Journal of Fluids and Structures最新文献

{"title":"Experimental study on vortex-induced vibrations of a circular cylinder elastically supported by realistic nonlinear springs: Vibration response","authors":"Yawei Zhao ,&nbsp;Zhimeng Zhang ,&nbsp;Chunning Ji ,&nbsp;Weilin Chen ,&nbsp;Jiahang Lv ,&nbsp;Hanghao Zhao","doi":"10.1016/j.jfluidstructs.2024.104233","DOIUrl":"10.1016/j.jfluidstructs.2024.104233","url":null,"abstract":"<div><div>This study presents an experimental investigation into the vortex-induced vibrations (VIV) of a single circular cylinder supported by various nonlinear springs. Unlike previous studies focused on systems satisfying the Duffing equation, this study explores a realistic scenario with nonlinear restoring forces derived from different magnet configurations. Experiments were conducted in a low-speed circulating water flume across a Reynolds number range of <em>Re</em> = 232-20930, a mass ratio (<em>m*</em>) ranging from 3.39 to 5.55, and a nonlinear strength coefficient (<em>λ</em>) from -1.48 to 1.70. The results demonstrated that predicted nonlinear VIV amplitudes using linear VIV data align well with experimental observations, validating the applicability of the prediction theory (Mackowski and Williamson, PoF, 2013) to general nonlinear systems. An equivalent reduced velocity (<em>U_eq</em>) was introduced to rescale vibration responses, effectively collapsing the envelopes for linear and hardening nonlinear systems, although shifts to higher <em>U_eq</em> values were observed for softening systems. A detailed analysis of the nonlinear coefficient's impact on VIV characteristics, including amplitude, frequency, phase lag, and displacement history, identified four distinct VIV response groups: softening, weak hardening, intermediate hardening, and strong hardening nonlinear VIV. A notable finding is the presence of two lock-in regions in nonlinear VIV responses, characterized by superharmonic synchronization, and multiple-value sections and gaps in vibration envelopes at specific transitions. These behaviors are attributed to variations in the natural frequency (<em>f_n</em>(<em>A*</em>)) with vibration amplitude. This study provides valuable insights into the complex dynamics of general nonlinear VIV, offering a foundation for future research and practical applications.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104233"},"PeriodicalIF":3.4,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142759307","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":"On the mechanism of frequency lock-in vibration of airfoils during pre-stall conditions","authors":"Jingge Quan ,&nbsp;Sijia Zhang ,&nbsp;Chuanqiang Gao ,&nbsp;Zhengyin Ye ,&nbsp;Weiwei Zhang","doi":"10.1016/j.jfluidstructs.2024.104227","DOIUrl":"10.1016/j.jfluidstructs.2024.104227","url":null,"abstract":"<div><div>Potential frequency lock-in vibration can frequently occur in aircraft flying at separated flow conditions during take-off and landing stages, severely threatening the safety of the aircraft. A deeper understanding of the lock-in phenomenon in pre-stall (steady separated flow) conditions is necessary to improve aircraft reliability and safety. In this paper, a reduced-order model (ROM) for the pitching NACA0012 airfoil in steady separated flow is established. A linear aeroelastic model is then obtained by coupling the ROM with the structural dynamical equation with the pitching degree of freedom, and it is verified by the computational fluid dynamics/computational structural dynamics (CFD/CSD) simulation. Next, the mechanism of frequency lock-in vibration is revealed by the ROM-based aeroelastic model of different structural natural frequencies. Results from the complex eigenvalue analysis indicate that the instability can be divided into two patterns. At high frequencies, the flutter frequency locked onto the natural frequency of the structure, and it is dominated by the instability of structural mode. At low frequencies, the flutter frequency follows the fluid characteristic frequency, which is dominated by the instability of the fluid mode. Finally, the effects of the angle of attack and mass ratio are investigated. The damping of dominant fluid mode decreases with the increase of angle of attack, which affects the structural mode through coupling effects. Therefore, the angle of attack influences the upper boundary of the coupling system’s instability (high frequency boundary). On the contrary, the mass ratio mainly influences the lower boundary of instability (low frequency boundary), because fluid mode becomes unstable at low frequencies merely when the mass ratio is relatively low.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"133 ","pages":"Article 104227"},"PeriodicalIF":3.4,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142759302","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":"VIV mechanisms of a non-streamlined bridge deck equipped with traffic barriers","authors":"Bernardo Nicese ,&nbsp;Antonino Maria Marra ,&nbsp;Gianni Bartoli ,&nbsp;Claudio Mannini","doi":"10.1016/j.jfluidstructs.2024.104195","DOIUrl":"10.1016/j.jfluidstructs.2024.104195","url":null,"abstract":"<div><div>Vortex-induced vibration (VIV) has been addressed in the literature mostly for quasi-streamlined and shallow π-deck sections, typical of long-span bridges, since the latter are particularly prone to wind-induced oscillations. In contrast, although full-scale observations demonstrate that even steel-box girder bridges, usually characterized by a shorter span length if compared to suspension and cable-stayed bridges, can experience a violent VIV response, systematic studies for these bluffer cross-section geometries are less frequent. In addition, the aerodynamic optimization of non-structural additions (barriers, screens, fairings) is rarely carried out for this bridge typology. Therefore, a wind tunnel investigation is conducted on a non-streamlined box-girder sectional model (inspired by the Volgograd Bridge, Russia) equipped with two typologies of traffic barriers giving rise to a large ratio of barrier height to deck width. A realistic range of angles of attack (from −3° to 3°) are considered, and static forces, aeroelastic vibrations and wake velocity fluctuations are measured. A large and even unexpected variability in the vibration amplitude and lock-in curve pattern is found, emphasizing the possible existence of competing excitation mechanisms. Indeed, low-porosity barriers can alter the characteristics of vortex shedding, in particular creating a cavity on the upper side of the deck, which is known to foster the impinging-shear-layer instability, as in H-shaped sections. This vortex-shedding mechanism may co-exist with Kármán-vortex shedding and may be responsible for significant anticipation of the VIV onset compared to the predictions based on the Strouhal number measured during static tests. The intensity of a secondary excitation mechanism and its interaction with the dominant mechanism strongly depend on the angle of attack and is largely responsible for profound changes in the VIV bridge response, both in terms of qualitative pattern and peak amplitude. In some cases, the tracks of these competing vortex-shedding mechanisms are even clearly visible in the VIV response curves of the tested bridge model. Finally, the wind tunnel results are also reconsidered based on the quasi-steady theory, highlighting some, even qualitative, discrepancies.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"132 ","pages":"Article 104195"},"PeriodicalIF":3.4,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702048","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":"Nonlinear aeroelastic behavior of a two-dimensional heated panel by irregular shock reflection considering viscoelastic damping","authors":"Yiwen He ,&nbsp;Aiming Shi ,&nbsp;Earl H. Dowell ,&nbsp;Shengxi Zhou","doi":"10.1016/j.jfluidstructs.2024.104230","DOIUrl":"10.1016/j.jfluidstructs.2024.104230","url":null,"abstract":"<div><div>This paper investigates the aeroelastic stability and nonlinear aeroelastic behavior of a two-dimensional heated panel in irregular shock reflection and extends prior work to include the effects of viscoelasticity. The aeroelastic model is formulated using the von Kármán large deflection plate theory and the Kelvin–Voigt damping model, accompanied by the quasi-steady thermal stress theory. The unsteady aerodynamic pressure is evaluated through the piston theory and the compressibility-corrected potential theory. The Galerkin approach is used to discretize the governing equation. The Lyapunov indirect method is applied to conduct theoretical analysis, obtaining the aeroelastic stability boundary. Also, the nonlinear aeroelastic response is numerically simulated via the fourth-order Runge–Kutta method. The proper orthogonal decomposition is applied to the panel deflection to manifest the influence of various system parameters. It is demonstrated that the shock wave aggravates the aerodynamic heating, lowering the critical buckling temperature. The viscoelastic damping restricts the impact of shock impingement location and shock strength on the stability boundary and also transforms the chaotic motions into periodic LCOs.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"132 ","pages":"Article 104230"},"PeriodicalIF":3.4,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702049","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":"Estimation of wind force time-history using limited floor acceleration responses by modal analysis","authors":"Daiki Sato ,&nbsp;Razelle Dennise A. Soriano ,&nbsp;Alex Shegay ,&nbsp;Kou Miyamoto ,&nbsp;Jinhua She ,&nbsp;Kazuhiko Kasai","doi":"10.1016/j.jfluidstructs.2024.104203","DOIUrl":"10.1016/j.jfluidstructs.2024.104203","url":null,"abstract":"<div><div>Time-history analyses are usually performed to design and examine the performance of tall structures subjected to strong wind loading. An accurate estimate of the time history of wind forces is required to carry out time-history analysis. However, previous studies conducted to estimate the time-history of wind forces require a lot of priori information, such as complete structural parameters and wind-induced responses, which are generally not available in actual conditions. This work addresses the estimation of the time-history of wind forces acting on each story of a ten degree-of-freedom model under the assumption that only the mass and acceleration responses measured on three stories are known. First, cubic spline interpolation is used to determine the unknown acceleration responses and frequency domain integration is used to obtain the velocity and displacement responses. Then, unknown structural parameters (particularly stiffness and damping) are estimated by the Frequency Domain Decomposition method. Finally, the obtained responses and structural parameters are used to estimate the wind forces using the equation of motion. It is demonstrated that the proposed methodology can accurately estimate the input wind forces on the structure.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"132 ","pages":"Article 104203"},"PeriodicalIF":3.4,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702011","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":"Mode split prediction for rotating disks with flexible stator coupling","authors":"Lucas Berthet ,&nbsp;Philippe Blais ,&nbsp;Bernd Nennemann ,&nbsp;Christine Monette ,&nbsp;Frederick P. Gosselin","doi":"10.1016/j.jfluidstructs.2024.104224","DOIUrl":"10.1016/j.jfluidstructs.2024.104224","url":null,"abstract":"<div><div>High-head turbine runners are subject to multiple sources of excitation. Coupled with the added mass of water, rotation induces a mode split in the natural frequencies of runners, where co-rotating and counter-rotating waves travel through the runner at different relative speeds. Disks, by displaying a similar behavior, can be used as a geometrically simpler model. Mode split is characterized for a rotating disk in dense fluid but, in high-head turbines, the runner and the compliant confinement are coupled through the axial gap fluid. In this article, we develop an analytical model of coupled stationary and rotating disks to analyze the effect of their interaction on the mode split phenomenon. First, we apply the potential flow theory, considering the fluid as irrotational, inviscid and incompressible. We assume that the modeshapes of the disk in a dense fluid are similar to their shapes in vacuum. We then derive the potential flows that respect the no-penetration boundary conditions. One after the other, each disk is considered flexible while the other one is rigid. By applying the superposition principle, we then couple the two obtained fluid flows through the structural equations of motion. A finite-element vibro-acoustic modal analysis was developed to verify the analytical model and propose a fast numerical tool for hydraulic turbine design. Analytical results show that rotation induces a split of the coupled rotor–stator frequencies as for a lone rotor, while the ratio of their amplitudes varies slightly. A change in the relative thickness of the rotor and stator affects their individual frequencies in vacuum, and in turn their coupling by the fluid, with a potential shift in dominance.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"132 ","pages":"Article 104224"},"PeriodicalIF":3.4,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702047","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":"Fluid-structure interaction analysis of an elastic surface-piercing propellers","authors":"M Pakian Bushehri ,&nbsp;MR Golbahar Haghighi ,&nbsp;P Malekzadeh ,&nbsp;E Bahmyari","doi":"10.1016/j.jfluidstructs.2024.104228","DOIUrl":"10.1016/j.jfluidstructs.2024.104228","url":null,"abstract":"<div><div>In high-speed planing craft, surface-piercing propellers (SPPs) operate semi-submerged in a two-phase air-water environment, facing stress and displacement from variable forces. In this paper, the fluid-structure interaction (FSI) of the SPP is investigated at immersion ratios of 30 %, 50 %, 70 % and 90 %, under low and high advance coefficients. A coupling of Reynolds-averaged Navier–Stokes equations (RANS) and elasticity theory are used to simulate fluid dynamics and the blade deformation with the multi-physics computational fluid dynamics software STAR-CCM+. The analysis is performed after several rotations of the SPPs at five different positions. The results show that at the advance coefficient of 0.4, a higher immersion ratio increases torque, thrust, efficiency, maximum stress, and maximum displacement. When the advance coefficient is equal to one, the efficiency, maximum stress, and maximum displacement remain constant for the immersion ratio above 50 %. The maximum displacement occurs at the blade tip, while maximum stress is at the trailing edge root. Most blade deformations happen where the blade enters the water, aligns perpendicularly with the water surface, and exits. The two-phase flow around the blade increases its displacement.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"132 ","pages":"Article 104228"},"PeriodicalIF":3.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702009","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":"Unsteady load mitigation through passive pitch","authors":"Yabin Liu ,&nbsp;Riccardo Broglia ,&nbsp;Anna M. Young ,&nbsp;Edward D. McCarthy ,&nbsp;Ignazio Maria Viola","doi":"10.1016/j.jfluidstructs.2024.104216","DOIUrl":"10.1016/j.jfluidstructs.2024.104216","url":null,"abstract":"<div><div>Mitigation of load fluctuations due to flow unsteadiness is critical in a broad range of applications, including wind/tidal turbines, and aerial/underwater vehicles. While the use of active control systems is an established practice in engineering, passive systems are not well understood, and the limits of their efficacy are yet to be ascertained. To this end, the present study aims to provide new insights into the effectiveness of passive pitching in the mitigation of lift fluctuations in the most demanding case of fast, high-amplitude variations of the free stream speed and direction. We perform fluid-structure interaction simulations of a two-dimensional free-to-pitch rigid foil. Our study reveals that the lift amplitude of the force fluctuations can be decreased by at least two-thirds through passive pitching. The efficacy of the unsteady load mitigation is only weakly dependent on the exact pitching axis location, and the optimal position is upstream and close to the axis of the foil. These results may inform the design of passive control systems of wind/tidal turbines and aerial/underwater vehicles and provide new insights into interpreting the control strategy of natural flyers such as insects and birds.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"131 ","pages":"Article 104216"},"PeriodicalIF":3.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707336","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":"Numerical investigation of fluid–structure interaction in a pilot-operated microfluidic valve","authors":"Ahmed Aissa-Berraies ,&nbsp;E. Harald van Brummelen ,&nbsp;Ferdinando Auricchio","doi":"10.1016/j.jfluidstructs.2024.104226","DOIUrl":"10.1016/j.jfluidstructs.2024.104226","url":null,"abstract":"<div><div>The present paper is concerned with numerical investigation of the performance of a pilot-operated control valve based on shape memory alloy actuation control. The valve under investigation can be integrated into miniaturized hydraulic systems and is developed to perform precise dispensing, mixing, or dosing tasks while being able to withstand relatively high pressure differences. The study evaluates the valve’s response under the current ON/OFF and the desired proportional control regimes using numerical methods for fluid–structure interaction. The computational model replicates the operation of the valve, which requires an understanding of the complex interactions between the fluid flow with the pressurized valve and the contact with the valve seat during the opening and closing processes. In addition, the model leverages advanced numerical techniques to overcome several complexities arising mainly from the geometrical, material, and contact nonlinearities, and to mitigate the shortcomings of the partitioned fluid–structure interaction approach. Several 3D fluid–structure-contact-interaction simulations are conducted to examine the valve’s structural and flow behavior under varying pressure conditions. Results indicate that the valve is adequate for ON/OFF actuation control but is susceptible to flow-induced vibrations during the proportional control regime that occurs due to the sharp pressure drop in the valve-seat gap and the ensuing Venturi effect, which counteract the opening of the main valve. The fluid–structure-interaction simulations provide insight into the mechanism underlying the flow-induced vibrations, which can serve to improve the design and enhance the performance of the valve in microfluidic applications.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"132 ","pages":"Article 104226"},"PeriodicalIF":3.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702010","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":"Flow-induced buckling of a bistable beam in uniform flow","authors":"Leixin Ma ,&nbsp;Wenyu Chen ,&nbsp;Ruosi Zha ,&nbsp;Alejandra Hernandez Escobar","doi":"10.1016/j.jfluidstructs.2024.104220","DOIUrl":"10.1016/j.jfluidstructs.2024.104220","url":null,"abstract":"<div><div>Recent developments in soft materials enable the design and manufacturing of bistable flexible structures. Their fast snap-through buckling mechanisms have been utilized to introduce fast locomotion. In this paper, we aim to understand the impact of fluid–structure interaction (FSI) on the dynamics of bistable structures. We report the numerical analysis of the snap-through buckling phenomena for several bistable flexible structures fixed at both ends. The motion is driven by the fluid loading of different flow speeds. The large deformation of the bistable structure is coupled with the incoming fluid flow via the Arbitrary Lagrangian–Eulerian (ALE) method. During the snap-through buckling process, the corresponding structural deformation patterns, hydrodynamic force distributions, and fluid patterns are discussed. Larger steady-state deformation is found for the bistable structure, compared to its mono-stable counterpart in the same flow condition. The Cauchy number is found to be the critical parameter affecting the buckling dynamics and dimensionless strain energy stored in the system. A prediction model for the dimensionless strain energy as a function of the Cauchy number is proposed. The hydrodynamic lift force generated by the fluid is found to increase the total strain energy of these bistable structures. The research could provide insight in designing morphable marine energy devices and lightweight bioinspired propulsion systems.</div></div>","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"131 ","pages":"Article 104220"},"PeriodicalIF":3.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142707335","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}