Numerical Simulation Method Research Articles

Omnidirectional Bending Sensor with Bianisotropic Structure for Wearable Electronics.

Bending sensors are critical to the advancement of wearable electronics and can be applied in the dynamic monitoring of flexible object morphology. However, current bending sensors are constrained by sensing range and precision, especially in full-range detection. The maximum sensing range of existing flexible bending sensors is 0-240°. This study introduces a bianisotropic responsive structure into the design of an all-textile bending sensor, thereby realizing 0-360° full-range omnidirectional bending sensing. First, the project elucidated the sensing mechanism of the piezoresistive bianisotropic structured bending sensor and identified critical factors through a numerical simulation method. Then, the bianisotropic structured bending sensors were produced through the stitch method and analyzed on their electromechanical performance. Further, the recognition model for both bending angle and direction parameters was developed via numerical calculation, achieving a high accuracy with an error rate of 2.82%. Last, according to the ergonomics of body joints, the sensors were customized and validated in body joint monitoring scenarios. This work significantly enhances the performance of flexible bending sensors in sensing range, accuracy, and comfort for the wearer. The versatility of this bending sensor positions it as a promising candidate to supplant traditional heavy equipment or rigid devices, particularly in wearable joint motion monitoring and soft robotics.

Numerical simulation study of enhanced heat transfer and flow resistance characteristics of twisted tape and twisted elliptical tube composite

ABSTRACT In this paper, the numerical simulation method is used to explore the effect of wall twisting and twisted tape composite to enhance heat transfer in tubes. Comparative analysis of the flow characteristics of fluids in tubes with different Reynolds numbers between 10,000 and 20,000, and with different length/short axis ratios and twist ratios. The results showed that when the length/short axis ratio of twisted elliptical tubes is increased from 1.30 to 2.15, the Nusselt number of twisted elliptical tubes with inserted twisted tapes increases by 10.5–28.6% and the friction coefficient increases by 101.5–128.8% compared with that of smooth elliptical tubes. When the twist ratio is reduced from 2/3 to 1/6, the Nusselt number of the twisted elliptical tube with inserted twisted tape increases by 9.8–37.7%, and the friction coefficient increases by 101.9–164.7%. Increasing the length/short axis ratio and decreasing twist ratio can help to improve the heat transfer performance of the twisted elliptical tube, but all of them are at the expense of increasing the resistance to flow of the fluid inside the tube.

Analysis and control of the causes of the uplift of the invert of deep tunnels

When traversing a complex and fractured geological formation, a deep-buried highway tunnel in Yunnan Province encountered a significant uplift problem in the invert. The causes of the tunnel’s uplifted section were analyzed through on-site observations and monitoring of the lining structure’s deformation, combined with numerical simulation methods. The results indicate that the primary factors leading to the invert uplift are the softening of the surrounding rock at the invert base due to water seepage and the high water pressure in the fractured zone. The softening of the surrounding rock is crucial to the safety of the inverted uplift structure. Based on the tunnel’s engineering characteristics and the causes of the invert uplift, remediation measures such as “enhancing the drainage system, grouting with steel flower pipes, and demolishing and replacing the invert” were adopted. These measures effectively controlled the invert uplift. After the remediation, the convergence rate of the secondary lining decreased, and the deformation stabilized, indicating that the invert uplift remediation plan was reasonable and effective

Comprehensive Analysis of Feasibility by Ascending Mining in Coal Mine

In order to study the feasibility of upward mining in a certain coal mine, the mechanical parameters of the coal rock mass were obtained based on on-site investigation and rock mechanics experiments. A numerical model that conforms to the on-site mining layout was established using numerical simulation methods. The stress, displacement, and plastic zone distribution characteristics of the upper coal rock mass at different positions along the X, Y and Z directions after the initial mining of layered coal were analyzed. The critical thickness for tensile failure of the roof during upward mining was calculated using the thick plate theory. A ground penetrating radar was used on site to conduct three-dimensional detection of the fragmentation characteristics of the overlying roof rock. The results show that after the mining of 5# coal, the stress of the overlying roof surrounding rock in the goaf exhibits a dynamic change process of rising peak falling. As the vertical height from the working face increases, the stress in the center of the goaf and around the working face gradually decreases; the displacement distribution extends outwards from the center of the working face, forming a sinking basin with an upward opening in the direction of inclination and direction of the working face. The maximum displacement value is at the bottom of the basin; there is a tensile stress zone above the working face, and the plastic zone has the largest range at the center of the working face direction and inclination. The plastic zone has not evolved to coal 4# and coal 3#; the maximum critical thickness for tensile failure of the roof is 55.4 m, which is much smaller than the actual thickness of 99.82 m on site, and upward mining can be adopted.

An Interpretation Method of Gas–Water Two-Phase Production Profile in High-Temperature and High-Pressure Vertical Wells Based on Drift-Flux Model

With the increasing demand for oil and gas, the depth of some vertical gas wells can reach 6000 m. At this time, the downhole fluid is in a state of high temperature and pressure, and interpretation of the production logging output profile faces the problem of inaccurate production calculations and difficulty judging the water-producing layer. The drift-flux model is usually used to calculate the gas–water two-phase flow. The drift-flux model is widely used to describe the two-phase flow in pipelines and wells because of its accuracy and simplicity. The constitutive correlations used in drift-flux models, which specify the relative motion between phases, have been extensively studied. However, most of the correlations are only extended by laboratory data of small pipe diameters at standard temperature and pressure and do not apply to high-temperature and high-pressure large-diameter gas wells. Therefore, we improved the distribution coefficient and drift velocity of drift-flux correlations in this study for high-temperature and high-pressure gas wells with large pipe diameters. Therefore, this study improved the distribution coefficient and drift velocity of the drift-flux correlations for high-temperature and high-pressure gas wells with large pipe diameters. In practical application, the coincidence rates of gas production and water production calculated by the new drift-flux model were 12.68% and 19.39%, respectively. For high-temperature and high-pressure deep wells, the measurement errors of production logging instruments are significant, and surface laboratory pipelines are challenging to configure and equip with actual high-temperature and high-pressure conditions. Therefore, this study used the method of numerical simulation to study the flow characteristics of the two phases of high-temperature and high-pressure gas and water to provide a basis for identifying the water layer. Combined with the proposed drift-flux correlations and the new method of determining the water-producing layer, a new method of production profile interpretation of high-temperature and high-pressure gas wells is obtained.

Dual-band photodetector based on a large circular dichroism

Room temperature near-infrared photodetector has important applications in military, aerospace, and other fields. However, the development of highly efficient and highly selective circularly polarized photodetectors is still a challenge. Here, we theoretically demonstrate a near-infrared photodetector based on the dual-band perfect absorber in a filleted L-shaped chiral dielectric metal metasurface, and the optical, thermal, and electrical properties are analyzed in detail. Numerical simulation results show that two absorption peaks at λ=1129 nm and λ=1148 nm under right-hander circularly polarized (RCP) are achieved, and the absorption rate is both greater than 90%, while the electromagnetic waves are almost completely reflected under left-hander circularly polarized (LCP), which indicates that the proposed system has strong optical chirality. Then, we investigate the effects of polarization angle and structure period on the absorption spectra. The relationship between the surface temperature of the thermo-sensitive material and the wavelength is calculated when the absorber is used as the heat source. Finally, two kinds of chiral photodetectors based on different effects, thermoelectric and pyroelectric effects, are designed, and the temperature time-varying relationship of the thermo-sensitive material is mainly discussed at λ=1129 nm. By constructing a complete external circuit, the correlated electrical properties of the system to the load are analyzed. This integrated photothermoelectric numerical simulation method can comprehensively consider the optical, thermal, and electrical effects so as to more accurately predict the overall performance of the photo-detection system in practical applications, which can significantly improve the overall efficiency of the system and achieve better energy utilization and performance.

Prevention and Control of Spontaneous Combustion of Coal in the Goaf Under Z+I Ventilation Based on 2GN00 mining Process

ABSTRACT Traditional coal pillar mining technology will cause the waste of resources, and the roadway excavation. The N00 process eliminates the need for roadway excavation and coal pillar storage. The ventilation mode under the N00 construction method differs from conventional U-shaped ventilation. It is difficult to determine the danger area of spontaneous combustion. Therefore, this paper takes 21607 goaf with Z+I ventilation under the 2GN00 construction method in a mine in Guizhou province as the engineering background and adopts experimental research and numerical simulation methods to prevent and control coal spontaneous combustion hazards. Firstly, the spontaneous combustion tendency experiment determines the grade of spontaneous combustion tendency of coal samples. Secondly, the Fluent numerical simulation method is used to screen the optimal wind speed ratio of the two air inlets. Finally, numerical simulation is used to select the optimal spraying distance. The results show that the spontaneous combustion grade of coal samples makes it easy to produce spontaneous combustion. By analyzing the numerical simulation results of 6 groups of wind speed ratios, the best wind speed ratio of the two inlets is 1:1. Currently, the risk area of spontaneous combustion in the goaf is 5440.8 m2. Then the numerical simulation of the best slurry spraying distance is carried out with the wind speed ratio 1:1. The optimum distance of 90 m was finally determined. The area of the spontaneous combustion hazards area was reduced to 2223.8 m2. The results provide theoretical guidance and technical support for engineering applications.

Complexity Analysis and Control of Output Competition in a Closed-Loop Supply Chain of Cross-Border E-Commerce Under Different Logistics Modes Considering Chain-to-Chain Information Asymmetry

To investigate the dynamic complexity of chain-to-chain output decisions in a closed-loop supply chain system of cross-border e-commerce (CBEC), this study decomposes the system into four product–market (PM) chains, based on the e-commerce platform’s information-sharing strategy and the manufacturer’s selected logistics mode (direct mail or bonded warehouse). By combining game theory with complex systems theory, discrete dynamic models for output competition among PM chains under four scenarios are constructed. The Nash equilibrium solution and stability conditions of the models are derived according to the principles of nonlinear dynamics. The stability of the model under the four scenarios, as well as the impacts of the initial output level and comprehensive tax rates on the stability and stability control of the system, are analyzed using numerical simulation methods. Our findings suggest that maintaining system stability requires controlling the initial output levels, the output adjustment speeds, and tariff rates to remain within specific thresholds. When these thresholds are exceeded, the entropy value of the model increases, and the system outputs decisions to enter a chaotic or uncontrollable state via period-doubling bifurcations. When the output adjustment speed of the four PM chains is high, the direct-mail logistics mode exhibits greater stability. Furthermore, under increased tariff rates for CBEC, the bonded warehouse mode has a stronger ability to maintain stability in system output decisions. Conversely, when the general import tax rate increases, the direct-mail mode demonstrates better stability. Regardless of the logistics mode, the information-sharing strategy can enhance the stability of system output decisions, while increased e-commerce platform commission rates tend to reduce stability. Interestingly, the use of a non-information-sharing strategy and the direct-mail logistics mode may be more conducive to increasing the profit levels of overseas manufacturers. Finally, the delayed feedback control method can effectively reduce the entropy value, suppress chaotic phenomena in the system, and restore stability to output decisions from a fluctuating state.

Two-Dimensional Numerical Method for Predicting the Resistance of Ships in Pack Ice: Development and Validation

This study presents a 2D numerical simulation method for predicting the resistance of ships navigating in pack ice. The key contribution of this study lies in the derivation of analytical closed-form solutions for calculating the flexural deformation and stress distribution in an elastic plate using Symplectic Mechanics and Hooke’s laws. These solutions are used to determine the failure mode of ice floes. Linear Elastic Fracture Mechanics (LEFMs) and the weight function method are utilized to analyze crack initiation, propagation, and fracture. Ice is broken when a crack propagates to 14.5% of the ice length. The compressive strength of ice and the contact area are used to calculate the ice load. A collision method was developed based on the Sweep and Prune (SAP) and Gilbert–Johnson–Keerthi (GJK) algorithms. A program for predicting the resistance of ships navigating in pack ice was developed based on MATLAB and the aforementioned theories. The navigation resistance of RV Xuelong at different ice concentrations and speeds was simulated and compared with the model test results from an ice tank. The comparison shows that the simulation results are consistent with the test results, with an average error of 9.05%, indicating the effectiveness and reliability of this numerical method. This study lays a solid foundation for future research on autonomous ship navigation in pack ice.

Design of CO2 Huff-n-Puff Parameters for Fractured Tight Oil Reservoirs Considering Geomechanical Effects

CO2-Huff-n-Puff (CO2-HnP) is an effective method for improving oil recovery in conventional reservoirs and has been widely applied to tight oil reservoirs. Recently, there has been a series of studies published on the oil increase mechanism and huff-n-puff parameter optimization of CO2-HnP. However, the understanding of the influence of fracture characterization, threshold pressure gradient (TPG), and geomechanical effects on CO2-HnP in fractured tight oil reservoirs is still limited. In this paper, a numerical model based on the embedded discrete fracture model (EDFM) was constructed to investigate the impact of TPG and geomechanical effects on cumulative oil production (COP). The effects of various huff-n-puff parameters, including bottomhole pressure, oil recovery rate, total CO2 injection amount, number of huff-n-puff cycles, timing of production transfer injection, production time, injection time, CO2 injection rate, and soaking time on the COP and oil replacement ratio were also explored in the paper. The results include the following: (1) The TPG and geomechanical effects led to significantly reduced COP. (2) A positive correlation with COP was found for parameters such as timing of production transfer injection and production time, while negative correlations were found for cycles, soaking time, and injection rate. For oil replacement ratio, soaking time and injection rate were positively correlated, while CO2 injection amount and number of cycles showed negative correlation. (3) With a constant injection volume, it is crucial to avoid an excessive number of cycles that reduce COP. On the basis of this parameter optimization, the oil replacement ratio can be enhanced by advancing the production transfer injection, shortening the injection time, and extending the soaking time. The findings can help optimize CO2-HnP strategies to improve oil recovery and economic benefits from the reservoir. This paper provides an effective numerical simulation method for CO2-HnP in fractured tight oil reservoirs, which has certain reference value.

Numerical Simulation of Backfilling Construction for Underground Reinforced Concrete Grain Silos

Food security is an important guarantee for national security and public health. Underground reinforced concrete (RC) grain silos can provide a quasi-low temperature environment for grain storage, effectively ensuring the quality of the stored grain. The stress status of the underground silo during soil backfilling construction is complex, which puts the structure at risk of failure. The present study developed a numerical simulation method to investigate the mechanical properties of underground silos during backfilling construction processes. A finite element (FE) analysis of the backfilling construction process of an underground RC grain silo was conducted, and the nonlinear contact between the underground silo and the surrounding soil, as well as the material nonlinear behavior of the soil, was considered. The deformation characteristics and stress distribution of the underground silo during the backfilling construction process were revealed. The results indicate that the underground RC grain silo exhibits good mechanical performance. The underground silo underwent overall settlement during the backfilling construction process, with a total settlement of 21 mm. The maximum radial displacement of the silo wall and the maximum deflection of the radial primary beam were 0.84 mm and 5.67 mm, respectively, both of which were smaller than the limit values. After the completion of backfilling construction, there was a high risk of concrete cracking of the silo wall. The maximum radial and circumferential tensile stresses of the concrete at the silo top were both high, which led to cracking in the top of the silo. Our research results provide important support for the design and evaluation of underground RC grain silos.

OPTIMIZATION OF Al-BASED AMORPHOUS COATINGS BY WARM SPRAYING BASED ON A NUMERICAL SIMULATION AND A RESPONSE-SURFACE METHODOLOGY

Al-based fully amorphous coatings with low porosity were prepared using a warm-spraying technology by combining numerical simulations and a response-surface methodology (RSM). The influences of spraying parameters (reactant flow rate, oxygen/fuel (O/F) ratio, coolant flow rate, and spraying distance) on the particle temperature and velocity were investigated using numerical simulation methods. On this basis, the response-surface equations for temperature and the velocity of the particles were established using the Box-Behnken Design (BBD) methods. The RSM was used to analyze the influence of the interactions between the spraying parameters on the temperature and the velocity of the particles. The optimum spraying parameters (OSP) predicted by the response optimizer were 0.012047 kg/s for the reactant flow rate, 0.011034 kg/s for the coolant flow rate, 2.7 for the O/F ratio, and 142 mm for the spraying distance. According to the OSP, the Al-based fully amorphous coatings with a porosity of 0.08% were obtained by warm-spraying experiments. This work provides guidance for the production of Al-based fully amorphous coatings with low porosity using warm spraying.

Experimental and Numerical Simulation of Flow Modes in Flow Focusing/Blurring Nozzle

The flow mode of the flow focusing/blurring nozzle was studied through experimental and numerical simulation methods. The experimental results indicate that the flow mode of the nozzle can be classified into flow focusing, transition, and flow blurring based on the location of the liquid jet breakup. Numerical simulation studies have found that the transformation of flow mode is mainly related to viscous shear force, gas pressure on the jet surface, and liquid inertia force. The increase in the gas flow rate changes the flow mode by affecting the viscous shear force. The increase in the liquid flow rate changes the flow mode by affecting the liquid inertial force. When the liquid flow rate is high, the increase in the liquid flow rate affects the flow mode by affecting the gas pressure on the jet surface. The study also found that excessive gas flow rates can hinder the flow of liquid inside the nozzle, while excessive liquid flow rates can hinder the breakup of liquid inside the nozzle. Therefore, the normal operation of the flow focusing/blurring nozzle requires ensuring that the gas and liquid flow rates are within the normal range.

Comparing numerical simulation methods for evaluating hysteretic response of self-centering shear walls reinforced with SMA-ECC under cyclic loading

Under the action of earthquake, the traditional shear wall structure has the problems of excessive residual deformation and macroscopic cracks. The SMA-ECC composite material formed by the combination of smart materials such as shape memory alloy (SMA) and high ductility engineered cementitious composite (ECC) not only has good energy dissipation capacity, but also can obtain superior self-centering ability and damage self-healing ability, thereby improving the seismic performance and durability of shear wall structures. In this paper, in order to explore the nonlinear behavior of the self-centering shear wall under earthquake action and accurately simulate it, ECC and SMA material tests are carried out to establish the uniaxial constitutive relationship of the material. Using OpenSees finite element analysis platform, considering the micro and macro perspectives, a variety of finite element models are established, namely layered shell model, fiber model and multi-vertical rod model. Combined with the low-cycle reciprocating loading test of shear walls, the numerical simulation results are compared with the experimental data. By considering the parameters such as yield load, peak load and simulation time, the feasibility, stability and calculation efficiency of these models are evaluated. The results show that among the three models, the model based on fiber element can capture well the hysteretic response of new materials, and simulate the hysteretic performance, pinch effect and stiffness degradation of various shear wall members. The simulated values and experimental values can be well matched. Compared with the microscopic model, the computational efficiency of the fiber model is greatly improved, and the model has good feasibility, accuracy and efficiency.This work provides a basis for further research on the optimization of design parameters of SMA-ECC shear wall.

Corrosion test and corrosion fatigue numerical simulation research on marine structures

The corrosion tests on Q235B steel in artificial seawater with conventional room temperature and high-temperature & high-humidity are first conducted. The test results show that increasing the acidity and temperature of the corrosion solution, as well as adopting the alternating dry-wet, can significantly enhance the corrosion rate of materials. In addition, the corrosion tests exhibit good simulation and acceleration characteristics compared to at sea tests. Then, the corrosion and corrosion-fatigue numerical simulation methods based on COMSOL and MATLAB are proposed. Meanwhile, the corrosion of Q235B steel in neutral artificial seawater and corrosion fatigue damage of a T-shaped structure under the coupling of artificial seawater with fatigue load are simulated and analyzed. The corrosion simulation results indicate that when the temperature is 40 °C and 20 °C, the average corrosion rates of specimens increase by 96.61% and 15.25%, respectively. Furthermore, when the temperature is 20 °C, the average corrosion rates obtained from numerical simulation and corrosion test are 0.068 mm/a and 0.062 mm/a, respectively, with a relative error of 9.7%, verifying the validity of the corrosion numerical simulation method. Based on the corrosion fatigue simulation, it is found that the maximum corrosion thickness increases by about 23% compared to pure corrosion condition in the weld region, and the structural fatigue damage increases by about 21.36% compared to pure fatigue condition after 10 years of corrosion.

Influence of Free Surface on the Hydrodynamic and Acoustic Characteristics of a Highly Skewed Propeller

The noise analysis of a large-scale aquaculture vessel reveals that during its navigation, the primary equipment noise, particularly from the propeller, exerts a notable influence on the aquaculture environment for large yellow croaker. The free surface greatly impacts the noise performance of propellers, which is a significant factor affecting the fish’s habitat. This study adopts the numerical simulation method to analyze the hydrodynamic and acoustic characteristics of the E1619 propeller operating near the free surface. The open-water performance and noise calculations of the propeller are verified through experiments, and the effects of different immersion depths and advance coefficients on the propeller are explored. The results demonstrate that the free surface significantly affects the thrust, torque, and noise of the propeller, especially at shallow immersion depths and low advance coefficients. Surface wave pattern causes the instability and breakup of tip vortices, causing increased thrust and torque fluctuations, reduced efficiency, and significant overall sound pressure levels in the entire flow field. As immersion depth and advance coefficients increase, the interaction between tip vortices and the free surface weakens, wake vortex instability decreases, and noise levels gradually reduce. These analyses and conclusions can guide the design of next-generation propellers for aquaculture vessels to optimize performance near the free surface.

Numerical simulation method of grease flow in a grease groove with experimental validation

The flow process and characteristics of lubricating grease have a significant impact on the lubrication performance of bearings. Based on the rheological parameters of lubricating grease and the Cross rheology model, this paper proposed a lubricating grease flow simulation method in the grease groove based on user defined functions (UDFs) combined with the Finite Volume Method (FVM) and verifies the rationality of the simulation method through visualization experiments. The flow characteristics of lubricating grease in the grease groove were studied under three different grease delivery angles. Additionally, it was observed that the lubricating grease ceased to flow in the groove during the delivery process, and the simulation method was used to analyze and explain this phenomenon.

Numerical simulation study of hydrogen/air flame propagation and detonation characteristics in an annular cross section of gas turbine combustion chamber

The trends and future directions of hydrogen safety research cannot be separated from the thermodynamic behavior of combustion and explosion, hydrogen spontaneous combustion, flame propagation behavior, thermodynamic mechanisms, and other related topics. In this paper, through the method of numerical simulation, considering the hydrogen flame propagation and detonation characteristics in the annular section of the combustion chamber commonly used in gas turbines, the form of detonation and detonation impact in the channel are evaluated. By discussing the deflagration to detonation transition of hydrogen/air premixed gas and premixed gas under different working conditions, it is found that the flame in the annular channel propagates close to the inner wall and forms a strong expansion and turbulence between the outer wall and the outer wall of the flame. The flame surface and the airflow shear accelerate the detonation of hydrogen. The area close to the wall on the outer side of the flame surface and the tip of the flame surface are prone to set off detonation. The high-pressure area after the detonation mainly acts on the symmetrical end face of the outer wall surface and ignition area. There is a critical working temperature to make the impact strength strongest when the detonation occurs. Reducing the equivalence ratio of the filling gas can significantly reduce the reaction speed and weaken the impact strength of the wall. When the equivalence ratio is less than a certain value, the filling gas is completely consumed in the form of deflagration.

Traveling waves in an ensemble of excitable oscillators: The interplay of memristive coupling and noise

Using methods of numerical simulation, we demonstrate the constructive role of memristive coupling in the context of the traveling wave formation and robustness in an ensemble of excitable oscillators described by the FitzHugh–Nagumo neuron model. First, the revealed aspects of the memristive coupling action are shown in an example of the deterministic model where the memristive properties of the coupling elements provide for achieving traveling waves at lower coupling strength as compared to non-adaptive diffusive coupling. In the presence of noise, the positive role of memristive coupling is manifested as significant, increasing a noise intensity critical value corresponding to the noise-induced destruction of traveling waves as compared to classical diffusive interaction. In addition, we point out the second constructive factor, the Lévy noise, whose properties provide for inducing traveling waves.

Gas layer charge influence law study of underwater explosion bubble pulsation

Abstract To discuss the influence of the gas layer on underwater explosion load, the influence of gas layer thickness on bubble pulsation period maximum radius, pressure peak value, and specific impulse during underwater explosion was first discussed. A simulation model of underwater explosion with gas layer charge is established by numerical simulation method, and the influence law of gas layer on the pulsation of underwater explosion bubble is calculated and analyzed. The results show that the pulsation period and maximum radius of the underwater explosion bubble increase with the increase of gas layer thickness. The peak value of bubble pulsation pressure decreases, while the specific impulse increases first and then decreases. The research conclusion shows that in a certain gas layer, the damage risk of protective structure may be increased due to the increase of pulsating pressure ratio impulse or the resonance between pulsating frequency and structure.