We study a rigid finite-span cylinder mounted on an elastic cantilever beam transversely to the direction of subsonic airflow in a wind tunnel. The purpose is to identify and analyze various types of vortex-induced resonant excitation for use in energy harvesters based on vortex-induced vibrations. The results of the experimental study show that in contrast to similar works with a similar model configuration that performs two-dimensional translational oscillations, we have discovered a previously unexplored three-dimensional type of VIV in which the cylinder rotates around the cantilever support. It has been experimentally proven that a lock-in regime exists for this type of oscillation, and the von Kármán vortex streets, generated by upper and lower parts of the cylinder, are shifted in phase by . We conduct a detailed analysis of this new type of VIV.
{"title":"Experimental investigation of rotational vortex-induced vibrations of a circular cylinder attached to an elastic beam","authors":"Yaroslav Demchenko , Oleg Ivanov , Vasily Vedeneev","doi":"10.1016/j.jfluidstructs.2025.104266","DOIUrl":"10.1016/j.jfluidstructs.2025.104266","url":null,"abstract":"<div><div>We study a rigid finite-span cylinder mounted on an elastic cantilever beam transversely to the direction of subsonic airflow in a wind tunnel. The purpose is to identify and analyze various types of vortex-induced resonant excitation for use in energy harvesters based on vortex-induced vibrations. The results of the experimental study show that in contrast to similar works with a similar model configuration that performs two-dimensional translational oscillations, we have discovered a previously unexplored three-dimensional type of VIV in which the cylinder rotates around the cantilever support. It has been experimentally proven that a lock-in regime exists for this type of oscillation, and the von Kármán vortex streets, generated by upper and lower parts of the cylinder, are shifted in phase by <span><math><mi>π</mi></math></span>. We conduct a detailed analysis of this new type of VIV.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104266"},"PeriodicalIF":3.4,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141271","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 : 2025-01-17DOI: 10.1016/j.jfluidstructs.2025.104267
Esmaeel Masoudi , Lian Gan , David Sims-Williams , Adam Marshall
In this study, fluid structure interactions of a fixed and oscillating pentagonal cylinder are studied using experimental approaches. Specifically, flow induced vibration (FIV) of a pentagonal cylinder is studied with six different incidence angles () in a recirculating wind tunnel at fixed mass damping ratios. A series of free oscillation experiments are carried out in order to explore galloping behaviour as well as the lock-in region for vortex induced vibration (VIV). It is found that VIV for a pentagonal cylinder is substantially stronger than for a circular cylinder with a similar mass ratio. VIV maximum amplitude changes non-monotonically with incidence angle, and is smaller for incidences where galloping is dominant. Also, galloping was found to be substantially stronger where the stiffness of the system is lower.
{"title":"Flow induced vibration (FIV) of a pentagonal cylinder with high mass-damping ratio","authors":"Esmaeel Masoudi , Lian Gan , David Sims-Williams , Adam Marshall","doi":"10.1016/j.jfluidstructs.2025.104267","DOIUrl":"10.1016/j.jfluidstructs.2025.104267","url":null,"abstract":"<div><div>In this study, fluid structure interactions of a fixed and oscillating pentagonal cylinder are studied using experimental approaches. Specifically, flow induced vibration (FIV) of a pentagonal cylinder is studied with six different incidence angles (<span><math><mi>α</mi></math></span>) in a recirculating wind tunnel at fixed mass damping ratios. A series of free oscillation experiments are carried out in order to explore galloping behaviour as well as the lock-in region for vortex induced vibration (VIV). It is found that VIV for a pentagonal cylinder is substantially stronger than for a circular cylinder with a similar mass ratio. VIV maximum amplitude changes non-monotonically with incidence angle, and is smaller for incidences where galloping is dominant. Also, galloping was found to be substantially stronger where the stiffness of the system is lower.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104267"},"PeriodicalIF":3.4,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097241","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 : 2025-01-11DOI: 10.1016/j.jfluidstructs.2024.104262
Nikhilesh Tumuluru Ramesh , Serhiy Yarusevych , Chris Morton
The transient response of an elastically-mounted rigid cylinder released from rest in a steady freestream is investigated experimentally through simultaneous displacement and two-component velocity field measurements in conjunction with force estimation. The Reynolds number is maintained constant at 4,400, while the reduced velocity is varied between 4.5 and 11.5. The amplitude response indicates distinct transient behavior across all response branches, including a notable amplitude overshoot in the initial branch and continuous amplitude growth to quasi-steady state in the upper and lower branches. Following cylinder release, forcing is shown to transition from purely von Kármán frequency to nonlinear forcing, and comparisons to a linear oscillator show key differences in system behavior during this transition. Following lock-in, the time taken to attain quasi-steady state increases, while the maximum amplitude growth rate decreases with . The observed differences in the transient amplitude growth rate are linked to distinct changes in the forcing characteristics, primarily driven by the phase difference between forcing and cylinder displacement. The presented analysis of the transient flow development reveals a close relationship between the timing of vortex shedding and the forcing phase difference. Additionally, the mechanisms underlying the transition from initial von Kármán shedding to quasi-steady lock-in behavior, highlighted by notable changes in wake characteristics, are identified for transients in each response branch.
{"title":"Transient vortex-induced vibrations of a cylinder released from rest","authors":"Nikhilesh Tumuluru Ramesh , Serhiy Yarusevych , Chris Morton","doi":"10.1016/j.jfluidstructs.2024.104262","DOIUrl":"10.1016/j.jfluidstructs.2024.104262","url":null,"abstract":"<div><div>The transient response of an elastically-mounted rigid cylinder released from rest in a steady freestream is investigated experimentally through simultaneous displacement and two-component velocity field measurements in conjunction with force estimation. The Reynolds number is maintained constant at <span><math><mrow><mi>R</mi><mi>e</mi><mo>≈</mo></mrow></math></span> 4,400, while the reduced velocity is varied between <span><math><mrow><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>≈</mo></mrow></math></span> 4.5 and 11.5. The amplitude response indicates distinct transient behavior across all response branches, including a notable amplitude overshoot in the initial branch and continuous amplitude growth to quasi-steady state in the upper and lower branches. Following cylinder release, forcing is shown to transition from purely von Kármán frequency to nonlinear forcing, and comparisons to a linear oscillator show key differences in system behavior during this transition. Following lock-in, the time taken to attain quasi-steady state increases, while the maximum amplitude growth rate decreases with <span><math><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span>. The observed differences in the transient amplitude growth rate are linked to distinct changes in the forcing characteristics, primarily driven by the phase difference between forcing and cylinder displacement. The presented analysis of the transient flow development reveals a close relationship between the timing of vortex shedding and the forcing phase difference. Additionally, the mechanisms underlying the transition from initial von Kármán shedding to quasi-steady lock-in behavior, highlighted by notable changes in wake characteristics, are identified for transients in each response branch.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104262"},"PeriodicalIF":3.4,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-07DOI: 10.1016/j.jfluidstructs.2024.104263
Hyeon-Ho Yang, Sang-Gil Lee, Eun-Hyuck Lee, Jae-Hung Han
This study presents an efficient numerical simulation framework for analyzing the flight dynamics of bird-inspired ornithopters in forward flight. The framework integrates a modified Unsteady Vortex Lattice Method (UVLM) with a Multi-Flexible-Body Dynamics (MFBD) model to simulate the Fluid-Structure Interaction (FSI) that occurs during the flapping flight. The UVLM is enhanced with a Pseudo-Leading-Edge Vortex (PLEV) model and an Adaptive Wake-Shedding (AWS) scheme to address limitations related to the leading edge vortex and spanwise wake-shedding. Additionally, the structural model of the ornithopter's flexible main wing is modeled using a modal-based reduced-order model generated through component mode synthesis. The framework is validated through wind tunnel tests on rigid and flexible wing models, demonstrating errors of <10 % in predicting mean lift and thrust forces. The ORNithopter Integrated Simulation Program (ORNISP), developed as a MATLAB App, is utilized to perform a flight dynamic simulation under free-flight conditions. The trim conditions for a forward flight of an ornithopter prototype named KRoFalcon (KAIST Robotic Falcon) are estimated. The simulation results show errors within 7 % for flight speed and angle of attack compared to flight test data. Additionally, the simulation results under free-flight and restricted degrees of freedom conditions are compared, and it shows that the flight simulation with restricted heaving and pitching can overestimate the aerodynamic forces. The proposed FSI simulation framework shows more efficient computational time than the FSI simulation using computational fluid dynamics and structural dynamics solvers, ensuring sufficient fidelity in aerodynamic force estimation.
{"title":"Numerical simulation framework of bird-inspired ornithopter in forward flight","authors":"Hyeon-Ho Yang, Sang-Gil Lee, Eun-Hyuck Lee, Jae-Hung Han","doi":"10.1016/j.jfluidstructs.2024.104263","DOIUrl":"10.1016/j.jfluidstructs.2024.104263","url":null,"abstract":"<div><div>This study presents an efficient numerical simulation framework for analyzing the flight dynamics of bird-inspired ornithopters in forward flight. The framework integrates a modified Unsteady Vortex Lattice Method (UVLM) with a Multi-Flexible-Body Dynamics (MFBD) model to simulate the Fluid-Structure Interaction (FSI) that occurs during the flapping flight. The UVLM is enhanced with a Pseudo-Leading-Edge Vortex (PLEV) model and an Adaptive Wake-Shedding (AWS) scheme to address limitations related to the leading edge vortex and spanwise wake-shedding. Additionally, the structural model of the ornithopter's flexible main wing is modeled using a modal-based reduced-order model generated through component mode synthesis. The framework is validated through wind tunnel tests on rigid and flexible wing models, demonstrating errors of <10 % in predicting mean lift and thrust forces. The ORNithopter Integrated Simulation Program (ORNISP), developed as a MATLAB App, is utilized to perform a flight dynamic simulation under free-flight conditions. The trim conditions for a forward flight of an ornithopter prototype named KRoFalcon (KAIST Robotic Falcon) are estimated. The simulation results show errors within 7 % for flight speed and angle of attack compared to flight test data. Additionally, the simulation results under free-flight and restricted degrees of freedom conditions are compared, and it shows that the flight simulation with restricted heaving and pitching can overestimate the aerodynamic forces. The proposed FSI simulation framework shows more efficient computational time than the FSI simulation using computational fluid dynamics and structural dynamics solvers, ensuring sufficient fidelity in aerodynamic force estimation.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104263"},"PeriodicalIF":3.4,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141270","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 : 2025-01-03DOI: 10.1016/j.jfluidstructs.2024.104264
Wenjie Li, Xiangxi Kong, Qi Xu, Ziyu Hao
The stress concentration defect inevitably occurs at the interface of different materials or structures in the classical periodic pipe. This paper innovatively combines Phononic Crystals with functionally graded materials (FGM) to investigate the effects of introducing FGM on bandgap tuning and stress distribution in fluid-filled periodic pipes. Initially, a novel functionally graded (FG) unit cell is designed, accompanied by a theoretical model of a fluid-filled periodic pipe under external axial stress. Next, by integrating the finite element idea with traditional bandgap calculation methods, a hybrid strategy suitable for FG periodic structures is proposed. Then, the accuracy and applicability of the proposed strategy are validated through a comparison with the Element-spectral element method and Element-transfer matrix method. The effectiveness of stress concentration mitigation is highlighted through COMSOL simulation. Finally, a detailed discussion is provided on the effects of structural parameters, material properties, and external axial stress on the bandgap characteristics and stress distribution. This study not only provides solutions to the common problem of stress concentration in Phononic Crystals but also offers theoretical support for calculating the bandgap of periodic structures with continuously varying parameters.
{"title":"Bandgap tuning and stress concentration reduction in fluid-filled periodic pipes via functionally graded materials","authors":"Wenjie Li, Xiangxi Kong, Qi Xu, Ziyu Hao","doi":"10.1016/j.jfluidstructs.2024.104264","DOIUrl":"10.1016/j.jfluidstructs.2024.104264","url":null,"abstract":"<div><div>The stress concentration defect inevitably occurs at the interface of different materials or structures in the classical periodic pipe. This paper innovatively combines Phononic Crystals with functionally graded materials (FGM) to investigate the effects of introducing FGM on bandgap tuning and stress distribution in fluid-filled periodic pipes. Initially, a novel functionally graded (FG) unit cell is designed, accompanied by a theoretical model of a fluid-filled periodic pipe under external axial stress. Next, by integrating the finite element idea with traditional bandgap calculation methods, a hybrid strategy suitable for FG periodic structures is proposed. Then, the accuracy and applicability of the proposed strategy are validated through a comparison with the Element-spectral element method and Element-transfer matrix method. The effectiveness of stress concentration mitigation is highlighted through COMSOL simulation. Finally, a detailed discussion is provided on the effects of structural parameters, material properties, and external axial stress on the bandgap characteristics and stress distribution. This study not only provides solutions to the common problem of stress concentration in Phononic Crystals but also offers theoretical support for calculating the bandgap of periodic structures with continuously varying parameters.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104264"},"PeriodicalIF":3.4,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141268","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 : 2025-01-03DOI: 10.1016/j.jfluidstructs.2024.104265
Shuqi Wang , Ji Tang , Chenyin Li , Renwei Ji , E. Fernandez-Rodriguez
A horizontal-axis tidal turbine (HATT) connected to a floating carrier experiences six degrees of freedom due to surface waves, significantly deviating the relative operating velocity and performance. To improve the output power, the HATT must employ a variable rather than conventional fixed speed control strategy, although the outcomes and disadvantages remain unclear. Therefore, this paper develops a CFD model to estimate the response of the HATT in wave-current states, under pitch motion using a speed control strategy. The results indicate that the speed control strategy can effectively improve the output power of the HATT during the pitching motion. The performance is approximated as the sum of a constant and pitch-dependent terms: damping and added mass. The best-fitted performance coefficients of load, power and moment are investigated with the pitch amplitude and period effect. The results indicate that the amplitudes of fluctuations are related with the amplitude and frequency of the pitch due to larger interference in the HATT operating velocities and dynamics of blade performance. The added mass is smaller than the damping term and can be ignored. The findings can be useful for the implementation of modern turbine control systems, to improve the cost-effectiveness of floating tidal energy systems.
{"title":"Performance evaluation and fast prediction of a pitched horizontal-axis tidal turbine under wave-current conditions using a variable-speed control strategy","authors":"Shuqi Wang , Ji Tang , Chenyin Li , Renwei Ji , E. Fernandez-Rodriguez","doi":"10.1016/j.jfluidstructs.2024.104265","DOIUrl":"10.1016/j.jfluidstructs.2024.104265","url":null,"abstract":"<div><div>A horizontal-axis tidal turbine (HATT) connected to a floating carrier experiences six degrees of freedom due to surface waves, significantly deviating the relative operating velocity and performance. To improve the output power, the HATT must employ a variable rather than conventional fixed speed control strategy, although the outcomes and disadvantages remain unclear. Therefore, this paper develops a CFD model to estimate the response of the HATT in wave-current states, under pitch motion using a speed control strategy. The results indicate that the speed control strategy can effectively improve the output power of the HATT during the pitching motion. The performance is approximated as the sum of a constant and pitch-dependent terms: damping and added mass. The best-fitted performance coefficients of load, power and moment are investigated with the pitch amplitude and period effect. The results indicate that the amplitudes of fluctuations are related with the amplitude and frequency of the pitch due to larger interference in the HATT operating velocities and dynamics of blade performance. The added mass is smaller than the damping term and can be ignored. The findings can be useful for the implementation of modern turbine control systems, to improve the cost-effectiveness of floating tidal energy systems.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104265"},"PeriodicalIF":3.4,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141267","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 : 2025-01-02DOI: 10.1016/j.jfluidstructs.2024.104261
Jingyu Cui , Xiang Zhu , Lanlan Xiao , Zuchao Zhu , Renyong Lin , Xiao Hu , Yuzhen Jin
This study numerically investigates the conveyance of a long flexible filament in the near field of a jet flow using the immersed boundary-lattice Boltzmann method (IB-LBM) and large eddy simulations (LES). The filament is introduced into the jet flow field from an external domain, delivered by a turbulent jet at a Reynolds number of 4500. This research analyzes the filament's dynamics and morphological evolutions, highlighting the effects of bending stiffness (Kb*), linear density (mf*), and initial velocity (U0*) on conveyance stability. Initially, the filament exhibits stable forward motion with minimal fluctuations in the jet's potential core region. However, as the filament's leading section enters the developing region, a bulging shape forms in the middle section, leading to instability and morphological fluctuations. Increasing mf* and U0* enhance conveyance stability by delaying the bulging formation in the middle section and reducing morphological fluctuations. The leading section of the filament experiences the most significant fluctuations, suggesting that inertia effects dominate upstream. Varying Kb* primary affects the filament's behavior post-instability while does not significantly impact the position of instability onset. Additionally, when U0* is less than half of the inlet airflow speed, the morphological fluctuations are significantly amplified. To improve conveyance stability for long filaments under similar conditions, it is recommended to accelerate the filament to at least half of the inlet jet velocity. These findings provide insights into optimizing long filament conveyance in industrial processes and biomedical applications, where precise control of filament behavior is crucial.
{"title":"Dynamics of a long flexible filament conveyed in the near field of a turbulent jet","authors":"Jingyu Cui , Xiang Zhu , Lanlan Xiao , Zuchao Zhu , Renyong Lin , Xiao Hu , Yuzhen Jin","doi":"10.1016/j.jfluidstructs.2024.104261","DOIUrl":"10.1016/j.jfluidstructs.2024.104261","url":null,"abstract":"<div><div>This study numerically investigates the conveyance of a long flexible filament in the near field of a jet flow using the immersed boundary-lattice Boltzmann method (IB-LBM) and large eddy simulations (LES). The filament is introduced into the jet flow field from an external domain, delivered by a turbulent jet at a Reynolds number of 4500. This research analyzes the filament's dynamics and morphological evolutions, highlighting the effects of bending stiffness (<em>K<sub>b</sub>*</em>), linear density (<em>m<sub>f</sub>*</em>), and initial velocity (<em>U</em><sub>0</sub><em>*</em>) on conveyance stability. Initially, the filament exhibits stable forward motion with minimal fluctuations in the jet's potential core region. However, as the filament's leading section enters the developing region, a bulging shape forms in the middle section, leading to instability and morphological fluctuations. Increasing <em>m<sub>f</sub>*</em> and <em>U</em><sub>0</sub><em>*</em> enhance conveyance stability by delaying the bulging formation in the middle section and reducing morphological fluctuations. The leading section of the filament experiences the most significant fluctuations, suggesting that inertia effects dominate upstream. Varying <em>K<sub>b</sub>*</em> primary affects the filament's behavior post-instability while does not significantly impact the position of instability onset. Additionally, when <em>U</em><sub>0</sub><em>*</em> is less than half of the inlet airflow speed, the morphological fluctuations are significantly amplified. To improve conveyance stability for long filaments under similar conditions, it is recommended to accelerate the filament to at least half of the inlet jet velocity. These findings provide insights into optimizing long filament conveyance in industrial processes and biomedical applications, where precise control of filament behavior is crucial.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104261"},"PeriodicalIF":3.4,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092739","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 : 2025-01-01DOI: 10.1016/j.jfluidstructs.2024.104255
Ming-Jyh Chern, Tai-Yi Chou, Desta Goytom Tewolde, Fandi D. Suprianto
This study employs the Direct-Forcing Immersed Boundary (DFIB) method to model the flow-induced vibration (FIV) behavior of three types of airfoils—NACA0009, NACA0012, and NACA0015—within a flow field. The analysis investigates the vibration characteristics of these airfoils in a fully passive mode under specific conditions, including a fixed airfoil pitching center at , a mass ratio of 2.0, a Reynolds number of Re, and undamped conditions with both aerodynamic damping coefficients set to zero (). The stiffness of the linear spring () and the torsional spring () are both defined as . The study examines the oscillatory responses, vortex patterns, and energy conversion efficiencies of the three types of airfoils across 12 reduced velocities (). Oscillation response patterns are categorized into three distinct regions: S-I, T-II, and S-III, while vortex patterns are classified into four types: ‘2P’, ‘2P + 2S’, ‘mP,’ and ‘P + S.’ Notably, all three airfoils achieve their peak energy conversion efficiency at , with NACA0009 reaching 43.9%, NACA0012 achieving 44.2%, and NACA0015 reaching 36.3%.
{"title":"Fully Passive Energy Harvesting from Heaving and Pitching Airfoils: Oscillation Response Patterns and Vortex Dynamics in Fluid Flow","authors":"Ming-Jyh Chern, Tai-Yi Chou, Desta Goytom Tewolde, Fandi D. Suprianto","doi":"10.1016/j.jfluidstructs.2024.104255","DOIUrl":"10.1016/j.jfluidstructs.2024.104255","url":null,"abstract":"<div><div>This study employs the Direct-Forcing Immersed Boundary (DFIB) method to model the flow-induced vibration (FIV) behavior of three types of airfoils—NACA0009, NACA0012, and NACA0015—within a flow field. The analysis investigates the vibration characteristics of these airfoils in a fully passive mode under specific conditions, including a fixed airfoil pitching center at <span><math><mrow><mfrac><mrow><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><mi>c</mi></mrow></math></span>, a mass ratio of 2.0, a Reynolds number of Re<span><math><mrow><mo>=</mo><mn>400</mn></mrow></math></span>, and undamped conditions with both aerodynamic damping coefficients set to zero (<span><math><mrow><msubsup><mrow><mi>b</mi></mrow><mrow><mi>a</mi></mrow><mrow><mo>∗</mo></mrow></msubsup><mo>=</mo><msubsup><mrow><mi>b</mi></mrow><mrow><mi>a</mi><mi>θ</mi></mrow><mrow><mo>∗</mo></mrow></msubsup><mo>=</mo><mn>0</mn></mrow></math></span>). The stiffness of the linear spring (<span><math><msubsup><mrow><mi>k</mi></mrow><mrow><mi>a</mi></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span>) and the torsional spring (<span><math><msubsup><mrow><mi>k</mi></mrow><mrow><mi>a</mi><mi>θ</mi></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span>) are both defined as <span><math><msup><mrow><mrow><mo>(</mo><mn>2</mn><mi>π</mi><mo>/</mo><msubsup><mrow><mi>U</mi></mrow><mrow><mi>a</mi></mrow><mrow><mo>∗</mo></mrow></msubsup><mo>)</mo></mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>. The study examines the oscillatory responses, vortex patterns, and energy conversion efficiencies of the three types of airfoils across 12 reduced velocities (<span><math><msubsup><mrow><mi>U</mi></mrow><mrow><mi>a</mi></mrow><mrow><mo>∗</mo></mrow></msubsup></math></span>). Oscillation response patterns are categorized into three distinct regions: S-I, T-II, and S-III, while vortex patterns are classified into four types: ‘2P’, ‘2P + 2S’, ‘mP,’ and ‘P + S.’ Notably, all three airfoils achieve their peak energy conversion efficiency at <span><math><mrow><msubsup><mrow><mi>U</mi></mrow><mrow><mi>a</mi></mrow><mrow><mo>∗</mo></mrow></msubsup><mo>=</mo><mn>1</mn><mo>.</mo><mn>63</mn></mrow></math></span>, with NACA0009 reaching 43.9%, NACA0012 achieving 44.2%, and NACA0015 reaching 36.3%.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104255"},"PeriodicalIF":3.4,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092738","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}
This study focuses on discerning the role of structural parameters on the bifurcation characteristics and the underlying synchronization mechanism in an aeroelastic system undergoing nonlinear stall behaviour. To that end, wind tunnel experiments are performed on a NACA 0012 airfoil capable of undergoing bending (plunging) and torsional (pitching) oscillations under scenarios involving nonlinear aerodynamic loads, i.e., dynamic stall conditions. Flow conditions under both deterministic/sterile flows and fluctuating/stochastic flows are fostered. The structure possesses continuous or polynomial-type stiffness nonlinearities and therefore is an aeroelastic experiment involving both structural and aerodynamic nonlinearities. We discern the bifurcation routes for a range of key structural parameters, such as frequency ratio, static imbalance, and the extent of structural nonlinearity. In addition to interesting and atypical routes to stall-induced instabilities, we systematically demonstrate the role of modal interactions – via a synchronization analysis – over the manifestation of these instabilities. To the best of the authors’ knowledge, this is perhaps the first study to document the role of multiple structural parameters on a stall-induced aeroelastic system and in turn cast the physical mechanism behind these dynamical transitions through the framework of synchronization.
{"title":"Effect of structural parameters on the synchronization characteristics in a stall-induced aeroelastic system","authors":"Dheeraj Tripathi , Chandan Bose , Sirshendu Mondal , J. Venkatramani","doi":"10.1016/j.jfluidstructs.2024.104246","DOIUrl":"10.1016/j.jfluidstructs.2024.104246","url":null,"abstract":"<div><div>This study focuses on discerning the role of structural parameters on the bifurcation characteristics and the underlying synchronization mechanism in an aeroelastic system undergoing nonlinear stall behaviour. To that end, wind tunnel experiments are performed on a NACA 0012 airfoil capable of undergoing bending (plunging) and torsional (pitching) oscillations under scenarios involving nonlinear aerodynamic loads, <em>i.e.</em>, dynamic stall conditions. Flow conditions under both deterministic/sterile flows and fluctuating/stochastic flows are fostered. The structure possesses continuous or polynomial-type stiffness nonlinearities and therefore is an aeroelastic experiment involving both structural and aerodynamic nonlinearities. We discern the bifurcation routes for a range of key structural parameters, such as frequency ratio, static imbalance, and the extent of structural nonlinearity. In addition to interesting and atypical routes to stall-induced instabilities, we systematically demonstrate the role of modal interactions – via a synchronization analysis – over the manifestation of these instabilities. To the best of the authors’ knowledge, this is perhaps the first study to document the role of multiple structural parameters on a stall-induced aeroelastic system and in turn cast the physical mechanism behind these dynamical transitions through the framework of synchronization.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104246"},"PeriodicalIF":3.4,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141269","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 : 2024-12-30DOI: 10.1016/j.jfluidstructs.2024.104253
Christine Lynggård Hansen , Hugh Wolgamot , Paul H. Taylor , Adi Kurniawan , Jana Orszaghova , Henrik Bredmose
This paper presents a comprehensive analysis of measurements from a wave basin campaign investigating the use of Design Waves for the hinge response of the M4 wave energy converter (WEC). The experiments were carried out at a scale of 1:15 relative to a kW-scale ocean trial currently being built for deployment in King George Sound, off the coast of Albany, Western Australia. By averaging the largest body motion responses from long irregular wave realisations of extreme sea states, we determined the most probable extreme response — the NewResponse. The Design Wave was constructed by averaging the surface elevation time histories driving instances of the largest responses. Subsequently, the identified Design Wave was replicated in the wave basin. Our results show that the identified Design Wave is able to produce the hinge angle NewResponse of the M4 device with reasonable accuracy. The methodology applies to any linear system, and Design Waves of this type are expected to be applicable for a wide range of WEC motion responses. In addition to the experimental reconstruction of identified Design Wave signals, we analyse the effect of dunking – full submergence of the centre floats – and compare the maximum response and Design Wave signals for three severe sea states pertinent to the King George Sound location. In limiting-steepness severe sea states, the wave peak frequency is lower than the hinge motion natural frequency, and the NewResponse is largely independent of the sea state. However, the Design Waves are found to be somewhat sea state dependent. We relate both of these findings to the narrow-band nature of the hinge response at its natural frequency and the invariance of the spectral tail for fixed wave steepness.
{"title":"Design Waves and extreme responses for an M4 floating, hinged wave energy converter","authors":"Christine Lynggård Hansen , Hugh Wolgamot , Paul H. Taylor , Adi Kurniawan , Jana Orszaghova , Henrik Bredmose","doi":"10.1016/j.jfluidstructs.2024.104253","DOIUrl":"10.1016/j.jfluidstructs.2024.104253","url":null,"abstract":"<div><div>This paper presents a comprehensive analysis of measurements from a wave basin campaign investigating the use of Design Waves for the hinge response of the M4 wave energy converter (WEC). The experiments were carried out at a scale of 1:15 relative to a kW-scale ocean trial currently being built for deployment in King George Sound, off the coast of Albany, Western Australia. By averaging the largest body motion responses from long irregular wave realisations of extreme sea states, we determined the most probable extreme response — the NewResponse. The Design Wave was constructed by averaging the surface elevation time histories driving instances of the largest responses. Subsequently, the identified Design Wave was replicated in the wave basin. Our results show that the identified Design Wave is able to produce the hinge angle NewResponse of the M4 device with reasonable accuracy. The methodology applies to any linear system, and Design Waves of this type are expected to be applicable for a wide range of WEC motion responses. In addition to the experimental reconstruction of identified Design Wave signals, we analyse the effect of dunking – full submergence of the centre floats – and compare the maximum response and Design Wave signals for three severe sea states pertinent to the King George Sound location. In limiting-steepness severe sea states, the wave peak frequency is lower than the hinge motion natural frequency, and the NewResponse is largely independent of the sea state. However, the Design Waves are found to be somewhat sea state dependent. We relate both of these findings to the narrow-band nature of the hinge response at its natural frequency and the invariance of the spectral tail for fixed wave steepness.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104253"},"PeriodicalIF":3.4,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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