In this study, a coupled electro-magneto-mechanical composite pipe model is developed to simultaneously collect vibration energy via piezoelectric and electromagnetic mechanisms. The material properties of the rectangular pipe are continuously distributed along both the width and height directions, forming a bi-directional functionally graded (2D FG) structure. An internal fluid flows with a constant velocity. The bimorph pipe is arranged together with a pair of permanent magnets and multi-turn coils at the free end, and both the piezoelectric and electromagnetic components are connected to resistance circuits to achieve synchronous energy harvesting. The system dynamics are formulated based on the coupled electro-magneto-mechanical Lagrangian equations, and the harmonic balance method (HBM) is employed to measure the steady-state vibration and electrical responses. Results demonstrate that compared to a single piezoelectric or electromagnetic harvester, the proposed hybrid structure achieves enhanced voltage and power generation, and enables dual-source energy output. The 2D FG properties majorly affect higher-order electricity characteristics. Additionally, it is found that fluid-structure interaction (FSI) effects degrade the energy harvesting performance, while the impacts of load resistance on the output voltage, current and power remain nonuniform, highlighting the need for careful parameter optimization in practical designs.

Fluid-conveying pipes are widely used in aerospace, nuclear, marine, and biomedical engineering, where their dynamic stability is critical to system performance and safety. Deeply understanding instability mechanisms, particularly those arising from fluid-structure interaction (FSI), and developing effective vibration control strategies are essential for ensuring reliable operation under various serving conditions. This paper presents a comprehensive review of recent advances in the dynamics and vibration control of fluid-conveying pipes, aiming to synergize cutting‑edge modeling techniques, control design methodologies, and empirical findings for a holistic framework in managing pipe-fluid dynamics. The discussion begins with classical and emerging models, covering the dynamic behaviours of spinning, curved, hyperelastic, nano-scale pipes, and systems with complex constraints. Special attention is given to the interplay among material properties, geometric configurations, and FSI effects. Subsequent survey is directed toward the passive, active vibration control strategies and structural optimization techniques, with emerging approaches in vibration energy harvesting also being considered. In addition to theoretical progress, representative experimental studies are highlighted to validate and improve the analytical frameworks. This review provides broad insights and serves as a reference for researchers and engineers engaged in the analysis and design of fluid-conveying pipe systems across diverse applications.

To address the limitations of conventional piezoelectric energy harvesting, such as narrow operational bandwidth, uncontrollable band distribution, and poor material durability, this paper develops an efficient energy harvester based on a motional bi-directional piezoelectric pipe. The sandwich square pipe spins around its longitudinal axis, and a steady fluid flows inside. Two groups of piezoelectric bimorph are symmetrically arranged on the orthogonal exterior surfaces of the pipe, each connected to a resistive load circuit. The simply supported and cantilevered configurations are both considered. Numerical results demonstrate superior performance of the proposed energy harvester as follows: i) the spinning motion transforms voltage response from a unimodal to bimodal pattern, greatly improving the electricity output bandwidth; ii) the energy harvesting band can be manipulated by tuning the spinning speed; iii) the gyroscopic effect simultaneously activates voltages in both transverse directions, achieving synchronous multi-source energy output. It is also found that the voltage response to the fluid-structure interaction (FSI) effect is highly sensitive to the support condition. Additionally, the impacts of pipe length, fiber orientation angle in the face layers, and core layer property on the energy harvesting performance are investigated, clarifying comprehensive parametric regulation mechanisms.

To address the inherent narrow-bandwidth limitation of conventional linear energy harvesting, this study proposes a nonlinear fluid-structure interaction (FSI) energy harvester based on a bimorph pipe conveying fluid constrained by retaining clips, which introduces two distinct nonlinear mechanisms: i) boundary nonlinearity due to the equivalent nonlinear stiffness, and ii) geometric nonlinearity from the extensible centerline of the pipe. The electro-mechanical governing equations of such nonlinear FSI system are established via the Hamilton principle, whereby the complex eigenfrequencies are first obtained for stability analysis. The vibration and electrical responses are further attained to evaluate the energy harvesting performance. In particular, a novel supercritical analysis is conducted to predict the harvester behaviour under buckling and flutter instabilities. Numerical results demonstrate that the designed nonlinear harvester significantly improves the operational bandwidth, and its performance can be regulated by tuning various system parameters. Interestingly, the FSI effect contributes to a broader energy harvesting bandwidth in the low-frequency region, but leads to a reduced peak voltage in the flutter state. In addition to force excitation, displacement excitation is also concerned, under which a better energy harvesting performance is exhibited. However, high nonlinear stiffness in this pattern may result in numerical divergence.

Retaining clips are indispensable components in aircraft engines, applied to secure oil pipes and enhance their stiffness. This paper develops a fluid-conveying pipe with multiple parallel retaining clips, which function as isolators to prevent vibrations from foundation excitations. The nonlinear governing equation is formulated using the Hamilton principle and discretized by the Galerkin method. The complex frequencies are obtained and validated via finite element (FE) simulation and comparison with existing literature, whereby the pipe stability is examined. The vibration isolation performance is evaluated in terms of the amplitude-frequency response and displacement transmissibility, which are attained by the harmonic balance method (HBM) combined with the arc-length continuation method, and are further verified using the Runge-Kutta (R-K) procedure. Numerical results demonstrate the excellent stability and vibration isolation performance achieved by the arranged retaining clips. However, they are sensitive to the clip parameters, including stiffness, damping, installation position and clip number. The fluid-structure interaction (FSI) broadens the high-frequency vibration isolation bands of the retaining clips, but it reduces the stability of the system. Therefore, a careful balance of various system parameters is required to ensure both robust stability and efficient vibration isolation.

Based on the Timoshenko beam theory, this paper proposes a nonlocal bi-gyroscopic model for spinning functionally graded (FG) nanotubes conveying fluid, and the thermal-mechanical vibration and stability of such composite nanostructures under small scale, rotor, and temperature coupling effects are investigated. The nanotube is composed of functionally graded materials (FGMs), and different volume fraction functions are utilized to control the distribution of material properties. Eringen's nonlocal elasticity theory and Hamilton's principle are applied for dynamical modeling, and the forward and backward precession frequencies as well as 3D mode configurations of the nanotube are obtained. By conducting dimensionless analysis, it is found that compared to the Timoshenko nano-beam model, the conventional Euler-Bernoulli (E-B) model holds the same flutter frequency in the supercritical region, while it usually overestimates the higher-order precession frequencies. The nonlocal, thermal, and flowing effects all can lead to buckling or different kinds of coupled flutter in the system. The material distribution of the P-type FGM nanotube can also induce coupled flutter, while that of the S-type FGM nanotube has no impact on the stability of the system. This paper is expected to provide a theoretical foundation for the design of motional composite nanodevices.

In this paper, a novel electro-mechanical meta-riser structure is designed aiming to suppress its vibration and wave propagation. The riser is made of porous functionally graded material (FGM), and is periodically attached with piezoelectric layers, each of which is connected with a multi-mode resonant shunt circuit to trigger multiple locally resonant (LR) band gaps (BGs). The periodically varying rigidity due to piezoelectric layers can also generate Bragg scattering (BS) BGs, resulting in a hybrid meta-structure. A point defect is introduced into the system by removing a certain piezoelectric layer. Theoretical analysis and finite element (FE) simulation both demonstrate the superior vibration control effect of the present meta-structure. Owing to the presence of defect, the riser presents a remarkable vibration response within the original BS BGs, reflecting the vibration energy localization and enabling energy harvesting by meta-structure designs. Different circuit designs and parameters can be used to regulate LR BGs, while the particular material composition of the riser will contribute to enhancing the BS BG performance. This study can provide a technical scheme for the vibration and elastic wave control of marine riser structures, and lay a theoretical foundation for the vibration energy harvesting by utilizing dynamical meta-structures.

This paper aims to improve the flexural stability of rotating pipes conveying fluid by introducing a smart piezoelectric feedback structure. The pipe is laminated along the radial direction, and a steady fluid flows inside the pipe. In the meantime, the pipe rotates around a vertical axis at one end. A pair of piezoelectric sensor and actuator connected with a feedback gain circuit are designed to place on the pipe in order to reduce the transverse vibration by providing dynamic stiffness. Theoretical modeling finds it a fully coupled system among the axial, in-plane and out-of-plane transverse direction due to the presence of the piezoelectric feedback structure. However, such smart structure is demonstrated to have excellent capability of enhancing the natural frequency and static and dynamic critical flow velocities of the pipe. Vibration response analysis also reveals an interesting phenomenon that under the gyroscopic effect of flowing fluid, the introduced piezoelectric design is able to attenuate the vibration of the system periodically, similar to a beat vibration. This study is expected to provide a technical way for enhancing the stability of engineering motional pipes.

This paper is aimed at exploring the potential of a composite meta-pipe conveying fluid for simultaneously suppressing vibration and collecting energy. The pipe features a sandwich design, with the outer layers composed of glass fiber-reinforced composite and the core layer made of carbon fiber-reinforced composite. Meanwhile, the pipe is periodically attached with piezoelectric layers connected with shunting circuits to both trigger frequency band gaps (BGs) and generate electricity. A point defect is further introduced into the pipe by modifying the position and length of the piezoelectric layers, enabling energy localization in the defect segment. Numerical results demonstrate the achieved dual functionality of the proposed fluid-structure interaction (FSI) integrated meta-structure, and reveal the essential relations between vibration isolation and energy harvesting. The FSI and composite effects on the dual functionality are elucidated. More importantly, the findings clarify the distinct roles of defect in energy harvesting across the Bragg scattering (BS) BG and locally resonant (LR) BG, highlighting the effects of different types of defect on the integration performance. This research will facilitate the development of smart pipe structures in engineering applications, and offer new perspectives on the vibration isolation and energy harvesting in FSI systems.

This paper focuses on a class of marine riser supported by retaining clips and subjected to internal and external annular flows, and a nonlinear energy sink (NES) is strategically integrated to suppress its nonlinear flutter triggered by fluid-structure interaction (FSI) and geometric nonlinearity. The nonlinear governing equation is formulated using the Hamilton principle and discretized via the Galerkin method. Following stability analysis, the Runge-Kutta (R-K) time-domain simulation is conducted to explore the suppression mechanisms of nonlinear flutter. The results indicate flutter and buckling instabilities in the riser system, and further reveal three flutter suppression mechanisms of the NES, where the NES interacts with different riser modes via transient resonance capture (TRC), effectively mitigating nonlinear flutter. Complex modal coupling and energy transfer between the NES and the riser significantly affect the dynamic behaviour of the riser. The mass ratio, damping, stiffness, and installation position of the NES play a crucial role in determining the flutter suppression region, vibration amplitude, and critical flow velocity of the system. Moreover, the study examines the vibration reduction performance of the NES under various initial conditions, and further quantifies the parameter range ensuring strong robustness for nonlinear flutter suppression in the riser.

In this paper, the flexural wave propagation and its control of a novel piezoelectric composite pipe conveying fluid are investigated. Dual piezoelectric layers used as sensor and actuator are periodically arranged on the pipe, and a feedback amplifying circuit is applied from sensor to actuator, forming a self-powered phononic crystal (PC) control structure. The vibration reduction performance can be actively tuned by adjusting the feedback control gain instead of conventional changing the construction of pipe itself. The pipe is composed of functionally graded material (FGM), in which the material properties vary continuously along the radial direction, and a poroelastic medium is introduced. By using the Timoshenko beam theory and Hamilton’s principle, a set of electromechanical coupling equations governing flexural vibration of the pipe is deduced. The band structure, band gap (BG) distribution and frequency response are presented by applying the spectral element technology. Comprehensive parametric studies are carried out. The results obtained validate the excellent vibration control effect of the proposed design, and further demonstrate the significant impacts of material, piezoelectric layers, feedback control and flowing fluid on the BG characteristics. This paper is expected to provide a technological reference for the vibration and elastic wave control of engineering composite pipe structures.

Based upon the wave manipulating characteristics of phononic crystals (PCs), this paper aims to isolate flexural vibration of laminated composite pipes conveying fluid by introducing a self-powered periodic piezoelectric design. The pipe is composed of three layers of fiber-reinforced composites along the thickness, and is periodically attached with a number of shunted piezoelectric sensor/actuator pairs along the axis. A negative proportional feedback strategy is adopted to amplify the sensing voltage to the actuators, which can generate periodic active stiffness to the pipe and thus enable tunable wave propagation and frequency band gap (BG). The dynamical equation of motion for a single piezoelectric laminated pipe conveying fluid is deduced from classical laminated beam theory as well as one-dimensional piezoelectric constitution. The BG distribution and amplitude transmission of topological structure are obtained by the spectral element method (SEM). Numerical results demonstrate that the present self-powered piezoelectric PC design can achieve excellent vibration isolation effect for the laminated composite pipe conveying fluid. Major parameter regulations including cross-ply angle, lamina sequence, feedback control gain, geometry of piezoelectric layers and fluid effect are examined. Free vibration and stability of the system are also discussed to perfect the vibration isolation design.

Bragg scattering and local resonance are two fundamental mechanisms for bandgap (BG) formation of phononic crystals (PCs) and acoustic metamaterials (AMs). In this paper, a new class of motional two-dimensional (2D) hybrid Bragg-locally resonant (LR) meta-pipe model is developed, and the BG interaction behaviors of such a meta-structure are explored. The pipe is axially composed of alternate materials, and is periodically encircled with dual-layer rings, which are used to simultaneously trigger Bragg scattering and local resonance. Meanwhile, the pipe conducts an axially spinning motion, and a steady fluid flows inside the pipe. Compared to static periodic structures, the orthogonal traveling waves due to spin bring about a 2D meta-structure, and the spinning local resonators yield an additional centrifugal effect on the pipe. The results reveal the formation of hybrid Bragg-LR BGs in such a motional meta-structure, and further demonstrate their complicated evolutions with the location, number and geometry of the local resonators as well as the pipe material. The impacts of motional properties on the hybrid BGs are discussed, and they are compared with the behavior of Euler-Bernoulli model. This study provides a more in-depth interpretation for the interaction of Bragg and LR BGs, which is especially beneficial to the vibration and noise reduction of rotors and fluid-transporting devices.

Flexural vibration and torsional vibration pervasively exist in slender structures, which often lead to noise emission and fatigue failure of structures. In order to effectively suppress coupled flexural–torsional vibrations of defective devices transporting fluid, this paper introduces an eccentric fluid-conveying pipe axially made of periodically varying materials, and the flexural–torsional bandgap (BG) characteristics of such phononic crystal pipe system are investigated. With consideration of warping effect, coupled flexural–torsional motion equations are established. The complex band structure of sub-structure and frequency response function and attenuation configuration of topological structure are attained by applying the spectral element method. In comparison with literatures only yielding total merging BG of flexural and torsional vibrations, this paper presents a novel result of completely separate flexural BG and torsional BG, which enables individual manipulation of the two elastic waves. Meanwhile, broadband frequency BGs are harvested in the proposed pipe structure, especially for torsional vibration, demonstrating an excellent vibration isolation property. Complicated regulation mechanism of eccentric, warping effects and some critical parameters is explored. This study is expected to provide a new approach for flexural–torsional vibration reduction of engineering fluid-transporting devices.

Gyroscopic characteristics extensively exist in motional components, which can lead to coupling of motions along different directions. However, the vibration and stability mechanism of complicated gyroscopic structures still remains unclear. This paper proposes a novel class of triply-gyroscopic system — fluid-conveying pipes conducting simultaneous rotating and spinning motions. Based on a Rayleigh beam model, the coupled differential equations governing in-plane and out-of-plane flexural vibrations and axial vibration are deduced, which fully account for the rotating gyroscopic force, spinning gyroscopic force and fluid gyroscopic force. The Galerkin technique is applied to discretize the governing equations, and the characteristic frequency method is further utilized for solution. Via an in-depth dimensionless analysis, the resonant frequency and stability evolution with the three motions is drawn, and its dependence on the triple gyroscopic and centrifugal effects is revealed. The impacts of significant geometrical and physical properties are also discussed. Three-dimensional (3D) backward and forward whirling shapes of the pipe are simulated, where the rotating motion is involved as novelty. Nonplanar configurations and ‘traveling wave’ vibrations are observed as a result of gyroscopic effects. The study will contribute to in-depth understanding of gyroscopic dynamics, and provide theoretical and designing base for the engineering gyroscopic structures.

In this paper, a novel fluid-conveying phononic crystal (PC) pipe model is proposed. The pipe is composed of different materials arranged alternately, and an axially spinning motion is considered. The flexural wave motions along the orthogonally transverse directions trigger a two-dimensional (2D) PC structure. A planar spectral element (SE) model of the system is established, and the transverse free vibration and wave attenuation performance of such spinning periodic structure are explored thereby. The transfer matrix method is also utilized for validation. It is found that different pseudo Bragg band gaps (BGs) exist in the two transverse directions, while the effective BGs are actually located in their coupled regions, in which the vibration is truly self-suppressed. Such peculiar BG characteristic has not been theoretically revealed previously. Additionally, the spinning motion will reduce the effective BG regions of the periodic pipe. The impacts of the number of cells, flow velocity and component geometry on the natural frequencies and coupled BGs are also studied. The results obtained will provide theoretical basis and design reference for the potential applications of PC-type fluid-conveying devices.

Thermal shock load has an important influence on dynamic characteristics of blades in turbomachines. Due to higher level operating thermal shock for improving the efficiency, the damage to the blades has greatly increased. Considering the major effect of variable thickness and large deflection on thermal dynamic behavior of blades, their thermo-large deflection-variable thickness coupled dynamic characteristics are unknown. This paper develops a thermo-large deflection coupled semi-analytical model based on a rotating variable thickness plate under thermal shock. Geometric nonlinear governing equation and an analytical solution of heat transfer equation are derived. Numerical examples of natural frequencies are investigated to validate the proposed model. The non-uniform temperature distribution features of the rotating variable thickness plate are found. Besides, when the thermal shock is serious, the large deflection theory must be considered to analyze thermo-large deflection coupled dynamic characteristics. Based on theoretical and experimental results, deformation characteristic of the cantilever plate subjected to thermal shock is obtained, which is helpful to find the optimal thickness distribution. Finally, the effect of variable thickness on thermo-large deflection coupled dynamics of the rotating plate is demonstrated. The vibration induced by thermal shock can be reduced by thickening the plate on its free side or both fixed-free sides. However, when thickening other positions, the vibration is either intensified or unchanged. Results are helpful to reduce blade's vibrations under thermal shock.

Phononic crystal (PC) structures have been applied in various engineerings since their vibration can be suppressed efficiently by the periodicity of the physical and geometrical properties. Inspired by this idea, in this paper, the free vibration and band gap (BG) characteristics of a fluid-conveying PC pipe composed of periodically varying materials are explored. The dispersion equation of the periodic pipe conveying fluid is established based on the Timoshenko beam model. By applying the spectral element method (SEM) in conjunction with the finite element method (FEM), the natural frequencies and vibration modes of the pipe are obtained, and the BG regions and vibration attenuation shapes are further achieved. The Euler–Bernoulli (E–B) beam model is also introduced for comparison. Comprehensive parametric studies are conducted. It is found that different BG location and width are presented for the Timoshenko and E-B pipe models. The number, physical and geometrical properties of the substructures and the fluid–structure interaction all have significant effects on the natural frequency, mode shape and BG performance of the PC pipe. In addition, as compared with the traditional transfer matrix method and FEM, the SEM is demonstrated a more efficient procedure to deal with not only the BG characteristics, but also natural properties of the PC dynamical structures.

Surface biofouling will seriously affect the performance of solid-liquid contact surfaces. Antimicrobial peptides (AMPs) are considered as potential agents for surface antifouling due to its broad-spectrum antimicrobial ca-pacity. In this study, a derived AMP was synthesized by the reaction between a marine originated AMP and monomolecular dopamine, which was then used to modify 304 stainless steel. Mass spectrometry analysis confirmed the synthesis reaction of DP, and the co-culture essays with E11 and 293 T cells proved DP's excellent compatibility. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis confirmed that DP was grafted on surface successfully, meanwhile, atomic force microscope, contact angle and 3D optical profilometer results demonstrated that surface morphology and wettability changed remarkably after modifi-cation. The results of Vibrio natriegens and Phaeodactylum tricornutum adhesion assays illustrated that DP treated surface possessed great antifouling capacity, and the antibacterial and anti-algal properties of the DP modified surface can reach 97.78% and 90.01%, respectively. Electrochemical results indicated that DP modified surface exhibited superior anticorrosion. The stability test results showed that DP modified surface possessed long-lasting properties in antifouling and anticorrosion. These findings may provide a useful tethering process for producing excellent antifouling surfaces in marine equipment, medical devices and other relevant fields.

With the rapid development of processing technology, phononic crystals (PCs) have been gradually applied from conceptual model to practical engineering structure. In this paper, a novel motional two-dimensional (2D) PC structure — spinning periodically multi-stepped pipes is proposed. Due to the spinning motion, there will be two flexural waves respectively in the orthogonally transverse directions, forming such a planar PC structure. Considering a constant internal flow, the wave propagation and self-attenuation characteristics of the system are explored. Improved spectral element method and transfer matrix method are applied to treat such spatial wave motion. Based on the attained band structure in conjunction with the frequency response and wave shape, a significant mechanism is revealed that for a spinning periodically multi-stepped pipe conveying fluid, there are two sets of pseudo band gaps (BGs) generated owing to the gyroscopic effect, which do not exist in a static PC structure. However, the effective BG regions, where both the flexural waves truly attenuate, are actually located in their coincident frequency areas. Furthermore, the effects of number and geometry of sub-segments and motional parameters on the BG are discussed in detail. The present research will develop the PC dynamics in motional structures, and provide an in-depth theoretical basis for vibration suppression of engineering pipe system.