Fluid-solid Coupling Simulation Research Articles

Stress analysis of different air inlet modes for underwater compressed air energy storage considering fluid influence

Abstract Underwater compressed air energy storage has broad application prospects in the fields of marine energy development, deep-sea exploration, and energy storage away from land. The gas storage device is the core component of its energy storage, and there are two intake modes between the current gas storage device and the pipeline, the upper intake mode and the lower intake mode. There are differences in the stability of the airbag between the two modes, which affects the reliability and stability of the whole system. Therefore, it is necessary to analyze the stress of different intake modes of the gas storage device. Firstly, this paper gives the principle and structure of underwater compressed air energy storage and then establishes the model of the airbag and the corresponding parameters. Based on the finite element fluid simulation analysis system, the dynamic mesh fluid-solid coupling simulation is carried out. By comparing and analyzing the deformation of the two modes due to the impact of water flow in the flow field and the distribution of the equivalent stress at the connection between the main body of the airbag and the pipeline, it is concluded that the stress of the gas storage device in the lower air inlet mode is less than that in the upper air inlet mode, and then it is verified that its safety is better than that of the upper air inlet mode.

Research on UAV Downwash Airflow and Wind-Induced Response Characteristics of Rapeseed Seedling Stage Based on Computational Fluid Dynamics Simulation

Multi-rotor unmanned aerial vehicles (UAVs) are increasingly prevalent due to technological advancements. During rapeseed’s seedling stage, UAV-generated airflow, known as wind-induced response, affects leaf movement, tied to airflow speed and distribution. Understanding wind-induced response aids early rapeseed lodging prediction. Determining airflow distribution at various UAV heights is crucial for wind-induced response study, yet lacks theoretical guidance. In this study, Computational Fluid Dynamics (CFD) was employed to analyze airflow distribution at different UAV heights. Fluid–solid coupling simulation assessed 3D rapeseed model motion and surface pressure distribution in UAV downwash airflow. Validation occurred via wind speed experiments. Optimal uniform airflow distribution was observed at 2 m UAV height, with a wind speed variation coefficient of 0.258. The simulation showed greater vertical than horizontal leaf displacement, with elastic modulus inversely affecting displacement and leaf area directly. Discrepancies within 10.5% in the 0.5–0.8 m height range above the rapeseed canopy validated simulation accuracy. This study guides UAV height selection, leaf point determination, and wind-induced response parameter identification for rapeseed seedling stage wind-induced response research.

3D Printer Nozzle Structure Form Optimal Structural Analysis

The most representative technology of 3D printing is fused deposition modeling (FDM). To improve the printing accuracy of FDM technology, this paper first takes the outlet diameter, angle of convergence, and rectifier section length of the nozzle as the influencing factors. It takes the melt outlet speed stability, viscosity, and outlet pressure as the indexes to design the orthogonal test. Then, COMSOL Multiphysics fluid–solid coupling simulation was used to simulate and analyze the structural characteristics of the 3D printer nozzle, and the range analysis method was used to analyze the data. Finally, the two-phase flow combination was used to simulate the morphological characteristics of the melt flowing out of the nozzle. The results show that the simulation results of the two materials are similar. As the nozzle diameter decreases, the melt pressure decreases, the velocity increases, and the viscosity decreases. For PLA wire rods, the optimal structure of the nozzle is that the outlet diameter is 0.2 mm, the rectifier section length is 1.5 mm, and the angle of convergence is 60°. For ABS wire, the optimum structure of the nozzle is that the outlet diameter is 0.2 mm, the rectifier section length is 1.5 mm, and the angle of convergence is 30°. The nozzle outlet diameter is inversely proportional to the printing accuracy for ABS and PLA materials. The research results provide a theoretical reference for optimizing the nozzle structure for 3D printing.

Nonlinear Dynamic Mechanical Characteristics of Air Springs Based on a Fluid–Solid Coupling Simulation Method

The use of air springs has become widespread in various industries due to their exceptional superelastic properties; however, their strong nonlinear characteristics have become a hindrance to numerical simulations of air springs and have garnered increasing attention. This paper examined the nonlinear dynamic mechanical characteristics of air springs from a fluid–structure interaction perspective and verified the accuracy of the simulation analysis model through quasistatic tension and compression experiments. The average relative errors for air spring load and gas pressure were found to be 8.1% and 7.7%, respectively, which supports the validity of the model. The impact of frequency and amplitude excitations on the axial load characteristics of air springs was investigated through tension and torsion testing. The results showed that increasing the excitation frequency improves the stability of the axial load, while increasing the excitation amplitude enhances the axial load value. The change in axial compression was found to be more significant than that in axial tension, as it was affected not only by the axial load but also by the radial load, which is a key factor affecting the dynamic characteristics of air springs. A radial load analysis model was established to study the influence of frequency and amplitude excitations on the axial load characteristics of air springs. The simulation results indicated that under different amplitudes, the radial load of air springs goes through four stages: a steady period, rising period, steady period, and falling period. Additionally, under the same amplitude, the radial load value increases with an increase in frequency. This research on the dynamic load characteristics of air springs under amplitude and frequency excitations is important for their application in low-frequency and low-amplitude vibration environments, and its findings can be utilized to improve the technical parameters of air springs for suspension damping.

Research on the comparison of impact resistance characteristics between energy absorption and conventional hydraulic columns in fluid–solid coupling

Rock burst disaster affects underground mining safety. The energy-absorbing hydraulic support for preventing tunnel impact has been implemented in rock burst mines. In order to compare the impact resistance characteristics of conventional columns and energy-absorbing columns, based on the derivation of energy theory, the CEL fluid–solid coupling simulation algorithm is used to simulate the process of static load 1000 kN superimposed impact load 1500 kN on φ180 mm type conventional column and energy-absorbing column. Combined with the static-dynamic combined test of the 6500 kN impact testing machine on the column, the accuracy and reliability of the CEL simulation column impact response are verified. The results showed that compared with conventional columns, the reaction force of energy-absorbing columns is reduced by 32.55%. The stress and expansion of the cylinder are significantly reduced. The acceleration of the mass movement has been reduced by 59.46%. The addition of the energy-absorbing device enhances the system's energy absorption by 33.46%, thereby reducing the energy absorption of the column itself to 23.58%. Additionally, the deformation of the energy-absorbing device increases the effective displacement by 239.45%. This also prolongs the impact duration, ensuring sufficient time for the safety valve to open, safeguarding the support from damage, and enhancing the overall integrity of the tunnel.

Precise determination of reaction conditions for accurate quantification in digital PCR by real-time fluorescence monitoring within microwells

Real-time digital polymerase chain reaction (qdPCR) provides enhanced precision in the field of molecular diagnostics by integrating absolute quantification with process information. However, the optimal reaction conditions are traditionally determined through multiple iterative of experiments. Therefore, we proposed a novel approach to precisely determine the optimal reaction conditions for qdPCR using a standard process, employing real-time fluorescence monitoring within microwells. The temperature-sensitive fluorophore intensity presented the real temperature of each microwell. This enabled us to determine the optimal denaturation and annealing time for qdPCR based on the corresponding critical temperatures derived from the melting curves and amplification efficiency, respectively. To confirm this method, we developed an ultrathin laminated chip (UTL chip) and chose a target that need to be absolutely quantitative. The UTL chip was designed using a fluid‒solid‒thermal coupling simulation model and exhibited a faster thermal response than a commercial dPCR chip. By leveraging our precise determination of reaction conditions and utilizing the UTL chip, 40 cycles of amplification were achieved within 18 min. This was accomplished by precisely controlling the denaturation temperature at 2 s and the annealing temperature at 10 s. Furthermore, the absolutely quantitative of DNA showed good correlation (R2 > 0.999) with the concentration gradient detection using the optimal reaction conditions with the UTL chip for qdPCR. Our proposed method can significantly improve the accuracy and efficiency of determining qdPCR conditions, which holds great promise for application in molecular diagnostics.

Impact of the Motor Length‐to‐Diameter Ratio on the Selection of Cooling Water Channels for the Permanent Magnet Synchronous Motor

Aiming at the problem of difficulties in heat dissipation for a permanent magnet synchronous motor (PMSM) with high power/torque density, the effect of motor length‐to‐diameter ratio (r0) on the selection of cooling water channels is investigated from the perspective of the geometric parameters of the PMSM in this paper. First, the 3‐D fluid–solid coupled heat transfer models of three actual motors with the length‐to‐diameter ratios of 0.27, 0.81 and 2.04 are established. Every model is calculated under spiral, axial and circumferential cooling water channels, respectively. The cooling effect, cooling energy loss and motor thermal balance are compared and analyzed. Then the optimal cooling water channel for each of three motors is confirmed. Further, the motor temperature rise and fluid differential pressure are plotted. The threshold of motor length‐to‐diameter ratios is determined at which the overall performance of the axial and circumferential cooling water channel is highly similar. The general conclusions of selection of cooling water channels for PMSMs with different geometry shape are summarized. Finally, a prototype with r0 = 0.27 is fabricated and tested, verifying the validity of the fluid–solid coupling simulation analysis. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Evolution mechanism of tunnel water and sand inrush considering water-rich sandy dolomite hazard-causing structures

Water-rich sandy dolomite stratum is prone to water and sand inrush disasters during tunnel construction. It is of great significance to explore its hazard-causing structure and water inrush mechanism for disaster control. The physical and mechanical properties of dolomite samples are tested to reveal the difference between unsanded dolomite and sandy dolomite. Based on the advanced geological prediction and geological sketching, three types of water and sand inrush hazard-causing structures are identified. Furthermore, three types of water and sand inrush mechanisms under different hazard-causing structures are explored by using fluid–solid coupling model test. One is the progressive failure type of water and sand inrush caused by crack coalescence for the broken unsanded dolomite outburst prevention structure, another is the failure type in which the seepage failure of sandy dolomite strips promotes the crack coalescence of unsanded dolomite, and the other is seepage failure type for the overall sandy dolomite outburst prevention structure. Finally, fluid–solid coupling simulation is used to discuss the failure characteristics of outburst prevention structure with different factors. The results show that the critical sandy dolomite area ratio of the three types is 25 % and 75 %. The factors affecting the inrush disaster are ranked as follows: sandy dolomite area ratio > unsanded dolomite fragmentation degree > buried depth > water storage structure pore pressure > water storage structure size. The findings provide valuable reference for disaster control in water-rich sandy dolomite area.

Performance analysis of compact thermoelectric generation device for harvesting waste heat

In order to save energy and to effectively utilize the waste heat from diesel engines, a compact thermoelectric power generation (TEG) device with two heat collectors and three water coolers was designed. A three-dimensional steady-state fluid–solid coupling simulation was carried out for the structure formed by the heat collector-thermoelectric modules (TEMs)-water coolers of the device. The heat transfer characteristics, temperature and flow fields of the heat collector-TEMs-water coolers were analyzed. The output voltage and power of the device were experimentally investigated on a TEG test bench. The results show that the average temperature difference on both sides of each layer of TEMs ranges from 43 to 48 K. The temperature differences in the upper TEMs are slightly greater than those in the lower TEMs. There is small difference among the heat transfer coefficients of each TEM module with an average of about 82.6 W/(m2·K). The device generates the maximum output power of 15.8 W with a 560 K inlet air temperature and a hot air volume flow of 171 L/min. It is shown that more studies are required to perform cooperative the optimization of multiphysics simulation and comprehensive evaluation of heat transfer and power generation performance.

Performance analysis on the liquid cooling plate with the new Tesla valve capillary channel based on the fluid solid coupling simulation

Liquid cold plates are extensively utilized for heat dissipation in new energy vehicle fuel cell stacks. However, practical applications have revealed issues such as uneven heating and significant pressure loss in the heat dissipation channel. To address these concerns, this study introduces the design of a forward Tesla valve capillary heat dissipation channel and a reverse Tesla valve capillary heat dissipation channel, aimed at mitigating the eddy current issue at bends inside the capillary bionic flow channel. Under the same working conditions, the performance indicators such as the pressure distribution of the original, forward and reverse heat dissipation channel of liquid cold plates were obtained respectively. The results show that the forward cooling channel significantly reduced the pressure loss of the liquid cooling plate whilst the reverse channel effectively improved the heat transfer. Aiming at the problem of excessive pressure difference encountered in the reverse Tesla valve capillary channel, different numbers of valves and branches were designed on the reverse Tesla valve capillary cooling channel. It was found that a higher cooling capacity can be obtained with less pumping power when the aspect ratio between the number of valves and the number of branches of the reverse Tesla valve capillary liquid cooling plate was controlled in the range from 1.13 to 1.6.

Fluid-solid coupling simulation study on fuel leakage and deformation characteristics of precision coupling component in common rail injector and influence of pressure equalizing structure

In the foreseeable future, the use of fossil energy is still irreplaceable, makes efficient use of fossil energy and reduce emissions became important topics. Diesel engines have a very high share in the transportation field, and high-pressure common rail system has highly improved the performance of diesel engines. As the most important component of common rail system, the performance of common rail injector directly affects the engine. Precision coupling components are composed of moving parts with very precise clearance fit in the injector. With the wear of parts, fuel leakage of precision coupling components may reach the same level as injection quantity, which will seriously affect the injection pressure actually established, and then affect the power, efficiency, and emission performance of diesel engine. Many researchers have studied fuel leakage of precision coupling components, and put forward different methods to reduce fuel leakage, including improving the machining accuracy and machining annular grooves on parts. However, the wear of parts makes it a high-cost and low-effective method to improve machining accuracy. Besides, researchers have not fully considered the deformation of parts. In this work, fluid-solid coupling simulations were performed to analyze deformation and static fuel leakage characteristics, and to investigate effects of pressure equalizing structure on deformation and leakage of precision coupling component in common-rail injector. Different from the previous researches, the influence of machining the annular groove on the plunger sleeve instead of on the plunger, and influence of coexistence of annular groove and deformation were considered. The results show the deformation characteristics of the parts, the fuel flow characteristics in the gap, and the influence of the annular groove on the fuel leakage. The connection between the deformation of parts and fuel leakage, and potential methods to reduce the leakage are also discussed.

Numerical Simulation of Dynamic Fluid-Solid Coupling of Saturated Soil

Numerical Simulation of Dynamic Fluid-Solid Coupling of Saturated Soil

A Thermal Fluid–Solid Coupling Simulation of Gas Fuel Control Valves for High-Precision Gas Turbines

Gas fuel control valves play important roles in the control of gas flow in high-precision gas turbines. To clarify the influence of coupling between the structure and the fluid system, a thermal fluid–solid coupling mechanism is presented based on numerical investigations carried out using a dynamic mesh technique. Valve core deformation can affect the outlet gas flow accuracy. At 2% valve opening, the gas temperature contributes 93% to the deformation. The effect of deformation on the flow accuracy at 6% valve opening and 4% valve opening is increased by 4.8% and 7.3%, respectively. The fluctuation range of the gas temperature and pressure in front of the valve should be strictly controlled to ensure the high precision and high stability of the outlet flow. These results help to clarify the processes that occur in the valve flow path, leading to the flow control instability observed in the control valve.

Numerical analysis of initial cloud of powder dynamic dispersion

Numerical simulations were performed to investigate the explosion dispersion characteristics of powder materials with respect to the implicated velocity, and a fluid–solid coupling simulation model of the explosion dispersion process of the initial cloud was established. Explicit dynamics models of Finite-element method and smooth particle hydrodynamics for the detonation driving stage of central charge and the cloud isentropic expansion stages were developed, the pressure loads of the explosive-driven were generated using the user-defined function program, and computational fluid dynamics models for the isentropic expansion and free expansion stages of the initial cloud were developed. Additionally, the maximum expansion radius of the cloud in explosion dispersion tests and theoretical calculations were compared with the radius in the numerical simulation results to verify the accuracy of the simulation model. Analyses of the morphology, concentration, and turbulence field in the numerical simulation revealed that vortex stratification occurred in the “two wings” of the initial cloud in its development process and that a particle-free “hollow” area is subsequently formed. Analyses also revealed that the vortex stratification occurs earlier as the implicated velocity of powder material increases. Additionally, an increase in the implicated velocity can effectively weaken the concentration of cloud and make the distribution of cloud particles more uniform.

Study on the temperature distribution of motor and inverter in an electric scroll compressor for vehicle air conditioning under refrigeration conditions

In the electric scroll compressor for vehicle air conditioning, the heat generated by motor and inverter is mainly taken away by suction gas. It is necessary to maintain the working temperature of motor and inverter within a safe range to void overheat or burnout. The temperature distribution of motor and inverter under refrigeration conditions are studied using computational fluid dynamics (CFD) simulation in this paper. At first, a CFD fluid-solid coupling simulation model is developed and verified by temperature measurement experiment. The maximum deviation between the simulated temperature at three points on the compressor housing and the measured results does not exceed ±3°C. Then the velocity and pressure distribution of fluid domain, and the temperature distribution of solid domains including the compressor housing, the stator coils and insulated gate bipolar transistor (IGBT) modules are analyzed. Next, the effects of operation conditions on the maximum working temperature and temperature distribution unevenness of stator coils and IGBT modules are discussed in detail. In addition, the working reliability of IGBT modules under refrigeration conditions is checked and the heat dissipation of IGBT modules is analyzed.

Structure improvement and parameter optimization of micro flow control valve

Aiming at the sticking phenomenon between the valve core and the valve sleeve when the valve core moves, and to solve the problem that the torque required to drive the valve core to rotate is large, the fluid–solid coupling simulation analysis of the valve core is carried out in this study, and then the valve core structure of the valve core is improved and its parameters are optimized based on the bird colony algorithm. The combination structure of the valve sleeve and valve core is studied, and the fluid–solid coupling model is established by Ansys WorkBench, and the static structure simulation analysis of valve sleeve and valve core before and after structural improvement and parameter optimization is performed. The mathematical models of triangular buffer tank, U-shaped buffer tank and combined buffer tank are established, and the structural parameters of the combined buffer tank are optimized by bird swarm optimization. The results demonstrate the triangular buffer tank has good depressurization effect but great impact, the pressure of the U-shaped buffer tank is stable and gentle but the depressurization effect is not ideal, while the combined buffer tank has obvious depressurization effect and good stability. At the same time, the optimal structural parameters of the combined buffer tank are cut-in angle of 72, plane angle of 60 and depth of 1.65 mm. The excellent structure and parameters of the combined buffer groove are obtained, so that the pressure buffer of the regulating valve at the key position of the valve port achieves the best effect, and an effective solution is provided for solving the sticking problem of the valve core of the regulating valve when working.

Evaluation of mechanical properties and biocompatibility of three-layer PCL/PLLA small-diameter vascular graft with pore diameter gradient

A three-layer small-diameter vascular graft (SDVG) of polycaprolactone (PCL) and l-polylactic acid (PLLA) with pore diameter gradient was prepared through combining variable-extrusion speed iterative electrospinning and ultrasonic reaming. The SEM results showed that the three-layer PCL/PLLA SDVG has distinct pore diameter gradient. The Young’s modulus, ultimate tensile strength (UTS), burst pressure (BP) and compliance of the vascular graft were high as 20.116 ± 0.465 MPa, 2.259 ± 0.141 MPa, 2050 ± 249 mmHg and 4.203 ± 0.330 %/100 mmHg, respectively. The UTS of the graft is similar to human coronary arteries. The BP meets the basic requirements to prevent aneurysmal dilation, and the compliance is higher than that of sheep carotid artery. The fluid–solid coupling simulation results showed that the graft had high mechanical properties to withstand the same blood flow velocity as human coronary arteries, and there was no stress concentration in the wall. Besides, it had good biocompatibility, promoting the adhesion and proliferation of rat vascular endothelial cells (ECs). The successful preparation of the small-diameter vascular graft with high mechanical properties for preventing itself from rupturing and ensuring the overall function, provides more possibilities for the clinical transplantation of small-diameter vascular grafts.

Airflow ejection-wrapped clamping type seedling picking method and parameter optimization.

Since the current clamp-type and push-out-type seedling picking method brought damage to seedlings, this study aimed to proposed an airflow ejection-wrapped clamping type seedling picking method, which used airflow to eject out seedling and the seedlings were wrapped clamped to reduce the damage of seedlings during seedling picking process. The parameter model was established through theoretical design, then the parameters were optimized through coupling simulation analysis, and the validity of these parameters was verified through experiments. We found that the diameter of the airflow nozzle was selected as 3.5mm to match with the drainage outlet of the plug tray, and the airflow pressure which could eject out seedlings was calculated as 0.146 Mpa~0.315 Mpa on the basis of gas jet dynamic. The fluid-solid coupling simulation of airflow ejection in Comsol proposed that the seedlings could be ejected out under the airflow pressure was equal to or greater than 0.4 Mpa, and the airflow should be maintained for about 0.3 s to ensure the posture of the seedlings ejected out for better seedling clamping. The further fluid-discrete body simulation of airflow ejection by using Fluent-Edem coupling method indicated that the seedling was damaged under airflow pressure of 0.5 MPa, so the airflow pressure should be set as 0.4 MPa during seedling ejection process. Besides, a wrapped clamping type effector which clamped the seedlings from all sides in the form of flexible package was also designed to match with the airflow ejection method, and the RecurDyn-Edem coupling simulation showed that the end-effector could tightly clamp the seedling without damage when the angle between the clamping slices and the vertical direction was 8.5°. Finally, the airflow ejection-wrapped clamping type seedling picking device was manufactured, and the verification tests verified the simulation results. This research can provide some references for the automatic seedling picking technology.

Simulation Analysis of Torsion Beam Hydroforming Based on the Fluid-Solid Coupling Method

Hydroformed parts are widely used in industrial automotive parts because of their higher stiffness and fatigue strength and reduced weight relative to their corresponding cast and welded parts. This paper reports a hydraulic-forming experimental platform for rectangular tube fittings that was constructed to conduct an experiment on the hydraulic forming of rectangular tube fittings. A finite element model was established on the basis of the fluid–solid coupling method and simulation analysis. The correctness of the simulation analysis and the feasibility of the fluid–solid coupling method for hydraulic forming simulation analysis were verified by comparing the experimental results with the simulation results. On the basis of the simulation analysis of the hydraulic process of the torsion beam using the fluid–solid coupling method, a sliding mold suitable for the hydroforming of torsion beams was designed for its structural characteristics. The effects of fluid characteristics, shaping pressure, axial feed rate, and friction coefficient on the wall thicknesses of torsions beams during formation were investigated. Fluid movement speed was related to tube deformation. Shaping pressure had a significant effect on rounded corners and straight edges. The axial feed speed was increased, and the uneven distribution of wall thicknesses was effectively improved. Although the friction coefficient had a nonsignificant effect on the wall thickness of the ladder-shaped region, it had a significant influence on a large deformation of wall thickness in the V-shaped area. In this paper, a method of fluid-solid coupling simulation analysis and sliding die is proposed to study the high pressure forming law in torsion beam.

Surface texture and heat treatment on the friction performance of cam tappet experimental and fluid-solid coupling numerical study

In order to improve tribological properties of tappets made of GCr15 bearing steel, a combination of martensitic heat treatment and surface texture was applied to the GCr15 bearing steel. The texture was designed based on a fluid-solid coupling simulation performed using COMSOl, and effectiveness of the designed texture was verified by performed wear tests using a pin-disk line contact rotary motion tester under oil lubrication condition. The worn surface morphology and wear mechanism for the friction pair were analyzed with three-dimensional scanning microscopy and scanning electron microscopy to reveal the antifriction behavior and wear resistance. Results of the study show that the heat treatment increased the surface hardness and significantly reduced wear of the GCr15 bearing steel. The designed surface texture helped reduce the contact area, store tiny wear debris, and increase the oil film pressure, thus improving the tribological performance. However, the texture edge was prone to severe plastic deformation due to the stress concentration and lowered lattice confinement. The martensitic heat treatment involving tempering effectively reduced plastic flow at the edge of texture. The combination of texture and the martensitic heat treatment considerably improved the tribological properties of GCr15 steel.