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Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the issue of flow induced vibration of spillway emersed radial gates under partially opening conditions, a fluid structure coupling transfer mathematical model for gates and spillway flow was constructed by using Computational Fluid Dynamics (CFD) software Fluent and Computational Structural Dynamics (CSD) software Mechanical APDL. Calculated and analyzed the vibration characteristics of the gate during discharge, developed a gate flow induced vibration back analysis program based on the principle of modal superposition, and achieved back analysis of the dynamic response results of the gate flow induced vibration. Taking the exposed arch gate of a certain project in Wujiang as an example for forward and backward analysis, the results indicate that the fluctuating pressure on the gate panel obtained from the Large Eddy Simulation (LES) turbulent model exhibits characteristics of low frequency, narrowband, and approximately gaussian distribution. The structural dynamic field of the gate is calculated by combining modal coordinates, vibration mode vectors, and stress vectors. The results of the back analysis of the dynamic displacement field and dynamic stress field are basically consistent with the results of the full method forward analysis, demonstrating the rationality of the back analysis method and the applicability of the program. [ABSTRACT FROM AUTHOR]

Supergravity is a noncontact volumetric force; when there is a density difference between the two phases, supergravity can strengthen their separation. The removal of nonmetallic inclusions in steel by supergravity technology not only does not cause molten steel to stir back to the mixing but also promotes the rapid floating of inclusions and shortens their floating time in the molten steel. Small inclusions that are difficult to remove can be removed using a supergravity field. The shape of the inclusions affects their floating behavior in molten steel. To study this effect, this study uses the fluid–structure interaction method to track the computational fluid–solid interface state, constructs three inclusions with different aspect ratios in a two-dimensional longitudinal section, and performs simulation studies of the floating behavior of the inclusions in a supergravity field. The effects of the different initial angles of the inclusions on their floating behavior were also compared. The simulation results show that the floating velocity of the inclusions is related to their shape and floating angle, and the faster the floating velocity, the closer the aspect ratio is to 1, or the floating angle is too vertical. For a given length, inclusions with a larger equivalent diameter float faster. In the supergravity field of G = 1000, the inclusions with a length of 1 μm did not undergo rotation; the inclusions with lengths of 10 and 20 μm rotated from the initial angle (45°, 90°) to the horizontal and then floated steadily. The floating velocity of inclusions is related to the real-time angle of inclusions. The rotational state of the inclusions gradually decreases as the gravity coefficient decreases. When G = 50, the inclusions with a length of 20 μm (initial angle of 90°) fail to rotate completely, which also proves that the inclusions are more likely to rotate when initially inclined instead of vertically. In addition, it was concluded that supergravity does not cause anisotropy in steel properties and that the method of removing inclusions from steel by supergravity does not have a substantial negative effect on steel properties. Finally, this study noted that the prediction of the supergravity treatment time using this model should be based on the floating velocity of the inclusions in the horizontal state, and an approximate time for the floating removal of the inclusions is provided based on this conclusion.

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the immersed boundary method, a resolved CFD-DEM algorithm is proposed to tackle fluid-solid interaction problems which widely exist. In the proposed method, the fluid filed is described by the computational fluid dynamics in the Eulerian framework, while the movement and collision of the solids are simulated by the discrete element method in the Lagrangian framework. In order to deal with the moving interfaces between the fluid and the solids, several immersed boundary points are allocated on the boundaries of the solids. Two classic test cases are calculated to verify the accuracy of the proposed method, including the vortex-induced vibration of a cylinder and the rotational galloping of a rectangular rigid body. Good agreements are achieved between the current results and those in previous references and the reliability of the present method in modelling the fluid-solid interaction problems are proved. Finally, the sedimentation of multiple solids is simulated and the ability of the proposed CFD-DEM method in solving the complex fluid field and the collision among the solids with arbitrary shapes are verified.

As a short-process hydrometallurgical technology, slurry electrolysis (SE) collects the stirring that improves the suspension of ore, the membrane bag that acts as purifying, and the cathodic and anodic plates that promote ion migration in one tank. The stirring helps to maintain the ore suspended. As the SE tank is stirred, the membrane bag will deform and become damaged, severely limiting production efficiency. In this research, the one-way fluid-structure interaction (FSI) was used to examine the impact of the solid–liquid suspension on membrane deformation, which was based on the computational fluid dynamics (CFD) and solid finite element method (FEM). Through the full 3D quantitative analysis, the database of membrane deformation under various conditions was established. The membrane was extruded to the center during the initial stirring conditions, and the greatest deformation measured 891.66 mm. Primarily, membrane deformation was brought on by the pressure differential brought on by liquid velocity, solid concentration distribution, and liquid level. The maximum deformation of the membrane first decreased and then increased with the increased liquid level difference between the cathode and anode. With the upper fixed constraint, the maximum deformation of the membrane appears at y = 1.2 m. The larger the stirring speed is, the smaller the optimal liquid level difference required to minimize the membrane deformation. The stirring speed changes the overall pressure distribution by changing the dynamic pressure in the anode domain. The maximum deformation of the membrane decreases first and then increases with the increase of electrolyte density in the cathode domain. The membrane bag is extruded to the cathode domain when the pressure in the cathode region is insufficient because of the low electrolyte density in the cathode domain. When the cathode pressure increases, the membrane bag bulges to both sides, and the inner bulge is greater than the outer. With an increase in solid volume concentration (SL) in the anode domain, the maximum membrane deformation first reduces and subsequently increases. When SL = 15%, the membrane deformation reaches the minimum value of 226.7 mm. The closer to the bottom of the tank, the greater the influence of solid content on absolute pressure. The maximum membrane deformation is drastically decreased to 0.664 mm when the frame restrictions are considered. It can support the industrial control process via visual analysis.

To overcome the significant challenges to accurate numerical simulations of water entry problems, like the treatment of the moving boundaries, the description of highly distorting free water surface and the reflection of strong coupling effect between fluid and solids, a CFD-DEM-IBM approach, which incorporates the computational fluid dynamics-discrete element method (CFD-DEM), the immersed boundary method ( IBM) and the improved conservation level set (ICLS) method, is proposed for the precise prediction of water entry phenomenon. Fixed Cartesian grids are used to discretize the computational domain, with CFD and DEM used to describe the motion of fluid and the motion of solid bodies, respectively. IBM is introduced to track the solid boundaries and obtain accurate fluid-solid interaction forces. The free water surface is captured using the ICLS method which can ensure both the validity of interface properties and the conservation of mass. A partitioning algorithm is employed to perform multiple alternating iterations within a time step to reflect the strong coupling effect between fluid and solid, establishing a high-resolution CFD-DEM-IBM numerical model. Water entry of a cylinder with prescribed motion, symmetric and asymmetric water entry of a wedge and water entry of multiple bodies are then performed. The results show that the detailed resolution of the fluid phase along with the strong coupling effect can be reasonably reflected by the CFD-DEM-IBM approach, and it is remarkable in addressing water entry problems even when multiple rigid bodies are involved. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Computer-Aided Design & Computer Graphics / Jisuanji Fuzhu Sheji Yu Tuxingxue Xuebao is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Jinyun Mountain forest fire event in August 21 to 26, 2022 has attracted extensive attention in China. The forest fire hazard has a long-term impact on the nature soil of forest plant and soil. In addition to the mechanism and prevention measures of forest fire, the safety prediction for post-hazards (such as landslide) can also be one of the most urgent tasks at present. But now, the main challenge is the long-term estimation of dynamical root reinforcement for the lack of monitoring data on plant root death and regrowth post fire. This study aims to clarify the mechanism of forest slope failure, and then to predict the landslide risk post fire. The field and lab tests were performed on the physical properties of root soil in the burned woodland in the Hutou Village near Jinyun Mountain. The SIDLE curve model was selected to predict the dynamics of root reinforcing strength after forest timber harvesting. Finally, the simulation was conducted for the post-40 years slope stability using COMSOL. Specifically, a double-layer slope model was assembled, according to the surveyed slope size and soil property. A systematic analysis was made on the root strength time inflection points of common trees and shrubs in published literature and according to which the SIDLE parameters of shrub in this work were inversed and dopted for simulation work of slope deformation and stability in the future. Both the general and extreme rainfall conditions with an intensity of 80 mm/d were considered in the simulation. The results show that: 1) The common type of forest margin slope in Jinyun Mountain was characterized by the double-layer soil slope structure consisting of sandy loam and deeper sandy mudstone. There was a significant difference in the magnitude of average conductivity and shear strength parameters between the upper sandy loam and lower layer sandy mudstone. The conductivity of the surface layer was 5.2×10−6 m/s on average, 3.47 times that of the lower layer. The cohesion and internal friction angle of the surface layer were 5.5 kPa and 18°, respectively, which were 3.06 and 0.69 times that of the sublayer, respectively. 2) In the general situation without rainfall infiltration, the slope was in a stable state with a potential sliding surface located in the deep layer (FOS>2), while under extreme rainfall conditions, a waterlogged zone was prone to appear on the upper and lower interface with the positive pressure of 10 kPa. The factor of the safety of the bar slope (FOS=1.13) was lower than that of the vegetated case (FOS=1.32), indicating the key role of plant roots for soil strength compensation and slope stability. 3) Within a few years after the fire, there was less impact of the fire event on the stability in general situation, because the critical sliding surface was located in deep soil that was far below the root zone. By contrast, the potential sliding surface was quite shallow under extreme rainfall conditions. As such, the FOS versus annual time presented a ‘rapid decreasing and then slowly increasing’ shape curve, indicating a landslide-prone period last for several years. Consequently, a dramatic variation was found in the strength and permeability of the upper and lower layers of soil under the common type of sandy loam-mudstone slope in Jinyun Mountain. A waterlogged zone was prone to appear on the soil interface under extreme rainfall conditions, leading to the reduction of local effective stress. This was the main reason for the slope failure. In current time, the FOS of bar slope and vegetated slope are 1.13 and 1.41 respectively under the extreme rainfall condition, owing to root reinforcement of 19.8% contribution. Taken the root decay and recovery process into account, it is conservatively estimated that the landslide-prone period occurres in 6-9 years after the fire event with a FOS between 1.22 and 1.32, while the slope recovered to the initial stability level of at least 18-24 years. This preliminary prediction can also be required long-term observation and verification in the future. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The simulation of fish autonomous swimming has always been an important problem concerned by many disciplines, such as bionics, fish behavior and ecological hydraulics. Based on fluid structure coupling numerical simulation technology and deep reinforcement learning algorithm, an intelligent fish adaption behavior decision-making platform was established, which can realize the fish adaption swimming with the optimal decision-making scheme under different surrounding environment conditions. Deep reinforcement learning method was used to realize fish brain function, which simulating its continuous learning and final decision-making. The flow field and fish motion were simulated by immersed boundary-Lattice Boltzmann method to provide rich training samples for fish and execute fish brain decision. Based on this platform, the typical prey capture and Karman gait of fish were simulated and the training effect were analyzed. The simulation results show that in the prey capture simulating, the fish with different initial position angles can reach the target point with the optimal trajectory. In Karman gaiting, the fish tail beat frequency can be adjusted to approach the vortex shedding frequency, so as to absorb energy from the Karman vortex field to stabilize the gait in the vortex street. In the research of fish adaption swimming, the decision-making platform has stronger adaptability to complex flow field than traditional physical experiments, and can provide technical support for digital twinning in the fields of hydraulic engineering, ecological environmental engineering. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A CFD-DEM-IBM method with high resolution is proposed based on the immersed boundary method（IBM） to describe the sedimentation phenomenon accurately and to investigate the underlying influence mechanism between fluid and particles in dense fluid-particle systems. The fluid phase is analyzed by the computational fluid dynamics（CFD） while the discrete element method（DEM） is utilized to simulate the motion of individual particles. The IBM is introduced to tackle the moving boundaries of particles and the interaction forces between fluid and particles are considered by an extra body force added to the Navier-Stokes momentum equation. The strongly coupled fluid-solid system is then achieved through the successive iterative scheme where several iterations are required within each time step until the convergence conditions are exactly satisfied. Sedimentations of one, two and multiple particles are simulated, which reveal that the proposed method could obtain the accurate interaction forces among discrete particles and fluid along with the fully resolved fluid phase around the particles compared with the conventional unresolved CFD-DEM method. The agreement between present results and previous work demonstrates the accuracy and validity of the presented method, and the applicability together with the superiority of the CFD-DEM-IBM method is also proved when the dense particulate flows occur. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Computational Mechanics / Jisuan Lixue Xuebao is the property of Chinese Journal of Computational Mechanics Editorial Office, Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Shenzhen University Science & Engineering is the property of Editorial Department of Journal of Shenzhen University Science & Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Ballistics / Dandao Xuebao is the property of Journal of Ballistics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A two-dimensional numerical model for the rolling process of mud barge under periodic waves was established by using two-phase flow model and overset mesh technique. The influence of liquid-solid interactions during slurry sloshing, barge rolling and waves on the stability of the vessel was investigated. The impact of slurries with different loading levels on the rolling suppression ability of the barge was analyzed. It is found that under the same periodic wave, the mud barge roll angle of 8% at empty load is reduced to 4% after full load of slurry, and the amplitude of vertical bump is also reduced by 40%. The analysis shows that the slurry sloshing in the mud bin often has the opposite trend of movement with the waves, making the effect of suppressing the wave-shaking, but sometimes it also causes the reverse shaking of the mud barge. Ignoring the change of the inertia of the whole ship, the mud bar rolling suppressing performance is not always positively related to the mud load. For a specific wave, loading a proper amount of slurry or even clear water in the mud chamber can make the barge or similar hopper dredger have the best navigation stability. [ABSTRACT FROM AUTHOR]

BACKGROUND: The main treatment for valvular heart disease is heart valve replacement. The design and performance optimization of artificial heart valves are currently the areas of research. Numerical analysis and experimental methods are major keys to analyzing the mechanical properties of artificial heart valves. Analyzing the mechanical properties of the valves by finite element method and displaying the mciro-stress of the valves in vivo provide more accurate data for the design and performance optimization of artificial heart valve. OBJECTIVE: To establish a more realistic vascular model and investigate the effects of stratified vessels on the deformation characteristics and stress distribution of aortic valves, providing theoretical mechanical data for further improving the design of artificial heart valve. METHODS: Finite element geometric models and mathematical models including aortic valve, vessel wall and blood were established, in which the vessel wall was stratified. The effects of stratification characteristics on the fluid-solid interaction deformation and stress of the aortic valve were investigated to verify the importance of the stratified vessel wall. RESULTS AND CONCLUSION: Valve deformation mainly occurred in the leaflets, the arterial wall had no obvious deformation, the highest level of free deformation was observed at the leaflet free edge. The deformation from the free edge of the leaflet to the suture edge showed a gradient decrease tendency. The maximum equivalent stress of the whole heart valve model was located on the outer arterial wall (near the suture point of the valve leaflet and the arterial wall). The inner and outer arterial walls were greatly different in force. The equivalent stress value of the inner arterial wall was much smaller than that of the outer arterial wall. The stress between inner and outer arterial walls was not continuous. The maximum equivalent stress of the leaflets was at the suture edge of the leaflets and the arterial wall. Compared with the previous studies that did not consider the stratification characteristics of the arterial wall, the maximum equivalent stress value of the leaflets was closer to the ex vivo failure stress of the human mitral valve leaflets. [ABSTRACT FROM AUTHOR]

Towoard the bearing capacity design issue for the stirring shaft， the torque， deformation and the stress situations were studied based on computational fluid dynamic simulation and fluid-structure interaction analysis by working with various viscosity materials， for the multi-layer stirring and fermentation machine for high viscosity material. The strength-safe viscosity limits and range are calculated according to the torque force of the stirring device， as well as the torque of stirring device under different filling height was analyzed. The results indicated that the on-paddle torque in the first layer is the largest， and the largest deformation happens in the finally the sixth layer. Besides the maximum stress occurs in the shaft segment between the short shaft and the first layer stirring paddle. The safe viscosity limit is 205Pa·s. The height variation of the filling material has little effect to the torque in the stirring device and the optimum heitht range is 100~150mm from the material surface to the top of stirring tank. [ABSTRACT FROM AUTHOR]

The concentrated wind energy device is the core of the wind energy concentration generator, so the material choice of the former can influence directly the widespread application of the latter. This research adopts a fluid-solid interaction(FSI) method to study the viability of using organic glass to manufacture concentrated wind energy devices. The Poisson’s ratio, Young’s modulus and fracture stress of organic glass change with the temperature. Therefore, the wind pressure distribution on the surface of the concentrated wind energy device is worked out when air flows at the speed of 25 m/s at different temperatures under normal atmospheric pressure. Then, the maximum equivalent stress and the maximum deformation can be also worked out when the wind pressure distribution is loaded on the concentrated wind energy device at the corresponding temperature. So at first, a solid-field model of a concentrated wind energy device is created based on the size of the model by using the computer aided design(CAD) software. And the solid-field model is imported into the finite element analysis software and a cylinder is established, and the cylinder and the solid field have the same axial line. The radius of the cylinder is 10 m and the height is 30 m. The distance between the inlet of the fluid-field area and the bottom surface of the concentrated wind energy device is 5 m. Then through Boolean subtraction method, a geometric fluid field is established by subtracting the solid field area in the cylinder. With the help of the computational fluid dynamics(CFD) software, the fluid field is simulated and calculated in a specific wind field. A non-uniform tetrahedron meshing and an SST k-ω turbulence model are adopted. The fluid medium is air and the pressure is always 101325 Pa. The temperatures are 233.15, 243.15, 253.15, 263.15, 273.15, 283.15, 293.15, 303.15 and 313.15 K respectively. The density, the thermal conductivity coefficient, the constant-pressure specific heat capacity and the viscosity correspond to the pressure of 101 325 Pa and the temperature. And the mass flow rate, turbulent kinetic energy and specific dissipation rate can be calculated from the density, viscosity and size of fluid field. When the temperature is 293.15 K, the density, viscosity, thermal conductivity coefficient, constant-pressure specific heat capacity, mass flow rate, turbulent kinetic energy and specific dissipation rate are respectively 1.2054 kg/m3, 1.86×10-5 kg/(m·s), 0.02593 w/(m·K), 1013 J/(kg·K), 9 464.048 kg/s, 0.686 m2/s2 and 24 s-1. The mass flow inlet and pressure flow outlet are adopted. The surface roughness height of the concentrated wind energy device is set to 0.3 mm. When the component residual reaches 1.0×10-4 kg/s, the equation converges and the distribution of the wind speed and wind pressure in the fluid field under different temperatures are obtained. The diagram of wind speed distribution shows that, when the temperature is 293.15 K, the average wind speed inside the central cylinder exceeds 25 m/s. This indicates that the concentrated wind energy device has increased wind speed and concentrated the energy. In the structural static module, the solid field, as a whole, is split into tetrahedral meshes, and the size of the structural unit is 0.005 m. When the calculated results of the fluid field are loaded on the concentrated wind energy device, the stress cloud plot and the solid-field deformation plot are obtained. The plots show that, when the temperature is 293.15 K, the maximum stress is on the back of the outer edge of the shrinkable pipe, with a maximum stress of 1.5378 MPa, far less than the fracture stress of candidate organic glass of 71.704 MPa. And the maximum equivalent deformation is 3.0995 mm. Therefore, it is concluded that organic glass can be used as the material of the concentrated wind energy device. Meanwhile, the analytical process can provide the references for the analysis of probability of producing concentrated wind energy devices with the material whose mechanical properties change with temperature change. [ABSTRACT FROM AUTHOR]

The concentrated wind energy device is the core of the concentrated wind energy generator, and its material can directly affect the widespread application of the concentrated wind energy generator. This research adopts a fluid-solid interaction (FSI) method. At first, a solid-field model of a concentrated wind energy device is created with the help of the CAD software according to the size of the model. And a cylindrical area is established after the solid-field model is imported into the finite element analysis software. The cylindrical area has a radius of 10 m and a length of 30 m and the distance between the inlet of the fluid-field area and the inlet of the concentrated wind energy device is 5 m. Then in the cylindrical area, a geometric fluid field is established through Boolean subtraction of the solid field area. Based on the CFD software analysis of the fluid field, the wind flow is simulated in a specific wind field. A non-uniform tetrahedron meshing and an SST k-ω turbulence model are adopted. The fluid medium is air, with the temperature of 296.75 K, the density of 1.044 kg/m3, the pressure of 88 800 Pa, the viscosity of 1.85×10-5 kg/(m∙s), the thermal conductivity coefficient of 0.02623 W/(m∙K), and the constant-pressure specific heat capacity of 1 013 J/(kg∙K). During the simulation, the wind speed is set to 25 m/s, the mass flow rate is set to 8199.557 kg/s, and the corresponding turbulent kinetic energy and the specific dissipation rate are respectively 0.714963 m2/s2 and 24.67 s-1. The mass flow inlet and pressure flow outlet are adopted. The roughness height of surface is set to 0.3 mm. When the component residual reaches 1.0×10-4 kg/s, the equation converges and the distribution of the wind speed and wind pressure in the fluid field is obtained. The result shows that the maximum wind speed that the central cylinder can work on the wind turbine blades is 35 m/s and the fluent speed increases along the radial direction of the wall, with a maximum speed of 38.8 m/s at the central cylinder. This indicates that the concentrated wind energy device has increased wind speed and concentrated its energy. In the structural static module, the whole solid field is divided into tetrahedral meshes and the size of each structural unit is 0.02 m. The stress cloud plot and the solid-field deformation plot are obtained after the calculated results of the fluid field are loaded on the concentrated wind energy device. The plots show that the maximum stress area is on the outer edge of the diffusion pipe with a maximum stress of 3.267 MPa, which is far less than the yield strength of 66 MPa, the fracture stress of 65 MPa and the bending strength of 98 MPa in the candidate German Bayer's makrolon-2407 polycarbonate. Therefore, it is concluded that this type of polycarbonate can be used to make the concentrated wind energy device. Meanwhile, the results of the analysis can provide theoretical basis and reference for the later structural improvement and design optimization. [ABSTRACT FROM AUTHOR]

In view of fluid flow in cracks and rock deformation, the mathematical model for shale hydraulic crack propagation was established. The crack flow field and the rock stress field were solved with the finite element method and the extended finite element method respectively, and the two fields were coupled through the Picard iteration. The presented model gave results consistent with those of the classic model, which verified correctness of the former. Based on the model, the effects of the rock elasticity modulus, Poisson's ratio and injection rate on the crack geometry, and the dynamic process of a hydraulic crack approaching a natural crack at an arbitrary angle, were simulated. The numerical results show that the elasticity modulus and injection rate have significant influence on the crack geometry, while the Poisson's ratio has little effect; the more brittle the shale is, the longer and narrower the hydraulic crack will grow; the greater the principal stress difference and the approaching angle are, the easier the hydraulic crack crosses the natural crack; there is a relatively large decrease in the crack width at the intersection between a hydraulic crack and a natural crack; the extended finite element method avoids mesh reconstruction and refinement during computation, and reduces the computing time. The presented model provides an effective theoretical tool for the shale fracturing design. [ABSTRACT FROM AUTHOR]