Results Of Numerical Analysis Research Articles

Experimental and simulation analysis of erosion law of crude gas production channel in underground coal gasification production wellhead

In underground coal gasification, crude gas carrying coal ash and cinder has a serious significant erosion effect on the gas extraction area of a wellhead device. To study the erosion of the wellhead device, based on the gas-solid two-phase flow theory, this study uses the discrete phase model to describe the kinematics and trajectories of discrete solid particles and uses the Reynolds-averaged Navier-Stokes equation to calculate the fluid dynamics of the continuous phase. This study determines the main erosion position and the maximum erosion angle range of the wellhead device through numerical analysis, as well as the influence of the changes in solid particle size, particle mass flow rate, and crude gas flow rate on the erosion rate, and predicts the service lifetime of the small four-way and side valve I. The gas-solid erosion experiment verified the maximum erosion angle of the wellhead device. The experimental results were consistent with the numerical analysis results. This study also proposes an optimization method of surfacing to reduce the erosion of gas-solid two-phase flow on wellhead devices. The results show that the inner walls of the small four-way and side valve I are the most eroded. Factors such as particle size, particle mass flow rate, and crude gas flow rate have a greater impact on the erosion rate of the device, and the particle size has the greatest impact. Surfacing the severely eroded area of the wellhead device can effectively reduce the erosion and wear of the wellhead device caused by the gas-solid two-phase flow. This study provides guidance for the reasonable prediction and effective protection of severe erosion areas of wellhead devices.

Using the FEM Method in the Prediction of Stress and Deformation in the Processing Zone of an Elastic/Visco-Plastic Material during Diamond Sliding Burnishing

This article concerns the application of the FEM method for the prediction of stress and deformation states in the workpiece during diamond sliding burnishing (DSB). An updated Lagrange (UL) description was used to describe the phenomena at a typical incremental step. The states of strain and strain rate are described by non-linear relationships without linearization. The material parameters were estimated during tensile tests to determine the characteristics of the 41Cr4 steel. Its hardness was also tested. Its aim was to prepare a table with the material properties of the above-mentioned steel and its implementation for numerical analyses. A Cowper–Symonds material model was used to model the displacement process of the wedge on an elastic/visco-plastic body reflecting the DSB process. The computer model was validated, and a good convergence of the results was obtained. Applications in the ANSYS/LS-Dyna program were developed to simulate the process of DSB. The results of numerical analyses were presented, among others, to explain the influence of the rake angle on the condition of the surface after machining, as well as the phenomenon of chip formation. The results of numerical simulations were verified experimentally on a test stand.

Reaction and deformation mechanism of a slipping-stretching landslide: Example of the Liangtianao ancient landslide, Guangxi Province, China

Slipping-stretching landslides have long been recognized as a common type of landslide case, but such reactions have rarely been reported. There was a slipping-stretching landslide reaction at Liangtianao, Guangxi Province, China, and the geological background and deformation characteristics of the case were identified by detailed geological survey and long-term monitoring. A FEM model of the case was built using GEO5 to analyze the mechanism of reaction and deformation. The results are as follows. 1) The Liangtianao landslide is a bedding rock ancient landslide, which remained in a creeping state after the landslide occurred in geological history. 2) The new sliding surface in the Liangtianao landslide is basically consistent with the weak interlayers formed by ancient landslides, and the fault-type is a slipping-stretching type with the following deformation process: strain at leading edge by road excavation→ leading edge instability→ middle part shear and creep→ back edge tensile. 3) Micro-geomorphology, rock mass bedding, and weak interlayers are internal causes of the Liangtianao landslide reaction, while excavation unloading and rainfall are the external causes. The inclinometer indicates that the Liangtianao landslide is still highly sensitive to rainfall after the landslide reaction, which may trigger a secondary landslide reaction. 4) The numerical analysis results indicate that the maintenance of a passive state in the anti-sliding section is highly beneficial to maintaining basic stability after the landslide reaction; unloading only 1/20 of the sliding section makes the landslide stable in the long term.

Thermal Diffusivity of Concrete Samples Assessment Using a Solar Simulator.

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from 0.16×10-6m2s to 0.52×10-6m2s and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete.

Study on the ground attenuation of engine run-up and APU noise for developing the airport noise model in Japan

The correction for ground effect around airports is modeled based on the results of numerical analysis in order to make it possible to estimate the propagation of noise caused by ground operations in airports such as engine run-ups and APU to the vicinity of airports. The excess attenuation due to ground effects on sound caused by engine run-ups and APU is calculated using a PE method for typical jet aircraft and propeller aircraft, respectively. On the assumption that the ground around an airport consists of asphalt-paved surface and grass-covered surface in a certain ratio, the excess attenuation for the mixed impedance ground is calculated with the Fresnel-zone method using the results of PE calculation. The composition ratio of ground surface is assumed based on the composition ratio of asphalt-paved surface and grass-covered surface along the propagation path from the engine run-up spot to the airport site boundary of six major airports in Japan. In this paper, we introduce the excess attenuation calculated with the PE method and the correction model for ground effects on noise of engine run-ups and APU is discussed to implement it in the airport noise prediction model used in Japan.

NUMERICAL ANALYSIS OF LOAD‐BEARING FIRE TEST FOR REINFORCED CONCRETE SLABS

AbstractA numerical analysis is conducted for the load‐bearing fire test of composite flooring systems composed of flat RC slabs and unprotected beams (beams with no fire protection covering), and the test results and numerical analysis results are compared. The main aim of the numerical analysis is to verify the accuracy of the numerical analysis approach as well as to analyse the stress distribution within the composite floor when the membrane functions as intended, the data for which are difficult to obtain from the load‐bearing fire test.

Numerical Analysis and Experiments on Heavy Oil Heating of Shipwrecks

Analyze the change of oil temperature flow times during the heating process of wreck heavy oil and the temperature gradient change in the radiation area of the heating source. Using the result guide the heating process of low-temperature underwater oil recovery operations on the wreck. fluid software was used for the analysis process of the numerical simulation, and the physical model test is a simulation test of low temperature underwater electromagnetic heating of heavy oil. In this way, data related to the heating process of heavy oil can be obtained. from the numerical analysis results and the physical model test results, it can be concluded that the numerical simulation results are similar to the experimental verification results. The result can be used for engineering guidance. Due to the physical properties of heavy oil, the oil temperature decays faster during the heating process and the radiation effect of heat source is small, using the electromagnetic heater heats the heavy oil in the oil tank, and the heavy oil can be heated to meet the requirements of the pumping operation in a short time. The calculation model parameters are derived from actual operations. Numerical calculations and physical test results are of great significance to engineering guidance and can guide the underwater cryogenic oil pumping operation of shipwrecks.

Wave-based numerical investigation on diffraction correction for a low-height barrier in energy-based sound propagation model for road traffic noise

In energy-based noise propagation prediction methods, such as CNOSSOS-EU in Europe and ASJ RTN-Model in Japan, sound propagation is calculated by using the equation of sound attenuation by the geometrical divergence of the sound power from a sound source and adding various attenuation corrections such as diffraction effect and ground effect. In the ASJ RTN-Model, the insertion loss due to a semi-infinite barrier to a free field is generally used for the diffraction correction for a single barrier, the top of which is regarded as a knife wedge, whereas the diffraction correction for a low-height barrier is different from that for a general single barrier. It is given as the insertion loss due to a low-height barrier to a semi-infinite barrier, the top height of which is at the ground surface level, in a free field: the diffraction correction is zero when the low-height barrier is 0 m high. However, its range of application is not clear. In this paper, the diffraction correction for a low-height barrier is discussed by comparing the results of three-dimensional wave-based numerical analysis and propagation calculations using the ASJ RTN-Model.

Modeling and simulation of traffic flow based on memory effect and driver characteristics

In this paper, an improvement of the full velocity difference model is presented, which comprehensively considers driver characteristics which include aggressive and timid behaviors and memory effect. The stability condition of the improved model is obtained by making use of the small perturbation method. The Burgers, Korteweg–de Vries and modified Korteweg–de Vries equations are derived by means of the reductive perturbation method. Finally, through numerical simulation, the traffic flow evolution process of the improved model under two typical conditions is observed. The first is the starting process, and the second is the propagation process of disturbance in traffic flow. The results of numerical simulation and theoretical analysis demonstrate that the multiple driver characteristics considered in the improved model have important influences on traffic flow stability and the ease of traffic jams, and the model can quickly recover to its original state in case of the disturbance. • A new car following model is presented, which considers memory effect and driver characteristics including aggressive and timid behaviors. • The stability conditions of the extended model are obtained with the use of the small perturbation method. • The Burgers, Korteweg–de Vries and modified Korteweg–de Vries equations are derived by means of the reduced perturbation method. • The starting process and the propagation process of disturbance are carried out, the results are much closer to actual traffic.

Influence of Gas Medium State Parameters on the Pressure Port Design of Gas Wave Ejector

Objective: The objective of this study is to explore and emphasize the influence mechanism and law of gas parameters on pressure port design. Methods: CFD commercial software FLUENT was used for numerical simulation in this study, and a three-dimensional numerical model was employed to improve the accuracy of calculation. The GWE experimental platform was also built to verify the theoretical and numerical analysis results. Results: When the expansion ratio α is raised from 1.35 to 2.0, the average shock velocity vs can increase by about 4.9%, and when raising the compression ratio from 1.05 to 1.2, the change of vs is only 1.4% relatively. Raising the expansion ratio value from 1.35 to 2.0, the optimal offset of the high- and medium-pressure ports only changes by 5.3%, and the decrease of the ejection rate caused by the deviation of the aforementioned offset is only about 4.3%,which proves that the equipment has strong ability to resist fluctuations of working conditions. Conclusion: Moving velocity of the shock wave varies with temperature, working pressure ratio and adiabatic index of the gas. The increase of high- and low-pressure inlet gas temperatures will cause an increment of vs and as, and the influence of high-pressure inlet gas temperature Tht on vs is greater. There are optimal high- and medium-pressure port offsets under different pressure ratios as the experimental results have shown. When the pressure ratio remains constant, the change in pressure value does not have a significant impact on the optimal port design and equipment performance.

Kajian Perilaku Lentur Balok Finger Jointed Laminated Board (FJLB) Kayu Karet (Hevea Brasiliensis)

This study is aimed to determine the flexural behavior of Rubberwood FJLB (finger jointed laminated board) beams as building structural components. It was carried out through experimental approach and numerical analysis on six specimens of FJLB beams having a cross-section of 100 mm by 150 mm and a length of 2850 mm. The experiment was consisted of small specimen tests (BS-373:1957) and four-point bending test (EN-408) with two different cross-sectional orientations (flatwise and edgewise). The numerical analysis was performed by conducting 2-D finite element analysis developed in MATLAB program based on plane stress assumption. It was found that the average flexural capacity of beams tested under edgewise orientation was 24.6 kN, which is higher than that of the beams tested under flatwise orientation, 19.7 kN. However, the flexural stress (modulus of rupture) of those beams was about the same. All the beams experienced brittle failure caused by glueline failure between laminas or at finger joints. The results of strain measurement at mid-span of the beams throughout the test showed that the FJLB beams failed within elastic response. This finding was confirmed by the numerical analysis results.

Evaluasi Perilaku Seismik Akibat Ketidakberaturan Vertikal pada Bangunan Beton Bertulang Bertingkat Tinggi

This study investigated the behavior of high-rise reinforced concrete structures with vertical irregularities caused by seismic loading. The ability of the building to endure all of the load during operation should be considered in design process. The irregularities in the building cause to impair stiffness and performance of the structure, particularly during the earthquake. Therefore, it is necessary to evaluate the effects of vertical irregularities on building, especially high-rise buildings. This study employs an S-Shaped structure with five vertical irregularities. Numerical analysis was used by using STEDA 3D software. The dynamic load used is based on time history data from the previous earthquakes, including the El-Centro, Kobe, and Parkfield. The seismic behavior evaluated in this study consist of shear force, lateral deformation, structural stiffness, the relationship between base shear and top displacement, drift ratio, maximum acceleration response, capacity curve, and top orbit of the building. Based on the numerical analysis results, it can be concluded that each model has a different seismic performance even though it is given the same earthquake load and material properties. The vertical irregularity of the building greatly affects the behavior of the structure due to seismic analysis.

Numerical and Optimization Study on a Heat Exchanger Tube Inserted with Ring by Taguchi Approach

This paper presents an optimization study on a heat exchanger tube inserted with circular rings by using numerical analysis results. Pitch length (50, 100, and 200 mm), inner diameter (15, 12.5, and 10.0 mm), and thickness (1, 3, and 5 mm) of the rings are considered as factors to be optimized. Water is selected as working fluid and the tube is considered under constant heat flux of 20 kW/m2 and turbulent flow conditions. k-Epsilon simulate the turbulent flow through the tube. The L9 design of experiment model is used to reduce the number of numerical runs which is proposed by the Taguchi method. The optimization study is conducted as single and multi-objective optimization by using the Taguchi method and Grey relation analysis. Furthermore, the contribution effects of the considered parameters on the Nusselt number and the friction factor result are revealed by ANOVA. Numerical results showed that the Nusselt number and the friction factor increase as the pitch length, the diameter and the thickness decreases. It is found that the most effective parameter on both the Nusselt number and the friction factor is inner diameter of the rings. For the single objective optimization, the highest Nusselt number and the lowest friction factor is obtained with the tube configuration that are found as the pitch length of 50 mm, the diameter of 10 mm and the thickness of 5 mm and the pitch length of 200 mm, the diameter of 15 mm and the thickness of 3.0 mm, respectively. The pitch length of 50 mm, the diameter of 15.0 mm and the thickness of 5.0 mm presents the best thermal and hydraulic performance according to the multi-objective optimization study.

A Hybrid Marine Predator Sine Cosine Algorithm for Parameter Selection of Hybrid Active Power Filter

Power quality issues are handled very well by filter technologies. In recent years, the advancement of hybrid active power filters (HAPF) has been enhanced due to ease of control and flexibility as compared to other filter technologies. These filters are a beneficial asset for a power producer that requires a smooth filtered output of power. However, the design of these filters is a daunting task to perform. Often, metaheuristic algorithms are employed for dealing with this nonlinear optimization problem. In this work, a new hybrid metaheuristic algorithm (Marine Predator Algorithm and Sine Cosine Algorithm) has been proposed for selecting the best parameters for HAPF. The comparison of different algorithms for obtaining the HAPF parameters is also performed to show case efficacy of the proposed hybrid algorithm. It can be concluded that the proposed algorithm produces robust results and can be a potential tool for estimating the HAPF parameters. The confirmation of the performance of the proposed algorithm is conducted with the results of fitness statistical results, boxplots, and different numerical analyses.

Influence of Induced Variability of Unsaturated Soil Parameters on Seepage Stability of Ancient Riverbank

In the restoration of ancient water engineering, the loss of fine soil particles from the ancient riverbank can easily cause seepage instability problems such as piping during the flood transient process. This paper explores the influence mechanism of flood fluctuation on soil seepage stability based on indoor experiments, field monitoring and saturated-unsaturated soil seepage theory. The paper obtains the soil-water characteristic curve of unsaturated soil using laboratory tests, builds the transient seepage finite element model of porous media and modifies parameters monitoring data to verify the numerical analysis results. The results showed that the groundwater level, pore water pressure and seepage hydraulic gradient had changed. The maximum pore water pressure between the ancient riverbank and antiseepage structure increased by 13.4%, the maximum hydraulic gradient at the toe of the riverbank increased by 49.3% and the instability of seepage significantly increased. Through the modified lime grouting between the ancient riverbank and the antiseepage structure, the structure of the soil mass was changed, and the maximum hydraulic gradient was reduced by 55.6%, which restrains piping damage. This study can be used in the restoration of ancient riverbanks to solve piping problems.

Experimental study and numerical analysis of vacuum thermal characteristics of brush DC motor

Brush direct current (DC) motors have several qualities that make them very attractive for space flight applications. Considering the high reliability requirements of aerospace missions, the thermal characteristics and thermal failure of the brush DC motor in the space environment were studied. Using a motor thermal resistance network model, a special thermal test method was determined and combined with a thermal conductivity analysis model, the thermal parameters were obtained via item-by-item stripping, and the motor temperature field was constructed. By introducing the arc discharge factor to evaluate the electric-corrosion heat consumption, the numerical analysis results were in good agreement with the test results under the conditions of stalled rotor, normal rotation, single brush, and multiple brushes. The analysis and test results show that continuous operation for 110 s will lead to melting of the brush solder joints, and electrical corrosion heat consumption is one of the main factors that cannot be ignored. The reliability model of vacuum applications should be established in the normal working mode of at least two brushes in both the positive and negative electrodes. To improve the reliability, a sealed air-filled structure of the motor was proposed, a heat-flow co-simulation model of a continuous medium flow with a large curvature and constant without a gravity field was established, and the temperature and velocity fields under different sealed pressures were obtained. The results show that the temperature of the single brush reduced to below 140 °C from 204.5 °C in vacuum, which can meet the long-term continuous working requirement of high reliability of brush motors in space missions. In addition, it was found that with the decrease in pressure, the effect of convective heat transfer gradually weakens, the temperature gradually increases and converges to the unique heat conduction process of the gas, while the effect of convection is negligible. As the pressure continues to decrease, the sealed gas evolves from continuous medium flow to transitional and free molecular flow, and the heat conduction effect of the gas weakens again until it approaches the singleness solid conduction process.

Optimization Design and Experimental Verification for the Mixed-Flow Fan of a Stratospheric Airship

Large-flow, high-pressure fans are required to improve the shape-keeping and flight-height-adjusting ability of stratospheric airships. This study optimizes and analyzes a fan MIX-130 suitable for a stratospheric airship. Five design parameters are selected to optimize the fan’s static pressure rise and efficiency: impeller outlet installation angle, installation angle increment, blade thickness, diffuser tilt angle, and L16(45) orthogonal test for optimization research. Based on the optimization results, the fan is processed, a fan test bench is built to verify the accuracy of the fan numerical analysis method, and the fan’s performance curve in the stratosphere environment is given. The results demonstrate that after optimization, the static pressure rise in the MIX-130 fan increases by 47.5%, and the efficiency increases by 8%. The performance test data of the MIX-130 fan are consistent with the numerical analysis results. Furthermore, the flow pressure curve is significantly improved compared with the existing fan, satisfying the requirements of airship flight missions. The fan structure optimization and testing methods presented in this manuscript can provide a reference for designing and testing stratospheric airship fans.

A study on droplet group evaporation modeling based on interface resolved numerical simulations of two-phase flow

Large-scale numerical analyses of the evaporation of groups of 640 droplets and 2,964 droplets were conducted by the interface-resolved simulation method, and the effect of mutual droplet interference on the evaporation rate of droplets in groups was modeled. The interference effect reduces the evaporation rate of each droplet due to the increase in its surrounding fuel concentration caused by the evaporation of neighboring droplets. The evaporation rate interference coefficient, which is the ratio of the evaporation coefficient of each droplet in a group to that of a single droplet without interference, was modeled using three parameters: the distance between the droplets, the size of the droplet interfering with an object droplet, and the evaporation state of the interfering droplet. A new droplet evaporation rate parameter containing these model parameters was proposed, and it was confirmed that the proposed parameter properly models the evaporation rate interference coefficient calculated using the droplet group evaporation numerical analysis results. In addition, the accuracy of the model was improved by including a further parameter to express the positional relationship of a droplet within a group.

A study on optimization of delayed production mode of iron and steel enterprises based on data mining.

Delayed production mode has been adopted by an increasing number of process production enterprises as a method to realize mass customization of multi-products. This paper used the convolutional neural network-long short-term memory artificial neural network algorithm (C-LSTM) in data mining technology to analyze and determine factors that have an impact on delayed production mode in the internal and external production and operation of enterprises. Combined with the actual production situation of iron and steel enterprises, a quantitative model of the delayed production was constructed. Lastly, data from a large iron and steel enterprise with good operation was used to verify the validity of the proposed model and analyze key influencing factors. According to the research, in scenarios of considering PDP alone, considering CODP alone, considering both PDP and CODP, considering PDP and CODP and using data mining technology to model, the matching degree of these methods with the actual situation of the enterprise is 31.8%, 61.4%, 71.6% and 86.6%, respectively. The numerical analysis results of the model based on data mining technology show that in delayed production, when customer service level improves or the delay penalty coefficient increases, the optimal locations of the product differentiation point (PDP) and customer order decoupling point (CODP) move toward the end of production, and the total cost increases gradually. When the difference in production cost or benefit of early delivery between the candidate locations of PDP and CODP is small, optimal locations of PDP and CODP are close to the beginning of the general and dedicated production processes. With an increase of cost difference or early delivery benefit, the optimal locations of PDP and CODP jumped to the end stage of the general and dedicated production processes, and the total cost begins to decrease.

Behaviour of Precariously Balanced Rocks under Seismic Excitation

A naturally occurring geological formation is precariously balanced rocks (PBRs) which might easily topple by an earthquake with severe ground motion. These rocks have been at the same place for many years. Strong ground accelerations have not occurred in the area for thousands of years as shown by the zone of unstable rocks. So, they are significant in both the engineering and seismological domains since they provide source of data for the maximum earthquake ground motion occurring at a site over the rock’s life time. The precariously balanced rock taken for this study is Krishna Butter Ball which is in Mahabalipuram, Chengalpattu district. In the numerical analysis, the peak ground acceleration at which the Krishna butter ball may topple is obtained. To identify the possible future earthquake, deterministic seismic hazard analysis has been carried out for Chengalpattu district. For this analysis, fault details have been obtained from Geological Survey of India. Arc map 10.1 version in Geographical Information System (GIS) platform is used for the interpretation of data like fault length, source (fault) to site (Mahabalipuram) distance from the fault details given by GSI. From the results of Deterministic Seismic Hazard Analysis (DSHA), it is observed that the possible future earthquake may have the magnitude in the range of 6.03 to 7.9. The computed peak ground acceleration (PGA) value corresponding to those magnitude ranges from 0.027g to 0.49g. The maximum PGA value 0.49g corresponds to the Palar river fault which is just 28.53 km away from the Krishna butter ball. From the results of numerical analysis, the behavior of Krishna butter ball for three different PGA i.e. 0.05g, 0.1g, 0.15g has been observed. Newmark sliding block analysis said that the rock may topple at the PGA of 0.35g. From this it can be concluded that the toppling acceleration of Krishna butter ball is relatively low.