Structural Coupling Effects Research Articles

Study on dynamic response characteristics of radial steel gate under rare earthquake considering fluid structure coupling effect

The water resources in southwest China is abundant and the seismicity is strong, so it is necessary to study the dynamic response and safety of hydraulic structures under rare earthquake. Taking a typical radial steel gate as an example, a three-dimensional numerical model considering the interaction between water and gate during the earthquake is established. The accuracy and applicability of the model are verified by comparing with the measured results of the dynamic response of Zipingpu dam during the Wenchuan earthquake. Thereafter, the dynamic displacement and stress, and resonance frequency of the radial gate under the rare earthquake of two wave types are analyzed. The water-structure coupling effect has a great influence on the seismic dynamic response of the radial steel gate. The calculated result of the dynamic response of the gate considering the fluid-structure coupling effect is significantly larger than that of the specification, and the maximum ratio of the two is more than 2.27 times. Under the action of EI wave, the peak value of dynamic stress response is at the bottom of the panel, and the maximum value of resonance frequency (about49.13 Hz) is located in the middle and lower part of the panel. Under the action of far-field wave, the peak area of dynamic displacement response of the gate is basically the same as that under the action of EI wave, while the maximum value of some measuring points is only half of the maximum value under the action of EI wave. However, the resonance frequency is significantly greater than that of EI wave, the maximum value reaches 65.24 Hz, which appears at the top of the gate. The dynamic response of the gate structure caused by two different wave types of earthquakes is not completely consistent. The comprehensive consideration of different wave types is of significance for the structural design and safety evaluation of the radial steel gate in the earthquake-prone areas.

Synergistic Construction of Efficient Heterostructure Electrocatalysis for High-Performance Lithium–Sulfur Batteries

Since a sluggish conversion reaction and shuttling of polysulfides have been barriers to high-performance Li–S batteries, it is particularly critical to establish nanostructured electrocatalysts with high specific surface area and electron conductivity, an excellent anchoring capability, and long-term durability. Herein, a robust binary synergistic MoS2/MXene heterostructure is proposed by the homogeneous growth of MoS2 on an MXene substrate. Due to the hierarchical structure and strong interfacial coupling effect, the binary synergistic MoS2/MXene heterostructure not only suppresses the restacking of MoS2 and MXene nanosheets but also provides abundant active sites to capture polysulfides and catalyze its conversion reaction. Typically, polysulfides are immobilized by MoS2 nanosheets; then, the anchored polysulfides are rapidly transferred from MoS2 to MXene via heterointerfaces. The MXene surface is endowed with abundant oxygen terminations, which accelerates the polysulfide conversion kinetics to a great extent. Therefore, the assembled Li–S battery delivers a reversible capacity of 981 mA h g–1 at 0.5 C after 300 cycles. Even at high rate of 5 C, capacity is still maintained at an excellent level of 408 mA h g–1 after 500 cycles with a Coulombic efficiency of 96.5%. Even more fascinating, at 0.2 C, the MoS2/MXene cathode can realize a high sulfur loading of 4.0 mg cm–2 and with capacities of 608 mA h g–1 over 500 cycles, which will promote the practical applications of Li–S batteries.

Improved frequency-domain Spectral Element Method for vibration analysis of nonuniform pipe conveying fluid

The well-known Spectral Element Method (SEM) has a broad application in vibration analysis for various configurations, such as flat plates, beams and straight pipes. Considering the fluid–structure coupling effects in variable cross-section, it has one limitation in dealing with the nonuniform pipes conveying fluid. In the present work, an improved frequency-domain SEM (IFSEM) is proposed for the analysis of the nonuniform fluid-conveying pipes by introducing structural wave propagation. In the IFSEM, the wave propagation coefficient plays a critical role to construct the equivalent dynamic stiffness, improving the analysis accuracy and efficiency. And there is a rule that the propagation coefficients are mainly related to the pipe diameter, flow rate and hydrodynamic pressure. A Simplification is put forward to obtain these coefficients in advance, which can significantly facilitate the vibration analysis. Finally, the IFSEM is validated through several numerical examples and the results show that it can analyze the vibration of the liquid-conveying nonuniform pipes efficiently and accurately.

The effects of submergence depth on energy harvesting from the VIV of a four-cylinder oscillator with rigid connection

Numerical and experimental studies of energy harvesting driven by vortex-induced vibration (VIV) are currently focused on arranging the energy-captured structure in a uniform incoming flow at a certain depth, ignoring the effect of the free surface on VIV. The fluid–structure coupling effect can be enhanced when a column-group structure with rigid connection is arranged under uniform flow, which is helpful for the structure to concentrate hydrokinetic energy from low-velocity water flow. In this paper, a staggered arrangement of a four-cylinder oscillator with rigid connections is proposed as the energy converter, and the fluid–solid interaction numerical method is carried out to simulate the VIV of the four-cylinder structure under single-phase flow and free surfaces. In U* = 2–16 (flow velocity U = 0.16–1.28 m/s), the results of the energy harvesting magnitude, efficiency, and density of the four-cylinder oscillator under the arrangement depth ratios S* = 2, S* = 3, S* = 4, and S* = 5 are compared with the results obtained in the single-phase flow. It was found that the column-group structure has a broader resonance range of VIV in single-phase flows than a single cylinder and can capture more hydrokinetic energy concentratedly from low-velocity flow. The VIV responses of the four-cylinder oscillator are suppressed at low submergence depths with a narrower resonance range, and its captured energy is reduced. In contrast, at high submergence depth ratio S*, the VIV responses are not suppressed obviously by the free surface. The magnitude of captured energy, energy-harvesting efficiency, and density of the four-cylinder structure are basically consistent with the results obtained in single-phase flow at S* = 5.

Study on additives assisted reduction of celadons

Celadons were prepared in the reducing atmosphere with purple clay and other natural elements. Different concentrations of silicon powder, silicon carbide, and tin dioxide were used as auxiliary reducing agents to investigate their effects on celadons. The results showed that the brightness value of celadons increased and subsequently declined when Si and SiC were introduced, and the glaze color gradually shifted from yellowish-green to bluish-green. On the other hand, samples with SnO2 had an opaque yellowish-green tint. According to XPS data, the reducing ability of SiC was added, followed by Si and SnO2. The structural colors of samples containing Si, SnO2, and without reducing agents were weak. Otherwise, celadons with SiC could yield blue structural colors conforming to the “Rayleigh scattering” effect. In conclusion, the reducing atmosphere raised the quantity of Fe2+ in celadons, resulting in blue colors, and additives created a variety of chemical and structural color coupling effects, leading to different aesthetic effects.

Numerical Analysis of Flow-Induced Vibration of Deep-Hole Plane Steel Gate in Partial Opening Operation

Hydraulic steel gates are the core adjustment mechanism for water conservancy projects, the safety of which is related to the safety of the entire water conservancy project. In this study, the issue of flow-induced vibration under the influence of pulsing water pressure when the deep-hole plane steel gate construction is partially opened is investigated using a numerical calculation approach of CFD–CSD coupling. The time-history pulsating pressure loads of each part are first determined by tracking the upstream, bottom, and downstream pulsating water pressure loads under partially open operation conditions of the gate. The impact of the water in front of the gate on the natural vibration mode and frequency of the gate is then investigated based on the analysis of the dry/wet modes of the gate structure. Additionally, the hydrodynamic load is applied to the finite element model of the gate structure while taking into account the fluid–structure coupling effect, and the results of the gate flow-induced vibration response are obtained. Three typical local opening relative openings are chosen, with the operating state of the design water head (Hs = 70 m) of a deep-hole plane steel gate as an example. According to the analysis’s findings, the gate’s natural vibration frequency is greatly lowered under the influence of the water in front of it, and its amplitude increases by 50%. The pressure value pressing on the gate changes dynamically as it is partially opened and discharged. The maximum dynamic displacement value and the maximum dynamic stress value of the gate both appear in the middle and lower part of the gate under the condition of partial opening, and both occur when the relative opening is e/H = 0.125. The maximum displacement value is 3.43 mm, and the maximum stress value is 161 MPa. The maximum dynamic displacement and dynamic stress of each gate component steadily decrease with an increase in the relative openness. The gate dynamic response analysis approach described in this research can serve as a guide for hydraulic engineering design.

Feasibility study of percussion–acoustic‐based void identification for underwater concrete

Concrete has been widely used in underwater structures. However, accidental voids near the concrete protective layer may weaken the bearing capacity of the structures and can even lead to severe disasters. Therefore, it is necessary to develop an efficient and convenient method for quantitatively identifying voids in concrete and guaranteeing structural safety. A percussion–acoustic method is commonly used to identify voids in concrete exposed to air, owing to its high efficiency and low-cost. Nevertheless, its feasibility for underwater concrete remains questionable, owing to the complexity of the underwater environment. To address this limitation, this study conducted experimental and theoretical studies by using a percussion–acoustic-based method to identify voids in underwater concrete while considering the fluid–structure coupling effect. The results demonstrate that the frequency characteristics of percussive sound pressure underwater are significantly different from those in air and are determined by the void scopes and depths. Accordingly, this study provides a potentially applicable method for evaluating the voids in underwater concrete.

Experimental investigation of post-flutter properties of a suspension bridge with a [formula omitted]-shaped deck section

Paralleled experimental tests of a full-bridge model and a sectional model are conducted to investigate nonlinear post-flutter properties of a suspension bridge, including structural damping, motion amplitudes, phase angle, motion frequency and coupling effects. Structural damping is found to increase nonlinearly and remarkably as the motion amplitude increases. Modal shapes are found to evolve as the motion amplitudes increase. Nonlinear structural damping properties differ significantly between the two models. Flutter instability of both models end up with limit cycle oscillations (LCOs), which increase progressively with the oncoming wind speed. LCO amplitudes of the sectional model are significantly smaller than those of the aeroelastic model. LCOs of the full-bridge model are coupled motions among 3 major structural modes, one torsional (symmetric) and two vertical (symmetric and asymmetric). Comparisons between the two models indicate that the underlying mechanism is single DOF torsional flutter. Phase angles between the vertical and torsional motions are found to be non-zero and differ significantly between the two models. Further, the amount of time evolving from a flutter onset to a LCO state decreases obviously as the wind speed increases, and the evolution time differs obviously between the aeroelastic and section models.

Improved analytical method for gear body-induced deflections with tooth root crack considering structural coupling effect

There is no existing effective analytical method for calculating the mesh stiffness of spur gears with tooth root crack when the interactions between the neighboring teeth induced by gear body flexibility are considered, while this factor has been demonstrated to have a considerable effect on the mesh stiffness. In this paper, an improved method of spur gear mesh stiffness is proposed based on the theory of elastic mechanics for circular ring, which is capable of calculating the mesh stiffness with tooth root crack accurately. Then, the calculated gear body-induced stiffness results considering structural coupling effect with tooth root crack is validated by the finite element method. In addition, the effect of different hub hole radius and crack lengths on the stiffness caused by the structural coupling effect are investigated. The results indicate that the proposed analytical method is more accurate for spur gear mesh stiffness calculation with tooth root crack.

Nano-projectiles impact on graphene/SiC laminates

The ballistic performance of graphene/silicon carbide laminates under nano-projectile impact is studied using molecular dynamics method, where graphene acts as a barrier coating for its unique intra-layer honeycomb-like structure and interlayer coupling effects. We reveal that under nano-indentation two-layer graphene with AB-stacking on 4H-silicon carbide(0001) exhibits the highest hardness, ∼ 140.06 GPa, comparable to diamond. During impact, the specific total penetration energy of laminates increases with the number of graphene layers n, though the partial of graphene decreases as n ≤ 3, which results from the van der Waals coupling effect of graphene on silicon carbide substrate. The ballistic limit velocity of silicon carbide coated by five-layer graphene is 69.4% higher than that of bare silicon carbide, leading to an increase of specific total penetration energy, ∼ 43.3%. It is interesting that the ballistic performance of two-layer graphene/silicon carbide is enhanced by the formed sp3 bonds and residual bending deformation under secondary impact (after the first low-velocity impact treatment), with the ballistic limit velocity and specific total penetration energy increased by 6.5% and 14.3%, respectively. Graphene is a promising coating that can preserve the functional integrity of materials underneath against hypervelocity impact.

Thermal–Structural Coupling Analysis for Multiple Honeycomb Plates Connected by Hinges

The dynamical model of multiple honeycomb plates connected by hinges, including the thermal–structural coupling effect, is investigated in this paper. Under the assumption of small deformations and strains, the classical plate theory is used to establish the dynamical model of the honeycomb plate. The Chebyshev polynomial is adopted to describe the deformation of the plate and the linear torsional spring to represent the elastic hinge. Using the Rayleigh–Ritz method, the characteristic equation of the honeycomb sandwich structure is derived, from which the natural frequencies are obtained. Considering the thermal effect of the plate, the thermal–structural coupling dynamical equation is obtained. The thermal conduction in the thickness direction is calculated by the finite difference method. The present model is validated by comparing with the result generated by an equivalent orthotropic plate model established by the finite element (FE) software MSC Patran. The response analysis reveals the important effect of the metal skin and the hinge stiffness on the dynamic characteristics of the honeycomb sandwich structure. Numerical simulations reveal thermal–structural coupling features for the multi-honeycomb-plate structure from the perspective of the change in dynamic characteristics and the distribution of the temperature gradient. The thermal–structural coupling calculation method adopted herein can be used to solve the thermal conduction of the plate. It serves as the theoretical method for analyzing the dynamical behavior of the solar panel subjected to the solar heat.

Development of three-dimensional co-rotational beam model for nonlinear dynamic analysis of highly flexible slender composite blades

The main purpose of this work is to introduce a novel method analyzing the dynamic response of a highly flexible slender composite beam having anisotropic property and variable cross-section. A three-dimensional co-rotational model is developed. The beam deformation in dynamic conditions is obtained by applying HHT-α method as dynamic analysis tool. Validation studies with various boundary conditions, multiple external loads and pre-curved structures are performed. Furthermore, dynamic analysis with a large, flexible, and slender composite blade is performed with and without structural couplings. It is shown the developed beam model accurately predicts nonlinear three-dimensional response and anisotropic structural coupling effects.

Impedance Modelling Mechanisms and Stability Issues of Single Phase Inverter With SISO Structure and Frequency Coupling Effect

Multi-Input and Multi-Output (MIMO) impedance model considering the Mirror Frequency Effect (MFE) has been studied for single phase systems in the past five years. However, the resulting impedance matrix is mathematically intractable without practically physical meaning. Besides, another unique High Frequency Effect (HFE) existed only in single phase systems has received less attention. To tackle these problems, this paper presents a Single-Input and Single-Output (SISO) modeling mechanism for single phase inverter considering both MFE and HFE. Firstly, the accurate response of T/4 delay PLL is derived in this paper. Then, based on the harmonic linearization method, the inverter impedance model is successfully realized in the SISO structure, where MFE and HFE are represented by two additional impedance. And consequently, the influence of HFE on inverter impedance is analysed with varying PLL bandwidth. Applying the Nyquist criteria, the proposed overall impedance model can precisely predict the sub/super-synchronous oscillation that occurs in the weak grid. Finally, all the theoretical analysis results are validated by simulation cases. The proposed work could significantly simplify the traditional MIMO modeling procedure with a more straightforward impedance structure, which might be helpful for solving potential oscillation issues of renewable energy integration.

DC Ice Melting Operation of Ground Wire Based on Thermal Structure Coupling Effect Characteristic Research

DC Ice Melting Operation of Ground Wire Based on Thermal Structure Coupling Effect Characteristic Research

Insights on the role of defects on the magnetic and magneto electric coupling effects in nano BiFeO3

BiFeO3 nanoparticles prepared through sol-gel route using citric acid are studied for their structural, magnetic and magneto-electric coupling effects and are compared with that of calcined BiFeO3 particles prepared with tartaric acid as the fuel. Nanoparticles of BiFeO3 prepared with the use of citric acid were observed to be more strongly ferromagnetic and weakly ferroelectric, as compared to that of the bismuth ferrite nanoparticles prepared using tartaric acid as the fuel.Magneto-electric coupling effects were studied in BiFeO3 prepared by these methods using Raman spectroscopy. These results were further confirmed based on the direct experimental evidence in terms of the variation of polarization with respect to electric field (P-E loop) studies carried out in the nanoparticles of BiFeO3 under the application of magnetic field.This study brought out new insights on the important role of defects for the observed variations in magnetic and hence magneto-electric coupling effects in BiFeO3 nano particles prepared using different fuels, as elucidated based on the Mössbauer studies.

Experimental study on wind-induced vibration and aerodynamic mitigation measures of a building over 800 meters

The new-generation high-rise buildings are taller and more flexible than before. Rigid model and aeroelastic model tests of a proposed steel super high-rise building with a height of 838 m were carried out in two simulated typical wind fields defined in the Chinese code [1] and the ISO standard (ISO 4354) in an atmospheric boundary layer wind tunnel. The wind pressure distributions of the building were obtained through the rigid model tests and then the wind-induced vibration responses of the building were calculated. Through the aeroelastic model test, the vibration responses of the building, which naturally include the wind–structure coupling effects, were directly obtained. The test results shows that strong crosswind vortex-induced resonance may appear at high wind speeds. Based on these results, the crosswind aerodynamic damping of the building was then studied. Finally, seven aerodynamic measures for controlling the wind-induced vibrations of the building were proposed and tested. The results show that the seven proposed aerodynamic measures can reduce the dynamic responses of buildings in different degrees.

Magnetism and Its Structural Coupling Effects in 2D Ising Ferromagnetic Insulator VI3.

van der Waals (vdW) magnets have emerged as a tunable platform for exploring a variety of layer-dependent magnetic phenomena. Here we probe the thickness-dependent magnetism of vanadium triiodide (VI3), a material known as a layered ferromagnetic Mott insulator in its bulk form, using magnetic circular dichroism microscopy. Robust ferromagnetism is observed in all thin layers, down to the monolayer limit with large coercive fields. In contrast to known vdW magnets, the Curie temperature shows an anomalous increase as the layer number decreases, reaching a maximum of 60 K in monolayers. Second harmonic generation measurements reveal broken inversion symmetry in exfoliated flakes, down to trilayers. This observation demonstrates that the exfoliated flakes take a layer stacking arrangement that differed from the inversion-symmetric parent bulk counterpart. Our results suggest a coupling effect between magnetic and structural degrees of freedom in VI3 and its potential for engineering layer and twist angle-dependent magnetic phenomena.

Study on the Influence of Sudden Change of Water Level on High Fill Canal Segment

Extreme conditions will cause the water level of high fill canal segment to change suddenly, which will affect the velocity and pore pressure of the slope. In this paper, numerical method is used to study the influence of water level sudden change on seepage characteristics of high fill canal segment. HyperMesh software is used to establish the finite element model of typical high fill canal segment under complex foundation conditions. Through the combination of secondary development program and fluid-structure coupling calculation method, the fluid structure cou-pling effect of canal under sudden change of water level is analyzed in ABAQUS. The results show that when the water level changes suddenly, the pore pressure below the free water surface and the velocity near the free surface will be greatly affected.

Aeroelastic Behavior of Two Airfoils in Proximity

This paper investigates the aeroelastic behavior of elastically supported airfoils due to structural and aerodynamic coupling effects between them in an incompressible uniform flow. The flow is modeled based on a potential theory for thick and thin airfoils considering the coupled interference effect. Coupled aeroelastic equations of motion are formulated in a state-space form and solved explicitly using a predictor–corrector scheme. The numerical analyses are presented for airfoils in proximity with and without structural coupling. It is shown that the airfoils in proximity oscillate out of the phase and destabilized the airfoils at lower speeds. The closer the airfoils are, the lower the speed at which flutter instability occurs. Also, the interference effect becomes more significant on reducing the flutter speed for thick airfoils in proximity. For structurally coupled airfoils, the flutter instability occurs at lower speeds for the lower coupling stiffness value. It is further worsened in the presence of aerodynamic interference. Although, for a larger stiffness value, the flutter instability could be delayed in the presence of aerodynamic interference. This study finds that the lifting surfaces in proximity without structural coupling can become unfavorable in the aeroelastic design. The results provide preliminary insights into the coupled structural and aerodynamic interference effects on the flutter instability for a multiple lifting surface configuration.

Highly Efficient Multiscale Fog Collector Inspired by Sarracenia Trichome Hierarchical Structure.

Fog harvesting through bionic strategies to solve water shortage has drawn considerable attention. Recently, an ultrafast fog harvesting and transport mode was identified in Sarracenia trichome, which is mainly attributed to its superslippery capillary force induced by its unique hierarchical microchannel. However, the underlying effect of hierarchical microchannel‐induced ultrafast transport on fog harvesting and the multiscale structural coupling effect on highly efficient fog harvesting are still great challenges. Herein, a bionic Sarracenia trichome (BST) with an on‐demand regular hierarchical microchannel is designed using a one‐step thermoplastic stretching approach on a glass fiber bundle. The BST is engineered to harbor major channels confined by an inner gear pattern along with junior microchannels that are automatically assembled by the glass fiber monofilaments. The BST shows enhanced capillary condensation and fog harvesting performance, in part due to its coupling effect with a Janus membrane (JM). Hence, a highly efficient multiscale fog collector is developed, in which a gradient high‐pressure field is purposely formed to improve by threefold fog harvesting performance compared with a single‐scale structure. This easy manufacturing and low‐cost fog collector may represent a useful tool for harvesting fog water for production and living and pave the way for further investigations.