Journal of Fluids and Structures最新文献

{"title":"Flow-induced vibration of an S-shaped bluff elastic sheet","authors":"Junkyu Ham,&nbsp;Minho Song,&nbsp;Janggon Yoo,&nbsp;Daegyoum Kim","doi":"10.1016/j.jfluidstructs.2024.104120","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104120","url":null,"abstract":"<div><p>The dynamics of an S-shaped elastic sheet, in which the inclination angles of two clamped ends are normal to the direction of uniform flow and opposite to each other, are experimentally investigated. Flow-induced vibrations are ensured in this novel configuration by the substantial area perpendicular to the flow and the bluff shape. The motions of the sheet can be divided into three modes depending on the trends of the oscillation amplitude and frequency with respect to the flow velocity. At low flow velocities, the sheet undergoes small-amplitude oscillations with a nearly constant frequency. Beyond a certain threshold of flow velocity, the amplitude increases rapidly while the frequency declines. The dimensionless critical flow velocity is almost independent of the ratio between the clamp distance and sheet length, as predicted by simple scaling analysis. As the flow velocity increases further, the amplitude becomes saturated, while the frequency becomes almost proportional to the flow velocity. The most notable features of the sheet are the temporal and spatial distributions of its bending energy. The bending energy exhibits negligible fluctuations over time, and despite changes in the flow velocity, the time-averaged bending energy remains almost constant. However, by dividing the sheet into front, center, and rear parts, significant variations in the bending energy are found, and these are intensified at higher flow velocities. The S-shaped sheet exhibits more pronounced variations in local bending energy at lower flow velocities compared with a snap-through sheet model clamped at both ends.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"127 ","pages":"Article 104120"},"PeriodicalIF":3.6,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140554880","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 flexible sheet in the wake of a cylinder forced to rotate","authors":"Adrian Carleton,&nbsp;Yahya Modarres-Sadeghi","doi":"10.1016/j.jfluidstructs.2024.104110","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104110","url":null,"abstract":"<div><p>We discuss the behavior of a flexible sheet placed in the wake of a cylinder that is forced to rotate periodically. This is done through a series of experiments conducted in a water tunnel and by simultaneously visualizing the flow behavior and tracking the motion of the flexible sheet in the wake of the cylinder. We show how the response of a flexible sheet in the wake of a fixed cylinder, which is the result of the sheet’s interaction with the vortices that are shed at a frequency predicted by the Strouhal law can be changed to a “desired” response by forcing the upstream cylinder to rotate periodically. Large-amplitude oscillations at a frequency different from the Strouhal frequency can be imposed on the flexible sheet, and the sheet’s oscillations can be suppressed if the cylinder is forced to rotate at a higher frequency. The flexible sheet finds its way in between the vortices that are shed in the wake of the cylinder, and by controlling the frequency and location of the shed vortices in the wake of the cylinder, one can impose a desired motion on the sheet. Besides imposing a symmetric oscillatory response on the sheet, we show that asymmetric responses can be imposed on the sheet when an asymmetric waveform is used to force the upstream cylinder.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"127 ","pages":"Article 104110"},"PeriodicalIF":3.6,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140540707","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 interaction between galloping instability and vortices in corner-cut rectangular cylinders","authors":"Thinzar Hnin,&nbsp;Tomomi Yagi,&nbsp;Kyohei Noguchi,&nbsp;Manoj Pradhan,&nbsp;Rintaro Kyotani,&nbsp;Hisato Matsumiya","doi":"10.1016/j.jfluidstructs.2024.104108","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104108","url":null,"abstract":"<div><p>Studies on bluff-body aerodynamics have emphasized that galloping instability is strongly associated with the Kármán vortex. This study discusses the aerodynamic interactions between the galloping instability and Kármán and motion-induced vortices, analyzes the effects of these vortices on vortex-induced vibration and galloping, and investigates the stabilizing effects of various corner cuts on a rectangular cylinder. Wind tunnel tests were performed on a rectangular cylinder with a side ratio of 1.5 under a smooth flow for seven different corner shapes. The rectangular cylinder with cut corners significantly reduced both the aerodynamic force coefficients and the Kármán vortex shedding intensity. Furthermore, spring-supported free vibration tests indicated that the onset reduced wind velocities were high in the response amplitudes of all corner-cut sections that were analyzed despite the significantly low onset reduced wind velocities of the Kármán vortex-induced vibration, which were denoted as the reciprocal of the Strouhal number and closely associated with the onset of galloping. This was attributed to the motion-induced vortex dominating the vibration when the Kármán vortex shedding intensity was reduced. Therefore, this study clarified one of the factors that affected the onset-reduced wind velocity of galloping.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"127 ","pages":"Article 104108"},"PeriodicalIF":3.6,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140536454","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 theoretical fluid dynamics of spherical Savonius turbines operated in pipe flows","authors":"Yuichi Murai,&nbsp;Takahiro Umemura,&nbsp;Hyun Jin Park,&nbsp;Yasufumi Horimoto,&nbsp;Yuji Tasaka","doi":"10.1016/j.jfluidstructs.2024.104105","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104105","url":null,"abstract":"<div><p>The performance of Savonius turbines driven by flow in a pipe is experimentally investigated. The turbine is manufactured to have a spherical outline based on the pipe cross section at a small clearance. The torque and power of the turbine are obtained from the time derivative of the rotational speed measured using a high-speed camera and an equation of rotational motion. We find that the idling tip-speed ratio of the turbine exceeds 5, which is much greater than that of a turbine operating in an open free stream. This proves the dominance of pulsatile flow through the gap between two hemispherical blades in torque generation. Widely varying the gap (i.e., the overlap ratio <em>O_R</em> of the Savonius turbine) reveals that a turbine with <em>O_R</em> = 30 % has the highest power coefficient. The output efficiency exceeds 50 % for a tip-speed ratio of approximately 3. These experimental results are supported by fluid dynamics theory and computational fluid dynamics simulation, which clarify the driving mechanism of the turbine in a pipeline.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"127 ","pages":"Article 104105"},"PeriodicalIF":3.6,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140332934","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":"Angular vortex-induced vibrations of a cylinder","authors":"Adrian Carleton,&nbsp;Yahya Modarres-Sadeghi","doi":"10.1016/j.jfluidstructs.2024.104087","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104087","url":null,"abstract":"<div><p>We consider the response of a flexibly-mounted cylinder placed in flow and free to oscillate on a curved path about a pivot point. The curved path could be concave (i.e., bent toward the incoming flow) or convex (i.e., bent away from the incoming flow). We consider different radii of curvature for both the concave and the convex paths and show that oscillations are observed for radii of curvature larger than one cylinder diameter. In general, we show that the oscillations are of larger amplitudes in the convex orientation, reaching angles of oscillations of up to 38° and normalized (with respect to the cylinder's diameter) amplitudes of oscillations in the transverse and inline directions of up to 1.1 and 0.35, respectively. The oscillations on the concave path are of smaller amplitudes, but last up to higher values of reduced velocities than those in the convex orientation. The shedding and oscillation frequencies increase with increasing reduced velocity for the concave orientation reaching values of around 1.8 times the system's natural frequency in water at the end of the lock-in range, while for the convex orientation, the frequencies stay close to the natural frequency and only jump from values slightly lower than the natural frequency to values slightly higher than the natural frequency when the oscillation amplitude drops from an upper branch to a lower branch in the VIV amplitude response. Two single vortices are observed in the wake when oscillation amplitudes are relatively low, and two pairs of vortices of different sizes are observed in the wake when amplitudes are relatively larger. When two pairs of vortices are observed, the cylinder carries two bound vortices with it during its transverse oscillations and sheds them in the form of a pair of vortices of different sizes at the end of each half cycle. In the cases with the largest amplitudes of oscillations, besides the vortices that are shed synchronized with the oscillation frequency, several smaller-size vortices are shed in the wake as the cylinder traverses its crossflow path. We relate the reason for observing larger amplitudes of oscillations on the convex path to the relative orientation of the fluctuating forces that are exerted on the cylinder due to the shedding of vortices in its wake with respect to its oscillation path.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"126 ","pages":"Article 104087"},"PeriodicalIF":3.6,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140327715","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 Eulerian models for the numerical simulation of capsules with an elastic bulk nucleus","authors":"Florian Desmons ,&nbsp;Thomas Milcent ,&nbsp;Anne-Virginie Salsac ,&nbsp;Mirco Ciallella","doi":"10.1016/j.jfluidstructs.2024.104109","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104109","url":null,"abstract":"<div><p>In this paper, we present a computational framework based on fully Eulerian models for fluid–structure interaction for the numerical simulation of biological capsules. The flexibility of such models, given by the Eulerian treatment of the interface and deformations, allows us to easily deal with the large deformations experienced by the capsule. The modeling of the membrane is based on a full membrane elasticity Eulerian model that is capable of capturing both area and shear variations thanks to the so-called backward characteristics. In the validation section several test cases are presented with the goal of comparing our results to others present in the literature. In this part, the comparisons are done with different well-known configurations (capsule in shear flow and square-section channel), and by deepening the effect of the elastic constitutive law and capillary number on the membrane dynamics. Finally, to show the potential of this framework we introduce a new test case that describes the relaxation of a capsule in an opening channel. In order to increase the challenges of this test we study the influence of an internal nucleus, modeled as a hyperelastic solid, on the membrane evolution. Several numerical simulations of a 3D relaxation phenomenon are presented to provide characteristic shapes and curves related to the capsule deformations, while also modifying size and stiffness parameter of the nucleus.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"127 ","pages":"Article 104109"},"PeriodicalIF":3.6,"publicationDate":"2024-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140296885","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":"Low-frequency vibration reduction of an underwater metamaterial plate excited by a turbulent boundary layer","authors":"Wenkai Dong,&nbsp;Zhangkai Huang,&nbsp;Ting Wang,&nbsp;Meixia Chen","doi":"10.1016/j.jfluidstructs.2024.104103","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104103","url":null,"abstract":"<div><p>Flow-induced structural noise is an important component of hydrodynamic noise of underwater structures. Local resonance metamaterials are considered to have excellent performance and enormous potential in the field of low-frequency vibration and noise control. To verify its potential, the paper derived the underwater band gap of a lateral local resonance (LLR) plate through the plane wave expansion (PWE). Then, utilizing the modal superposition approach and Rayleigh integral technique, the vibro-acoustic response of a LLR plate under a turbulent boundary layer (TBL) excitation is obtained. Finite element certification is also conducted through an uncorrelated wall plane wave technique. Parametric study is conducted to analyse the factors which influence the control effects. The result shows that the plate exhibits excellent suppression performance for flow-induced vibration at band gap frequencies. The band gaps and suppression ranges generated by the underwater metamaterial plate, are dramatically narrowed due to the thick fluid load. The paper provides theoretical guidance for the control of flow-induced structural vibration and the application of acoustic metamaterials.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"126 ","pages":"Article 104103"},"PeriodicalIF":3.6,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140195616","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 two-step fluid–structure approach for the vibration analysis of flexible propeller blade","authors":"Quentin Rakotomalala ,&nbsp;Lucie Rouleau ,&nbsp;Cédric Leblond ,&nbsp;Mickaël Abbas ,&nbsp;Jean-François Deü","doi":"10.1016/j.jfluidstructs.2024.104091","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104091","url":null,"abstract":"<div><p>In this paper, a numerical approach able to evaluate the sound power emitted by a non-cavitating flexible marine propeller blade is proposed. With asymptotic expansions and order of magnitude analysis, two main phenomena are identified: the so-called propulsion and vibroacoustic phenomenon. The propulsion phenomenon is nonlinear and models the lift generation along the blade. It creates a pre-stress and a pre-strain on a deformed configuration on which the blade vibrates and emits sound waves. The vibroacoustic phenomenon is linearized and has no retroaction on the first static phenomenon. This simplified model allows to solve the fully coupled fluid–structure system in order to compute the radiated noise of a pre-stressed blade.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"126 ","pages":"Article 104091"},"PeriodicalIF":3.6,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0889974624000264/pdfft?md5=b7a83b2910d68e649e0d1510694af839&pid=1-s2.0-S0889974624000264-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140163706","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":"Control of vortex shedding and acoustic resonance of a circular cylinder in cross-flow","authors":"R. Noufal,&nbsp;M. Alziadeh,&nbsp;A. Mohany","doi":"10.1016/j.jfluidstructs.2024.104094","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104094","url":null,"abstract":"<div><p>This study experimentally investigates the effectiveness of a control rod in suppressing self-excited acoustic resonance within a range of Reynolds numbers (Re) spanning from <span><math><mrow><mn>2</mn><mo>.</mo><mn>1</mn></mrow></math></span> × <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> to <span><math><mrow><mn>1</mn><mo>.</mo><mn>6</mn></mrow></math></span> × <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>5</mn></mrow></msup></mrow></math></span>. The investigation focuses on specific parameters, including diameter ratio (<span><math><mrow><mi>d</mi><mo>/</mo><mi>D</mi></mrow></math></span>) values of 0.1, 0.2, and 0.3; gap ratio (<span><math><mrow><mi>G</mi><mo>/</mo><mi>D</mi></mrow></math></span>) values of 0.05, 0.1, and 0.2; and angular positions (<span><math><mi>θ</mi></math></span>) ranging from 0 to 180 degrees. Comparative analyses are conducted between cases featuring the control rod and a reference case (base case) without it. The near-wake flow field is characterized using Particle Image Velocimetry (PIV), and aeroacoustic response measurements are employed to quantify the aeroacoustic noise emission, particularly during self-excited acoustic resonance. Simultaneous measurements of fluctuating lift force and aeroacoustic response measurements, facilitate the quantification of energy transfer from the flow field to the acoustic field during self-excited acoustic resonance. The results reveal that the control rod’s placement significantly impacts the Strouhal periodicity, with outcomes heavily dependent on the rod’s angular orientation. At certain angular positions, the control rod reduces the sound pressure level (SPL) generated during acoustic resonance excitation. However, at different angular positions, the rod exacerbates resonance excitation. This variability is attributed to the control rod’s profound influence on the vortex core formation and the energy transfer mechanism during acoustic resonance.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"126 ","pages":"Article 104094"},"PeriodicalIF":3.6,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140163705","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 and analysis of a novel magnetic helical swimmer","authors":"Pouria Piranfar,&nbsp;Mahyar Naraghi,&nbsp;Ali Kamali Egoli","doi":"10.1016/j.jfluidstructs.2024.104093","DOIUrl":"https://doi.org/10.1016/j.jfluidstructs.2024.104093","url":null,"abstract":"<div><p>Magnetic helical swimmers are one type of robots that swim at low Reynolds number environments by rotating around the helix axis. Considering the importance and dramatic increase in the use of robots and microrobots in the near future, optimizing and increasing their efficiency is very important and noteworthy. Propulsion force and translational velocity are among the most important features of the magnetic helical swimmer, which improves the function of the swimmer as each of them increases. In this paper, a new design has been proposed for the magnetic helical swimmer by changing the geometry of the tail region, which has increased the propulsion force and improved its translational velocity. A suitable experimental setup has been designed and built in accordance with the required experiments to evaluate the translational velocity of the proposed swimmer. Using the experimental results, two models have been presented to express the translational velocity and propulsion force of the swimmer in terms of its angular velocity. The results of the experiments show that the propulsion force of the built swimmer is 698.89 % higher than that of the common magnetic helical swimmer with similar dimensions and the same environmental conditions in Newtonian fluid. At the end of the experiments, the motion of the proposed swimmer is simulated in the COMSOL software, and the results of the experiments are used to validate the simulation results. Finally, the effect of parameters such as the helix pitch and the number of turns of the helix on the translational velocity of the swimmer is investigated using the computer simulations.</p></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"126 ","pages":"Article 104093"},"PeriodicalIF":3.6,"publicationDate":"2024-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140137848","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}