Natural Frequencies Of Structure Research Articles

Numerical study on vortex-induced vibration of wind turbine airfoil at high angle of attack via free vibration simulation

Dynamic response of an elastically mounted wind turbine airfoil at 90° angle of attack is investigated with free vibration simulation. The airfoil motion and unsteady aerodynamic force due to vortex shedding couple with each other, possibly resulting in vortex-induced vibration. This situation may be encountered during wind turbine parking or idling operations, which potentially leads to structure damage. Considering the frequency lock-in phenomenon of the vortex-induced vibration, the shedding frequency will synchronize with the structure natural frequency that could cause limit cycle oscillations. The frequency lock-in range of the elastically mounted airfoil is first determined by employing the free vibration simulation. The amplitude and stability of the limit cycle oscillation predicted based on the aerodynamic damping solved by the prescribed vibration simulation are in good agreement with the free vibration simulation. The transient process of the vortex-induced vibration is illustrated for different incoming velocities, airfoil mass, and initial positions. The aerodynamic damping is proven an efficient way to understand and predict the complex aeroelastic behavior during vortex-induced vibration.

Transient Effect of Random Loads on Reinforced Cement Concrete Building on RCC Building with Staad Pro. V8i

Abstract. Dynamic load is one which changes with time quickly in comparison to the structure's natural frequency. If it varies quickly, the activity must be determined with a dynamic analysis. Explosive loads and impact loads are transients, or loads that are applied dynamically as one-half cycle of high amplitude. This transient load is applied only for a specific and typically short period of time in the case of blast loads typically less than one-tenth of a second. The response of the engineering structural building due to the reason of periodic load RCC building structure has been severely damaged, collapse and develop cracks. Bomb blast is the best example for impulsive load. To determine the response of a G+3 RCC building model in STAAD Pro subjected to triangular, rectangular and sinusoidal impulsive force for 0.5 seconds with maximum magnitude of 100kN. Effect of such loads on front, roof and side portion of the building studied. Observe that the critical deformations obtained on the front and roof portion of building. Effect of deformation along height of building was parabolic in nature with maximum deflection at top floor of building. It was also noted i.e sufficient reinforcement should be provided in beam, columns and slabs to impart ductility to the building against impulse loads.There is more demand for construction of high buildings due to increasing urbanization and population.

Dynamic Interactions of Multiple Wall-Mounted Flexible Plates in a Laminar Boundary Layer

The interactions between large arrays of wall-mounted flexible plates and oncoming laminar boundary-layer flows are studied numerically by using the immersed boundary method. The influences of bending rigidity, mass ratio and gap distance between adjacent plates on the dynamic behaviors are explored. With the variation of control parameters, five distinct dynamic modes, namely, static reconfiguration, sectional waving, regular waving, upright oscillation and cavity oscillation, are identified. The frequency lock-in phenomenon and various types of flow instability associated with different dynamic modes are discussed. The findings of this study indicate that the coherent motions of the arrays are governed by a coupled mechanism in which the frequency of flow instability is locked onto the structural natural frequency.

Free vibration response of auxetic honeycomb sandwich plates using an improved higher-order ES-MITC3 element and artificial neural network

This article presents the combination of mixed interpolation of tensorial components technique of triangular elements and the edge-based smoothed finite element method (ES-MITC3) developed on the higher-order shear deformation theory (HSDT). The free vibration behavior of auxetic honeycomb sandwich plates with the functionally graded material (FGM) skin layers generated by the proposed program is trained and predicted by an artificial neural network (ANN) model using Matlab coding for reducing computational time and saving computer resources, the proposed approach is expected suitable for practical engineering problems. The strain field of edge-based smoothed triangular elements is approximated by using the generalized C0-HSDT and Lagrange shape functions. Ultra-light features of sandwich plates are obtained by using the auxetic honeycomb core layer (negative Poisson’s ratio) and reinforced by FGM skin layers. The present results are compared with other published studies to verify the accuracy and reliability. Besides, the ANN model is also built to train obtained results and accurately predict the natural frequency of structures without running the code. Moreover, the effects of parameters such as geometrical and material properties (especially the auxetic parameters) on the free vibration behavior of auxetic honeycomb sandwich plates with FGM skin layers are investigated in detail.

Polypropylene Composite Material for Light Weight Fuel Tank Protection Shield

<div class="section abstract"><div class="htmlview paragraph">The fuel tank shield provides a protective boundary between the fuel tank and vehicle driveline in the event of a high-speed crash. Hence, it is important from the safety standpoint. The part must be carefully engineered to meet the challenging requirements in terms of stiffness, deflection, toughness, dimensional stability and thermal stability. In this paper, long glass fibre filled polypropylene material compound was selected and developed to meet the mentioned requirements for this part with significant mass reduction over other materials. The combination of material, optimized part and tool design led to weight savings and considerable cost reduction. This is a ready to mold material used in injection molding process.</div><div class="htmlview paragraph">This long glass fibre reinforced polypropylene compound has been explored for thin wall protection shield with wall thickness of 2.5 mm. This part has critical functional requirements such as driveline load versus deflection durability criteria, thermal stability, dimensional stability to overcome fouling and rattling with respect to interface parts, torque retention in mounting zones, gap and flush aspects. Structural durability of the design was validated by virtual engineering. Part design and material combinations with better tooling design iterations were analyzed by using mold flow analysis. Complete product performance was validated for predefined key test metrics such as structural durability, thermal aging, natural frequency, impact and torque retention. This part met the requirements. The combination of material, optimized part and tool design led to weight savings, balanced stiffness and toughness behavior, dimensional stability, and considerable cost reduction.</div></div>

Welding Residual Stress Distribution of U-Rib Stiffened Plates of Steel Box Girders and its Influence on Structural Natural Frequencies

This paper mainly explores the distribution of welding residual stress of U-rib stiffened plates of steel box girders and examines the influence of welding residual stress over the natural frequencies of these plates. The research focuses on two aspects, namely, the distribution of welding residual stress, and the dynamic behavior of U-rib stiffened plates in the context of that distribution. Firstly, we build two finite element models to analyses the welding process and study the dynamic behavior. Next, the authors discussed how different geometric parameters, as well as welding parameters, affect the residual stress distribution. In addition, the welding residual stress curves were fitted for steel box girders of varied sizes, and a simplified formula was deduced for the distribution of welding residual stress. After that, the simplified formula was applied to analyze the natural frequencies of stiffened plates in multiple sets of models. Through the analysis of natural frequency under different boundary conditions, it was learned that the welding residual stress has a remarkable influence on the natural frequencies of stiffened plates.

Influence of wind turbine design parameters on linearized physics-based models in OpenFAST

Abstract. While most physics involved in wind energy are nonlinear, linearization of the underlying nonlinear wind system equations is often important for understanding the system response and exploiting well-established methods and tools for analyzing linear systems. Linearized models are important for eigenanalysis (to derive structural natural frequencies, damping ratios, and mode shapes), controls design (based on linear state-space models), etc. In controls co-design, wherein methods often rely on linearized time-domain models of the physics, the physical structure (often called the plant) and controller are designed and optimized concurrently, so it is important to understand how changes to the physical design affect the linearized system. This work summarizes efforts done to understand the impact of design parameter variations in the physical system (e.g., mass, stiffness, geometry, and aerodynamic and hydrodynamic coefficients) on the linearized system using OpenFAST.

Mode transformation and interaction in vortex-induced vibration of laminar flow past a circular cylinder

An investigation of the mode transformation and interaction underlying the behavior of vortex-induced vibration (VIV) of a flow past a circular cylinder elastically mounted on a linear spring is conducted using a high-fidelity full-order model (FOM) based on computational fluid dynamics (CFD), a reduced-order model (ROM), and a dynamic mode decomposition (DMD) of the velocity. A reduced-order model for the fluid dynamics is obtained using the eigensystem realization algorithm (ERA), which is subsequently coupled to a linear structural equation to provide a state space model for the coupled VIV system, in order to provide a simplified computationally inexpensive mathematical representation of the system. This methodology is used to study the dynamics of laminar flows past an elastically mounted circular cylinder with Reynolds number Re ranging from 20 to 180, inclusive. The results of the simulations conducted using FOM/CFD and ROM/ERA, in conjunction with the power spectral analysis and DMD, are used to identify the characteristic natural frequencies and the growth/decay of various modes (including the complex interactions between the myriad wake modes and the structural mode) of the VIV system as a function of the Reynolds number and the reduced natural frequency Fs (or, equivalently, the reduced velocity Ur). A detailed analysis of the distribution of the eigenvalues of the transfer (or, system) matrix of the reduced VIV system shows that the frequency range of the lock-in can be partitioned into resonance and flutter lock-in regimes. The resonance lock-in (lower branch of the VIV response) dominates the fluid-structure interaction. Furthermore, it is shown that when the structural natural frequency is close to one of the eigenfrequencies associated with the wake modes, resonance lock-in (rather than flutter lock-in) will be the primary mechanism governing the VIV response even though the real part of the eigenvalues associated with structural mode is positive. With increasing Reynolds number, the instability of each wake mode is enhanced resulting in a transformation of the wake modes interacting with the structural mode. It is suggested herein that the weakened interaction between the wake modes and the structural mode at Re = 180 (associated with the greater separation between the root loci of the modes) results in the premature termination of the resonance lock-in at Fs=0.155 with increasing Ur. The DMD and power spectral analysis of the time series of the transverse displacement and lift coefficient are used to support the results obtained from ROM/ERA and, more specifically, to provide a clear demonstration of the balanced interaction between the wake modes and the structural mode. This result is used to explain the beating phenomenon, which occurs in the initial branch and the significant lag time that arises between the initial branch and the occurrence of a fully developed response in the lower branch.

고유진동수 제한을 갖는 골조구조의 GA 기반 최적설계 시스템

Normal strategy of structure optimization procedure has been minimum cost or weight design. Minimum weight design satisfying an allowable stress has been used for the ship and offshore structure, but minimum cost design could be used for the case of high human cost. Natural frequency analysis and forced vibration one have been used for the strength estimation of marine structures. For the case of high precision experiment facilities in marine field, the structure has normally enough margin in allowable stress aspect and sometimes needs high natural frequency of structure to obtain very high precise experiment results. It is not easy to obtain a structure design with high natural frequency, since the natural frequency depend on the stiffness to mass ratio of the structure and increase of structural stiffness ordinary accompanies the increase of mass. It is further difficult at the grillage structure design using the profiles, because the properties of profiles are not continuous but discrete, and resource of profiles are limited at the design of grillage structure. In this paper, the grillage structure design system under the constraint of high natural frequency is introduced. The design system adopted genetic algorithm to realize optimization procedure and can be used at the design of the experimental facilities of marine field such as a towing carriage, PMM, test frame, measuring frame and rotating arm.

A hybrid piezoelectric-electromagnetic energy harvester from vortex-induced vibrations in fluid-flow; the influence of boundary condition in tuning the harvester

In this paper, a hybrid piezoelectric-electromagnetic energy harvester is proposed to harvest energy from fluid flow around a bluff-body using vortex-induced vibration (VIV). The hybrid piezoelectric-electromagnetic harvester combines the two electromechanical transduction mechanisms through the bluff body excited by VIV: piezoelectric macro-fiber composite and an electromagnetic system. The piezoelectric composite is glued to a substrate beam to convert mechanical strain into electricity. A novel implementation of an internal electromagnetic harvester where the change in magnetic flux inside a coiled holder transduces change in magnetic flux to electricity. An analytical model is used to investigate the narrowband synchronization properties in VIV for different submerged conditions that can be tuned for vibration-based energy harvesting. Under synchronization, the structural natural frequency is the same as the vortex shedding frequency, which leads to the generation of a higher output voltage during frequency matching. Therefore, the effects of added mass and boundary conditions are validated experimentally in water flow to tune the submerged energy harvester with the new hydrodynamic properties to increase the harvesting performance. The results show that fully submerging the energy harvester increases the overall added mass, whilst confining it inside a submerged pipe adds stiffness and damping. This means the overall energy harvesting performance decreases with submerging depth and proximity to the boundary. The maximum voltage output occurs within the synchronization region, with piezoelectric output performing best when partially submerged while the electromagnetic oscillator performs best when fully submerged. Implementing a hybrid piezoelectric-electromagnetic energy harvesting system increased the voltage output by up to 23% compared to a conventional piezoelectric energy harvester.

Experimental study of wave impact on a vertical wall with overhanging horizontal cantilever slab and structural response analysis

Two-dimensional model test of a vertical wall with overhanging horizontal cantilever slab has been carried out with the scale factor of 1:30. Different influences of wave condition and structural geometry on wave load are investigated. Wave pressure of cantilever slab highly depends on structural clearance and reaches the peak when clearance close to 0.2 times wave height. Larger wave steepness is responsible for larger wave pressure for vertical wall. With the increasing length of slab, wave forces are reduced on slab while enlarged on vertical wall. Besides, a negative correlation between rise frequency and rise time is observed and corresponding empirical formula has been proposed. Through finite element analysis, the structural response of a simple plate under wave load has been studied. In general, the cut-off frequency has a dramatic effect on the dynamic magnification factor, where the actual dynamic response keeps stable when cut-off frequency larger than 4 times structural natural frequency. Finally, it is adoptable to determine the adequacy of the structure under wave load by considering the quasi-static wave load and corresponding impact factor from 2.0 to 6.0.

Investigation of Noise Generated by Railway Freight Wagon Bogie Type Y25Ls(s)e-K and Proposals of Noise Reduction

There have been numerous attempts and investigations carried out with the objective to reduce the noise generated by railway freight wagons because noise is one of ever-present negative environmental pollution phenomena. This resulted in strong legislation requirements on noise reduction in railway transport, in the case of freight wagons, only exterior noise is a problem. However, the extremely hard metal structures of the wagons running on hard rails naturally generate high magnitudes of acoustic energy. One big initiative, especially in Germany, seeks a solution in replacement of the cast iron brake pads with the composite one which should result in so-called “silent trains”. But braking is used only during a minor part of the train run, leaving most of the acoustic phenomena of the train run unaffected. In our research, we focused on freight bogies type Y25Ls(s)e-K that are used, including in Slovakia. We simulated the structural natural frequencies to predict vibrations and consequent sound generated by these vibrations. The idea was to localize the vibrations and propose possibilities of noise attenuation. The more realistic view about sound fields was obtained by practical measurements on a moving bogie. Measurements on the test track at a maintenance workshop were done by using a digital acoustic camera Soundcam. For attenuation of noise radiated by the bogie frame, acoustic silencers made from recycled porous fiber material have been applied to the bogie frame. To determine the acoustic difference, the material was applied only on half of the bogie, and then the measurements were carried out. The results showed a promising improvement in reduced noise radiation, which gives support for further research in this area with more precise simulations and more precise coating of the bogie frame as well as the proposal and measurement of noise-attenuating coatings of other structural parts of the freight wagons.

A experimental study of a cable-pulleys spring-damper energy dissipation system for buildings

An energy dissipation mechanism made of a cable-pulleys system placed in series with a spring-damper device (fluid viscous) is experimentally studied. The system aims to provide high damping ratios for all the structural modes by using a unique spring-damper device to dissipate the seismic energy of the entire structure (and all its structural modes). Shake table tests and pull-back tests are carried out on a scaled five-story structure to compare the dissipation capabilities provided by the proposed system. Therefore, the same structure is tested under different configurations that included: i) the structure itself without any energy mitigation device, ii) the structure with viscous dampers installed on each story, iii) the structure with the proposed cable-pulleys and the spring-damper system, and iv) the structure with the cable-pulleys system but without any dissipation device. The experimental results showed that the structure with the proposed system exhibits a highly nonlinear response (mainly explained by the cable-pulleys interaction) evidenced by the significant change of the structure's dynamic properties during the time. The Short-Time Transfer Function plots show that the structure's natural frequencies change significantly when the cable-pulleys system is included. Complementarily, a novel time-variant system identification approach, termed Mod-ζ(var), is proposed, which allows estimating the time-variant evolution of the structure's dynamic properties during seismic tests (natural frequencies, damping ratios, and mode shapes). Moreover, the Mod-ζ(var) approach also enables computing relevant engineering quantities such as the empirical response spectrum from experimental data. It is found that the analyzed energy dissipation system provides high damping ratios (>10%) for all the structural modes, allowing reducing the seismic demands in terms of the empirical response spectrum, inter-story drifts, inter-story shear forces, peak accelerations, and Housner Intensities at each floor.

Modal analysis of cracked cantilever beam using ANSYS software

All structures with a crack are prone to failure, depending on the failure mechanism of the resonance-induced vibration. Periodic forces acting on a structure are combined with that structure's natural frequency to form the resonance. As a result, the natural frequency should be determined toestimate the periodic load resonance condition.In this study, a mild steel cantilever beam with a length of 3 m, a width of 0.25 m, and a depth of 0.20 m is considered. Modal analysis was used to study the natural frequency, mode shapes, and deflection of the first three modes of transverse vibration for a cracked cantilever beam. The cantilever beam's modal analysis is performed with a crack located from a fixed end at 0.5 m, 1 m, 1.5 m, 2 m, 2.5 m from the top, middle, and bottom faces of the cantilever beam. For all models, the crack's width and depth are fixed to 0.002 m and 0.1 m, respectively. For better outcomes, hexahedral meshing is utilized for cracked beams. The FEA simulation is carried out with the help of the ANSYS software. The theoretically obtained results are validated with the finite element analysis results to ensure the accuracy and the obtained results are approximately the same. The natural frequency of cracked beams decreases for the top and bottom surfaces, but the crack at the middle surface of the beam remains constant. Also, the effect of a crack is not uniform across all modes of vibration. As a result, the failure of a cracked beam can be identified, and corrective steps can be taken prior to the occurrence of cantilever beam fractures.

Vibration and dynamic analysis of a cantilever sandwich microbeam integrated with piezoelectric layers based on strain gradient theory and surface effects

In this paper, size-dependent vibration and dynamic analysis of an advanced sandwich composite microbeam including piezoelectric layers based on higher-order strain gradient and surface effects theories are investigated. To evaluate and analyze the effect of surface energy, length scale parameters and dynamic response on the transverse vibration and stability of sandwich smart composite microbeam with piezoelectric layers, the partial differential equation of motion is obtained using Hamilton's principle. Subsequently, this equation is transformed into a set of ordinary differential equations according to the generalized differential quadrature method. The influences of various material length scale associated with strain gradient theory, geometry and surface parameters such as thickness to material length scale parameter, surface residual stress, Young's modulus of surface layer, surface mass density and surface piezoelectric constant on structural dynamic deflection behavior and natural frequency have been investigated. In addition, the vibration and dynamic responses of the model were compared with those micro sandwich beams based on modified couple stress and classical theories. The obtained results are compared with the results available in the literature to validate the correctness of the present solution method. The results indicated that strain gradient theory with considering the surface effects increases the model stiffness and shifts the amplitudes to lower magnitude faster in comparison to other theories. Moreover, the influences of material length related to dilatation gradient on vibrational frequency are significant among the other parameters. Also, the free vibrational frequency increases with decreasing the length to thickness ratio.

Vibration and damping analysis of smart sandwich nanotubes using surface-visco-piezo-elasticity theory for various boundary conditions

Present research includes damping as well as vibration evaluations of advanced sandwich nanotube. This nanostructure comprised of carbon nanotube (CNT) contains internal and external layers composed of ZnO provided as sensor and actuator. The structure is subjected to 2D magnetic and electric field as well. In order to presume this sandwich structure much more realistic, Kelvin model will be utilized and it is surrounded by visco-Pasternak foundation. Further, non-local piezoelasticity theory is employed regarding small scale influence. Gurtin-Murdoch model is noticed to account surface stresses. Besides zigzag shear-deformation theory for modeling the structure mathematically, Hamilton principle is applied to achieve motion equations. Generalized differential quadrature method (GDQM) is employed as numerical method for calculating sandwich structure's natural frequency and damping. So as to show accuracy of methods and validate, the obtained results are compared by another simplified cases. Finally, the influences of diverse traits and variables covering surface stresses, small scale parameter, magnetic and electric fields, surrounding medium and their effects on natural frequency will be studied. Citing the results, rise of nonlocal parameter results in reduction of natural frequency and regarding stress of surfaces leads to increase in natural frequency.

THE USE OF AN INERTER FOR BASE-ISOLATION SYSTEM IN A SINGLE-DEGREE-OF-FREEDOM STRUCTURE

This paper presents seismic performance of a single-degree-of-freedom (SDOF) structure equipped with a base isolation system (BIS). Common BIS employs rubber material to provide lateral flexibility in order to minimize the transmitted energy induced by the ground motion to the structure. The concept is to lower the structural natural frequency such that it falls far below the pre-dominant frequency of most earthquakes. A similar effect can also be achieved by using a device called inerter, a two-terminal device generated forces proportional to the relative acceleration between its two terminals. Instead of reducing stiffness, inerter amplifies the theoretical mass of the structure without significantly increase its physical mass. It is because, depending on the inertance-generation mechanism, an inerter is capable of generating inertance – a constant ratio of forces and relative accelerations of the inerter – several times higher than its physical mass. In this paper, the effectiveness of inerter for use as a BIS is compared to the common BIS concept. The results show that, for a similar natural frequency level, a BIS with inerter has narrower response around the resonance in the frequency domain. Furthermore, in the time domain analysis, the structure with an inerter has a lower response compared to the structure with a traditional BIS when subjected to a long-period earthquake ground motion

Investigation of time-varying structural dynamic properties of high-rise buildings under typhoon conditions

This paper investigates the time-varying structural dynamic properties of high-rise buildings under typhoon conditions via the covariance-driven stochastic subspace identification (SSI–COV) method. Firstly, a numerical simulation study on a three-degree-of-freedom model is conducted, and the results prove that the SSI–COV method can provide accurate identification of the time-varying structural dynamic properties. Then, based on field measurements on a 420-m-tall high-rise building during Super Typhoon Mangkhut (No. 1822), the time-varying structural dynamic properties of the skyscraper are presented and discussed. The results indicate that the structural natural frequencies exhibited a trend of first decreasing and then increasing, while the damping ratios and modal directions basically remained unchanged during the typhoon process. Moreover, the variation of structural dynamic properties of the fundamental sway modes of the monitored building during 16 typhoons is investigated. The results show that the degree of variation in structural natural frequencies generally increased with the peak acceleration response of the building or the maximum 10-min-mean wind speed atop the building during a typhoon. While the damping ratios of the fundamental sway modes did not vary significantly during these 16 typhoons, which were around 0.64%. This paper aims to further the understanding of structural dynamic properties of high-rise buildings during typhoons.

Power performance enhancement of vortex-induced vibration wind turbines using a semi-active control approach

ABSTRACT Bladeless wind turbines based on vortex-induced vibration usually consist of a cylindrical body mounted on a flexible support. An inherent feature of this kind of turbines is that the power generation is considerable only in a narrow wind speed band, when the frequency of shedding vortices is close to the structural natural frequency. The present study proposes a novel semi-active approach for tuning the turbine response to widen the effective power generation region. Based on numerical modeling of aeroelasticity interaction phenomenon, a parametric analysis is done and the effective parameters on the turbine performance are highlighted. The proposed tuning technique then works to maintain the effective parameters at the optimum value from the power generation point of view. To realize this, a supporting mechanism is suggested that can change the elastic member length and consequently structural natural frequency. However, to avoid phenomenon attenuation due to power extraction process, a second level of tuning the structure damping ratio is added. Results of numeric simulations showed that, compared to previous work, the proposed approach has considerably broadened the effective wind speed range. The conversion efficiency is greater than or equal 15% over a wind speed range of 3.3–6 m/s.

Aeroelastic mode decomposition framework and mode selection mechanism in fluid–membrane interaction

In this study, we present a global Fourier mode decomposition framework for unsteady fluid–structure interaction. We apply the framework to isolate and extract the aeroelastic modes arising from a coupled three-dimensional fluid–membrane system. We investigate the frequency synchronization between the vortex shedding and the structural vibration via mode decomposition analysis. We explore the role of flexibility in the aeroelastic mode selection and perform a systematic comparison of flow features among a rigid flat wing, a rigid cambered wing and a flexible membrane. The camber effect can enlarge the pressure suction area on the membrane surface and suppress the turbulent intensity, compared to the rigid flat wing counterpart. With the aid of our mode decomposition technique, we find that the dominant structural mode exhibits a chordwise second and spanwise first mode at different angles of attack. The structural natural frequency corresponding to this mode is estimated using an approximate analytical formula. By examining the dominant frequency of the coupled system, we show that the dominant membrane vibration mode is selected via the frequency lock-in between the dominant vortex shedding frequency and the structural natural frequency. From the fluid modes and the mode energy spectra at α=20∘ and 25°, the aeroelastic modes corresponding to the non-integer frequency components lower than the dominant frequency are observed, which are associated with the bluff body vortex shedding instability. The non-periodic aeroelastic behaviors observed at higher angles of attack are related to the interaction between aeroelastic modes caused by the frequency lock-in and the bluff-body-like vortex shedding. Using the mode decomposition analysis, we suggest a feedback cycle for flexible membrane wings undergoing synchronized self-sustained vibration. This feedback cycle reveals that the dominant aeroelastic modes are selected through the mode and frequency synchronization during fluid–membrane interaction to exhibit similar modal shapes in the membrane vibration and the pressure pulsation.