Fluid-structure Coupling Method Research Articles

Research on the Jet Distance Enhancement Device for Blueberry Harvesting Robots Based on the Dual-Ring Model

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.

Study of the Dynamic Reaction Mechanism of the Cable-Stayed Tube Bridge under Earthquake Action

In order to explore the failure mode of the cable-stayed pipe bridge under earthquake action, taking the structural system of an oil and gas pipeline–cable-stayed pipe bridge as the research object, the full-scale finite element calculation model of the cable-stayed pipe bridge–oil and gas pipeline structural system as well as the finite element calculation model considering the additional mass of the oil and gas medium and the fluid–structure interaction effect were established by using ANSYS Workbench finite element software. The stress and displacement of the cable under the earthquake action were analyzed in the time history, as were the response characteristics of the cable when subjected to both methods. The calculation results show that the overall failure of the pipeline is basically the same under the two methods. Compared with the additional mass method, the solution for the fluid–structure coupling method can be derived through a comprehensive analysis of the flow field and structure, respectively, avoiding the sudden change caused by model simplification or calculation error so that the analysis results can better simulate the actual situation. In summary, the fluid–structure interaction method enables a more precise prediction of the dynamic response of the structure, and the findings of this research can provide a theoretical foundation and technical guidance for optimizing the seismic performance of cable-stayed pipe bridges.

Fatigue Damage Assessment of Turbine Runner Blades Considering Sediment Wear

The wear phenomenon that occurs on the blades during operation has a significant impact on the fatigue life of the blades. To address the issue of fatigue life assessment for turbine runner blades subjected to increased dynamic stress due to sediment wear, taking a specific high-head hydropower unit’s mixed-flow turbine as the research subject, a hydraulic model of the turbine was established. The wear zones of the runner blades are determined based on the distribution of the flow field’s velocity and the sediment volume fraction. According to the wear rate formula for runner blade material, the amount of wear on the blades is determined, and the dynamic stress data for the dangerous areas of the blades under different degrees of wear are calculated using a unidirectional fluid–structure coupling method. The load spectrum of the time–stress history data for the dangerous area at different levels of wear was compiled using the rain-flow counting statistical method. The operating time ratios for the flood season and the non-flood season are combined. Based on the fatigue cumulative damage theory, the total fatigue damage at the maximum stress part of the runner blade was calculated for different stages of wear, providing a reference for the life calculation of mixed-flow hydraulic turbines.

Numerical analysis on heat transfer performance of spiral elastic copper tube heat exchanger with helical defectors

Based on the flow-induced vibration mechanism, three kinds of spiral elastic copper tube heat exchangers were proposed to improve the comprehensive heat transfer performance, involving the spiral elastic copper tube heat exchanger with no defector, the spiral elastic copper tube heat exchanger with forward helical deflector and the spiral elastic copper tube heat exchanger with reverse helical deflector. A both-way fluid–structure coupling method was utilized to investigate the effects of helical defectors and their arrangements on the vibration-enhanced heat transfer performance of the spiral elastic copper tubes at different inlet velocities by numerical simulation. The results indicate that: when the inlet velocity ranges from 0.1 m/s to 0.7 m/s, the heat exchanger with reverse helical deflector possesses better heat transfer performance than the other two heat exchangers. For the heat exchangers with no defector and forward helical deflector, the flow-induced vibration always promotes the comprehensive heat transfer performance. Compared with the heat exchanger with no defector, the comprehensive heat transfer performance of the heat exchanger with reverse helical deflector is higher 4.02 % averagely, while that of the heat exchanger with forward helical deflector is lower 29.34 % averagely. Furthermore, a structural optimization is presented to improve the existing disadvantages of the heat exchanger with reverse helical deflector, after structural optimization, the average amplitude of the heat exchanger with forward helical deflector is decreased by 3.26 % averagely and the heat transfer performance is raised to a maximum of 26.24 %, which are of great significance to extend the service life and improve the energy efficiency of heat exchanger.

Vibration Characteristics Analysis of Twin-Screw Compressor Shell Based on the Fluid-Solid Coupling Method

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 are 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.

Insight into blade tip vibration and deformation characteristics of boiler circulation pumps induced by tip leakage vortex under different tip clearances

For circulating pumps in large power plant boilers, tip leakage flow is the main cause of blade fatigue. To investigate the correlation between tip leakage vortex and blade fatigue, in this paper, the bidirectional fluid structure coupling method is used to simulate the full flow field of the boiler circulating pump under different tip clearance sizes. The accuracy of the delayed detached vortex simulation method is verified by combining the external characteristics and vibration characteristics of the pump. It is obtained that tip leakage vortex is the main cause of blade tip vibration and deformation. Under deep stall conditions, the increase in tip clearance size suppresses the vibration displacement of the blade leading edge, while the opposite is true under optimal conditions. After decomposing tip leakage vortex, it is found that the compression–expansion term played a major role in the deformation of the blade tip, while the viscous dissipation term and the stretching term mainly affected the vibration frequency. At optimal working conditions, the main frequency of blade vibration is basically consistent with the main frequency of vortex generation. In deep stall condition, as the tip clearance size increases, the amplitude of the vibration main frequency decreases and the number of harmonic frequencies decreases, while the optimal condition is the opposite.

Study on Explosion Energy Conversion of a Perforating Shaped Charge during Perforation Detonation

Summary The perforation-acidizing-testing combined technology has become the key technology for increasing the efficiency and speed of ultradeep well completion testing. However, the shock load and the wellbore pressure surge affect the stability and local strength of the lower packer string system during the perforation detonation. The energy generated by the perforation detonation is the fundamental source of the shock load and the wellbore pressure surge. The effect laws and distribution characteristics of the explosion energy of the perforating shaped charge is urgently needed. Therefore, a fluid-structure coupling method based on a structural-arbitrary Lagrangian-Euler algorithm (S-ALE) is used to construct a numerical model to forecast the explosion energy. The feasibility of the numerical model is verified by comparison with the field experimental results. The detailed studies on the output value and distribution characteristics of the explosion energy are carried out. The main control factors and influencing laws of the explosion energy are clarified. Then, an equation for the explosion energy prediction is fitted to lay the foundation for studying the wellbore pressure surge and the lower packer string system failure caused by the perforation detonation. The obtained results indicate that the explosion energy is mainly divided into three parts: the jet kinetic energy, the shell case energy, and the pressure surge energy. The pressure surge energy can reach 59.254 to 66.08%, the jet kinetic energy can reach 9.895 to 17.159%, and the shell case energy can reach 21.426 to 24.325%. The major sensitive parameters that affect the pressure surge energy are ranked as follows: the explosive mass, the explosive type, the shell thickness, the standoff distance, the cone angle of the liner, and the shot density. This work provides a reliable prediction method for the accurate description of the explosion energy conversion, which is critical for improving the success rate of the perforation-acidizing-testing combined technology.

Fluid–structure interaction simulation and optical fibre stress analysis of submarine cables in vortex‐induced vibration

AbstractUnder the current scouring, submarine cables are prone to be exposed, suspended, and even vortex‐induced vibration (VIV), threatening their mechanical and electrical properties. In this contribution, a finite element simulation model of 110‐kV single‐core optical fibre composite submarine cable is established. The natural frequency and resonant frequency of the model are obtained through wet mode analysis and harmonic response analysis. Then the VIV is simulated by the fluid–structure coupling method. Moreover, the stress extraction method of the torsional optical fibre position under the VIV is proposed. The results show that when the reduced speed is 2.57, the submarine cable appears beating vibration, which is composed of two vibrations with similar frequencies. When the reduced speed is 7.08, the vibration frequency is about 7.813 Hz, causing a rapid increase in vibration amplitude. The stress distribution of the torsional optical fibre presents a mirror image relationship at two moments separated by half a vibration cycle. Also, the frequency of stress change is the same as the frequency of VIV, which can judge whether the VIV occurs. The VIV range and position can be determined by the location where the stress changes the most.

Fluid-structure interaction study on the causes of mending material damage after sigmoid sinus wall reconstruction

Background and objectiveSigmoid Sinus (SS) Wall Reconstruction (SSWR) is the mainstream treatment for pulsatile tinnitus (PT), but it has a high risk of recurrence. The damage of mending material is the key cause of recurrence, and its hemodynamic mechanism is still unclear. The purpose of this study was to investigate the hemodynamic causes of mending material breakage. MethodsIn this study, six patient-specific geometric models were reconstructed based on the data of the computed tomography angiography (CTA). The transient fluid-structure coupling method was performed to clarify the hemodynamic state of sigmoid sinus and the biomechanical state of the mending material. The distribution of stress and displacement and the flow pattern were calculated to evaluate the hemodynamic and biomechanics difference at the mending material area. ResultsThe area of blood flow impact in some patients (2/6) was consistent with the damaged location of the mending material. The average stress (6/6) and average displacement (6/6) of damaged mending material were higher than those of complete mending material. All (6/6) patients showed that the high-stress and high-displacement proportion of the DMM region was higher than that of the CMM region. Moreover, the average stress fluctuation (6/6) and average displacement (6/6) fluctuation degree of damaged mending material is larger than that of complete mending material. ConclusionsThe impact of blood and the uneven stress and displacement fluctuation of the mending material may be the causes of mending material damage. High stress and high displacement might be the key causes of the mending material damage.

Numerical study on the influence of fabric permeability on the inflation process and aerodynamic characteristics of disk-gap-band parachute

Supersonic parachute plays a crucial role in Mars exploration missions. The disk-gap-band (DGB) parachute he been used in all the successful Mars exploration missions. The parachute is fabricated from different porous fabric materials, and the fabric permeability is an important design and performance parameter, now it has been proved that the fabric permeability of porous canopy has important effects on the complicated flow fields around the parachute and in turn effects the nonlinear deformation and aerodynamic performances of the flexible canopy. However, till now, the influence mechanism of fabric permeability on the fluid-structure interaction mechanism and aerodynamic performance of supersonic flexible porous parachute in the inflation process still remain unknown. Therefore, in this study, a fluid-structure coupling method was used to numerically simulate the inflation process of disk-gap-band parachute with different fabric permeability (i.e., different fabric materials), and the effect of fabric permeability on the aerodynamic performance of disk-gap-band parachute was also analyzed. The results showed that the fabric permeability has a significant effect on the inflation process of DGB parachute with different fabric materials. During the inflation process, the oscillation angle and drag coefficients of the parachute both gradually decreased with the increase of fabric permeability, while the stability performance of the parachute became more complicated. Furthermore, it was also found that the influence of fabric permeability was different under subsonic and supersonic conditions. The K5836-3 fabric used as canopy material has better stability under subsonic conditions, and the 42105 fabric material has the best stability under supersonic conditions.

Study on Flow-induced Vibration Characteristics of 2-DOF Hydrofoil Based on Fluid-Structure Coupling Method

Study on Flow-induced Vibration Characteristics of 2-DOF Hydrofoil Based on Fluid-Structure Coupling Method

Comparative Study on Numerical Calculation of Modal Characteristics of Pump-Turbine Shaft System

Because a pump-turbine mainly undertakes the role of energy conversion and pumped storage in the field of hydropower engineering, the complex transition process and frequent conversion between different working conditions lead to the increase in the stress and strain of core components such as the unit shaft system, and even cause resonance phenomena. Based on ANSYS finite element numerical calculation software, this paper adopts the acoustic fluid–structure coupling method to study the influence of the shaft of the pump-turbine on the dynamic characteristics of the runner. At the same time, the paper analyses the influence of different contact modes between the runner and the shaft on the modal characteristics of the shaft system. The numerical simulation results have shown that the runner is affected by the added mass of the water. The natural frequency reduction rate of each order of wet modal is ranged from 19% to 64%. The main shaft has a greater influence on the simplification of the shaft system calculation method. The type of contact surface between the main shaft and the runner has a smaller influence on the modal characteristics and the natural frequency of the shaft system. The research in this paper contributes an evaluation of the dynamic characteristics of the runner of a hydraulic turbine unit, which is of great significance for the optimization of the analysis algorithm of the runner structure for large pumped storage units.

Investigation of Pressure Variations in Hose Pumps under Different Flow Regimes Using Bidirectional Fluid–Structure Interaction

Hose pumps, renowned for their ability to efficiently transport highly viscous and corrosive fluids, hold an irreplaceable position in numerous engineering domains. With a wide range of fluid types being transported by hose pumps, the study of pressure variations during the conveyance of different fluid states is of paramount importance, as it positively contributes to optimizing hose pump structures, reducing noise, and enhancing hose pump longevity. To investigate pressure variations in hose pumps during the conveyance of varying fluid states, this paper employs a bidirectional fluid–structure coupling method and utilizes commercial finite element software, ANSYS. The research validates the causes of variations in hose pumps during fluid conveyance and examines the overall pressure distribution within the fluid domain of hose pumps conveying different fluid states at varying rotor speeds. The results indicate that when the fluid within the hose pump is in a turbulent state, pressure variations exhibit multiple minor amplitude oscillations, whereas in a laminar state, pressure variations display fewer oscillations but with more significant amplitudes. Moreover, higher rotor speeds exacerbate pressure variations. Recommendations include optimizing the shape of the squeezing roller and enhancing pressure variation control through shell angle optimization.

Influence of deflector direction on heat transfer capacity of spiral elastic tube heat exchanger

In order to improve the overall heat transfer capacity (HTC) of the spiral elastic tube (SET) heat exchangers, two heat exchanger schemes were proposed based on the arrangement direction of SETs and deflectors. Using a bi-directional fluid-structure coupling method, the vibration response and HTC of the SET based on two types of heat exchangers were studied: a same-direction deflector SET (SD-SET) heat exchanger and a reverse-direction deflector SET (RD-SET) heat exchanger. In addition, the structure of the RD-SET heat exchanger was optimized. The results show that in SET heat exchangers, the flow-induced vibration can effectively improve the HTC of SET, however, it is not necessarily the case that the larger the vibration amplitude of SET, the better the HTC enhancement effect. Under the conditions of Vin = 0.05–0.65 m/s, the HTC of SET in the SD-SET heat exchanger increased by 62.37 %, 27.04 %, 10.99 %, 5.68 %, and 3.46 % due to vibration, respectively, while the HTC of SET in the RD-SET heat exchanger increased by 3.03 %, 0.22 %, 0.17 %, 0.13 %, and 0.05 % due to vibration, respectively. By comparing the SD-SET heat exchanger with the RD-SET heat exchanger, it is found that the RD-SET heat exchanger has a higher overall HTC. Compared to the SD-SET heat exchanger, the overall HTC of the RD-SET heat exchanger is 3.96 %, 33.28 %, 43.285, 42.31 %, and 36.52 % higher, respectively. In addition, the structure optimization of the RD-SET heat exchanger results in an average increase of 0.49 % in the overall HTC and also extends the fatigue life of the SET, which is important for engineering applications.

The Design, Analysis, and Optimization of a New Pitch Mechanism for Small Wind Turbines

This article proposes and designs a novel variable pitch adjustment device for small wind turbines. The generator spindle is designed to be hollow so that the drive rod passes through it and connects the pitch drive mechanism to the pitch actuator. The article introduces the basic structure and working principle of the pitch mechanism and verifies the feasibility of the pitch device by using 3D printing technology to produce a small-scale model. The stress analysis of the wind turbine was carried out using the unidirectional fluid–structure coupling method. The results show that the maximum equivalent stress of the pitch mechanism is 27.42 MPa, the maximum tooth surface contact stress of the gear is 38.40 MPa, and the maximum tooth root bending stress is 18.13 MPa. The rack synchronous disk, blade handle, and gear rack mechanism were designed with light weight using various optimization schemes. The results of the optimization showed that the overall mass of the pitch mechanism was reduced by 33.2%, improving the applicability of the new pitch mechanism.

Torsional Optical Fiber Stress Analysis and Vortex-Induced Vibration Study of Three-Core Submarine Cable

Due to current scouring, submarine cables are prone to be exposed, suspended, and even vortex-induced vibration, which is not conducive to the safe operation of the power grid. In this contribution, the finite element simulation model of a 35 kV three-core optical fiber composite submarine cable with a suspended span length of 9.5 m is established. The natural frequency of the model is obtained through modal analysis. Then the vortex-induced vibration is simulated by the fluid–structure coupling method, and the stress distribution and change law of the torsional optical fiber is extracted. The results show that in the submarine cable, there appears to be a beating vibration and locking phenomena respectively, under two flow velocities. The transverse vibration amplitude of the latter increases significantly due to a resonance state. When the flow direction is perpendicular to the submarine cable, the stress distribution of the torsional optical fiber at the initial moment and at the 1/2 T moment of a vibration cycle approximately represents a mirror image relationship. In addition, the frequency of the stress change is the same as the frequency of the vortex-induced vibration, which can judge whether the vortex-induced vibration occurs. Moreover, the vortex-induced vibration range can be determined by the maximum stress change location.

Finite Element Strength Analysis and Optimization of Cutting Tools Based on Fluid-Structure Interaction

In this paper, taking a cutting tool as an example and aiming at the problem of cutting tool stress and fatigue evaluation and optimization, a finite element model including the tool, shaft, and washer was established by using the methods of simulation and testing, and the stress and strain analysis of the tool in the working process was completed. A single fluid-structure coupling method was applied to calculate the dynamic load of the cutting tool in the process of high-speed food cutting, and ABAQUS was used to analyze the stress and strain under this load. Practical engineering applications showed that the method was practical and feasible, and the calculation results were consistent with the actual measurements. The established analytical model can accurately reflect the real working conditions of the tool, and the stress and fatigue of the key parts of the tool can be quantitatively assessed, providing a reference for the optimal design of the tool.

Computational method for added mass of single graphite brick in molten salt reactor

The fluid–structure interaction (FSI) that occurs in the graphite core submerged in molten salt has a great influence on the vibration of the core under seismic conditions in thorium molten salt reactor-liquid fuel (TMSR-LF1). The added mass method is an important way to study the phenomenon. In this paper, a bidirectional fluid–structure coupling method was established to calculate the added mass of the graphite brick, and the numerical simulation results were in good agreement with the experimental results. On this basis, the sensitivity analysis of added mass factors was carried out, such as the size of gaps between components, the geometric shapes of graphite bricks and the molten salt temperatures, etc. The results show that these factors influence the added mass in different degrees and the size of the gap is the most important factor affecting the added mass. The results can provide FSI parameters for structural dynamic analysis and offer the assistance for the design and manufacture of the graphite core.

Calculation and analysis of fluid-solid coupling of rocket sled supersonic water bucket braking process

In order to solve the problem of structural damage during the braking process of a rocket sled supersonic water bucket, which affects the braking effect, it is proposed to use the FEM fluid-solid coupling calculation technology to analyze the process of the water bucket entering the water brake. The fluid-solid coupling calculation results show that the limit braking state After the water bucket enters the water brake for 0.06ms, the stress at the entrance position exceeds the yield limit of the material, and the structure is severely deformed and damaged; under normal braking conditions, the water bucket enters the water brake for 0.4ms, the plate at the entrance of the bucket bends, and the structure is seriously deformed at 2ms, The structure is destroyed at 3ms. Using the penalty function fluid-structure coupling method, the numerical analysis of the model water bucket was carried out under two working conditions. Due to the unreasonable design of the bucket, the bucket entrance deformed and destroyed during braking. It is recommended to increase the structural strength of the water inlet side plate.

Stability Analysis of Wind Turbine Blades Based on Different Structural Models

In order to better simulate the actual working conditions of wind turbines more realistically, this paper adopts the two-way fluid–structure coupling method to study the NREL 5 MW wind turbine, considering the blade coupling deformation and equivalent stress and strain distribution of the blades with different internal structures under different working conditions. The results show that the maximum equivalent stress and strain distribution of the beam–structure wind turbine blade was near the leading edge of the blade. The maximum equivalent stress and strain distribution of the shell structure wind turbine blade was near the leading edge of the blade root, and the dangerous area is obvious but smaller than that of the beam-type wind turbine. The coupled deformation of a wind turbine model with a shell structure blade with a web is significantly reduced, and the equivalent stress and strain distribution of the skin is similar to that of the shell structure, but the numerical value and the maximum equivalent stress distribution area are significantly smaller. From the comparison of the three, the shell structure blade with a web is the best.