Numerical Test Method Research Articles

Optimization Study of the Structural Parameters of an Artificial Percolation Intake Riverbed Based on a Numerical Orthogonal Test

Research on water abstraction techniques in sandy rivers is crucial for addressing water scarcity issues in northern China. This study introduces an artificial percolation water intake riverbed structural model designed to prevent sand intake and facilitate the extraction of clear water from sandy rivers, the main function of which is to artificially construct a helical flow field to realize the separation of water and sand and, at the same time, percolate the water. In this paper, we use a numerical orthogonal test method to study the influence of structural parameters and their combinations on water extraction by percolation, and the preferred combination of structural parameters. The main conclusions of this paper are as follows: Under the condition of certain structural parameters of the artificial riverbed, the single-width flow rate has an important effect on the mean circumferential flow rate of the vortex tube and the vortex tube seepage volume. The effect of different structural parameters on the mean circumferential flow rate of the vortex tube and the vortex tube seepage varies in magnitude. The longitudinal slope of artificial riverbed i had the greatest and most significant effect on the mean circumferential flow rate of the vortex tube, and each structural parameter had some effect on the vortex tube seepage Q but not to a significant level. When the sand content of the water flow is 15 kg/m3 and the maximum sand grain size of the suspended mass is 2 mm, the optimal structural parameter combinations of the artificial riverbed under different working conditions are as follows: Combination 20 is the optimal structural parameter combination for q = 0.3 m2/s; Combination 24 is the optimal structural parameter combination for q = 0.6 m2/s; and Combination 24 is the optimal structural parameter combination for q = 0.9 m2/s. The present study is of great significance for understanding the influence of each structural parameter and its combination on the effect of the water intake and sand discharge of an artificial percolation intake riverbed, and for optimizing the combination of the structural parameters of an artificial percolation intake riverbed.

Stability Analysis of Tunnel Rock Mechanical Parameters Based on Multi-Source Sensor Data Fusion

In this paper, the sensor is applied to the collection of rock parameter data. Aiming at the classification and evaluation of stability (i.e. rock quality), an attribute recognition model for the classification and evaluation of surrounding rock quality of underground engineering is established. Using multi-source data fusion and orthogonal numerical simulation test methods, the effects of rock mechanics parameters on the horizontal convergence of the tunnel, the settlement of the vault and the plastic zone coefficient are studied. Six factors (elastic modulus, Poisson’s ratio, internal friction angle, tensile strength, cohesion and density) and three levels of orthogonal experimental solutions were selected. The method of defining similar weight by using similar number to determine the weight of evaluation index, so as to calculate the comprehensive attribute measure, and apply confidence criteria to identify the stability of rock samples. Through the analysis and evaluation of rock mass quality classification of underground engineering, the application of the model and the evaluation method of rock mass quality classification are explained. The test results match the orthogonal test results; Considering the stability of tunnel envelope, the horizontal convergence, vault settlement and plastic zone coefficient after excavation should be comprehensively considered.

The Law and Mechanism of the Effect of Surface Roughness on Microwave-Assisted Rock Breaking

In physical engineering, a rock surface, whether naturally or artificially formed, is rough. When irradiating rocks, microwaves produce reflections and diffractions on the surface of rough rocks, which significantly affect the absorption of microwave energy by rocks, thus influencing the result of microwave irradiation. In order to explore the influence of rough rock surfaces on the effect of microwave-assisted rock breaking, microwave irradiation tests were carried out on basalt samples with different values of roughness to test the temperature and P-wave velocity of the samples before and after microwave irradiation. Numerical test methods were used to systematically study the influence of rough rock surfaces on microwave irradiation. The results show that, under the same microwave irradiation conditions, the effect of microwave irradiation on rough surface basalt is more significant than that of flat surface basalt. The surface temperature distribution range of flat surface specimens is narrow, the surface temperature range of rough surface specimens is wider and more inhomogeneous, and the maximum surface temperatures of rough surface specimens are much higher than those of flat surface specimens. After irradiation, new macroscopic cracks were generated on the surface of the samples, and the crack propagation of the rough surface samples was more obvious. The decrease in P-wave velocity before and after the irradiation of flat surface samples is small, and that of rough surface samples is larger. The main factors affecting the effect of microwave irradiation on the rough surface are the refraction and reflection of electromagnetic waves, heat conduction, and stress concentration on the surface.

Mechanism of Tire / Road Noise Emission and Reduction Technology

The significant noise reduction has been brought by recent electrification of power train of vehicles. More concern about impact on the health due to the environmental noise, especially road traffic noise, requires further reduction of tire / road noise emission caused by the contact between the tire and road surface. The tire / road noise emission mechanism can be described by three different systems such as the excitation, the response, and the propagation. The excitation is composed of the road excitation, the tread excitation, the air-pumping and the friction. The tire structural response and the acoustic response in the void formed inside contact patch are respectively excited by those sources. The recent technology development in numerical analysis and test methods allow us to investigate the detailed behavior of tire in various rolling condition. The present article gives progresses on the mechanism understanding of tire / road noise emission and some reduction technologies.

A Numerical Gear Rolling Test Method for Face-Hobbed Hypoid Gears

A numerical gear rolling test (NGRT) method for actual tooth surfaces was proposed. The non-uniform rational B-spline (NURBS) fitting method was adapted to reconstruct the actual tooth surface, and the instant meshing point as well as the transmission error of two meshing gears were solved. The instant contact ellipse boundary of each meshing point can be accurately searched, and then the contact pattern formed by a series of contact ellipses on the actual tooth surface can be obtained. Finally, the rolling test experiment for a pair of hypoid gears was conducted to verify the feasibility of the proposed method. The result shows that the contact pattern obtained is consistent with the actual rolling test result, the relative errors of the transmission error amplitudes were only 4.5% and 5.3% for the drive and coast sides, respectively, and the contact ellipse of the actual tooth surface is not necessarily a standard ellipse and the instant contact path is not necessarily a straight line. This NGRT method helps to reduce equipment and time costs in closed-loop gear manufacturing, which is of great significance for mass production.

Lightweight Optimization Design and Fatigue Lifetime Analysis for Anti-rolling Torsion Bar of Rail Vehicle

Based on the fatigue strength assessment method in the FKM standard, the lightweight design of a type of anti-rolling torsion bar is studied by using the finite element method. Firstly, the finite element model of the torsion bar structure is constructed by using the Creo software and the HyperMesh software, and then the finite element analysis is carried out by using the ABAQUS software. The numerical simulation results indicate that under the condition of ultimate load 29.2kN, the static strength, anti-rolling stiffness and fatigue strength of the torsion bar are all satisfy with the design requirements. Secondly, the orthogonal numerical test method is utilized to investigate the influence of geometric parameters on the anti-rolling stiffness and Factor of Strength (FOS) value of the torsion bar. Taking the structural geometric parameters as variables and the FOS value as the objective function, a second-order response surface model is established. The single objective and multi-factor optimization design for the torsion bar under the condition of stiffness constraint is conducted by using the Isight software and multi-island genetic algorithm. The results show that, comparing with the original structure, the weight of the optimized structure is reduced by 20.89%, and the static and dynamic strength, and anti-rolling stiffness of the optimized structure are match with the design requirements. Finally, the static and dynamic strength tests for the optimized torsion bar are individually operated at the ultimate load and under two-stage cyclic loading with amplitude 18.0kN and 29.2kN. the results show that the calculated stiffness coefficient is consistent with the test one, and the service lifetime of the torsion bar is satisfy with the design requirement.

A new numerical well test method of multi-scale discrete fractured tight sandstone gas reservoirs and its application in the Kelasu Gas Field of the Tarim Basin

The cretaceous gas reservoir in Kelasu Gas Field of the Tarim Basin is a rare ultra-deep and ultra-high pressure fractured tight sandstone gas reservoir where multi-scale discrete fractures of matrix, fracture and fault are developed, so its development cannot be conducted just based on static and dynamic reservoir description. In order to solve this problem, this paper establishes a numerical well test model of vertical wells based on matrix, fractures and faults (large fractures and small faults) by combining the random generation of natural fracture networks with the unstructured discrete fracture modeling method to break through the traditional continuous medium well test model. In addition, the model is solved by using the finite element method with mixed element, and the typical well test type curves under different random fracture networks are obtained. And the following research results are obtained. First, based on the observed data, the fracture network distribution modes of fractured tight sandstone gas reservoirs are classified into three categories. The influence of random generation of fracture networks on typical well test type curves is discussed. The results of discrete fracture well test model are compared with those of the traditional continuous medium well test model, and the applicable conditions of the traditional continuous medium well test model is determined. Second, there are great differences between the results of discrete fracture model and those of dual porosity medium model. 1 The dual porosity medium model is a special case of the discrete fracture model, in which the fractures are evenly distributed within infinitely small spacing. Third, the characteristics of well test type curves under three fracture network distribution modes are discussed. The well test type curves that cannot be interpreted by the conventional dual/triple porosity continuous medium model are successfully interpreted by using the established well test interpretation model of random discrete fracture. The curve matching effect is ideal and the interpreted parameters are reasonable. In conclusion, the new model and the new method reveal the development mechanism of step-by-step production and coordinated gas supply between media of different scales, explain the development characteristics of large inter-well productivity difference and abnormal rapid inter-well pressure response, and provide a reference for the development of similar gas reservoirs.

Understanding the Effects of Inlet Structure on Separation Performance Based on Axial Velocity Wave Zone Characteristics

There are many factors that affect the separation performance of the hydrocyclone, including the structure of the feed body, but the mechanism of influence of the internal flow field of the hydrocyclone on the Axial Velocity Wave Zone (AVWZ) is not yet clear. Based on the numerical test method, this paper analyzes the influence of the feed body structure on the internal flow field and the particle distribution characteristics of the AVWZ and its internal relationship with its separation performance. The results show that the influence mechanism of the structural parameters of the inlet structure on its separation performance is extremely complex, but all of them are reflected in the AVWZ’s characteristics, including the flow field characteristics, spatial distribution characteristics, and internal particle distribution. The changes on the inlet diameter will also influence the flow field, centrifugal strength, turbulence strength, and particle distribution, while the inlet aspect ratio is altered largely by changing the settling distance of particles. Finally, effects of inlet structure on the separation performance of the hydrocyclone can be explained from the AVWZ, which provides the basis for designing the inlet structure to improve separation performance.

Stability Influencing Factors and Control Methods of Residual Coal Pillars with Solid Waste Materials Backfilling Method

Affected by coal mining activities, the remaining coal pillars are very likely to be destabilized and cause safety accidents. The backfilling of the remaining goaf can maintain the stability of the coal pillar well, but the coal pillar in the unfilled zone may still be unstable. In this paper, the effect of backfilling materials on coal pillars and the reinforcement method are discussed using numerical simulation, statistical mathematics, elastic mechanics, and mechanical test methods. The results show that: backfilling with solid waste materials and reinforcing the coal pillar could maintain the stability of the bottom goaf, where the backfill body height is the main factor in the strength of the coal pillar. The propagation of the confining stress of the backfill body on the pillar in the unfilled zone is the primary way to influence the coal pillar strength. Changing the backfill body height filling can affect the coal pillar strength. By analyzing the propagation law of confining stress in the coal pillar, the minimum backfill body height is determined to be 7 m. Combined with mechanical tests and the Mohr–Coulomb criterion, the minimum confining pressure required to maintain the coal pillar stability under the peak ground pressure is analyzed. The ratio of solid waste materials is determined based on this. Field tests have proved that the coal pillar remains stable when the goaf is not filled, and the cement/fly ash ratio is 1:4, which can ensure product safety. The research has significant value and significance for the governance of the remaining coal pillars and production safety.

Experimental Study of the Damage and Failure Characteristics of the Backfill-Surrounding Rock Contact Zone.

Due to obvious differences in the properties of the filling body and surrounding rock, deformation always develops near the contact zone. Thus, determining the damage and failure characteristics of the contact zone between the backfill and surrounding rock is a precondition for safe production in mines. Taking Jinchuan mine as study area, the backfill-surrounding rock contact zones are divided into three models according to their different geometric shapes, namely, a linear model, embedded model, and multiple broken line model. A combined numerical simulation and physical model test method was adopted in this study. The research results show that the damage in the linear model begins at the seam, the failure is mainly concentrated in the filling body, and shear failure is dominant. The damage in the embedded model initially occurs around the inflection points, while the damage in the multiple broken line model initially occurs at the seams, and cracks always appear on the vertical contact surface first. Among the three contact models, the stability increases as follows: embedded > multiple broken line > linear. Moreover, the filling body enclosed by surrounding rock is the most stable, and the surrounding rock located in the footwall is more stable than the filling body located in the footwall. The conclusions of this study provide a theoretical basis for designing a mining scheme for Jinchuan mine and other mines with similar geological conditions and mining methods, and they provide a reference for studying the mechanical properties and stability of composite materials.

Research on the buoyancy motion of a submarine in calm water

ABSTRACT Prediction of submarine buoyancy motion is a prerequisite for exploring the characteristics of submarine control and safety. The present article thoroughly describes the numerical method and calculation procedure for the simulation of submarine buoyancy motion. The turbulence model and numerical discretisation scheme are described. The uncertainty of numerical calculations is analysed and the numerical results are verified based on the buoyancy test. The reliability of the numerical method is confirmed. Furthermore, the numerical calculation results are in good agreement with the experimental results, verifying the feasibility of the numerical method. The effect of positive buoyancy, the longitudinal position of the centre of gravity and diving depth on the submarine buoyancy are studied. The numerical scheme, test method and related conclusions can provide technical support for the research on submarine buoyancy.

Effects of Curved Wind Barrier on the Aerodynamic Characteristics of a Train–Bridge System and Its Static Wind Load

Wind barriers are important measures that guarantee the running safety of high-speed trains under crosswind conditions, however, they can change the aerodynamic coefficients of a train–bridge system and the distribution of the flow field around a train and bridge, and studies have often ignored the static wind load characteristics of wind barriers. In this paper, the effects of height and porosity on the curved and vertical fence-type wind barriers on the aerodynamic characteristics of a train–bridge system are investigated by using numerical simulation and wind tunnel test methods. The static wind loads of the two types of wind barriers are analyzed by comparing the drag coefficients and the surface wind pressure distributions. The results show that, compared with the vertical wind barrier, the curved wind barrier can reduce the drag force and moment of a train while reducing the impact of the aerodynamic forces on a bridge. The static wind load of the curved wind barrier is less than that of the vertical wind barrier, when a train is on the windward side of a bridge, the drag coefficient of the curved wind barrier is only about 35% of that of the vertical wind barrier.

Influence Mechanism of a Bridge Wind Barrier on the Stability of a Van-Body Truck under Crosswind

Understanding the crosswind stability of cars under strong wind loads and research on wind resistance methods is important for improving the safety performance of wind-induced driving on bridges. Taking van-body trucks as the research object, numerical calculation methods and wind tunnel test methods are used to conduct the wind-induced driving safety analyses of van trucks on a cross-sea bridge. The influence of the structural parameters of the barrier-type wind barrier on the aerodynamic characteristics and straight-line driving stability of the trucks on the bridge is studied and analyzed quantitatively. The results show that the decrease in the porosity of the wind barrier can effectively reduce the average wind speed of the bridge deck, and increasing the height of the wind barrier can effectively reduce the wind speed and increase the occlusion height of the bridge deck. The lateral acceleration, yaw rate, and lateral displacement of trucks decrease with the decrease in the porosity of the wind barrier and decrease with the increase in the height of the wind barrier. The research conclusions can not only provide data support for wind-induced driving safety analysis and the wind-resistant design of bridges but also provide a new method to balance the requirements of bridge wind-induced driving safety and bridge wind-induced structure safety.

Investigation on triaxial numerical test method and dilatancy behavior of asphalt mixture

To investigate factors affecting the dilatancy behavior of asphalt mixture, more accurate prediction and reduction of rutting are required. The dilatancy law of asphalt mixture was studied using an indoor triaxial test. Based on the triaxial numerical test, the effect of meso-model parameters on the test results was studied, and relevant model parameters were determined. Then, the effects of the loading speed, confining pressure levels, and pore and aggregate characteristics on the dilatancy performance of asphalt mixture were studied. The results show that the constructed triaxial numerical simulation method correlates well with the indoor triaxial test. Increasing the loading speed and confining pressure levels can improve the dilatancy resistance of the asphalt mixture numerical model. When pores are uniformly distributed, the dilatancy deformation of the numerical model decreases as the porosity increases; the dilatancy angle increases with the increase of aggregate content; and the rougher the surface of the coarse aggregate, the larger the dilatancy angle of the specimen; when the aggregate distribution characteristics are different, the corresponding dilatancy characteristics are also different.

Effects of porosity, orientation and connectivity of microcracks on dispersion and attenuation of fluid-saturated rocks using an upscaling numerical modelling of the squirt flow mechanism

Squirt flow is a wave-induced fluid flow mechanism to account for the velocity dispersion and attenuation of fluid-saturated porous media. Theoretical models of squirt flow cannot deal with complex microcrack-pore networks and thus cannot give accurate dispersion and attenuation curves with respect to frequency. We adopt a numerical oscillatory compressibility test method, based on the quasi-static poroelastic equation of Biot, to model the squirt flow and calculate corresponding P-wave modulus dispersion and attenuation. We also designed nine porous medium models containing different crack-pore configurations and investigated the effects of microcrack porosity, orientation and connectivity on the elastic responses. Modelling results show that not only microcrack porosity but also their orientation has control on the magnitude of the P-wave modulus dispersion and attenuation. Preferentially aligned microcracks may cause frequency-dependent anisotropy in the P-wave modulus and attenuation. Microcrack connectivity has a negligible influence on the dispersion and attenuation magnitude but a large influence on the characteristic frequency of the squirt flow, which is not predicted by theoretical models based on simple representative element volume of crack-pore structure. Therefore, detailed geometry of crack-pore network, of which microcrack porosity, orientation, aspect ratio and connectivity are vital factors, dictates the unique variations in the elastic modulus and associated attenuation with frequency caused by the squirt flow. Pore structure obtained by CT scanning representative of that of the whole rock is needed to obtain more accurate poroelastic responses of the rock with the numerical oscillatory compressibility test method. In this regard, we provide a powerful tool for evaluating dispersion and attenuation of fluid-saturated rock media with complex crack-pore structure, which have potential applications in seismic exploration of hydrocarbon in the subsurface.

Analysis on Effective Coefficient of Porous Continuous Medium in Seepage Field

When a porous continuous medium is in a saturated state, the effect of pore water pressure on its deformation depends on the effective coefficient in the stress equation. Determination of this coefficient is an important subject for analyzing the deformation of porous continuous media in the seepage field. This work considers a porous continuous medium with square pores to determine the effective coefficient by combining theoretical analysis and a numerical test method. The water element analysis method is applied to further verify the value of the effective coefficient and to analyze the influence of pore water pressure on the deformation of a porous continuous medium from a mesoscopic perspective. Then, the correctness of the pore water pressure is verified using the initial strain method. Through the above methods, the action mechanism of pore water pressure on porous continuous media could be further understood. A reasonable and accurate method for calculating the effective coefficient is also provided. The correct method for analyzing the deformation of porous continuous media in the seepage field is also explained.

Analysis of the Influence of Different Bionic Structures on the Noise Reduction Performance of the Centrifugal Pump.

The strong noise generated during the operation of the centrifugal pump harms the pump group and people. In order to decrease the noise of the centrifugal pump, a specific speed of 117.3 of the centrifugal pump is chosen as a research object. The bionic modification of centrifugal pump blades is carried out to explore the influence of different bionic structures on the noise reduction performance of centrifugal pumps. The internal flow field and internal sound field of bionic blades are studied by numerical calculation and test methods. The test is carried out on a closed pump test platform which includes external characteristics and a flow noise test system. The effects of two different bionic structures on the external characteristics, acoustic amplitude–frequency characteristics and flow field structure of a centrifugal pump, are analyzed. The results show that the pit structure has little influence on the external characteristic parameters, while the sawtooth structure has a relatively great influence. The noise reduction effect of the pit structure is aimed at the wide-band noise, while the sawtooth structure is aimed at the discrete noise of the blade-passing frequency (BPF) and its frequency doubling. The noise reduction ability of the sawtooth structure is not suitable for high-frequency bands.

Study on the influence of surrounding rock parameters on the stability of tunnel face

The surrounding rock is the construction environment and main load source of the tunnel, and its physical parameters have an important influence on the stability of the tunnel face. Based on orthogonal test method, with the Georgia E60 highway 3.0.04 - TA tunnel under construction as the engineering background, numerical test method is used to compare and analyze the influence of different surrounding rock parameters ( elastic modulus E, cohesion C, internal friction Angle φ) on the stability of tunnel face. The multiple linear regression fitting equations of three factors and extrusion deformation are given and verified. The results showed that the elastic modulus and cohesion of surrounding rocks had a significant influence on extrusion deformation of the tunnel face, while the internal friction Angle had no significant influence. The extrusion deformation of the tunnel face is negatively correlated with the elastic modulus, cohesion and internal friction Angle of surrounding rocks. The fitting equation can provide a means for predicting the stability of surrounding rock and guide the construction of the tunnel.

Floor water inrush analysis based on mechanical failure characters and microseismic monitoring

Failure characteristics of the coal seam floor above-confined aquifer are the key to understanding water inrush mechanism during mining. Due to the heterogeneity of coal strata and complex structures of the coal seam floor, it is still difficult to comprehensively reveal failure characteristics of the coal seam floor and accurately determine the floor failure depth during mining above the confined aquifer. In this research, Dongjiahe coal mine, where the coal seam floor is exposed to abundant Ordovician limestone water, is taken as a case study. An improved theoretical model is firstly proposed, in which the whole confined aquifer in the floor is taken into account for stress and failure analysis. Then, RFPA (Rock Failure Process Analysis), a numerical test method considering the heterogeneity of coal and rock, is adopted to simulate the progressive failure process of coal seam floor during mining. Moreover, The microseismic monitoring system is constructed and the 3D visualization is realized through virtual reality, which can sense the initiation and expansion of microdamage in real-time. Based on microseismic monitoring results, we investigate and calculate the floor disturbance depth. By comparing the failure characteristics obtained by different methods, we discuss the pros and cons of the above methods. Finally, a comprehensive analysis method and roadmap are proposed to analyze the failure characteristics of the coal seam floor more accurately based on theoretical calculation, numerical simulation, and microseismic monitoring. The results can provide some reference for the evaluation and prevention of floor water inrush hazards.

Numerical simulation and experimental study on floor failure mechanism of typical working face in thick coal seam in Chenghe mining area of Weibei, China

The hydrogeological conditions of Weibei coalfield in China are complex; the main mining No. 5 coal seam is seriously threatened by Ordovician limestone karst water disaster at the bottom of coal measures. Chenghe No. 2 Mine is a typical example. With the increase of mining depth, confined water pressure increases year by year. To find out the law of floor deformation and failure caused by No. 5 coal seam mining in Chenghe No. 2 Coal Mine, this paper takes 24,508 working face of Chenghe No. 2 Coal Mine as engineering geological background, and carries out research by numerical simulation and field test methods. The stress field, displacement field distribution law and plastic zone evolution characteristics of No. 5 coal seam roof and floor varying with the advancing degree of mining face are obtained by simulation calculation. The progressive failure process of the whole floor stratum is reproduced dynamically, and the development height of the water conducting fracture zone of overburden is given. The maximum failure depth of the floor occurs at the mining distance of about 1.5 times the mining width, at which time “the saddle shape” supporting pressure arch reaches its maximum. At the same time, the multi-point separated layer displacement meter is used to carry out field measurements. The results show that the maximum failure depth of floor occurs in the goaf, and the maximum range of the relative displacement of the floor is 8.0–8.5 m, which is close to − 6.1 m from the coal mining surface, consistent with the results of the numerical simulation. Comprehensive analysis shows that the maximum failure depth of coal seam floor in Chenghe No. 2 Coal Mine is 8.3 m. The conclusion provides a favorable basis for the rational formulation of water disaster control countermeasures. It provides reference and experience for mining under safe water pressure of aquifuge for prevention and cure water of similar working face in Chenghe mining area in the future.