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Recently, the phenomenon of tail-sustained swaying of the 160 km/h EMU in single-track tunnels has gained much attention, especially for the rear-powered vehicle. This phenomenon is investigated from the perspective of aerodynamic fluid–structure coupling vibration in this study. The aerodynamics simulation model of the train in tunnels and the multi-body dynamics model of the rear-powered vehicle were respectively established through the software of XFlow and Simpack, and then the fluid–structure coupling vibration was simulated by using real-time data dynamic exchange between the two models. Moreover, the carbody's vibration acceleration and the aerodynamic loads acting on the carbody under various wheel–rail contact geometrical conditions were discussed. Finally, the train tail swaying in field was tested, and the dominant frequencies were analyzed. The results show that the periodic aerodynamic loads and the frequency locking effect caused by the coupled vibration are the main factors for ride comfort deterioration. The violent vibration caused by fluid–structure coupling is named vortex-induced vibration (VIV) in some industries such as bridge and submarine pipeline. For the vehicle in this work, with the decrease of equivalent conicity in wheel–rail contact, the amplitude of carbody swaying increases owing to the carbody hunting, which enhances the fluid–structure coupling vibration, and further deteriorates the ride comfort. The swaying of the carbody is dominated by the vehicle hunting frequency, and the improvement of vehicle lateral stability can weaken this phenomenon. [ABSTRACT FROM AUTHOR]

Accidental burst of hydrogen pipeline can generate highly destructive blast wave, highlighting the importance of predicting the blast wave intensity for industrial safety and protection. However, current methods for predicting overpressure fail to consider the coupling effect between the blast wave and dynamic rupture. Therefore, a fluid-structure-rupture coupling model is constructed to address this limitation. The accuracy of the model is verified through a comparison of fracture morphology, crack propagation, and internal pressure decay between the simulation and experimental results. On this basis, the effects of dynamic rupture on blast wave formation and propagation, overpressure decay histories, and peak overpressure are investigated. Results indicate that the traditional CFD method tends to overestimate the peak overpressure in the near field while underestimating it in the middle and far fields. Furthermore, it is discovered that the blast waves from bursts of hydrogen pipelines with different diameters exhibit a consistent decay law under the same burst pressure by defining dimensionless distance and peak overpressure. Accordingly, the dimensionless blast curve is proposed for predicting overpressure from hydrogen pipeline burst with diameters ranging from 250 mm to 1000 mm and burst pressures ranging from 4 MPa to 12 MPa. The results can serve as a reference for the accurate and fast evaluation of blast wave intensity from hydrogen pipeline burst. • The proposed model effectively couples the dynamic rupture and blast wave. • Propagation of blast wave from hydrogen pipeline burst is quantitatively depicted. • Previous methods underestimate the peak overpressure in the middle and far fields. • Blast curve is developed to improve the prediction accuracy of peak overpressure. [ABSTRACT FROM AUTHOR]

With the trend towards larger and lighter designs of wind turbines, blades are progressively being developed to have longer and more flexible configurations. Under standstill conditions, the separated flow induced by a wide range of incident flow angles can cause complex aerodynamic elastic phenomena on blades. However, classical momentum blade element theory methods show limited applicability at high angles of attack, leading to significant inaccuracies in wind turbine performance prediction. In this paper, the geometrically accurate beam theory and high-fidelity CFD method are combined to establish a bidirectional fluid–structure coupling model, which can be used for the prediction of the aeroelastic response of wind turbine blades and the analysis of fluid–structure coupling. Aeroelastic calculations are carried out for a single blade under different working conditions to analyze the influence of turbulence, gravity and other parameters on the aeroelastic response of the blade. The results show that the dominant frequency of the vibration deformation response in the edgewise direction is always the same as the first-order edgewise frequency of the blade when the incoming flow condition is changed. The loading of gravity will make the aeroelastic destabilization of the blade more significant, which indicates that the influence of gravity should be taken into account in the design of the aeroelasticity of the wind turbine. Increasing the turbulence intensity will change the dominant frequency of the vibration response in the edgewise direction, and at the same time, it will be beneficial to the stabilization of the aeroelasticity response. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The axial-flow-induced vibration of fuel rods in the nuclear power plant is closely related to nuclear safety. In this article, a numerical study is performed on vibration of two elastic cylinders arranged side-by-side in axial flow. Large eddy simulation is employed to predict the turbulent flow. The numerical method has been verified using the experimental root-mean-square vibration amplitude of a single cylinder. A wide range of inflow velocities u∗, incident turbulence intensity Tu and space ratio P/D have been examined, where D and P are the diameter and centre-to-centre distance of the cylinders, respectively. The results show that the vibration amplitudes increase with an increasing u∗, comparable to the case of a single cylinder in axial flow. However, the two cylinders could bend outwards during a relatively high u∗ and low Tu. Although Tu significantly affects the amplitudes of the cylinders, it does not change the vibration frequency and the critical velocity at which buckling instability occurs. As the gap between the two cylinders is sufficiently small, the vibration amplitude enhances significantly due to the pronounced hydrodynamic interaction between the two elastic cylinders and surrounding fluid. The direction of buckling is no longer random but fixed.

Currently, cranes used at sea are insufficient in efficiency. Accordingly, a floating multi-robot coordinated towing system is proposed to meet offshore towing needs. However, the towing robot is prone to overturning because of the system's utilization of rope-driven robot flexibility and its floating attributes in fluid environments. First, the kinematics and dynamics of the towing system are analyzed through coordinate transformations and hydrodynamic theory. Subsequently, physical modeling of the towing system is conducted, with an emphasis on analyzing the system's fluid-structure coupling properties, supplemented by illustrative examples. Finally, the stability of the floating robot is assessed based on ship stability theory, encompassing analyses of the rope tension effects, size and shape of the floating base, and external environmental factors influencing system stability. Results show that the special shape of the floating base is beneficial in reducing water resistance and improving the stability of the floating robot in the flow field. The results provide a good basis for the system structural design and application. [ABSTRACT FROM AUTHOR]

The ureteral pain caused by kidney stones has long tormented humans and seriously affected their quality of life. However, currently, in clinical practice, due to the lack of quantitative analysis of the interaction between kidney stones and ureters, urologists are unable to develop precise personalized treatment and pain relief plans for different patients. In response to this issue, small-sized kidney stones were taken as an example and to analyze the interaction behavior between small-sized kidney stones entering the ureteral lumen and the ureter with a fluid-structure coupling finite element method based on the coupled Eulerian-Lagrangian (CEL) algorithm. With the established ureteral pain model, the ureteral pain caused by small-sized kidney stones was quantitatively studied. The finite element analysis results indicate that, when the stone diameter is smaller than the inner diameter of the ureter, the stone will dynamically contact the ureter under peristalsis of the ureter wall, causing dynamic stress on the inner wall of the ureter. The stone moving speed will increase with the peristaltic amplitude of the ureteral wall, but the contacting probability between the stone and the ureter will decrease, and the contacting stress on the ureteral wall will decrease as well. The stress results were input into the ureteral pain model to calculate the corresponding central transmission neuron cell membrane potential. The model results show that, the change in the pain level over time was similar to the trend of dynamic stresses over time. In the case of alternating stress changes, the pain level would not decrease below the pain threshold as the stress drops to 0, showing inconformity between the pain level and the stress level. The results can be combined with existing medical imaging technologies in clinical practices, as well as big data and artificial intelligence technologies in the field of computer science. The research provides a theoretical basis for personalized and accurate diagnosis of the condition of stone patients, quantitative evaluation of patient pain levels, and the development of personalized treatment plans for precise medical clinical strategies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ballistics / Dandao Xuebao is the property of Journal of Ballistics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the development of steel-structure construction technology in high-rise buildings, the design and construction of high-rise steel structures tend to be complicated. Based on the Zhuhai Tiejian Square project, the fluid-structure coupling calculation analysis and on-site monitoring are carried out in view of the wind load of the high-altitude steel-structure connecting bridge in the hoisting stage of the Zhuhai Tiejian Square project. The main structure of the project is four towers and five high-altitude, small-spacing steel structures connecting the four towers. The lifting process of the third zone is taken as the analysis object, and the hoisting idea of "low-altitude hoisting, overall lifting" is adopted. Because the span of the high-altitude steel-structure connecting bridge is small and the installation height is high, the influence of wind load on the hoisting process cannot be ignored. Therefore, the unidirectional fluid-structure coupling model of the high-altitude small-space steel-structure connecting bridge in the third zone was established by using CFD calculation software ANSYS Fluent 2022 R1, and the corresponding flow field and solid calculation results were obtained and analyzed. The analysis results show that the lifting structure still produces a certain deformation when the wind speed is 5 m/s or 10 m/s, and the calculation results show that the stress calculation results are still within the safe range of steel strength for the sensitivity of the lifting structure under wind load. With the increase of wind speed, the local maximum stress of the structure increases greatly, but the overall deformation remains stable, which indicates that the greatest challenge of hoisting steel structures under wind load may be the stability direction rather than the strength, so it is necessary to strictly monitor the displacement deformation of the structure during construction. Then, through the monitoring of the overall lifting process of the high-altitude, large-span, steel-connected structure of Zhuhai Tiejian Square from pre-lifting to formal lifting, real-time monitoring and data analysis show that the lifting process of the high-altitude steel bridge of Zhuhai Tiejian Square is safe and reliable, the force transformation of each component is reasonable, the lifting process is relatively stable, the external environment has little impact, and the expected monitoring effect has been achieved. The calculation simulation and on-site monitoring in this paper can provide theoretical and practical guidance for the construction safety under the influence of wind load in the construction process of high-altitude steel-structure hoisting, and provide an important reference value for similar projects. [ABSTRACT FROM AUTHOR]

The cutting force suffered by the machine tool in the cutting process can be assumed to be the combined force of the steady state force and the dynamic disturbing force.In order to investigate the dynamic characteristics of electric spindle system supported by gas bearings,sine wave was used as dynamic disturbance loading form,and the dynamic characteristics of a simplified model of a gas bearing rotor system were studied by combining the harmonic excitation method with the bidirectional fluid-structure coupling numerical simulation. The dynamic stiffness and damping coefficients were identified. Through modal analysis,the system vibration modes and natural frequencies of the rotor under different steady-state forces were obtained. The results show that with the increase of steady-state force,the growth rate of Kyy of the lower radial bearing is greater than that of Kxx,while the cross stiffness and cross damping are almost unchanged.The main stiffness of the lower radial bearing is greater than the cross stiffness,and the main damping is greater than the cross damping. When the steady-state force ranges from 50 N to 200 N,the y-shift at the lower end of the rotor first increases and then decreases with the increase of dynamic disturbance frequency. The resonance frequency of the system increases with the increase of the steady-state force. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on global initiatives such as the clean energy transition and the development of renewable energy, the pumped storage power station has become a new and significant way of energy storage and regulation, and its construction environment is more complex than that of a traditional reservoir. In particular, the stability of the rock strata in the underground reservoirs is affected by the seepage pressure and rock stress, which presents some challenges in achieving engineering safety and stability. Using the advantages of the numerical simulation method in dealing deal with nonlinear problems in engineering stability, in this study, the stability of the underground reservoir of the Shidangshan (SDS) pumped storage power station was numerically calculated and quantitatively analyzed based on fluid-structure coupling theory, providing an important reference for the safe operation and management of the underground reservoir. First, using the COMSOL software, a suitable mechanical model was created in accordance with the geological structure and project characteristics of the underground reservoir. Next, the characteristics of the stress field, displacement field, and seepage field after excavation of the underground reservoir were simulated in light of the seepage effect of groundwater on the nearby rock of the underground reservoir. Finally, based on the construction specifications and Molar-Coulomb criterion, a thorough evaluation of the stability of the underground reservoir was performed through simulation of the filling and discharge conditions and anti-seepage strengthening measures. The findings demonstrate that the numerical simulation results have a certain level of reliability and are in accordance with the stress measured in the project area. The underground reservoir excavation resulted in a maximum displacement value of the rock mass around the caverns of 3.56 mm in a typical section, and the safety coefficient of the parts, as determined using the Molar-Coulomb criterion, was higher than 1, indicating that the project as a whole is in a stable state. [ABSTRACT FROM AUTHOR]

Slamming impacts on water are common occurrences, and the whipping induced by slamming can significantly increase the structural load. This paper carries out an experimental study of the water entry of rigid wedges with various deadrise angles. The drop height and deadrise angle are parametrically varied to investigate the effect of the entry velocity and wedge shape on the impact dynamics. A two-way coupled approach combing CFD method software STAR-CCM+12.02.011-R8 and the FEM method software Abaqus 6.14 is presented to analyze the effect of structural flexibility on the slamming phenomenon for a wedge and a ship model. The numerical method is validated through the comparison between the numerical simulation and experimental data. The slamming pressure, free surface elevation, and dynamic structural response, including stress and strain, in particular, are presented and discussed. The results show that the smaller the inclined angle at the bottom of the wedge-shaped body, the faster the entry speed into the water, resulting in greater impact pressure and greater structural deformation. Meanwhile, studies have shown that the bottom of the bow is an area of concern for wave impact problems, providing a basis for the assessment of ship safety design. [ABSTRACT FROM AUTHOR]

Given that the complicated dynamics induced by the fluid–solid interaction seriously restrict the structural engineering application when the axially moving plate is immersed in the fluid, we introduce the shape memory alloy materials to reconstruct the plates to improve the mechanical environment by studying the dynamical behavior and time-delay control problem of the system under external excitation. Considering that the liquid is an ideal case with no viscosity, rotation, and incompressibility, as well as the present system is influenced by the axial tension, the fluid–structure interaction, and the polynomial constitutive relationship of the shape memory alloy, the nonlinear governing equation of the axially motion of the thin plate is established based on the Hamilton's principle and the small deflection plate assumption. The Galerkin method is utilized to discretize the dynamic equation. The plate's equilibrium point is qualitatively analyzed, and the fourth-order Runge–Kutta method is used for numerical simulation. Using bifurcation diagrams, phase diagrams, and Poincare section diagrams, the nonlinear dynamic characteristics of the system are disclosed with varying the excitation amplitude. At the same time, the influence of the external load on the system's time-domain waveform is discussed. The multi-scale method is used to study the bifurcation behavior of the present plates in the case of primary resonance. By introducing the time-delay feedback method, the dynamic response of the system is controlled by selecting appropriate displacement and velocity time-delay parameters. Results show that the time-delay feedback controller can eliminate the jumping phenomenon and improve the system's stability, which further enhances the strength and reliability. [ABSTRACT FROM AUTHOR]

Abstract A two-dimensional tube bundles fluid–structure coupling model was developed using the CFD approach, with a rigid body motion equation and the Newmark integral method. The numerical simulations were performed to determine the vibration coupling properties between various tube bundles of stiffness. Take the corner square tube bundles with a pitch ratio of 1.28 as the research object. The influence of adjacent tubes with different stiffness on the vibration of the central target tube was analyzed. The research results show that the vibration characteristic of tube bundles is affected by the flow field dominant frequency and the inherent frequency of tube bundles. The vibration of adjacent tube bundles significantly impacts the amplitude and frequency of the central target tube. The equal stiffness and large stiffness tubes upstream or downstream inhibit the vibration displacement of the target tube to some extent. The low-stiffness tubes upstream or downstream significantly enhanced the amplitude of the target tube. The findings can be used to provide a basis for reasonable design and vibration suppression of shell-and-tube heat exchangers.

The coupling relationship between the deformation field, the diffusion field, and the seepage field is an important factor in fluid transport mechanisms in the long-term coalbed methane (CBM) exploitation process. A mathematical model of gas–water two-phase fluid–structure coupling in a double-porosity medium in coal reservoirs is established in this paper. Taking Hancheng Block, a typical production block in Qinshui Basin, as the geological background critical desorption pressure, reservoir permeability anisotropy is considered in the model. COMSOL Multiphysics (COMSOL_6.0) was used to create the model. The accuracy and rationality of the model were verified by comparing field production data with the results of the simulation. Using the simulation, the influence law of various reservoir geological characteristics parameters (Langmuir strain constant, ratio of critical desorption pressure to reservoir pressure of coal seam (CDPRP), elastic modulus, initial water saturation, Langmuir pressure, etc.) on CBM productivity, reservoir pressure, and permeability ratio was discussed, and a thorough analysis of the factors affecting productivity was obtained using the orthogonal test method. The findings of this study indicate that the change in permeability is the result of the superposition effect of many factors. Different stages of drainage have different primary regulating factors. Rock skeleton stress has a consequence on coal matrix permeability in the early drainage stage, and coal matrix shrinkage is primarily impacted in the later drainage stage. Besides the initial water saturation, other reservoir geological parameters (e.g., CDPRP, Langmuir volume, Langmuir strain constant, elastic modulus) have a strong relationship with productivity. When the value of coal geological parameters increases, the degree of productivity release is higher (as the initial water saturation increases, the production decreases correspondingly). Different coal and rock parameters have varying levels of impact on the drainage stage of CBM wells. The influences of the CDPRP, Langmuir volume, Langmuir strain constant, and elastic modulus on gas production are mainly concentrated in the initial and intermediate drainage stages and begin to fall off during the last drainage stage. Per the multi-factor analysis, the main coal–rock parameters affecting the productivity release are the Langmuir strain constant, followed by the CDPRP and other parameters. The analysis findings can offer theoretical guidance for CBM well selection and layer selection and enhance the block's overall CBM development level. The improved productivity prediction model for CBM, which is based on fluid–structure coupling theory, can offer a new technical benchmark for CBM well productivity prediction. [ABSTRACT FROM AUTHOR]

Under the action of the flow field force and the constraint reaction force of the negative rotor and the positive rotor, the twin screw compressor shell will produce vibration, which will affect the life of the parts and produce noise. The rotors restraint reaction force is calculated by fluid-structure coupling method. The shell inherent frequency is solved by modal analysis, and the shell resonance is analyzed during the rotors meshing process. On this basis, the flow field force and rotor constraint reaction force are used as the compressor shell vibration excitation sources, and the vibration response of the compressor shell under the action of excitation force is studied. The research results can provide some reference for the optimized design of compressor shell structure. [ABSTRACT FROM AUTHOR]

AliCPT-1 is the first cosmic microwave background (CMB) experiment in China dedicated to achieving accurate measurements of B-mode polarization. Situated in Ali of Tibet, China, this telescope is currently undergoing deployment and will operate in two frequency bands centered at 90 and 150 GHz. The far-field flat mirror (FFF) is a calibration device of the AliCPT-1 telescope for far-field beam mapping. The design of the FFF is optimized for easy assembly and adjustment. Meteorological station data reveal that the maximum wind speed near the FFF is 17.5 m/s, while the maximum wind speed on the windward side is 8 m/s. The wind pressure on the FFF was analyzed using a maximum wind speed of 17.5 m/s as the input condition, based on the fluid–structure coupling method in ANSYS. The results demonstrate that it is safe and reliable when withstanding combined gravity and wind pressure loads. The torque on the mount is within the motor rated torque. The flatness of the FFF reflective surface can be adjusted to an RMS value of 0.05 mm when taking into account the effect of gravity and assembly accuracy. The deformation caused by the maximum wind loads is approximately 0.0587 mm under the protection of the wind-proof wall. The combined deformation is 0.077 mm in RMS value combining the two influences, which is less than 1/20 of wavelength. The FFF mirror assembly is stable and precise for telescope calibration. [ABSTRACT FROM AUTHOR]

Coupled fluid-structure-rupture model was developed to evaluate the blast field from X65 hydrogen pipeline burst. Johnson-Cook material model was implemented considering the high strain rates of material at crack tips. Internal hydrogen decompression, outer blast wave generation and propagation, and dynamic rupture of pipeline were simulated simultaneously and validated with experiments. Results demonstrated that the crack primarily ran axially at an average speed of about 120 m/s, while the maximum speed was about 200 m/s. Due to the dynamic growth of rupture opening, the outer blast wave experienced a process of first form and then strengthened by subsequent compression waves. This makes the maximum peak overpressure along the jetting direction appears at a certain standoff distance above rupture. The blast overpressures along the jetting direction were compared and discussed with those from traditional CFD method, TNT equivalence method and Baker-Tang blast curves. It was found the effective volume to calculate the burst energy needs to be further studied. Also, new blast curves were required for quick and rational estimation of blast overpressure from hydrogen pipeline burst. • Coupled fluid-structure-rupture method offers improvements of hazards assessments. • Flow behavior and dynamic rupture of pipeline were well coupled together. • Maximum peak overpressure appears at a certain standoff distance above rupture. • New blast curves are needed to estimate blast overpressure along jetting direction. [ABSTRACT FROM AUTHOR]

To predict the wave loads of a flexible trimaran in different wave fields, a one-way interaction numerical simulation method is proposed by integrating the fluid solver (Star-CCM+) and structural solver (Abaqus). Differing from the existing coupled CFD-FEA method for monohull ships in head waves, the presented method equates the mass and stiffness of the whole ship to the hull shell so that any transverse and longitudinal section stress of the hull in oblique waves can be obtained. Firstly, verification study and sensitivity analysis are carried out by comparing the trimaran motions using different mesh sizes and time step schemes. Discussion on the wave elevation of uni- and bi-directional waves is also carried out. Then a comprehensive analysis on the structural responses of the trimaran in different unidirectional regular wave and bi-directional cross sea conditions is carried out, respectively. Finally, the differences in structural response characteristics of trimaran in different wave fields are studied. The results show that the present method can reduce the computational burden of the two-way fluid-structure interaction simulations. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The wings of birds exhibit multi-degree-of-freedom motions during flight. Among them, the flapping folding motion and chordwise passive deformation of the wings are prominent features of large birds in flight, contributing to their exceptional flight capabilities. This article presents a method for the fast and accurate calculation of folding passive torsional flapping wings in the early design stage. The method utilizes the unsteady three-dimensional panel method to solve the aerodynamic force and the linear beam element model to analyze the fluid–structure coupling problem. Performance comparisons of folding flapping wings with different kinematics are conducted, and the effects of various kinematic parameters on folding flapping wings are analyzed. The results indicate that kinematic parameters significantly influence the lift coefficient, thrust coefficient, and propulsion efficiency. Selecting the appropriate kinematic and geometric parameters is crucial for enhancing the efficiency of the folding flapping wing. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas & Oil is the property of Editorial Department of Natural Gas & Oil and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The marine net cage is an essential facility and equipment for deep-water aquaculture in China, and its hydrodynamic characteristics are directly related to its operational stability. This paper established a finite element model for a marine net cage with three-layer and employed a fluid-structure interaction method to simulate the hydrodynamic characteristics of the net cage under the frontal flow conditions of a level 17 typhoon. Furthermore, a comparative analysis of the variation patterns in the hydrodynamic characteristics of the net cage with and without a netting structure was conducted. The results showed that under the frontal flow of the typhoon, the main areas of stress concentration in the net cage were the lateral support points of the bait chamber, the upmost walkway board connecting pipes on the windward side, and the cross-points of the mid-level load-bearing structure. When the net cage was equipped with a netting structure, the pendulum distance decreased, but the yawing motion intensified. In other words, the netting structure contributed to the vertical stability of the net cage but increased its yawing motion intensity. With the inclusion of the netting structure, due to the improved vertical stability of the frame, the maximum stress at the lateral support points of the bait chamber, the upmost walkway board connecting pipes on the windward side, decreased by 5.1% and 3.2% respectively, while the maximum stress at the cross-points of the mid-level load-bearing structure exhibited little change. However, the maximum stress on the windward side of the mid-lower level connecting pipes decreased by 8.7%.

With the trend towards larger and lighter designs of wind turbines, blades are progressively being developed to have longer and more flexible configurations. Under standstill conditions, the separated flow induced by a wide range of incident flow angles can cause complex aerodynamic elastic phenomena on blades. However, classical momentum blade element theory methods show limited applicability at high angles of attack, leading to significant inaccuracies in wind turbine performance prediction. In this paper, the geometrically accurate beam theory and high-fidelity CFD method are combined to establish a bidirectional fluid–structure coupling model, which can be used for the prediction of the aeroelastic response of wind turbine blades and the analysis of fluid–structure coupling. Aeroelastic calculations are carried out for a single blade under different working conditions to analyze the influence of turbulence, gravity and other parameters on the aeroelastic response of the blade. The results show that the dominant frequency of the vibration deformation response in the edgewise direction is always the same as the first-order edgewise frequency of the blade when the incoming flow condition is changed. The loading of gravity will make the aeroelastic destabilization of the blade more significant, which indicates that the influence of gravity should be taken into account in the design of the aeroelasticity of the wind turbine. Increasing the turbulence intensity will change the dominant frequency of the vibration response in the edgewise direction, and at the same time, it will be beneficial to the stabilization of the aeroelasticity response.

For large bird-like flapping wing aircraft, the fluid–structure coupling problem is very important. Through the passive torsional deformation of the wing, sufficient thrust is generated and propulsion efficiency is ensured. Moreover, spanwise bending deformation will affect lift and thrust. The flow field on the surface of the wing and the geometric nonlinearity caused by the large deformation of the wing should be considered during the design process. Existing research methods do not solve this problem accurately and efficiently. This paper provides a method to analyze the fluid–structure coupling problem of the flapping wing which adopts the three-dimensional unsteady panel method to solve the aerodynamic force, and adopts the linear beam element model combined with the corotational formulation method to consider the geometric nonlinear deformation of the wing beam. This article compares the performance of the flapping wing with different torsional and bending stiffness, and analyzes the airfoil surface pressure coefficients at different portions of the wing during the period. The results show that torsional stiffness has a large influence on the lift coefficient, thrust coefficient and propulsion efficiency. Meanwhile, the torsional stiffness of the wing beam and the initial geometric twist angle of the wing need to be well coordinated to achieve high efficiency. Moreover, appropriate bending stiffness of the wing is conducive to improving propulsion efficiency. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of thermal stress in the exhaust manifold of a gasoline engine is considered. The problem is addresses in the frame of a combined approach where fluid and structure are coupled using the GT-POWER and STAR-CCM+ software. First, the external characteristic curve of the engine is compared with a one-dimensional simulation model, then the parameters of the model are modified until the curve matches the available experimental values. GT-POWER is then used to transfer the inlet boundary data under transient conditions to STAR-CCM+ in real-time. The temperature profiles of the inner and outer walls of the exhaust manifold are obtained in this way, together with the thermal stress and thermal deformation of the exhaust manifold itself. Using this information, the original model is improved through the addition of connections. Moreover, the local branch pipes are optimized, leading to significant improvements in terms of thermal stress and thermal deformation of the exhaust manifold (a 7% reduction in the maximum thermal stress). [ABSTRACT FROM AUTHOR]

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During the operation of pumped storage power stations, complex operating conditions can lead to different internal flow characteristics, which can cause different vibration characteristics or even damage to the structural components of the pump-turbine units. The time–frequency characteristics of the structural components' response are of great significance for the safe operation of the unit. In this study, a three-dimensional flow field and structural field model of a large high head prototype pump-turbine is built in order to study the flow and the flow-induced dynamic response characteristics in different turbine operating conditions. The analyzed results show that the maximum deformation occurs at the inner head cover, and the maximum value of stress is located at the fillets on the outlet side of the stay vanes. Under the 50% load condition, the vortices in the runner caused by changes in the opening of the guide vanes result in the main response frequency of 4  f n  of the stationary components. The research results can provide references for the structural optimization design of other pump-turbine units. [ABSTRACT FROM AUTHOR]

The classical groundwater seepage theory was established on the basis of the principle of water equilibrium, which cannot explain the phenomenon of well water level change caused by natural seismic activities and other external loads, and is not conducive to the in-depth understanding of the role of groundwater seepage movement in various environmental geological disasters. To solve this problem, a mathematical model of pore pressure change of a confined aquifer driven by seismic wave stress is constructed based on the fluid-structure coupling dynamic theory. The numerical verification of the model is realized by using the software Comsol. The change characteristics of well water level are inversely performed by using the Cooper theory, and the results are compared with the change characteristics of well water level caused by strong earthquakes in the Sichian-Yunnan region. The influencing factors of seepage movement of a confined aquifer under earthquake are studied by changing the simulation parameters. The results show that when seismic wave loads act on the confined aquifers, pore pressure oscillates in the same period as the seismic waves, and the amplitude, frequency and hydraulic slope of the seismic waves have significant effects on the pore pressure, while the coefficient of permeability and porosity have little effect on the change characteristics. At the initial stage of seismic wave loading, pore pressure increases rapidly, and then part of the water in the aquifer is slowly discharged. The load pressure gradually transfers to the granular framework, and the rate of change of pore pressure slows down and tends to reach a new equilibrium. The variation characteristics of well water level are closely related to pore pressure, and the oscillation period and variation pattern are consistent with pore pressure, but the amplitude is different. Generally, the oscillation rises and tends to be stable, which is basically the same with the variation pattern of well water level observed in the Sichuan-Yunnan region. The results are of valuable exploration significance for the establishment and improvement of groundwater seepage theory under stress, and can enrich and expand the research ideas and application fields of traditional groundwater dynamics and classical fluid-structure coupling theory.

With the development of steel-structure construction technology in high-rise buildings, the design and construction of high-rise steel structures tend to be complicated. Based on the Zhuhai Tiejian Square project, the fluid-structure coupling calculation analysis and on-site monitoring are carried out in view of the wind load of the high-altitude steel-structure connecting bridge in the hoisting stage of the Zhuhai Tiejian Square project. The main structure of the project is four towers and five high-altitude, small-spacing steel structures connecting the four towers. The lifting process of the third zone is taken as the analysis object, and the hoisting idea of “low-altitude hoisting, overall lifting” is adopted. Because the span of the high-altitude steel-structure connecting bridge is small and the installation height is high, the influence of wind load on the hoisting process cannot be ignored. Therefore, the unidirectional fluid-structure coupling model of the high-altitude small-space steel-structure connecting bridge in the third zone was established by using CFD calculation software ANSYS Fluent 2022 R1, and the corresponding flow field and solid calculation results were obtained and analyzed. The analysis results show that the lifting structure still produces a certain deformation when the wind speed is 5 m/s or 10 m/s, and the calculation results show that the stress calculation results are still within the safe range of steel strength for the sensitivity of the lifting structure under wind load. With the increase of wind speed, the local maximum stress of the structure increases greatly, but the overall deformation remains stable, which indicates that the greatest challenge of hoisting steel structures under wind load may be the stability direction rather than the strength, so it is necessary to strictly monitor the displacement deformation of the structure during construction. Then, through the monitoring of the overall lifting process of the high-altitude, large-span, steel-connected structure of Zhuhai Tiejian Square from pre-lifting to formal lifting, real-time monitoring and data analysis show that the lifting process of the high-altitude steel bridge of Zhuhai Tiejian Square is safe and reliable, the force transformation of each component is reasonable, the lifting process is relatively stable, the external environment has little impact, and the expected monitoring effect has been achieved. The calculation simulation and on-site monitoring in this paper can provide theoretical and practical guidance for the construction safety under the influence of wind load in the construction process of high-altitude steel-structure hoisting, and provide an important reference value for similar projects.

Slamming impacts on water are common occurrences, and the whipping induced by slamming can significantly increase the structural load. This paper carries out an experimental study of the water entry of rigid wedges with various deadrise angles. The drop height and deadrise angle are parametrically varied to investigate the effect of the entry velocity and wedge shape on the impact dynamics. A two-way coupled approach combing CFD method software STAR-CCM+12.02.011-R8 and the FEM method software Abaqus 6.14 is presented to analyze the effect of structural flexibility on the slamming phenomenon for a wedge and a ship model. The numerical method is validated through the comparison between the numerical simulation and experimental data. The slamming pressure, free surface elevation, and dynamic structural response, including stress and strain, in particular, are presented and discussed. The results show that the smaller the inclined angle at the bottom of the wedge-shaped body, the faster the entry speed into the water, resulting in greater impact pressure and greater structural deformation. Meanwhile, studies have shown that the bottom of the bow is an area of concern for wave impact problems, providing a basis for the assessment of ship safety design.

The study seeks to improve liquid-filled pipeline fluid-structure coupling project management in order to forecast vibration response and fatigue damage. To manage the complexity of fluid-structure interactions, our project management system employs Lattice Boltzmann theory and innovative optimization approaches. The study includes fluid characterization, Lattice Boltzmann Model optimization, fluid-structure interaction coupling, and vibration response analysis. Surrogate modeling, adaptive mesh refining, and parallel processing all contribute to increased simulation efficiency. The Lattice Boltzmann Method was chosen for its adaptability and computational efficiency in complex liquid-filled pipeline dynamics with varying flow conditions and external stressors. This work aimed to improve performance and simplify project administration. The emphasis is on early fluid-structure interaction, effective communication, and project performance monitoring throughout the lifecycle. We simulate liquid-filled pipeline dynamics in a variety of operating situations to forecast natural frequencies, stress distributions, and fatigue damage indicators. The Lattice Boltzmann Method and other advanced computational techniques improve project management fluid-structure coupling. This study describes the advantages of the Lattice Boltzmann Method over alternative approaches. Modeling liquid-filled pipeline dynamics under varying flow conditions and external forces necessitates adaptability and processing efficiency. Better results and more efficient project management. This option improves the liquid-filled pipe fluid-structure coupling project management. The study assists engineers and project managers in designing and operating cost-effective, structurally sound liquid-filled pipelines. This study also lays the groundwork for more powerful and diverse fluid-structure interaction analysis tools that are more practical. We improve pipeline fluid-structure coupling and provide researchers and practitioners with new problem-solving tools.

To effectively reduce the specific fuel consumption of aeroengine and obtain the optimal geometric design parameters of compliant cylindrical intershaft gas film seal(CCIGFS) in the limited design space size, an optimal design method of CCIGFS based on the grasshopper swarm characteristics is established, and the optimal design parameters of CCIGFS for counter-rotating shafts are acquired by this method. In this paper, for the sake of leakage calculation, mechanical characteristics of the seal are analyzed and a fluid-structure coupling model of CCIGFS for counter-rotating shafts is built. This fluid-structure coupling model considers the influences of centrifugal expansion and rotor circular precession. Then, according to this method, the leakage rate with various seal widths and diameters is computed and the function relation of leakage rate with seal width and diameter is obtained by curve fitting method. Furthermore, by changing the design parameters of the seal width and diameter, the functional relation between the mass and the seal width and diameter is obtained by curve fitting method too. Thus, the multi-objective optimization design model about the design variables of the CCIGFS is developed. Finally, the state-of-the-art multi-objective grasshopper optimization algorithm is adopted to obtain the corresponding Pareto frontier, and the geometric structure design parameters of the seal are selected according to the actual situation. This paper provides a complete and systematic method for the engineering design and analysis of CCIGFS in the counter-rotating shafts.

Marine risers typically experience nonlinear vibration failure problems caused by the ocean vortex excitation force. To resolve this, the Hamilton variational principle is applied to establish a vortex-induced vibration (VIV) model for a flexible riser. A wake oscillator model is employed to simulate the vortex-induced forces of cross flow (CF) and inline flow (IL) and their coupling, considering the effect of top tension and internal flow on the riser. The VIV model is solved by combining the Newmark–β and Runge–Kutta methods and then verified by comparing the calculation results of the proposed vibration model with data in published literature. Based on the foregoing, the effects of uniform flow, top tension, and shear flow on the VIV behaviour of risers with a large aspect ratio are systematically investigated. Moreover, the VIV characteristics are identified. First, the results demonstrate that, when the top tension is 10 t, the IL vibration is 0.73 Hz and the CF vibration is 0.36 Hz, which shows that the IL vibration is twice as high as the CF vibration. Moreover, the amplitude of the latter is between 7 and 21 times that of the former, which are respectively 0.018 and 0.12 m. Second, the shear velocity and top tension also have considerable influence on the IL vibration under shear flow. Third, the CF vibration has a frequency-locking effect under shear flow and uniform flow conditions. The IL vibration exhibits a frequency-locking effect under uniform flow and a multifrequency effect under shear flow. The study led to the formulation of a theoretical method for safety evaluation and a practical approach for effectively improving the service life of marine risers. [ABSTRACT FROM AUTHOR]

As the offshore engineering industry continued to develop, issues such as damage to storage structures due to liquid shaking became increasingly prevalent. This paper explored the dynamic response of liquid within a rigid cylindrical water tank subjected to harmonic excitation through vibration table tests, analyses, and numerical simulations. Using the Laplace equation and the Bessel function of the first kind, the analytical formula of liquid dynamic response was derived. A numerical model was established by ANSYS software to verify the accuracy of the analytical solution. At the same time, the response characteristics of hydrodynamic pressure and liquid level wave height were studied by vibration table tests. In this experiment, a rigid cylindrical water tank with varying depths of liquid was subjected to harmonic excitations utilizing a vibration table. In most cases, the experimental results agreed well with the analytical formula. However, under conditions of relatively severe liquid sloshing, there was a discrepancy in peak values between the experiment and the analytical formula. The experimental data indicated that both the hydrodynamic pressure and liquid level wave height increase with an increase in harmonic excitation frequency and amplitude. [ABSTRACT FROM AUTHOR]

To investigate the failure mode of the cable-stayed pipeline bridge under seismic loading, this study focuses on an oil and gas cable-stayed pipeline bridge as the research subject. A full-scale finite element calculation model of the structural system is established using ANSYS Workbench 14.0 software, considering the stress characteristics and structural properties of the oil and gas pipeline. Additionally, a fluid–structure coupling effect finite element model is developed to account for the influence of medium within the pipeline. The analysis includes evaluating deformation, stress, strain, and other responses of the oil and gas pipeline subjected to seismic waves from different directions. The results indicate that the overall damage in the pipeline is consistent with maximum deformation, stress, and strain, concentrated at both the inlet/outlet ends and side spans; however, variations exist in terms of seismic damage depending on wave directionality. Furthermore, by considering interactions between various components within the oil and gas cable-stayed pipeline bridge's structural system during strong earthquakes, this study analyzes failure mechanisms caused by the support–pipeline interaction as well as excessive displacement-induced failure patterns in bridge towers. Finally, a proposed failure mode for pipe bridge systems resulting from longitudinal slip between supports and pipelines, along with excessive displacement of bridge towers, is presented. [ABSTRACT FROM AUTHOR]

Copyright of Journal of East China University of Science & Technology is the property of Journal of East China University of Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The flutter of the linear compressor valve plate is the main factor that affects the working life and performance of the compressor. Because the flutter of the valve plate will aggravate the fatigue failure of the valve plate and affect the stability of the mass flow through the valve plate. In order to study this problem, this paper uses a three-dimensional fluid-structure interaction (FSI) model to simulate the opening and closing process of the exhaust valve of a linear compressor. This method can effectively predict valve plate flutter and valve plate reflux. Based on the FSI model, the influence of compressor working pressure ratio and piston operating frequency on valve flap vibration period and valve flap return was studied. According to the simulation results, an empirical correlation between the predicted valve plate flutter period and the piston operating frequency is obtained. [ABSTRACT FROM AUTHOR]

A multi-dimensional morphing wing skeleton mechanism is proposed with double-sided triangular pyramid units, which can realize continuous variable span-wise bend, span-wise twist, and sweep. A lockable morphing unit is designed, and its mechanism/structure characteristics, degree of freedom, and the deformable function of its deformable wing skeleton mechanism are analyzed. One kind of flexible skin is proposed to meet the performance requirements, consisting of an internal metastructure and a flexible surface bonded on both sides. The morphing wing skeleton mechanism and the equivalent treated metastructure flexible skin are then combined. Subsequently, a two-way fluid–structure interaction analysis is conducted to investigate the influence of aerodynamic loads on the flexible skin and skeleton mechanism in different deformation states, including the influence of structural passive deformation on the aerodynamic characteristics of the morphing wing. The computational fluid dynamics method is employed to analyze the aerodynamic characteristics of the morphing wing in its initial state, as well as in three deformation states, and to study its aerodynamic performance in different flight environments. [ABSTRACT FROM AUTHOR]

The aerodynamic characteristics of the vertical-axis wind turbine with three, four, five, and six blades are studied numerically. A coupling model of fluid flow and solid turbine blade is established to model the interactions between air and wind turbine. The pressure distribution and blade deformation affected by air are obtained and discussed. For the four wind turbines with different numbers of blades, the maximum pressure in the entire machine structure occurs at the variable angle position of the blades in the windward region under the same wind speed. Mainly due to the rapid airflow variation, complex turbulence, and significant influence of the wind field on the blades in this position, this part of the blades is prone to bending or damage. Under identical external wind field conditions, wind turbines with four and six blades exhibit significantly higher equivalent pressures on their surfaces compared to those with five and three blades. The maximum equivalent pressure of six blades can reach 3.161 × 10 6 Pa. The maximum deformation of the blade basically occurs at the tip and four sides of the blade. The six-blade wind turbines withstand higher and non-uniform surface pressures on their blades, resulting in the largest deformation of up to 11.658 mm. On the other hand, the four-blade wind turbine exhibits the smallest deformation. The above conclusions provide theoretical guidance for the design and optimization of vertical-axis wind turbines. [ABSTRACT FROM AUTHOR]