a regression layer, is trained using the generated data, in which features such as cilia tip deflection and base angle at three time instances are used to sense the particle size and shape. Using unseen simulation data, we show that the trained model is capable of predicting the size and aspect ratio of the particle within an average prediction error of 6 percent over the entire dataset. The model using cilia base deflection appears to be less sensitive to particle aspect ratio compared to the model using cilia tip deflection, especially for smaller particles. This non-optical sensing technique is especially useful for detecting particle size and shape in opaque liquids.
{"title":"Machine learning based sensing of particle shape and size using passive artificial cilia","authors":"Divyaprakash, Amitabh Bhattacharya","doi":"10.1016/j.jfluidstructs.2025.104446","DOIUrl":"10.1016/j.jfluidstructs.2025.104446","url":null,"abstract":"<div><div>Passive biological cilia function as sensory organelles in various animal cells and microorganisms. In this computational study, we demonstrate that tip and base perturbations in an array of flexible passive artificial cilia may be used to detect the size and aspect ratio of ellipse-shaped particles immersed in an oscillatory Couette flow setup. Two-dimensional numerical simulations of the system are carried out for varying particle shape and size, and the immersed boundary method is used to couple the fluid and structure solvers. Kirchhoff rod theory and finite element method are used to evolve the elastic forces in cilia and particle, respectively. A machine learning model, comprising a Long Short-Term Memory (LSTM) network coupled with a regression layer, is trained using the generated data, in which features such as cilia tip deflection and base angle at three time instances are used to sense the particle size and shape. Using unseen simulation data, we show that the trained model is capable of predicting the size and aspect ratio of the particle within an average prediction error of 6 percent over the entire dataset. The model using cilia base deflection appears to be less sensitive to particle aspect ratio compared to the model using cilia tip deflection, especially for smaller particles. This non-optical sensing technique is especially useful for detecting particle size and shape in opaque liquids.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"140 ","pages":"Article 104446"},"PeriodicalIF":3.5,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145475023","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 : 2025-11-03DOI: 10.1016/j.jfluidstructs.2025.104447
Yang Huang , Qing Xiao , Liu Yang , Saishuai Dai , Saeid Lotfian , Feargal Brennan
Flexible wave energy converters (FlexWECs) have emerged as a promising solution to address the limitations of conventional rigid devices in harsh marine environments. Among them, oscillating water column (OWC) systems integrated with dielectric elastomer generators (DEGs) offer simplified architectures, enhanced adaptability, and direct wave-to-electric energy conversion. However, the complex multiphysics interactions between fluid, structure, and electric fields remain poorly understood, hindering design optimization and performance prediction. This study develops a high-fidelity computational framework to simulate the coupled fluid-structure-electric behaviour of a flexible OWC wave energy converter (WEC) with a DEG membrane. The framework is first validated against experimental data, demonstrating good agreement in capturing the deformation of the flexible membrane induced by the coupled electrostatic and hydrodynamic forces. Subsequently, the model is applied to investigate how electric field influences the WEC system behaviour under regular wave excitation. Results show that applying an electric field reduces the effective stiffness of the membrane, leading to increased deformation. Additionally, it does raise overall structural stress levels, especially near the membrane centre and edge regions, where the maximum stresses are observed. Notably, electric excitation induces a secondary deformation mode in the membrane during the near-flat phase. These effects become more pronounced with increasing initial voltage, which also leads to an approximately quadratic increase in output power. The insights gained from this study provide a deeper understanding of fluid-structure-electricity (FSE) interactions in flexible OWC WECs and offer design guidance for enhancing energy harvesting efficiency in next-generation WEC devices.
{"title":"Multiphysics analysis of a flexible oscillating water column wave energy converter with dielectric elastomer membrane","authors":"Yang Huang , Qing Xiao , Liu Yang , Saishuai Dai , Saeid Lotfian , Feargal Brennan","doi":"10.1016/j.jfluidstructs.2025.104447","DOIUrl":"10.1016/j.jfluidstructs.2025.104447","url":null,"abstract":"<div><div>Flexible wave energy converters (FlexWECs) have emerged as a promising solution to address the limitations of conventional rigid devices in harsh marine environments. Among them, oscillating water column (OWC) systems integrated with dielectric elastomer generators (DEGs) offer simplified architectures, enhanced adaptability, and direct wave-to-electric energy conversion. However, the complex multiphysics interactions between fluid, structure, and electric fields remain poorly understood, hindering design optimization and performance prediction. This study develops a high-fidelity computational framework to simulate the coupled fluid-structure-electric behaviour of a flexible OWC wave energy converter (WEC) with a DEG membrane. The framework is first validated against experimental data, demonstrating good agreement in capturing the deformation of the flexible membrane induced by the coupled electrostatic and hydrodynamic forces. Subsequently, the model is applied to investigate how electric field influences the WEC system behaviour under regular wave excitation. Results show that applying an electric field reduces the effective stiffness of the membrane, leading to increased deformation. Additionally, it does raise overall structural stress levels, especially near the membrane centre and edge regions, where the maximum stresses are observed. Notably, electric excitation induces a secondary deformation mode in the membrane during the near-flat phase. These effects become more pronounced with increasing initial voltage, which also leads to an approximately quadratic increase in output power. The insights gained from this study provide a deeper understanding of fluid-structure-electricity (FSE) interactions in flexible OWC WECs and offer design guidance for enhancing energy harvesting efficiency in next-generation WEC devices.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"140 ","pages":"Article 104447"},"PeriodicalIF":3.5,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145475027","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}
Oceangoing ships may encounter rarely occurring waves like freak waves during their operational lifespan, which largely affects the safety of ships. In this paper a two-way CFD-FEM fluid-structure coupled method is adopted to simulate ship motions and wave load responses in three-dimensional (3D) freak waves. First, in-house code using MATLAB is developed to generate wave parameters which are used for generating short-crested waves and 3D freak waves in the CFD solver. The simulated freak waves are examined and the evolution of freak waves during propagation process is analyzed. Then, ship motions and wave loads considering hydroelastic response in 3D short-crested waves and in 3D freak waves are analyzed. The increase in motions and load responses when ship encountering freak waves is studied quantitatively. This study provides some insights into ship extreme dynamic responses in realistic seaways and in extreme freak waves.
{"title":"Numerical simulation of ship hydroelastic responses in 3D realistic ocean waves with occurrence of freak waves","authors":"Jialong Jiao , Zhenwei Chen , Yuanming Chen , Shuai Chen , Caixia Jiang","doi":"10.1016/j.jfluidstructs.2025.104448","DOIUrl":"10.1016/j.jfluidstructs.2025.104448","url":null,"abstract":"<div><div>Oceangoing ships may encounter rarely occurring waves like freak waves during their operational lifespan, which largely affects the safety of ships. In this paper a two-way CFD-FEM fluid-structure coupled method is adopted to simulate ship motions and wave load responses in three-dimensional (3D) freak waves. First, in-house code using MATLAB is developed to generate wave parameters which are used for generating short-crested waves and 3D freak waves in the CFD solver. The simulated freak waves are examined and the evolution of freak waves during propagation process is analyzed. Then, ship motions and wave loads considering hydroelastic response in 3D short-crested waves and in 3D freak waves are analyzed. The increase in motions and load responses when ship encountering freak waves is studied quantitatively. This study provides some insights into ship extreme dynamic responses in realistic seaways and in extreme freak waves.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"140 ","pages":"Article 104448"},"PeriodicalIF":3.5,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145475028","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 : 2025-10-24DOI: 10.1016/j.jfluidstructs.2025.104439
Rahul Kumar, Devranjan Samanta, Srikant S. Padhee
Drawing inspiration from the adaptive wing shape of birds in flight, this study introduces a bio-inspired concept for shape adaptation utilizing bend-twist coupling (BTC) in composite laminates. The primary aim of the design optimization is to identify the optimal fibre orientation angles needed to produce the required bending and twisting deformations, which directly contribute to the design's goal of maximizing lift without relying on external mechanisms for twisting. This novel technique increases lift by up to five times compared to a curved bending wing. We have highlighted the vortex dynamics to provide insight into the underlying reasons for such a significant lift increment. In addition, the study presents the Von Mises stress experienced by the wing, offering a comprehensive understanding of the structural behavior. Furthermore, it highlights a significant improvement in efficiency, particularly within the optimal reduced frequency range of 0.25 to 0.4. These findings underscore the potential of this method for future applications in biomimetic drones, unmanned flapping wing vehicles (UFWVs), and other flapping wing-based systems, ultimately paving the way for new advancements in aerodynamics and structural optimization for next-generation aerial vehicle designs.
{"title":"Lift augmentation by incorporating bend twist coupled composites in flapping wing","authors":"Rahul Kumar, Devranjan Samanta, Srikant S. Padhee","doi":"10.1016/j.jfluidstructs.2025.104439","DOIUrl":"10.1016/j.jfluidstructs.2025.104439","url":null,"abstract":"<div><div>Drawing inspiration from the adaptive wing shape of birds in flight, this study introduces a bio-inspired concept for shape adaptation utilizing bend-twist coupling (BTC) in composite laminates. The primary aim of the design optimization is to identify the optimal fibre orientation angles needed to produce the required bending and twisting deformations, which directly contribute to the design's goal of maximizing lift without relying on external mechanisms for twisting. This novel technique increases lift by up to five times compared to a curved bending wing. We have highlighted the vortex dynamics to provide insight into the underlying reasons for such a significant lift increment. In addition, the study presents the Von Mises stress experienced by the wing, offering a comprehensive understanding of the structural behavior. Furthermore, it highlights a significant improvement in efficiency, particularly within the optimal reduced frequency range of 0.25 to 0.4. These findings underscore the potential of this method for future applications in biomimetic drones, unmanned flapping wing vehicles (UFWVs), and other flapping wing-based systems, ultimately paving the way for new advancements in aerodynamics and structural optimization for next-generation aerial vehicle designs.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"140 ","pages":"Article 104439"},"PeriodicalIF":3.5,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145340659","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 : 2025-10-23DOI: 10.1016/j.jfluidstructs.2025.104444
D.A. Pulido-Caviedes , J.A. Licea-Salazar , A. Cros
We study the stability of a rectangular, flexible plate subject to twisting motions and immersed in a uniform, incompresible axial flow. The twisting motion is characterized by the angle where is the axial coordinate and is time, in such a way that no spanwise curvature is allowed. The complex fluid–structure interaction is governed by the torque which comes from the pressure difference between both faces of the plate. By writting the boundary conditions in the Fourier space, the three-dimensional flow potential generated by the twisting flexible plate is calculated and the torque is estimated. Subsequently, the Galerkin method enables the estimation of the frequency and growth rate of each plate mode as a function of three nondimensional parameters: a reduced fluid velocity, the mass ratio between the fluid and plate densities, and the aspect ratio of the plate. Three different boundary conditions are analyzed: clamped-free, clamped-clamped and free-free. We find that, in all three cases, mode 1 first destabilizes through divergence when the fluid velocity is increased. At higher speed values, fluttering develops as a combination of the first two modes in both the free-free and clamped-clamped configurations. Our findings also suggest that greater plate mass and reduced width contribute to improved plate stability and for a given aspect ratio, the critical velocities evolve as .
{"title":"Stability analysis of a twisting flexible plate immersed in an axial airflow","authors":"D.A. Pulido-Caviedes , J.A. Licea-Salazar , A. Cros","doi":"10.1016/j.jfluidstructs.2025.104444","DOIUrl":"10.1016/j.jfluidstructs.2025.104444","url":null,"abstract":"<div><div>We study the stability of a rectangular, flexible plate subject to twisting motions and immersed in a uniform, incompresible axial flow. The twisting motion is characterized by the angle <span><math><mrow><mi>ϕ</mi><mrow><mo>(</mo><mi>x</mi><mo>,</mo><mi>t</mi><mo>)</mo></mrow></mrow></math></span> where <span><math><mi>x</mi></math></span> is the axial coordinate and <span><math><mi>t</mi></math></span> is time, in such a way that no spanwise curvature is allowed. The complex fluid–structure interaction is governed by the torque which comes from the pressure difference between both faces of the plate. By writting the boundary conditions in the Fourier space, the three-dimensional flow potential generated by the twisting flexible plate is calculated and the torque is estimated. Subsequently, the Galerkin method enables the estimation of the frequency and growth rate of each plate mode as a function of three nondimensional parameters: a reduced fluid velocity, the mass ratio <span><math><mi>M</mi></math></span> between the fluid and plate densities, and the aspect ratio of the plate. Three different boundary conditions are analyzed: clamped-free, clamped-clamped and free-free. We find that, in all three cases, mode 1 first destabilizes through divergence when the fluid velocity is increased. At higher speed values, fluttering develops as a combination of the first two modes in both the free-free and clamped-clamped configurations. Our findings also suggest that greater plate mass and reduced width contribute to improved plate stability and for a given aspect ratio, the critical velocities evolve as <span><math><mrow><mn>1</mn><mo>/</mo><msqrt><mrow><mi>M</mi></mrow></msqrt></mrow></math></span>.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"140 ","pages":"Article 104444"},"PeriodicalIF":3.5,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145340657","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 : 2025-10-23DOI: 10.1016/j.jfluidstructs.2025.104443
Jiayun Zhang , Yongshun Zeng , Peijian Zhou , Wei Wang , Lingjiu Zhou , Zhifeng Yao
This paper investigates the modal characteristics of an underwater disc at different rotation speeds through modal testing. Modal testing was performed on the underwater disc within a rotation speed range of 0 to 720 rpm using a specially designed experimental setup. Modal analysis was conducted to extract the natural frequencies, damping ratios, and mode shapes of the disc. The study focuses on the characteristics of Coupled Nodal Circle and Diameter (CNCD) modes related to rotation speeds. The results show that: (1) the mode shapes and natural frequencies of the non-rotating underwater disc are consistent with the analytical predictions; (2) experiments show that CNCD mode frequencies agree with the analytical model’s forward-wave predictions, exhibit no splitting due to weak Coriolis force and circulatory forces effects, and that backward waves are overdamped due to higher shear; (3) for RC〈 0.43, CNCD mode damping ratios remain stable under hydrostatic viscous damping. When RC〉 0.43, the (2,1) mode exhibits a significant damping increase, indicating dominance of dynamic hydroelastic damping; (4) resonance was amplified when CNCD modes overlapped with nodal diameter modes, and these speeds should be avoided in engineering practice. The findings provide insights for the design of impellers in high-head pump turbines and the operational performance of such units.
{"title":"Experimental study on modal characteristics of an underwater rotating disc in coupled nodal circle and diameter modes","authors":"Jiayun Zhang , Yongshun Zeng , Peijian Zhou , Wei Wang , Lingjiu Zhou , Zhifeng Yao","doi":"10.1016/j.jfluidstructs.2025.104443","DOIUrl":"10.1016/j.jfluidstructs.2025.104443","url":null,"abstract":"<div><div>This paper investigates the modal characteristics of an underwater disc at different rotation speeds through modal testing. Modal testing was performed on the underwater disc within a rotation speed range of 0 to 720 rpm using a specially designed experimental setup. Modal analysis was conducted to extract the natural frequencies, damping ratios, and mode shapes of the disc. The study focuses on the characteristics of Coupled Nodal Circle and Diameter (CNCD) modes related to rotation speeds. The results show that: (1) the mode shapes and natural frequencies of the non-rotating underwater disc are consistent with the analytical predictions; (2) experiments show that CNCD mode frequencies agree with the analytical model’s forward-wave predictions, exhibit no splitting due to weak Coriolis force and circulatory forces effects, and that backward waves are overdamped due to higher shear; (3) for <em>RC</em>〈 0.43, CNCD mode damping ratios remain stable under hydrostatic viscous damping. When <em>RC</em>〉 0.43, the (2,1) mode exhibits a significant damping increase, indicating dominance of dynamic hydroelastic damping; (4) resonance was amplified when CNCD modes overlapped with nodal diameter modes, and these speeds should be avoided in engineering practice. The findings provide insights for the design of impellers in high-head pump turbines and the operational performance of such units.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"140 ","pages":"Article 104443"},"PeriodicalIF":3.5,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145340658","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 : 2025-10-22DOI: 10.1016/j.jfluidstructs.2025.104442
Arthur Haudeville , Xavier Amandolese , Boris Lossouarn , Christophe Giraud-Audine , Olivier Thomas
The present work investigates the ability of a reduced-order fluid–structure model to estimate the vortex-induced vibrations (VIV) of marine lifting surface under hydrodynamic flow, such as hydrofoils. A particular VIV area is scrutinized, for which a hydrodynamic excitation mechanism due to a Kármán-type vortex wake organization successively locks the first twisting and second bending mode of a cantilever truncated hydrofoil. Coupling two structural oscillators with a Van der Pol wake oscillator satisfactorily reproduces the amplitude response and the lock-in frequency. This work also investigates the ability of a piezo-elasto-hydrodynamic model to anticipate the vibration amplitude of the hydrofoil when mitigated thanks to a resonant piezoelectric shunt. Composed of an inductance in series with a resistance connected to a piezoelectric patch, the passive shunt was tuned to minimize the vibration amplitude in the frequency lock-in range. The proposed semi-empirical models are fitted to experimental results in order to reproduce the coupled system’s dynamic.
{"title":"Low-order coupled model for vortex-induced vibrations mitigation by resonant piezoelectric shunt","authors":"Arthur Haudeville , Xavier Amandolese , Boris Lossouarn , Christophe Giraud-Audine , Olivier Thomas","doi":"10.1016/j.jfluidstructs.2025.104442","DOIUrl":"10.1016/j.jfluidstructs.2025.104442","url":null,"abstract":"<div><div>The present work investigates the ability of a reduced-order fluid–structure model to estimate the vortex-induced vibrations (VIV) of marine lifting surface under hydrodynamic flow, such as hydrofoils. A particular VIV area is scrutinized, for which a hydrodynamic excitation mechanism due to a Kármán-type vortex wake organization successively locks the first twisting and second bending mode of a cantilever truncated hydrofoil. Coupling two structural oscillators with a Van der Pol wake oscillator satisfactorily reproduces the amplitude response and the lock-in frequency. This work also investigates the ability of a piezo-elasto-hydrodynamic model to anticipate the vibration amplitude of the hydrofoil when mitigated thanks to a resonant piezoelectric shunt. Composed of an inductance in series with a resistance connected to a piezoelectric patch, the passive shunt was tuned to minimize the vibration amplitude in the frequency lock-in range. The proposed semi-empirical models are fitted to experimental results in order to reproduce the coupled system’s dynamic.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"139 ","pages":"Article 104442"},"PeriodicalIF":3.5,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145363700","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 : 2025-10-22DOI: 10.1016/j.jfluidstructs.2025.104438
Jiawei Shen , Shixiao Fu , Xuepeng Fu , Torgeir Moan , Svein Sævik
Flow-induced vibration (FIV) commonly occurs in rigidly coupled twin-pipe structures. However, the limited understanding of their FIV responses and hydrodynamic features presents a major challenge to the development of reliable engineering designs. To bridge this gap, the present study experimentally investigates the FIV characteristics of a rigidly coupled twin-pipe model with elastic support using a virtual physical framework (VPF), which enables flexible control of structural parameters during physical testing. A distinctive feature of twin-pipe structures is the presence of in-line hydrodynamic interactions and torsional moments arising from the rigid coupling. The in-line interaction is primarily compressive and becomes more pronounced as the mass ratio increases. The torsional moment coefficient exhibits a rise–fall trend with increasing reduced velocity and stabilizes around 0.46 at low mass ratios. In addition, an “amplitude drop” phenomenon is observed near , attributed to energy dissipation from the downstream pipe. The mass ratio significantly affects FIV amplitude, frequency, and hydrodynamic coefficients. As the mass ratio decreases, the synchronization region broadens and the hydrodynamic coefficients become more stable. Meanwhile, at mass ratio of 1.0, a “resonance forever” behavior is observed. Damping primarily suppresses FIV amplitude, with minimal impact on dominant frequency and hydrodynamic coefficients. These findings provide valuable insights into twin-pipe FIV mechanisms and support a scientific basis for future structural design optimization.
{"title":"Flow-induced vibration of twin-pipe model with varying mass and damping: A study using virtual physical framework","authors":"Jiawei Shen , Shixiao Fu , Xuepeng Fu , Torgeir Moan , Svein Sævik","doi":"10.1016/j.jfluidstructs.2025.104438","DOIUrl":"10.1016/j.jfluidstructs.2025.104438","url":null,"abstract":"<div><div>Flow-induced vibration (FIV) commonly occurs in rigidly coupled twin-pipe structures. However, the limited understanding of their FIV responses and hydrodynamic features presents a major challenge to the development of reliable engineering designs. To bridge this gap, the present study experimentally investigates the FIV characteristics of a rigidly coupled twin-pipe model with elastic support using a virtual physical framework (VPF), which enables flexible control of structural parameters during physical testing. A distinctive feature of twin-pipe structures is the presence of in-line hydrodynamic interactions and torsional moments arising from the rigid coupling. The in-line interaction is primarily compressive and becomes more pronounced as the mass ratio increases. The torsional moment coefficient exhibits a rise–fall trend with increasing reduced velocity <span><math><msub><mrow><mi>U</mi></mrow><mrow><mi>R</mi></mrow></msub></math></span> and stabilizes around 0.46 at low mass ratios. In addition, an “amplitude drop” phenomenon is observed near <span><math><mrow><msub><mrow><mi>U</mi></mrow><mrow><mi>R</mi></mrow></msub><mo>=</mo><mn>6</mn></mrow></math></span>, attributed to energy dissipation from the downstream pipe. The mass ratio significantly affects FIV amplitude, frequency, and hydrodynamic coefficients. As the mass ratio decreases, the synchronization region broadens and the hydrodynamic coefficients become more stable. Meanwhile, at mass ratio of 1.0, a “resonance forever” behavior is observed. Damping primarily suppresses FIV amplitude, with minimal impact on dominant frequency and hydrodynamic coefficients. These findings provide valuable insights into twin-pipe FIV mechanisms and support a scientific basis for future structural design optimization.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"139 ","pages":"Article 104438"},"PeriodicalIF":3.5,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145363699","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 : 2025-10-18DOI: 10.1016/j.jfluidstructs.2025.104440
Wenlong Luo , Bo Huang , Lihua Wang , Jing Chen , Hongbo Su , Jianting Zhou , Hao Ding , Ke Li , Liang Cheng , Dan Zhong
The submerged floating tunnel (SFT) is a new type of transportation structure used to cross water areas. In complex marine environments, the long-span SFT is subjected to nonlinear coupled effects of multiple loads, resulting in extremely complex dynamic responses. At present, the calculation methods for the dynamic response of the long-span SFT in marine environments have the following main deficiencies: (1) When different cable models, tube-end boundary conditions, and load patterns are adopted, the resulting mathematical models of the SFT often exhibit different expressions, with complex governing equations. The models lack flexibility and generality when considering different cable arrangements and load combinations. Existing studies are typically limited to fixed structural configurations under single-load effects. (2) Restricted by computational costs, the Morison equation is commonly used to calculate fluid loads on long-span SFTs. This equation can only account for one-way fluid-structure interaction (FSI) effects, fails to compute the torque exerted by fluids on the SFT tube, and ignores the influence of seabed topography on the flow field. Addressing the current research gaps in the analysis of dynamic characteristics of the long-span SFT under marine conditions, particularly the challenges in two-way FSI computation for long-span configurations, this paper proposes a time-domain computational method for dynamic response analysis of the long-span SFT under coupled action of multiple loads, which provides a general computational framework for dealing with the multi-load action problems of SFTs. The computational framework incorporates a two-way FSI calculation model based on a system of two-dimensional potential flow wave flumes, which overcomes the limitations in computational efficiency in bidirectional coupling analysis of the long-span SFT, and addresses the challenges in the applicability of the Morison equation under complex working conditions. This paper verifies the correctness of the proposed method for calculating structural dynamic responses by comparing the calculation results of finite element mode. The accuracy of the potential flow flume in calculating wave loads is also verified by comparing with the calculation results of the viscous fluid model. Finally, by comparing with the results of the frequency-domain calculation of dynamic responses of the SFT, it demonstrates the reliability of the FSI calculation.
{"title":"A time-domain computational method for the assessment of the dynamic response of long-span submerged floating tunnels under coupled action of multiple loads in marine environments","authors":"Wenlong Luo , Bo Huang , Lihua Wang , Jing Chen , Hongbo Su , Jianting Zhou , Hao Ding , Ke Li , Liang Cheng , Dan Zhong","doi":"10.1016/j.jfluidstructs.2025.104440","DOIUrl":"10.1016/j.jfluidstructs.2025.104440","url":null,"abstract":"<div><div>The submerged floating tunnel (SFT) is a new type of transportation structure used to cross water areas. In complex marine environments, the long-span SFT is subjected to nonlinear coupled effects of multiple loads, resulting in extremely complex dynamic responses. At present, the calculation methods for the dynamic response of the long-span SFT in marine environments have the following main deficiencies: (1) When different cable models, tube-end boundary conditions, and load patterns are adopted, the resulting mathematical models of the SFT often exhibit different expressions, with complex governing equations. The models lack flexibility and generality when considering different cable arrangements and load combinations. Existing studies are typically limited to fixed structural configurations under single-load effects. (2) Restricted by computational costs, the Morison equation is commonly used to calculate fluid loads on long-span SFTs. This equation can only account for one-way fluid-structure interaction (FSI) effects, fails to compute the torque exerted by fluids on the SFT tube, and ignores the influence of seabed topography on the flow field. Addressing the current research gaps in the analysis of dynamic characteristics of the long-span SFT under marine conditions, particularly the challenges in two-way FSI computation for long-span configurations, this paper proposes a time-domain computational method for dynamic response analysis of the long-span SFT under coupled action of multiple loads, which provides a general computational framework for dealing with the multi-load action problems of SFTs. The computational framework incorporates a two-way FSI calculation model based on a system of two-dimensional potential flow wave flumes, which overcomes the limitations in computational efficiency in bidirectional coupling analysis of the long-span SFT, and addresses the challenges in the applicability of the Morison equation under complex working conditions. This paper verifies the correctness of the proposed method for calculating structural dynamic responses by comparing the calculation results of finite element mode. The accuracy of the potential flow flume in calculating wave loads is also verified by comparing with the calculation results of the viscous fluid model. Finally, by comparing with the results of the frequency-domain calculation of dynamic responses of the SFT, it demonstrates the reliability of the FSI calculation.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"139 ","pages":"Article 104440"},"PeriodicalIF":3.5,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321275","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 : 2025-10-18DOI: 10.1016/j.jfluidstructs.2025.104441
Huan-Wen Liu
The differential equations governing water surface gravity wave motion over uneven seabeds are generally difficult to be solved analytically. For the original Laplace equation together with appropriate boundary and radiation conditions, there appears to be only one closed-form solution, called Roseau’s solution. For the depth-averaged equations such as the mild-slope type equation, the Ye equation, and the Boussinesq equation, the closed-form solutions are rare because the wavenumber has never been solved exactly from the Airy dispersion equation since it was derived by Airy in 1841. In this paper, Airy dispersion equation is exactly solved for linear surface gravity waves propagating over a cluster of special terrains, called the L-type seabeds. Furthermore, based on the explicit Airy wavenumbers, closed-form solutions to the Ye equation for wave reflection by a trapezoidal hump/trench with the two slopes being the L-type terrains are successfully constructed. To this author’s knowledge, this is the first group of closed-form solutions to depth-averaged wave equations in the whole wave range from shallow-water waves to deep-water waves.
{"title":"Exact and explicit wavenumbers and closed-form solutions of the Ye equation for water wave propagation over L-type bed terrains","authors":"Huan-Wen Liu","doi":"10.1016/j.jfluidstructs.2025.104441","DOIUrl":"10.1016/j.jfluidstructs.2025.104441","url":null,"abstract":"<div><div>The differential equations governing water surface gravity wave motion over uneven seabeds are generally difficult to be solved analytically. For the original Laplace equation together with appropriate boundary and radiation conditions, there appears to be only one closed-form solution, called Roseau’s solution. For the depth-averaged equations such as the mild-slope type equation, the Ye equation, and the Boussinesq equation, the closed-form solutions are rare because the wavenumber has never been solved exactly from the Airy dispersion equation since it was derived by Airy in 1841. In this paper, Airy dispersion equation is exactly solved for linear surface gravity waves propagating over a cluster of special terrains, called the L-type seabeds. Furthermore, based on the explicit Airy wavenumbers, closed-form solutions to the Ye equation for wave reflection by a trapezoidal hump/trench with the two slopes being the L-type terrains are successfully constructed. To this author’s knowledge, this is the first group of closed-form solutions to depth-averaged wave equations in the whole wave range from shallow-water waves to deep-water waves.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"139 ","pages":"Article 104441"},"PeriodicalIF":3.5,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145321276","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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