Coupled Fluid Structure Simulations Research Articles

Numerical simulation and in vitro experimental study of the hemodynamic performance of vena cava filters with helical forms

Inferior vena cava filter (IVCF) implantation is a common method of thrombus capture. By implanting a filter in the inferior vena cava (IVC), microemboli can be effectively blocked from entering the pulmonary circulation, thereby avoiding acute pulmonary embolism (PE). Inspired by the helical flow effect in the human arterial system, we propose a helical retrievable IVCF, which, due to the presence of a helical structure inducing a helical flow pattern of blood in the region near the IVCF, can effectively avoid the deposition of microemboli in the vicinity of the IVCF while promoting the cleavage of the captured thrombus clot. It also reduces the risk of IVCF dislodging and slipping in the vessel because its shape expands in the radial direction, allowing its distal end to fit closely to the IVC wall, and because its contact structure with the inner IVC wall is curved, increasing the contact area and reducing the risk of the vessel wall being punctured by the IVCF support structure. We used ANSYS 2023 software to conduct unidirectional fluid–structure coupling simulation of four different forms of IVCF, combined with microthrombus capture experiments in vitro, to explore the impact of these four forms of IVCF on blood flow patterns and to evaluate the risk of IVCF perforation and IVCF dislocation. It can be seen from the numerical simulation results that the helical structure does have the function of inducing blood flow to undergo helical flow dynamics, and the increase in wall shear stress (WSS) brought about by this function can improve the situation of thrombosis accumulation to a certain extent. Meanwhile, the placement of IVCF will change the flow state of blood flow and lead to the deformation of blood vessels. In in vitro experiments, we found that the density of the helical support rod is a key factor affecting the thrombus trapping efficiency, and in addition, the contact area between the IVCF and the vessel wall has a major influence on the risk of IVCF displacement.

Research on the spiral case and external concrete structural response under limit operation state

Abstract As the key component of hydroelectric generating units, the spiral case is primarily responsible to make the fluid flow out in a uniform and axisymmetric way. The structural response of the spiral case and external concrete under hydraulic pressure will have an effect on the operational security and power generation efficiency of the whole unit. In this paper, a three-dimensional fluid-structure coupling model of the spiral case and concrete under limit operation state is established. Based on the computational fluid mechanics theory, the flow domain inside the spiral case is simulated to study the stress and deformation structural response of the spiral case and external concrete under the action of maximum inner hydraulic pressure. The value and position of the maximum stress and deformation are determined. The fluid-structure coupling simulation shows that severe turbulence occurs in the middle of the flow channel. The maximum equivalent stress of the spiral case is located near its tongue and there would possibly be a risk of local structural damage. The external concrete can effectively share part of the load from the spiral case, so as to keep the strength and stiffness of the overall structure being within safe levels under the limit state. The results can provide support to the structural optimization and construction of the spiral case, which is helpful for the safety and stability of station operation.

Coupled fluid-structure simulation of a flapping wing using free multibody dynamics software

AbstractComputer simulations offer invaluable insights into fluid-structure interaction phenomena, increasing our understanding of complex behaviors within fluid flows and enabling predictions of consequential effects. This paper explores flapping wing simulation using an original toolchain based on free software. The structural domain is modeled using multibody dynamics, interfaced with arbitrary fluid dynamics solvers through a general-purpose multiphysics coupling library. The proposed toolchain is validated against benchmark models, demonstrating its effectiveness in various applications. Our study, inspired by experimental ones, applies this coupling to investigate the hydroelastic behavior of a flexible wing. Wing motion characteristics, structural properties, and convergence criteria are analyzed through numerical simulations. While achieving appreciable agreement with experimental data on wing motion ratios, challenges in dealing with large displacements have been identified. Nonetheless, the present study provides valuable insights into fluid-structure interactions, laying the groundwork for future refinements in computational modeling techniques and advancing the understanding of bio-inspired flight mechanisms.

The Tribological and Mechanical Properties of Polyimide/Polyamide Imide/Epoxy Resin, Polytetrafluoroethylene-ZrO2 Coating on an Engine Bearing

To improve the poor tribological performances of the copper alloy used in engine bearings under boundary lubrication and dry sliding wear, a new polymer coating consisting of polyimide/polyamide imide/epoxy resin (PI/PAI/EP), polytetrafluoroethylene (PTFE) and ZrO2 has been designed. The tribological and mechanical characteristics of the coatings at various thicknesses were studied by friction and wear experiments, nanoindentation experiments, simulation experiments of the stress and deformation and fluid-structure coupling simulation tests. The results showed that when the thickness of the coating was 20 μm, the deformation of the coating was the lowest and the friction coefficient of the coating was 0.167. As the thickness of the coating was increased, the support effect of the substrate on the coating decreased, and the thickness of the coating increased under positive pressure. Compared with the substrate, the friction coefficient of the coating under boundary oil lubrication conditions was reduced by 53.85%. The fluid-structure coupling calculation showed that the boundary lubrication and dry sliding wear of the copper alloy were improved by the designed coating. The fluid-structure coupling calculation showed that the peak variation rates of the coating bearing pressure was 0.02%. The coating on the surface of the bearing had little influence on the oil pressure, but at the same time, improved the tribological properties of the engine bearing.

Adult rhinoceros beetles use a sweeping pattern to ingest high-viscosity fluid

More than half of all insect species utilize various natural liquids as primary diet. The concentrated liquids with energy-dense nutrition can provide highly favorable rewards, however, their high-viscosity poses challenges to the insect for ingesting. Here we show that rhinoceros beetles, Trypoxylus dichotomus (Coleoptera: Scarabaeidae), are capable of ingesting sugar solutions with viscosities spanning four orders of magnitude, exhibiting extraordinary adaptability to diverse natural liquid sources. We discovered a previously unidentified maxillae-sweeping motion that beetles preferentially adopt to consume highly viscous liquids, achieving a higher feeding rate than the more common direct sucking. By utilizing morphological characterizations, flow visualization, and fluid–structure coupling simulation, we revealed the underlying mechanisms of how this maxillary movement facilitates the transportation of viscous liquid. Our findings not only shed light on the multi-functionality of beetle mouthparts but also provide insights into the adaptability of generalized mouthparts to a broad range of fluid sources.

Improving the performance of galloping energy harvester with striped bluff body

To improve the performance and efficiency of ordinary galloping energy harvesters (GEHs), this paper proposes a GEH with a striped bluff body. The fluid-structure coupling simulation of the bluff body and the oscillator of the energy harvester was carried out using COMSOL Multiphysics. The cloud diagram in the flow field, tip displacement at the tip of the beam, lifting and dragging force, and trace and frequency response of the harvester are analyzed. Simulation results show that the GEH with a striped bluff body has the characteristics of rising frequency and falling peak compared with the ordinary GEH, which can be locked at a fixed peak to form a stable periodic response. Experimental results show that the striped bluff body energy harvester displays better energy harvest performance. The output root mean square voltage can be increased by 119.2% at 2 m/s wind speed, which means that the galloping harvester with a striped bluff body has more stable dynamic characteristics and shows better energy harvest performance.

Injection of Viscous Micro-Droplet via Nozzle-Driven Piezoelectric Micro-Jet and Its Performance Control Method.

The inkjet printing technology based on piezoelectric micro-jets can effectively realize the efficient and high-precision processing of special-shaped structures. In this work, a nozzle-driven piezoelectric micro-jet device is proposed, and its structure and micro-jet process are described. ANSYS two-phase, two-way fluid-structure coupling simulation analysis is carried out, and the mechanism of the piezoelectric micro-jet is described in detail. The effects of voltage amplitude, input signal frequency, nozzle diameter and oil viscosity on the injection performance of the proposed device are studied, and a set of effective control methods is summarized. The correctness of the piezoelectric micro-jet mechanism and the feasibility of the proposed nozzle-driven piezoelectric micro-jet device are proved by experiments, and an injection performance test is carried out. The experimental results are consistent with the ANSYS simulation results, which confirms the correctness of the experiment. Finally, the stability and superiority of the proposed device are verified via comparation experiments.

Impact Response of the Tail Beam Jack Based on Bidirectional Fluid-Structure Coupling Simulation.

In top coal caving mining, the coal rock collapse will cause an irregular impact on the tail beam jack of the caving control mechanism. The severe impact will lead to jack failure. The bidirectional fluid-structure coupling model is built on Fluent and Mechanical software to study the impact response of the tail beam jack. The dynamic flow velocity streamlines, hydraulic pressure distribution, stress field, and strain field of the jack under impact load are extracted. The response characteristics of the jack in the stationary state and motion state are analyzed. The conclusions are as follows: the stress and strain of the rodless cavity are much larger than those of the rod cavity, which is more likely to be damaged. The hydraulic pressure in the jack cavity is in vertical layered distribution. The flow velocity streamlines present spiral shapes. The response degree of the hydraulic pressure signal in the rodless cavity is stronger than that in the rod cavity, and the response degree of the flow velocity signal in the rod cavity is stronger than that in the rodless cavity. The impact response of the jack in the motion state is more sensitive and stronger than that in the stationary state. The coal rock collapse situation can be most effectively identified only by comprehensively analyzing the rodless cavity's pressure signal and the rod cavity's velocity signal. This paper innovatively visualizes the flow velocity streamlines and pressure distribution together. The bidirectional fluid-structure coupling method is innovatively applied to the tail beam jack. The findings of this study can help for better understanding of the tail beam jack's structural design and failure prevention. This study provides a certain research basis for the intelligent coal rock identification technology in mining coal based on jack vibration signals.

Force analysis and fatigue life evaluation of oil well pump valve cover

In the beam pumping system, the broken valve cover of the oil well pump frequently leads to oil well failure. This paper examined the alternating load of the oil well pump valve cover and predicted its fatigue life. First, the fluid–structure coupling simulation model of valve ball motion was established through the fluid dynamics simulation software Fluent to investigate the velocity of the valve ball impacting the valve cover. Based on the simulation results about the impact velocity of the valve ball, the mechanical model of the valve ball impacting the valve cover was constructed through ANSYS/LS-DYNA software, and the impact stress and change rule of the valve cover were analyzed. Then, the S-N fatigue curve of the common material of the valve cover was experimentally obtained. Based on the impact stress simulation results of the valve cover and the fatigue curve of the common material of the valve cover, the modified Miner’s Rule was applied to evaluate the fatigue life of the oil well pump valve cover. The results showed that the impact stress of the valve cover was positively related to the impact velocity of the valve ball, and the fatigue life of the 17-4 PH valve cover was longer than that of other materials. The above results not only provide a theoretical basis for the performance improvement and material selection of the valve cover but also contribute to the optimization of production parameters of the oil well.

Coupled fluid-structure simulations and experiments of DBD plasma actuator for damping of plate vibrations

In the present work, an experimental and numerical study has been performed to evaluate the suitability of the dielectric barrier discharge plasma actuators to reduce free vibrations of plates. Two configurations composed of two different plexiglass plates and identical actuators were manufactured. Experimental campaigns, in terms of laser doppler anemometer velocity measurements, flow visualization and proper orthogonal decomposition were carried out to characterize the plasma actuator and to validate the numerical models. The plasma-induced virtual body force for the numerical analysis has been calibrated based on the experimental body force and the induced flow field. Then numerical studies of the plasma effect on the flow around an oscillating plate was performed. An experimental modal analysis has been also performed to understand the vibration characteristics of the plate and to support the numerical study. A reduced-order model of the system, based on the harmonic oscillator, was developed to properly design an open loop controller (system natural frequency, amplitude and timing of the attenuation force). Eventually, the work demonstrates that the control strategy based on the plasma actuation is effective in reducing the plate vibrations. However, a deeper study and a more sophisticated control strategy would be required to significantly mitigate the flutter oscillations of airfoils in real applications.

Study on Separation Characteristics of Nozzles with Large Expansion Ratio of Solid Rocket Motors

In order to study the flow characteristics of a nozzle with large expansion ratio and its influence on the force on the nozzle, ground cold flow test research and a fluid–structure coupling simulation analysis were carried out (maximum expansion ratio ε = 30.25). The variation and pulsation characteristics of the pressure near the measuring point area and the inlet pressure were obtained through experiments. Through the analysis of the peak-to-peak value and average value, it was found that the average pressure after separation increases by 90%, but the peak-to-peak value increases by about five times, indicating that the pressure fluctuation after separation is much larger than before separation. The separation flow field under cold flow conditions was simulated using the CFD commercial calculation software Fluent to verify the correctness of the numerical calculations. The fluid–structure coupling analysis was carried out on a large expansion ratio (maximum expansion ratio ε = 48) full-scale nozzle, and the structural deformation characteristics of the nozzle under the separation conditions were studied. The research results show that flow separation occurs in the nozzle with a large expansion ratio under ground conditions. Before the separation point, the pressure pulsation on the nozzle wall is small, and the turbulent pulsation effect is weak. After the separation point, the pressure pulsation increases, and the turbulent pulsation effect is enhanced. When the total pressure decreases, the separation area of the nozzle increases, and the separation flow field presents a strong asymmetry. Reducing the total inlet pressure by half resulted in approximately 50 times the lateral load. Under the combined influence of the ground conditions and low total pressure, the large lateral load caused by the asymmetry of the separation flow field will cause the deformation of the nozzle structure to increase by 5.5 times. This research provides an important reference for the design and experiment of nozzles with a large expansion ratio.

Numerical Study on a Cylinder Vibrator in the Hydrodynamics of a Wind–Wave Combined Power Generation System under Different Mass Ratios

A hydrodynamic wind–wave combined power generation system is a new type of energy device that uses wind and ocean current energy to generate electricity. In this paper, the hydrodynamics of a wind–wave combined power generation system was simulated in Fluent. The fluid–structure coupling simulation of the vortex vibration of the cylindrical oscillator was realized using UDF and dynamic mesh technology. The Vortex-Induced Vibration (VIV) characteristics of the cylindrical oscillator were analyzed, and the reliability of the numerical simulation method was verified by comparing the amplitude and trajectory of the eddy-excited vibration with the classic experiments of Jauvtis and Williamson. The VIV characteristics of cylindrical oscillators with different mass ratios were studied in terms of vibration response, motion trajectory, and the streamwise equilibrium position. The effect of the mass ratio on the hydrodynamics of a wind–wave combined power generation system was simulated using spring damping, achieving the goal of carrying out preliminary research work simulating the wind–wave combined power generation device. Some useful conclusions were obtained through calculation, which provided data support for the corresponding platform device. This study shows that in cylindrical oscillators with different mass ratios, the overall trend at the same reduced velocity is that the larger the mass ratio, the smaller the crossflow amplitude. The cylindrical oscillators with mass ratios of one and two appear in the upper branch, while cylindrical oscillators with mass ratios of three and four do not appear, and with the increase in the mass ratio, the frequency ratio in the lower branch tends toward one. At the same reduced velocity, the lower the mass ratio, the larger the corresponding downstream equilibrium position, and the higher the energy acquisition efficiency.

Influencing Factors of the Distribution Accuracy and the Optimal Parameters of a Pneumatic Fertilization Distributor in a Fertilizer Applicator

A pneumatic fertilization distributor used for fertilizing in a fertilizer applicator is a key component of the applicator. The parameters of a pneumatic fertilization distributor affect the uniformity and accuracy of the fertilization of a fertilizer applicator. To obtain the optimal design parameters of a pneumatic fertilization distributor, a fluidstructure coupling simulation test and a bench test were carried out in the Intelligent Agricultural Machinery Laboratory of the Nanjing Institute of Agricultural Mechanization from March 2021 to July 2022. The curvature–diameter ratios of the elbow, bellow length, and air velocity were selected as the experimental factors, and the variation coefficient of the fertilizer discharge at each discharge outlet within 0.5–3 s was selected as the experimental index. A five-level quadratic regression orthogonal rotation combined test was carried out. The results showed that: (1) all three factors had a significant impact on the uniformity of the fertilizer discharge. The reasonable ranges of the curvature–diameter ratio, bellow length, and air velocity were 0.5–1.5, 350–550 mm, and 25–35 m/s, respectively. (2) The order of the influence of the three factors on the uniformity of the fertilizer discharge in descending order was as follows: the curvature–diameter ratio of the elbow, the bellow length, and the air velocity. When the bellow length was 460 mm, the curvature–diameter ratio was 0.6, and the inlet air velocity was 28 m/s. The uniformity of the fertilizer discharge was optimal. A pneumatic conveying system was redesigned according to the optimal parameters, and a bench test was carried out. The results showed that at different speeds, the coefficient of variation of each row’s displacement was not greater than 5%, and the simulation test results were consistent with the bench test results.

Deformation monitoring of propeller underwater operation based on fiber optic grating sensing network

Deformation monitoring of the propeller can help understand its deformation under various operating conditions, provide guidance for the optimization and theoretical design of its structure, and realize the health monitoring of its structure. In this paper, a contact measurement method based on Fiber Bragg Grating Sensor (FBG) is used to monitor the underwater operation status of the propeller. Using the inverse finite element method, the strain information collected by FBG is converted into the deformation information of the propeller to achieve deformation monitoring during the propeller operation. Fluid-structure coupling simulation analysis of the propeller is performed on the platform of ANSYS Workbench under different operating conditions. By comparing the reconstructed and simulated displacements of propellers operating underwater with different velocity coefficients and different rotational speeds, it can be found that relative errors between the reconstructed and simulated displacements of the propeller are within 15%, proving that it is feasible to monitor the operating deformation of the underwater propeller based on the FBG sensing network.

Effect of spoiler columns on heat transfer performance of aluminum nitride-based microchannel heat sink

Microchannel heat sinks (MCHSs) are among the most effective solutions for high-power heating elements; aluminium nitride (AlN) is widely used in various heat sinks owing to its high thermal conductivity. The study aims to investigate the effect of the spoiler column shape, number of rows, and position of the inlet/outlet on the temperature and pressure drop of AlN-based microchannel heat sink using a thermal fluid structure coupling simulation. The results showed that the circular spoiler column had the best dredging effect on the eddy current, which greatly improved the local Nusselt number and heat transfer efficiency. The maximum temperature of the heat sink with circular spoiler columns was 6.53 K lower than that without the spoiler column. The average flow velocity and heat transfer efficiency increased with an increase in the number of spoiler columns and the convective heat transfer area. However, the flow resistance and pressure drop between the inlet and outlet raised. When the inlet and outlet were arranged at the centreline, the flow velocity distribution in the heat sink is more uniform, and the maximum temperature was 160.78 K lower than that on the upper side. Heat transfer experiments were carried out by using three kinds of AlN-based microchannel heat sinks, which was machined by the pickling-assisted laser method. The heat transfer experiments showed that the error between simulation results and test data was less than 0.1%.

Analysis of grasping deformation of textile fabric based on fluid structure coupling

The grasping transfer deformation of textile fabrics is the primary problem faced by textile production automation. During the automatic transfer process of textile fabrics, due to its own flexibility, large deformations are brought about, which leads to the problem of overlapping folds before the fabric is formed. In this paper, the end gripper composed of non-contact Bernoulli suction cups is used to adsorb and transfer the textile fabric, and the fluid structure coupling analysis method is used to calculate the adsorption force under different inlet pressures by using the macroscopic continuous model of the end effector adsorbing the fabric. The fluid structure coupling adsorption model is established, and the effects of the number and layout of suction cups and different inlet pressure on the deformation of flexible fabric during clamping are analyzed and studied. The deformation effect of the end effector in the process of transferring fabric is verified by simulation and visual experiment. The results show that the optimal working parameters of the end effector obtained by fluid structure coupling simulation are consistent with the test. When the end effector adopts five suction cups and the air inlet pressure is 0.3 MPa, the deformation is the smallest. This study provides a new method to solve the problem of automatic grasping and transfer of textile fabrics, and provides technical support for improving the automation level of garment industry.

Numerical study on stress in a solid wall caused by the collapse of a cavitation bubble cloud in hydraulic fluid

The stress in a solid due to the collapse of a bubble cloud in hydraulic fluid is investigated by the numerical simulation, which considers the fluid-structure coupling and employs the bubbly flow model with Euler-Lagrange method. The dynamics of the bubble at the subgrid scale is described by the Keller-Miksis equation. Heat transfer at the bubble interface is considered to reproduce thermal damping effect. As the result of the fluid-structure coupling simulation, the high von Mises stress region is observed in the solid due to the collapse of the bubble cloud attached on the solid surface, and the propagation of longitudinal and transverse waves in the solid is reproduced. As the standoff distance YC from the solid surface to the center of the bubble cloud decreases, the peak von Mises stress in the solid increases, taking a maximum at YC=0.4RC, and then decreases. Thus, the peak von Mises stress is highest under the condition that the bottom quarter of the bubble cloud is on the wall. Due to the increase of the initial void fraction and the decrease of the initial bubble radius in the bubble cloud, the collapse pressure of the bubble cloud increases. Under certain conditions, the peak von Mises stress can be higher than the 0.2% yield stress value of 250MPa for a cast iron. This is expected to induce cavitation erosion of the solid surface.

Numerical Analysis of Dynamic Characteristics of Thermowell Based on Two-Way Thermo-Fluid-Solid Coupling

Because thermowells are prone to fatigue damage in petroleum cracking gas pipelines, in this paper, the LES method is used to simulate the flow around thermowells through two-way thermal-fluid-solid coupling, the internal causes of thermowell damage are explored, and measures for improving the thermowell safety are proposed. According to this study, when high-speed, high-temperature gas passes the thermocouple bushing, the main factors affecting the structural safety of the thermocouple bushing are the alternating stress caused by the vortex falling off, the thermal stress cycle due to the temperature gradient, and the pressure gradient impacted by the gas. Furthermore, this paper proposes improving the thermowell safety by installing the interference devices and optimizing the installation angle. The improvement measures were studied by conducting a two-way thermal fluid-structure coupling simulation. The results of this study show that after installing the interference device and optimizing the installation angle the displacement deformation of the thermowell and the equivalent stress is reduced by 57.2% and 72.1%, respectively, which indicates the safety improvement of the thermowell structure and the effectiveness of the method. The research contents of this paper can provide guidance for the installation and use of thermocouple bushing.

Numerical analysis of geometrical nonlinear aeroelasticity with CFD/CSD method

Abstract A nonlinear static aeroelastic methodology based on the coupled CFD/CSD approach has been developed to study the geometrical nonlinear aeroelastic behaviors of high-aspect-ratio or multi-material flexible aerial vehicles under aerodynamic loads. The Reynolds-averaged Navier–Stokes solver combined with the three-dimensional finite-element nonlinear solver is used to perform the fluid-structure coupling simulation. The interpolation technique for data transfer between the aerodynamic and structural modules employs radial basis function algorithm as well as dynamic mesh deformation. A high-aspect-ratio structure with multi-material is modeled by the finite element method to investigate the effects of geometrical nonlinearity on the aeroelastic behavior. Numerical simulations of the linear and nonlinear static aeroelasticity were conducted at transonic regime with different angles of attack. By comparing the aeroelastic behaviors of linear and nonlinear structure, it shows that geometrical nonlinearity plays an important role for flexible high-aspect-ratio wings undergoing the large static aeroelastic deformation and should be taken into account in aeroelastic analysis for such structures.

Study on the effect of fluid-structure coupling on the outlet Piping of reciprocating compressor

The fluid-structure coupling has been one of the hot issues of academic research in recent years, the achievements in various fields of study also emerge in an endless stream, but on the current research status, The study of fluid structure interaction in the field of moving equipment, especially compressor, is not very common, With the development of industrial compressor, it is developing towards the direction of large scale and high parameter, Coupling analysis of fluid structure interaction can be used to evaluate the safety and stability of the system, and the evaluations are more close to the actual situation. Therefore, it has gradually been valued. Through the comparison and analysis of the vibration test system of the reciprocating compressor before and after the pipeline inflation, the vibration response caused by the coupling factor is obtained, for the correctness verification of the fluid-structure coupling simulation. the numerical model of the experimental system is established based on ANSYS, and the boundary conditions of the model are simulated by the experimental data, verified the feasibility of simulation program. the experimental and simulation results show that the fluid solid coupling characteristics are not obvious in the vicinity of the reciprocating compressor, and the effect is significant at the top of the buffer tank and the installation position of the orifice plate.