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In order to accurately evaluate the dynamic characteristics of the hydraulic bushing, the fluid–structure coupling finite element modeling of the hydraulic bushing was carried out, and its fluid–structure coupling characteristics were analyzed. According to the dynamic characteristic response mechanism of hydraulic bushing, the characteristics of bushing temperature, main spring stiffness, liquid viscosity, inertia channel area, and suspension compensation hole were analyzed. The results show that the main spring stiffness, liquid viscosity, and inertial channel area have significant effects on the performance of the bushing. The basic parameters affecting the installation design are obtained. It provides some theoretical basis and parameter verification for hydraulic bushing design. It provides the basis for the multi-factor design of hydraulic bushing. [ABSTRACT FROM AUTHOR]

This paper presents an accurate and analytical method for investigating the sound transmission loss (STL) characteristics of honeycomb sandwich plate structure subjected to combined thermal and acoustic excitation. In the analysis, the governing equations of sandwich plate structure in thermal environments are established by first order shear deformation theory. Two types of thermal conditions with and without heat flux are considered. The fluid-structure coupling interaction between the plate structure and acoustic excitation is described analytically by applying velocity continuity condition at fluid-structure interfaces. By using the modal expansion approach, the sound transmission loss is described analytically. The experimental measurements of honeycomb sandwich plate are carried out to validate the theoretical model, and good agreement is achieved. Finally, the influences of honeycomb core dimensions, material parameter and temperature distribution on sound transmission loss behavior of honeycomb sandwich structure have been investigated. It has found that the resonance dips of STL curves move to higher frequencies with the increase of ratio of elastic modulus and honeycomb core wall thickness, but the increase of the honeycomb core side length causes the resonance dips to move to low frequencies. The magnitudes of the STL curves are found to be decreasing with increase of temperature values. [ABSTRACT FROM AUTHOR]

Current research on rock damage in mining floors primarily focuses on the seepage‐stress coupling effect, overlooking the fact that rock masses in coal measure strata are predominantly layered. To address this gap, cyclic loading and unloading triaxial tests were conducted. Additionally, theoretical analysis, mathematical statistics, and other methods were used to investigate the damage evolution law of layered rock masses in coal measures. This investigation was carried out under the coupled effects of a specific stress path, characterized by 'stress concentration‐stress unloading‐stress recovery', and a high confined water seepage field. The results show that the compression modulus increases with the increase in confining pressure and osmotic pressure, but its increasing trend gradually slows down. Within a certain range, increasing the confining pressure and osmotic pressure helps to close rock fractures and increase stiffness. [ABSTRACT FROM AUTHOR]

The seismic effect of well water level is complex and variable, and even if both wells are located in an area with similar tectonic and hydrogeological conditions, they exhibit slightly varying response characteristics to the same earthquake. Wells BB and RC, located about 100 km apart in the southwest of the Huayingshan fault zone in the Sichuan and Chongqing regions, exhibited obvious similarities and differences in their co-seismically response and sustained recovery characteristics during the Wenchuan Ms8.0 earthquake. Based on the dislocation theory and fluid–solid coupling theory, this study developed the seismic stress–strain model and the response model of pore pressure to seismic stress using Coulomb 3.3 and COMSOL 6.3, respectively. Simulation findings indicate that both BB and RC are located in the expansion zone, where their water levels show a co-seismic step-down. The amplitudes of BB and RC water levels are 83 cm and 81 cm, which are approximately 10 cm smaller than the actual values. The recovery times are 60 d for BB and 3 h for RC, closely resembling the actual values. Furthermore, the numerical results from different scenarios show that the recovery time of pore pressure is reduced by several times when the permeability of the confining layer overlying the observed aquifer increases by one order of magnitude or the thickness decreases, and this change is more sensitive to the permeability. It is clear that the confining condition has an important impact in the response time of sustained changes in well water levels, which may also help to explain the variations in the characteristics of sustained changes in wells BB and RC. [ABSTRACT FROM AUTHOR]

Analyzing the mechanisms of soil instability in tunnels due to sudden water ingress is essential for construction safety. This kind of problem belongs to the category of seepage deformation, mostly due to the near tunnel range of water pipeline blowing cracks and heavy rainfall flooding rainwater into the tunnel. Distinguished from general infiltration behavior, the relevant problems have the characteristics of rapid occurrence and short action time. This study develops a 3D fluid–solid coupling model for soil deformation in tunnels with water ingress, grounded in Biot's theory and Darcy's law while considering water level variations within the tunnel. The governing equations are discretized in space and time, and the model's accuracy is validated through comparison with actual measurements from a Zhengzhou subway project. The study analyzes pore pressure, stress-deformation responses, and surface settlement patterns in surrounding soil and rock mass under soil–water coupling. The findings show that (1) the tunnel cavern, as a seepage source, has minimal impact on the lateral settlement trough width, while seepage mainly affects the vertical deformation of surrounding rock; (2) pressure dissipation exhibits hysteresis in clay strata; (3) water ingress increases soil saturation and decreases effective stress, resulting in persistent surface settlement until drainage. There is a minimal discrepancy between model-calculated and measured settlements. [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.)

Considering the real stress and deformation state of impeller during the operation of centrifugal pump, the fluid-structure coupling numerical simulation of impeller of centrifugal pump model was carried out based on the software platform of Ansys Workbench and the computational fluid dynamics analysis software CFX. The strength of impeller of centrifugal pump under the combined action of centrifugal force and CFD pressure load was calculated. The position of the maximum stress on the impeller under the action of cyclic alternating stress during rotation is determined. Finally, nCode Designlife software was used to predict the fatigue life of the impeller. The results show that the maximum stress is located at the interface between the blade outlet edge and the cover plate, and the cyclic cyclic stress is the main cause of the fatigue damage of the impeller. The impeller meets the design of infinite life fatigue strength, and the impeller has no risk of fatigue failure. [ABSTRACT FROM AUTHOR]

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.

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]

In China, most blueberry varieties are characterized by tightly clustered fruits, which pose challenges for achieving precise and non-destructive automated harvesting. This complexity limits the design of robots for this task. Therefore, this paper proposes adding a jetting step during harvesting to separate fruit clusters and increase the operational space for mechanical claws. First, a combined approach of flow field analysis and pressure-sensitive experiments was employed to establish design criteria for the number, diameter, and inclination angle parameters of two types of nozzles: flat tip and round tip. Furthermore, fruit was introduced, and a fluid–structure coupling method was employed to calculate the deformation of fruit stems. Simultaneously, a mechanical analysis was conducted to quantify the relationship between jet characteristics and separation gaps. Simulation and pressure-sensitive experiments show that as the number of holes increases and their diameter decreases, the nozzle's convergence becomes stronger. The greater the inclination angle of the circular nozzle holes, the more the gas diverges. The analysis of the output characteristics of the working section indicates that the 8-hole 40° round nozzle is the optimal solution. At an air compressor working pressure of 0.5 MPa, force analysis and simulation results both show that it can increase the picking space for the mechanical claw by about 5–7 mm without damaging the blueberries in the jet area. The final field experiments show that the mean distance for Type I (mature fruit) is 5.41 mm, for Type II (red fruit) is 6.42 mm, and for Type III (green fruit) is 5.43 mm. The short and curved stems of the green fruit are less effective, but the minimum distance of 4.71 mm is greater than the claw wall thickness, meeting the design requirements. [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]

Purpose: To analyze the evolution law of precursor information of water and mud breakout on faults by taking the construction of drainage roadway through the fracture zone of Julong copper mine in Tibet as the engineering background. Method: Through numerical simulation, we investigated the changing rules of displacement, stress, plastic zone, and seepage field of surrounding rock during the construction of drainage roadway to the crushed zone under the effect of fluid-solid coupling, and analyzed the evolution law of premonitory information of water and mud breakout in the roadway through the crushed zone of the fault. Result: The results show that when the roadway is excavated to the fracture zone, the displacement of the palm face increases abruptly. At the same time, stress disturbance occurs in the fracture zone. The plastic zone of the surrounding rock expands in the direction of the crushing zone, and the rock body in the crushing zone undergoes plastic deformation, which is connected with the plastic zone of the palm face. When the roadway is excavated to the crushing zone, the seepage field in the surrounding rock changes obviously, the exposed crushing zone forms a drainage outlet, the water pressure of the surrounding rock decreases suddenly, and the roadway is prone to sudden water and mud accidents. Significance: The results of this paper provide a theoretical reference for the construction of Julong drainage road through the crushed zone. [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.)

In order to accurately evaluate the dynamic characteristics of the hydraulic bushing, the fluid–structure coupling finite element modeling of the hydraulic bushing was carried out, and its fluid–structure coupling characteristics were analyzed. According to the dynamic characteristic response mechanism of hydraulic bushing, the characteristics of bushing temperature, main spring stiffness, liquid viscosity, inertia channel area, and suspension compensation hole were analyzed. The results show that the main spring stiffness, liquid viscosity, and inertial channel area have significant effects on the performance of the bushing. The basic parameters affecting the installation design are obtained. It provides some theoretical basis and parameter verification for hydraulic bushing design. It provides the basis for the multi-factor design of hydraulic bushing.

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]

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]

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]

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.)

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.)

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]

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]

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.

Wind turbine blade pitch fault is easy to cause unstable ultra-high load, which can lead to structural failure and damage. Firstly, the aerodynamic characteristics of NREL 5 MW wind turbine blades with pitch fault/success were analyzed based on the computational fluid dynamics method. Then, the two-way strong fluid-structure coupling and bending analysis were used to study the state of blades with pitch fault under typical azimuths. The results show that average flapwise torque of the blade with pitch fault under the cut-out wind speed is 13. 8 times that of the blade with successful pitch, and the flow field wake of the former is more obvious. The fluctuation range of blade flapwise torque under two-way strong fluid-structure coupling is significantly wider than that without fluid-structure coupling, and the maximum tip displacement of the blade with pitch fault is 14. 1 times that of the blade with successful pitch. For the four typical azimuth angles of 0°, 60°, 120°, and 180°, the bending moment, tip displacement, bending degree, end effect, wake range and strength of the blade with pitch fault gradually decrease with the increase of the angle. Buckling analysis reveals that the buckling factor increases with the enlargement of azimuth angle, and the first-order buckling factor of 180°azimuth is 20.2% higher than that of 0° azimuth.

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%.

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]

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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.

In China, most blueberry varieties are characterized by tightly clustered fruits, which pose challenges for achieving precise and non-destructive automated harvesting. This complexity limits the design of robots for this task. Therefore, this paper proposes adding a jetting step during harvesting to separate fruit clusters and increase the operational space for mechanical claws. First, a combined approach of flow field analysis and pressure-sensitive experiments was employed to establish design criteria for the number, diameter, and inclination angle parameters of two types of nozzles: flat tip and round tip. Furthermore, fruit was introduced, and a fluid–structure coupling method was employed to calculate the deformation of fruit stems. Simultaneously, a mechanical analysis was conducted to quantify the relationship between jet characteristics and separation gaps. Simulation and pressure-sensitive experiments show that as the number of holes increases and their diameter decreases, the nozzle’s convergence becomes stronger. The greater the inclination angle of the circular nozzle holes, the more the gas diverges. The analysis of the output characteristics of the working section indicates that the 8-hole 40° round nozzle is the optimal solution. At an air compressor working pressure of 0.5 MPa, force analysis and simulation results both show that it can increase the picking space for the mechanical claw by about 5–7 mm without damaging the blueberries in the jet area. The final field experiments show that the mean distance for Type I (mature fruit) is 5.41 mm, for Type II (red fruit) is 6.42 mm, and for Type III (green fruit) is 5.43 mm. The short and curved stems of the green fruit are less effective, but the minimum distance of 4.71 mm is greater than the claw wall thickness, meeting the design requirements.