Journal of Fluids and Structures最新文献

{"title":"Bandgap tuning and stress concentration reduction in fluid-filled periodic pipes via functionally graded materials","authors":"Wenjie Li,&nbsp;Xiangxi Kong,&nbsp;Qi Xu,&nbsp;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}

{"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 ,&nbsp;Ji Tang ,&nbsp;Chenyin Li ,&nbsp;Renwei Ji ,&nbsp;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}

{"title":"Dynamics of a long flexible filament conveyed in the near field of a turbulent jet","authors":"Jingyu Cui ,&nbsp;Xiang Zhu ,&nbsp;Lanlan Xiao ,&nbsp;Zuchao Zhu ,&nbsp;Renyong Lin ,&nbsp;Xiao Hu ,&nbsp;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_b*</em>), linear density (<em>m_f*</em>), and initial velocity (<em>U</em>₀<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_f*</em> and <em>U</em>₀<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_b*</em> primary affects the filament's behavior post-instability while does not significantly impact the position of instability onset. Additionally, when <em>U</em>₀<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}

{"title":"Fully Passive Energy Harvesting from Heaving and Pitching Airfoils: Oscillation Response Patterns and Vortex Dynamics in Fluid Flow","authors":"Ming-Jyh Chern,&nbsp;Tai-Yi Chou,&nbsp;Desta Goytom Tewolde,&nbsp;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}

{"title":"Effect of structural parameters on the synchronization characteristics in a stall-induced aeroelastic system","authors":"Dheeraj Tripathi ,&nbsp;Chandan Bose ,&nbsp;Sirshendu Mondal ,&nbsp;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}

{"title":"Design Waves and extreme responses for an M4 floating, hinged wave energy converter","authors":"Christine Lynggård Hansen ,&nbsp;Hugh Wolgamot ,&nbsp;Paul H. Taylor ,&nbsp;Adi Kurniawan ,&nbsp;Jana Orszaghova ,&nbsp;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}

{"title":"Experimental study of wake-induced vibration response in a flexibly mounted tandem cylinder system with a prescribed dynamically oscillating upstream cylinder","authors":"Sarah Dulac,&nbsp;Hamed Samandari,&nbsp;Banafsheh Seyed-Aghazadeh","doi":"10.1016/j.jfluidstructs.2024.104247","DOIUrl":"10.1016/j.jfluidstructs.2024.104247","url":null,"abstract":"<div><div>The wake-induced vibration (WIV) of a flexibly mounted circular cylinder, positioned in tandem with an upstream circular cylinder, is investigated through experimental analysis. The upstream cylinder undergoes forced oscillations with a peak-to-peak amplitude of 0.5 times the cylinder’s diameter (<span><math><mi>D</mi></math></span>) and frequencies ranging from 0.5 to 2 times the natural frequency of the downstream cylinder. By imposing a prescribed motion on the upstream cylinder, this study diverges from conventional investigations of WIV in tandem cylinder arrangements. In our approach, the downstream cylinder responds to a wake characterized by independently controlled dynamics – such as wake width and shedding frequency – distinct from the geometry and inherent characteristics of the source cylinder. This study examines oscillation amplitudes, frequencies, and flow forces in a reduced velocity range of <span><math><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span> = 2.9 – 18.0, corresponding to Reynolds numbers of 650 to 3500, across various center-to-center spacings of <span><math><mrow><mi>S</mi><mo>/</mo><mi>D</mi></mrow></math></span> = 4, 6, 8. Qualitative and quantitative flow field assessments are conducted using hydrogen bubble imaging and a volumetric Particle Tracking Velocimetry (PTV) technique, respectively.</div><div>The dynamic response shows that the downstream cylinder experiences WIV for each forcing frequency ratio. Due to the distinct wake dynamics created in each case, the downstream cylinder experiences continuous large-amplitude oscillations persisting to the highest reduced velocity tested at a frequency ratio of 1. At a frequency ratio of 2, the onset of oscillations is delayed to higher reduced velocities. The frequency contents of the observed oscillations directly correspond to the prescribed upstream motion, indicating the detection of the incoming wake. The wake structure developed downstream shows a strong dependence on the dynamic characteristics of the upstream cylinder. A Q-criterion analysis reveals the dominant structures prevailing downstream of the tandem pair and their three-dimensional nature. Additionally, a spatiotemporal mode analysis using the proper orthogonal decomposition technique elucidates the coherent vortical structures responsible for the various downstream cylinder responses observed in each upstream condition.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104247"},"PeriodicalIF":3.4,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092737","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}

{"title":"Theoretical analysis of liquid wave motion in rotating cylinder depending on liquid depth ratio","authors":"Fumitaka Yoshizumi","doi":"10.1016/j.jfluidstructs.2024.104250","DOIUrl":"10.1016/j.jfluidstructs.2024.104250","url":null,"abstract":"<div><div>The fluid force caused by the wave motion of liquid that partially fills a hollow rotor was theoretically investigated, with a focus on the motion's relationship with the radial liquid depth. The fluid force causes a self-excited whirl of the rotor. To obtain the excitation force as a function of the liquid depth, a nonlinear analysis method that does not use shallow water approximation is presented. Gravity is negligible and the liquid motion is assumed to be axially uniform. The linear eigenmodes of the two-dimensional flow in the radial and circumferential directions are nonlinearly coupled through the Galerkin method. The periodic solution of the wave response to the whirl motion is obtained and is compared with the conventional shallow water approximation. In the present theory, the excitation force reaches its maximum at a specific liquid depth that is consistent with previous experimental studies, while the maximum does not appear in the shallow water approximation. Furthermore, the present theory indicates that the response of the first eigenmode that causes the excitation force is suppressed by nonlinearity when the liquid is shallow; in contrast, when the liquid is deep, the first eigenmode self-balances with disturbance of the whirl motion without the help of nonlinearity. The decrease in the helping role of nonlinearity in a deep liquid comes from the ratio of the radial flow velocity to the circumferential flow velocity in the eigenfunction becoming large as the liquid depth ratio increases.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104250"},"PeriodicalIF":3.4,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141310","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}

{"title":"Performance and mechanism of the hydrodynamic noise reduction for biomimetic trailing-edge serrations of a submarine","authors":"Zhihao Ma ,&nbsp;Peng Li ,&nbsp;Hang Guo ,&nbsp;Kuai Liao ,&nbsp;Yiren Yang","doi":"10.1016/j.jfluidstructs.2024.104256","DOIUrl":"10.1016/j.jfluidstructs.2024.104256","url":null,"abstract":"<div><div>As submarine speed increases, the hydrodynamic noise generated by the sail of a submarine becomes more pronounced. Inspired by the noise reduction capabilities demonstrated by the serration on the owl’s wing trailing edge, this paper proposes the serration noise reduction structure applied to the sail trailing edge of the submarine. The large eddy simulation and the Ffowcs Williams–Hawkings equation are employed to examine the impact of serration on flow and noise characteristics at the sail. The quadrupole noise source is captured by the permeable surface combined with the formulation Q1A. The physical mechanisms underlying trailing edge serration, which reduce flow noise, are revealed. The accuracy of the hydrodynamic and acoustic calculation methods is verified by experimental data. This study demonstrates that the serration exerts the double effect on the flow noise, which is a combination of dipole and quadrupole noise. Total noise is reduced by up to 4.32 dB. The impact of serration on dipole noise is the combined behavior of multiple physical mechanisms. First, the serration induces flow separation at the trailing edge and block water convergence at the serration peak, thereby diminishing turbulent fluctuations within the boundary layer; Secondly, it causes the decoherence effect on the vertical pressure fluctuations at the trailing edge, resulting in destructive interference in the dipole noise source. The serrations extend the continuous Stream vortex, delaying its evolution into the Hairpin vortex and subsequent fragmentation into small-scale vortex. This distortion of the spatial vortex structure intensifies the magnitude of the Lamb vector <span><math><mrow><mo>|</mo><mi>ℒ</mi><mo>|</mo></mrow></math></span> and Lighthill stress, thereby enhancing the energy of quadrupole noise source. Flow noise reduction is achieved by applying sail trailing edge serration in a submarine, but the submarine hull diminishes its noise reduction performance. The reason involves turbulent interference in the boundary layer of the hull altering the incoming flow conditions at the trailing edge serration, which increases the unsteady pressure fluctuations at the serration valley, thereby amplifying the intensity of the dipole noise source.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104256"},"PeriodicalIF":3.4,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141309","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}

{"title":"Effect of confinement on the hydrodynamic performance of a fully-passive oscillating-foil turbine","authors":"Sierra Mann ,&nbsp;Guy Dumas ,&nbsp;Peter Oshkai","doi":"10.1016/j.jfluidstructs.2024.104258","DOIUrl":"10.1016/j.jfluidstructs.2024.104258","url":null,"abstract":"<div><div>An experimental study was conducted to assess the effects of flow confinement on the hydrodynamic performance of a fully-passive oscillating-foil turbine at a Reynolds number of 19,000. The experiments were performed using a National Advisory Committee for Aeronautics (NACA) 0015 foil with an aspect ratio of 7.5 in a water tunnel equipped with adjustable lateral walls. The kinematic parameters of the foil oscillations and its energy harvesting performance were measured at eight blockage ratios, ranging from 21 % to 60 %. Quantitative flow imaging was performed using particle image velocimetry (PIV) to observe the timing of the leading-edge vortex (LEV) formation and shedding. Loading on the foil was related to the flow structure by calculating the moments of vorticity with respect to the pitching axis of the foil. The efficiency and the power coefficient increased with increasing confinement and constant upstream velocity. At the highest level of confinement, the proximity of the foil to the walls during parts of the oscillation cycle resulted in a change in the phase lag between the pitching and the heaving components of the foil motion. In turn, this shift in the kinematic parameters led to a sharp decrease in the energy-extraction performance of the turbine.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104258"},"PeriodicalIF":3.4,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143141308","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}