Journal of Fluids and Structures最新文献

{"title":"Identification of low-wavenumber wall pressure field beneath a turbulent boundary layer using vibration data","authors":"Hesam Abtahi ,&nbsp;Mahmoud Karimi ,&nbsp;Laurent Maxit","doi":"10.1016/j.jfluidstructs.2024.104135","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104135","url":null,"abstract":"<div><p>Although the most energetic part of the wall pressure field (WPF) beneath a turbulent boundary layer (TBL) is within the convective region, this region is mostly filtered out by the structure when excited by a low Mach number turbulent flow. Therefore, structural vibration is primarily induced by the low-wavenumber components of the WPF. This highlights the importance of an accurate estimation of the low-wavenumber WPF for predicting flow-induced vibration of structures. Existing semi-empirical TBL models for the WPF agree well in the convective region but significantly differ from one another in estimating the low-wavenumber levels. In this study, we aim to investigate the feasibility of estimating the low-wavenumber WPF by analyzing vibration data from a structure excited by a TBL. The proposed approach is based on the relationship between the TBL forcing function and structural vibrations in the wavenumber domain. By utilizing vibration data obtained from a structure excited by a TBL and incorporating the sensitivity functions of the respective structure, it is possible to estimate the cross-spectrum density of the pressure fluctuations in the wavenumber domain. To demonstrate the effectiveness of the proposed method, an analytical model of a simply-supported panel excited by a reference TBL model is employed. The vibration data of the panel is then used in an inverse method to identify the low-wavenumber levels of the pressure fluctuations, which are then compared to those of the reference TBL model. The performance of the proposed method is examined through a parametric study and virtual experiments.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0889974624000707/pdfft?md5=a708e02becc4171cb57c926d3beb4fd4&pid=1-s2.0-S0889974624000707-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141090656","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":"The experimental investigation on wake dynamics of flow around a circular cylinder with the splitter plate","authors":"Jiankang Zhou ,&nbsp;Xiang Qiu ,&nbsp;Jiahua Li ,&nbsp;Bofu Wang ,&nbsp;Quan Zhou ,&nbsp;Yulu Liu","doi":"10.1016/j.jfluidstructs.2024.104130","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104130","url":null,"abstract":"<div><p>The wake dynamics of flow around a circular cylinder with the splitter plate are investigated using particle image velocimetry (PIV). The Reynolds number based on the cylinder diameter <span><math><mi>D</mi></math></span> is <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>3.9</mn><mspace></mspace><mo>×</mo><msup><mrow><mn>10</mn></mrow><mn>3</mn></msup></mrow></math></span>, and the ratio of the splitter plate length <span><math><mi>L</mi></math></span> on the cylinder diameter varies from <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>0</mn></mrow></math></span> to <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>2.5</mn></mrow></math></span>. The wake characteristics and vortex dynamics are strongly dependent on <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi></mrow></math></span>. There are main and secondary recirculation regions behind the cylinder, and the range of the recirculation region presents an obvious increase as <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi></mrow></math></span> increases from 0 to 1 due to the elongations of the cylinder shear layers. Moreover, the maximum velocity defect and the wake width are increased with increasing <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi></mrow></math></span>, and the short splitter plate has important influences on the wake characteristics for <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi><mo>≤</mo><mn>1</mn></mrow></math></span>. Based on the vortex dynamics, the splitter plate length can be divided into three regions. (i) For <span><math><mrow><mn>0</mn><mo>≤</mo><mi>L</mi><mo>/</mo><mi>D</mi><mo>&lt;</mo><mn>1</mn></mrow></math></span>, the shear layers elongate downstream further to form Karman vortex sheets as <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi></mrow></math></span> increases, and the wake vortices induce formation of the secondary vortex on the trailing edge of the plate. (ii) For <span><math><mrow><mn>1</mn><mo>≤</mo><mi>L</mi><mo>/</mo><mi>D</mi><mo>&lt;</mo><mn>2</mn></mrow></math></span>, the secondary vortex moves upstream along the plate and gradually lifts up, and the wake vortices are easily broken into some small-scale vortices due to the disturbance of the plate. (iii) For <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi><mo>≥</mo><mn>2</mn></mrow></math></span>, the wake vortices are reattached on the plate, and the secondary vortex is mainly distributed behind the cylinder. The Strouhal number <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span> decreases nearly by 26.34 % from <span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>0.205</mn></mrow></math></span> at <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>0</mn></mrow></math></span> to <span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>0.151</mn></mrow></math></span> at <span><math><mrow><mi>L</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>1</mn></mrow></math></span>, and <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span> presents an ","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141090654","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":"A frequency-independent second-order framework for the formulation of experimental fluidelastic forces using hidden flow variables","authors":"J. Antunes ,&nbsp;P. Piteau ,&nbsp;X. Delaune ,&nbsp;R. Lagrange ,&nbsp;D. Panunzio","doi":"10.1016/j.jfluidstructs.2024.104127","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104127","url":null,"abstract":"<div><p>The importance of fluidelastic forces in flow-excited vibrations is crucial, in view of their damaging potential. Flow-coupling coefficients are often experimentally obtained from vibration experiments, performed within a limited experimental frequency range. For any given flow velocity, these coefficients are typically frequency-dependent, as amply documented in the literature since the seminal work of Tanaka and Takahara. Such frequency dependence, which seems quite natural in view of the flows intricacies, not only is awkward for attempting physical interpretations, but also leads to numerical difficulties when performing time-domain computations. In this work, we address this problem by assuming that the measured fluidelastic forces encapsulate \"hidden\" (non-measured) dynamics of the coupled flow. This leads to the possibility of modelling the flow-structure coupled dynamics through conventional ordinary differential equations with constant parameters. The substructure analysis of such a model, augmented with a set of \"hidden\" flow variables, readily highlights an inevitability of the frequency-dependence found in the measured flow forces, when these are condensed at the measurement degrees of freedom. The formulation thus obtained clearly suggests the mathematical structure of the measured fluidelastic forces, in particular providing the formal justification for a modelling approach often used in unsteady aeroelasticity. Then, inspired by previous work in the fields of viscoelasticity and soil-structure interaction, we proceed by identifying adequate frequency-independent second-order flow-coupling matrices from the frequency-dependent experimental data, which is a challenging identification problem, even for the specific case of symmetric coupling detailed here. Finally, the developed concepts and procedures are applied to experimental results obtained at CEA-Saclay (France), for the fluidelastic interaction forces acting on a flexible tube within a rigid bundle, although the problem addressed embraces a much wider range of applications. The proposed flow modelling and identification approach shows significant potential in practical applications, with many definite advantages.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140906863","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":"Aerodynamic performance and flow mechanism of 3D flapping wing using discrete vortex method","authors":"Rahul Kumar,&nbsp;Srikant S. Padhee,&nbsp;Devranjan Samanta","doi":"10.1016/j.jfluidstructs.2024.104128","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104128","url":null,"abstract":"<div><p>In this work, we have performed numerical simulations of the flapping motion of a rectangular wing in a three-dimensional flow field using the discrete vortex method (DVM). The DVM method is computationally more convenient because it does not require the generation of a grid for the flow field at each time step as in other conventional simulation methods. In addition to the rigid wing case, the aerodynamic characteristics of a deformable wing are also investigated. The deformable wing is studied in various configurations, such as bending, twisting, and bending-twisting coupling (BTC), to provide a comprehensive analysis of its performance. In this study, we have introduced a novel aerodynamic technique in wing twisting. Unlike traditional wing rotation about a fixed root axis, our approach involves rotating the wing about a dynamically adjusted point located at the root of the leading edge. This novel approach was found to be effective in increase in the requisite aerodynamic force. The BTC wing represents reflects a sophisticated aerodynamic approach that optimally coordinates both twisting and bending deformations of the wing, resulting in a substantial improvement in its overall aerodynamic efficiency. The investigation of all four modes involves a detailed analysis of the flow mechanisms and vortex dynamics, which play a crucial role in influencing the aerodynamic forces, namely lift and thrust. The study aims to understand how these flow patterns change under different operating conditions and how these changes impact the generation of lift and thrust. The lift, thrust, and propulsive efficiency of all four modes are compared to provide a detailed understanding of their aerodynamic characteristics. The bent wing showed minimal improvements in lift and thrust compared to the rigid wing. In contrast, the twisted wing showed greater improvements in both lift and thrust. The BTC wing proves to be the most efficient method to improve aerodynamic performance during flapping. The parametric dependence of kinematic parameters such as asymmetric ratio (downstroke speed to upstroke speed), aspect ratio and reduced frequency on the aerodynamic performance was also investigated.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140879560","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":"Experimental investigation of rear flexible flaps interacting with the wake dynamics behind a squareback Ahmed body","authors":"J.C. Muñoz-Hervás ,&nbsp;M. Lorite-Díez ,&nbsp;C. García-Baena ,&nbsp;J.I. Jiménez-González","doi":"10.1016/j.jfluidstructs.2024.104124","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104124","url":null,"abstract":"<div><p>We have conducted an experimental study on the use of rear flexible vertical flaps as adaptive solutions to reduce the drag of a squareback Ahmed body, and on the fluid–structure interaction mechanisms at the turbulent wake. To that aim, wind tunnel experiments were conducted to compare the performance of various configurations including the baseline body, the body with rigid flaps and with flexible flaps. These configurations were tested under different aligned and cross-flow conditions. The results reveal that the flexible adaptive devices effectively reduce the drag within for low values of the dimensionless stiffness quantified through the Cauchy number, <span><math><mrow><mi>C</mi><mi>a</mi></mrow></math></span>. Thus, the two-dimensional deformation of the flexible flaps, which undergo progressive inwards reconfiguration (with an averaged tip deflection angle of <span><math><mrow><mi>Θ</mi><mo>≃</mo><mn>4</mn><mo>°</mo></mrow></math></span>), reduces the bluffness of the flow separation at the body base, thus shrinking the recirculation region. This reconfiguration leads to increased base pressure, resulting into a 8.3% decrease in the global drag, <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>D</mi></mrow></msub></math></span>, under aligned conditions. Similar drag reductions are observed under yawed conditions.</p><p>Two regimes are identified in terms of the coupled fluid–structure dynamics. For low <span><math><mrow><mi>C</mi><mi>a</mi></mrow></math></span>, the passive reconfiguration of the flaps include small amplitude, periodic oscillations corresponding to the first free deformation mode of a cantilevered beam. Alongside these weak oscillations, the flaps are deformed guided by the changes in the value of the horizontal base pressure gradient, depicting bi-stable behavior which is caused by the synchronization between the Reflectional Symmetry Breaking (RSB) mode, typically present in the wake of three-dimensional bluff bodies, and the flaps deformation. For higher values of <span><math><mrow><mi>C</mi><mi>a</mi></mrow></math></span>, the flexible flaps deflect inwardly by about <span><math><mrow><mi>Θ</mi><mo>≃</mo><mn>20</mn><mo>°</mo></mrow></math></span> on average, but exhibit vigorous oscillations combining the first and second free deformation modes of a cantilevered beam. These large amplitude oscillations excite the flow separation at the model’s trailing edges, leading to significant fluctuations in the separated shear layers and a consequent 31% increase in the global drag. Under yawed conditions, the flaps responses for large values of <span><math><mrow><mi>C</mi><mi>a</mi></mrow></math></span> are different due to the asymmetry of the corresponding recirculation region.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0889974624000598/pdfft?md5=ff4d8a2a1aaa5858948b2ef46c1da408&pid=1-s2.0-S0889974624000598-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140825373","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":"Flutter characteristics of a sheet with an elastic support in three-dimensional uniform flow","authors":"Keiichi Hiroaki,&nbsp;Masahiro Watanabe","doi":"10.1016/j.jfluidstructs.2024.104129","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104129","url":null,"abstract":"<div><p>In the manufacturing processes of thin flexible plates (sheets) such as polarizing films, the flutter can be caused to the sheets due to the interaction between the motion of the sheets and fluid flow. Then, the flutter can cause serious damage to the sheets, leading to the wrinkles and scratches. Thus, it is crucial to investigate a detailed characteristics and excitation mechanism of the flutter. In the present study, a detailed flutter characteristics and excitation mechanism of a rectangular sheet with an elastic support is investigated. The elastic support is implemented using a fine flexible wire. The influence of bending stiffness of the support section on the flutter velocity and frequency is clarified through wind-tunnel experiments and numerical analysis. Moreover, the work done by the fluid force on the sheet surface was determined.</p><p>The flutter velocity and frequency drastically decrease owing to decrease in bending stiffness of the support section regardless of the aspect and mass ratio. Then, the positive work region around the leading edge of the sheet expands owing to the large-amplitude oscillation around the leading edge. The expansion of positive work region owing to a large-amplitude oscillation around the leading edge of the sheet destabilizes the system.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140822012","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":"Generating periodic vortex pairs using flexible structures","authors":"Gaurav Singh ,&nbsp;Arahata Senapati ,&nbsp;Arnab Atta ,&nbsp;Rajaram Lakkaraju","doi":"10.1016/j.jfluidstructs.2024.104126","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104126","url":null,"abstract":"<div><p>In fluid dynamics, a planar starting flow through a narrow slit gives rise to a distinctive fluid mass in the form of counter-rotating vortex pairs, which do not undergo any propulsive detachment, known as ‘pinch-off’, from the tip-attached fluid layer. Our study envisions instigating the ‘pinch-off’ phenomenon in these vortex pairs using flexible plates as the slit edges to enhance momentum transport and self-propagation. In this study, considering a flow evolution model, we show that the growth rate of such ejected vortex pair scales as proportional to the square root of time. Using flexible plates to form the slit, we unearth a critical plate flexibility case with the Cauchy number, <span><math><mrow><mi>C</mi><mi>a</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>01</mn></mrow></math></span>, which induces a ‘pinch-off’ of the resultant vortex pair, a phenomenon absent in the case of rigid plates. We observe a train of vortex pairs generating one after the other, and the time period closely matches the plates’ oscillation period as the plates’ oscillation frequency locks-in with the shedding frequency of the vortex pairs. The streamwise speed of the leading vortex pair varies non-monotonically with <span><math><mrow><mi>C</mi><mi>a</mi></mrow></math></span>, showing an increase in the speed up to <span><math><mrow><mi>C</mi><mi>a</mi><mo>≈</mo><mn>0</mn><mo>.</mo><mn>04</mn></mrow></math></span>, and thereafter decreased speed due to upstream propagation of small-sized vortices. The new insights into inducing and controlling vortex pair behaviours pave the way for innovative applications in fluid transport and advanced flow manipulation techniques.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140816390","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":"Experimental and coupled model investigation of an active jet for suppressing vortex-induced vibration of a box girder","authors":"Guanbin Chen ,&nbsp;Wen-Li Chen ,&nbsp;Changlong Chen ,&nbsp;Donglai Gao ,&nbsp;Hao Meng ,&nbsp;Kyung Chun Kim","doi":"10.1016/j.jfluidstructs.2024.104119","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104119","url":null,"abstract":"<div><p>Owing to the availability of the jet flow control strategy in mitigating strongly alternating vortex motion and shedding in the wake flow structure, an active jet produced by an air velocity regulator installed on a box girder is proposed to alleviate the fluctuating aerodynamic force imposing on a fixed box main girder model. The pressure distributions on the top and bottom surfaces of the deck's two sections were recorded using a digital miniature pressure scanner system. The investigation manifests that the fluctuation of the outer surface pressure (OSP) distribution of the deck is alleviated, and the mean value is stable in all test cases. Wavelet coherence analysis of the OSP between two sections on the deck was performed to determine the relationship between the surface pressures varying with frequency over time. Based on the OSP distribution, the aerodynamic force was obtained to macroscopically display the availability of the active jet. Moreover, an active jet was applied to a free-vibrating box girder model to study its ability in suppressing vortex-induced vibration (VIV). The results of the oscillation response obtained by a laser displacement apparatus show that the box girder with the active jet has a lower vibration amplitude, and the VIV can be entirely suppressed when the non-dimensional jet momentum coefficient reaches a certain value. In addition, a coupled model of VIV was developed to predict the vibration response of the deck. The calculated results of the vibration response of the deck obtained by the coupled model are close to those of the experiments.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140647238","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":"A frequency-domain hydroelastic analysis of a membrane-based offshore floating photovoltaic platform in regular waves","authors":"Yifan Zhang ,&nbsp;Xiantao Zhang ,&nbsp;Yongqiang Chen ,&nbsp;Xinliang Tian ,&nbsp;Xin Li","doi":"10.1016/j.jfluidstructs.2024.104125","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104125","url":null,"abstract":"<div><p>This study presents an approach for analyzing the hydroelastic response of membrane-based floating photovoltaic (PV) platforms. The structural deformation of the platform’s main components, including a floater and a membrane, is further described through a comprehensive set of in-plane and out-of-plane modes. This analysis employs potential flow theory and 3D hydroelasticity theory to evaluate the hydrodynamic loads. Additionally, the Morison equation is utilized to express the drag term associated with the floater’s in-plane motion. Addressing the connection between the floater and the membrane is achieved through the Lagrange multiplier method. Ultimately, this study establishes a frequency-domain coupled dynamic equation for the platform. The response results provide modal amplitudes and displacement data for test points, revealing that under low-frequency conditions, the flexible floater and the membrane conform to wave profiles. As the frequency increases, the impact of the floater’s stiffness becomes prominent, resulting in a substantial three-dimensional interaction effect. In addition, this study examines various structural parameters, specifically the membrane pretension, elastic modulus, and the bending stiffness of the floater, to illustrate their influence on the motion and deformation of the platform. This work contributes to a deeper comprehension of membrane-based floating PV systems and their practical applications.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140645673","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":"Spatio-temporal relationship between three-dimensional deformations of a collapsible tube and the downstream flowfield","authors":"Vikas N. Bhargav ,&nbsp;Nicola Francescato ,&nbsp;Holger Mettelsiefen ,&nbsp;Abdullah Y. Usmani ,&nbsp;Stefania Scarsoglio ,&nbsp;Vrishank Raghav","doi":"10.1016/j.jfluidstructs.2024.104122","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104122","url":null,"abstract":"<div><p>The interactions between fluid flow and structural components of collapsible tubes are representative of those in several physiological systems. Although extensively studied, there exists a lack of characterization of the three-dimensionality in the structural deformations of the tube and its influence on the flow field. This experimental study investigates the spatio-temporal relationship between 3D tube geometry and the downstream flow field under conditions of fully open, closed, and slamming-type oscillating regimes. A methodology is implemented to simultaneously measure three-dimensional surface deformations in a collapsible tube and the corresponding downstream flow field. Stereophotogrammetry was used to measure tube deformations, and simultaneous flow field measurements included pressure and planar Particle Image Velocimetry (PIV) data downstream of the collapsible tube. The results indicate that the location of the largest collapse in the tube occurs close to the downstream end. In the oscillating regime, sections of the tube downstream of the largest mean collapse experience the largest oscillations in the entire tube that are completely coherent and in phase. At a certain streamwise distance upstream of the largest collapse, a switch in the direction of oscillations occurs with respect to those downstream. Physically, when the tube experiences constriction downstream of the location of the largest mean collapse, this causes the accumulation of fluid and build-up of pressure in the upstream regions and an expansion of these sections. Fluctuations in the downstream flow field are significantly influenced by tube fluctuations along the minor axes. The fluctuations in the downstream flowfield are influenced by the propagation of disturbances due to oscillations in tube geometry, through the advection of fluid through the tube. Further, the manifestation of the LU-type pressure fluctuations is found to be due to the variation in the propagation speed of the disturbances during the different stages within a period of oscillation of the tube.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":null,"pages":null},"PeriodicalIF":3.6,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140645672","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}