In this article,the anaglyph video maker is employed for generating realistic 3-D flows and the software FlowAnimator is developed using that technology.Based on Microsoft Windows Presentation Foundation(WPF),the re...In this article,the anaglyph video maker is employed for generating realistic 3-D flows and the software FlowAnimator is developed using that technology.Based on Microsoft Windows Presentation Foundation(WPF),the real 3-D scene is set up and marker particles are distributed in it randomly in order to create a more natural flow scenario.The trajectory of the particle motion is calculated with Lagrangian description in 3-D space.During the simulation,the viewport can be changed in order to focus on different parts of the model by panning,zooming,rotating and inclination variation etc.Marker particles may appear in different shapes:spheres,tracking-balls,cylinders and ribbons in order to fit different flows.It is the first time that the video anaglyph technology is employed in the 3-D hydrodynamic simulation,which removes the obstacles for 3-D scenes to be rendered on a flat-panel display.展开更多
Basing on the analysis of the traits of the roll forging process, a system-model of computer simulation has been established. Three-dimensional rigid-plastic FEM has been used for the simulation of the deformation pro...Basing on the analysis of the traits of the roll forging process, a system-model of computer simulation has been established. Three-dimensional rigid-plastic FEM has been used for the simulation of the deformation process in the oval and round pass rolling, including the entering, rolling, and separating stages. The analysis was conducted using the Deform-3D ver.5.0 code. The important information concerned with the deformation area characteristic, material flow, and velocity field has been presented. Otherwise, the location of the neutral plane in the deformation area was shown clearly.展开更多
In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since...In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since river bends are not uniform-some are divergent and others convergent-in this study, after the SSIIM 3-D model was calibrated using the result of measurements along a uniform 180° bend with a width of 0.6 m, a similar but convergent 180v bend, 0.6 m to 0.45 m wide, was simulated using the SSI1M 3-D numerical model. Flow characteristics of the convergent 180° bend, including lengthwise and vertical velocity profiles, primary and secondary flows, lengthwise and widtbwise slopes of the water surface, and the helical flow strength, were compared with those of the uniform 180° bend. The verification results of the model show that the numerical model can effectively simulate the flow field in the uniform bend. In addition, this research indicates that, in a convergent channel, the maximum velocity path at a plane near the water surface crosses the channel's centerline at about a 30° to 40° cross-section, while in the uniform bend, this occurs at about the 50° cross-section. The varying range of the water surface elevation is wider in the convergent channel than in the uniform one, and the strength of the helical flow is generally greater in the uniform channel than in the convergent one. Also, unlike the uniform bend, the convergent bend exhibits no rotational cell against the main direction of secondary flow rotation at the 135° cross-section.展开更多
A 3- D free surface flow in open channels based on the Reynolds equations with the k-ε turbulence closure model is presented in this paper. Insted of the 'rigid lid' approximation, the solution of the free su...A 3- D free surface flow in open channels based on the Reynolds equations with the k-ε turbulence closure model is presented in this paper. Insted of the 'rigid lid' approximation, the solution of the free surface equation is implemented in the velocity-pressure iterative procedure on the basis of the conventional SIMPLE method. This model was used to compute the flow in rectangular channels with trenches dredged across the bottom. The velocity, eddy viscosity coefficient, turbulent shear stress, turbulent kinetic energy and elevation of the free surface can be obtained. The computed results are in good agreement with previous experimental data.展开更多
The standard three dimensional(3D) k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Compariso...The standard three dimensional(3D) k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.展开更多
Effectively and accurately modelling the spatial relation of fracture surfaces is crucial in the design and construction of large hydropower dams having a complex underlying geology. However, fracture surfaces are ran...Effectively and accurately modelling the spatial relation of fracture surfaces is crucial in the design and construction of large hydropower dams having a complex underlying geology. However, fracture surfaces are randomly formed and vary greatly with respect to their spatial distribution, which makes the construction of accurate 3-D models challenging. In this study, we use an optimal Monte Carlo simulation and dynamic conditioning to construct a fracture network model. We found the optimal Monte Carlo simulation to effectively reduce the error associated with the Monte Carlo method and use dynamic conditioning to ensure the consistency of the model with the actual distribution of fractures on the excavation faces and outcrops. We applied this novel approach to a hydropower station on the Jinshajiang River, China. The simulation results matched the real sampled values well, confirming that the model is capable of effectively and accurately simulating the spatial relations in a fracture network.展开更多
The anti-slide support structure is widely used in the anti-seismic reinforcement of bridge foundations,but related experimental research was processing slowly. Based on the prototype of the Jiuzhaigou bridge at the C...The anti-slide support structure is widely used in the anti-seismic reinforcement of bridge foundations,but related experimental research was processing slowly. Based on the prototype of the Jiuzhaigou bridge at the Chengdu-Lanzhou Railway,a 3-D simulation model was established on the basis of the shaking table model test,and the rationality of the dynamic analysis model was verified by indicators such as the bending moment of the bridge piles,peak soil pressure,and PGA amplification factors. The results show that the inertia force of the bridge pier has an important influence on the deformation of the pile foundation. The bending moment and shearing force are larger in lateral bridge piles,and the maximum value is near the pile top. The PGA amplification factor is stronger in the back of the rear anti-slide piles and so is it in front of the bridge pier,and the soil is prone to slip and damage. The bedrock is rigid and the dynamic response is maintained at a low level. The anti-slide piles in the rear row play a major role in the anti-seismic reinforcement design,and the anti-slide piles in the front row can be used as an auxiliary support structure.展开更多
A 3-D finite-element numerical simulation model of temperature field for CIESC casting solidification process was developed with the aid of ANSYS software and a series of corresponding experiments were made. The resul...A 3-D finite-element numerical simulation model of temperature field for CIESC casting solidification process was developed with the aid of ANSYS software and a series of corresponding experiments were made. The results showed that the good agreement was obtained between the numerical simulation and the experiments. Based on the numerical simulation results, the characteristics of temperature distribution in the castings during CIESC solidification process were analyzed and summarized. According to the G/R-1/2 method and numerical simulation results, there is no any shrinkage defect in the CIESC casting and structure or casting is fine and compact.展开更多
Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package PO...Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package POLYFLOW. Based on the velocity fields calculated, the particle trajectories in both machines are visualized using particle tracking technique. The numerical results indicate that the flow patterns in three-screw extruders are similar to those in twin-screw extruders. The triangularly-arranged three-screw extruder has the largest pumping capacity and also the highest extrusion stability in terms of flowrate fluctuation with screw rotation. The instantaneous mixing and cumulative residence time distribution (RTD) characteristics are also analyzed and compared with traditional intermeshing co-rotating twin-screw extruders. It is shown that the start section of the cumulative RTD curve for the triangularly-arranged machine has a small shoulder, which is attributed to the faster flow in the central region of this type of extruder.展开更多
This paper concerns the sonic-supersonic structures of the transonic crossflow generated by the steady supersonic flow past an infinite cone of arbitrary cross section.Under the conical assumption,the three-dimensiona...This paper concerns the sonic-supersonic structures of the transonic crossflow generated by the steady supersonic flow past an infinite cone of arbitrary cross section.Under the conical assumption,the three-dimensional(3-D)steady Euler equations can be projected onto the unit sphere and the state of fluid can be characterized by the polar and azimuthal angles.Given a segment smooth curve as a conical-sonic line in the polar-azimuthal angle plane,we construct a classical conical-supersonic solution near the curve under some reasonable assumptions.To overcome the difficulty caused by the parabolic degeneracy,we apply the characteristic decomposition technique to transform the Euler equations into a new degenerate hyperbolic system in a partial hodograph plane.The singular terms are isolated from the highly nonlinear complicated system and then can be handled successfully.We establish a smooth local solution to the new system in a suitable weighted metric space and then express the solution in terms of the original variables.展开更多
Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of...Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.展开更多
A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from d...A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.展开更多
Effective management of a river reach requires a sound understanding of flow and sediment transport generated by varying natural and artificial runoff conditions. Flow and sediment transport within the Ning-Meng reach...Effective management of a river reach requires a sound understanding of flow and sediment transport generated by varying natural and artificial runoff conditions. Flow and sediment transport within the Ning-Meng reach of the Yellow River(NMRYR), northern China are controlled by a complex set of factors/processes, mainly including four sets of factors:(1) aeolian sediments from deserts bordering the main stream;(2) inflow of water and sediment from numerous tributaries;(3) impoundment of water by reservoir/hydro-junction; and(4) complex diversion and return of irrigation water. In this study, the 1-D flow & sediment transport model developed by the Yellow River Institute of Hydraulic Research was used to simulate the flow and sediment transport within the NMRYR from 2001 to 2012. All four sets of factors that primarily control the flow and sediment transport mentioned above were considered in this model. Compared to the measured data collected from the hydrological stations along the NMRYR, the simulated flow and sediment transport values were generally acceptable, with relative mean deviation between measured and simulated values of 〈15%. However, simulated sediment concentration and siltation values within two sub-reaches(i.e., Qingtongxia Reservoir to Bayan Gol Hydrological Station and Bayan Gol Hydrological Station to Toudaoguai Hydrological Station) for some periods exhibited relatively large errors(the relative mean deviations between measured and simulated values of 18% and 25%, respectively). These errors are presumably related to the inability to accurately determine the quantity of aeolian sediment influx to the river reach and the inflow of water from the ten ephemeral tributaries. This study may provide some valuable insights into the numerical simulations of flow and sediment transport in large watersheds and also provide a useful model for the effective management of the NMRYR.展开更多
In this paper a new spherical actuator is designed and its advantages are compared to an existing spherical actuator, which function is limited by several design bottlenecks. First the output torque is too small. Seco...In this paper a new spherical actuator is designed and its advantages are compared to an existing spherical actuator, which function is limited by several design bottlenecks. First the output torque is too small. Second, the attitude is difficult to be accurately detected. The new three-dimen- sional magnetic pole array can solve these major problems. The new actuator features an outer rotor with multiple permanent magnet (PM) poles. Using an analytical solution and the finite element so- lution simulation, the feasibility of the approach is verified. A prototype was developed, tested, and experiments were conducted to obtain the practical value of the magnetic flux density.展开更多
According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15...According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200mm. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.展开更多
According to environmental and energy issues,renewable energy has been vigorously promoted.Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously.Heat sto...According to environmental and energy issues,renewable energy has been vigorously promoted.Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously.Heat storage is a considerable solution for this problem and thermochemical energy storage is the most promising way because of its great energy density and stability.However,this technology is not mature enough to be applied to the industry.The reactor is an important component in the thermochemical energy storage system where the charging and discharging process happens.In this paper,a spiral coil is proposed and used as a reactor in the thermochemical energy storage system.The advantages of the spiral coil include simple structure,small volume,and so on.To investigate the flow characteristics,the simulation was carried out based on energy-minimization multi-scale model(EMMS)and Eulerian two-phase model.CaCO_(3) particles were chosen as the reactants.Particle distribution was shown in the results.The gas initial velocity was set to 2 m·s^(-1),3 m·s^(-1),and 4 m·s^(-1).When the particles flowed in the coil,gravity,centrifugal force and drag force influenced their flow.With the Reynold numbers increasing,centrifugal and drag force got larger.Accumulation phenomenon existed in the coil and results showed with the gas velocity increasing,accumulation moved from the bottom to the outer wall of the coil.Besides,the accumulation phenomenon was stabilized whenφ>720°.Also due to the centrifugal force,a secondary flow formed,which means solid particles moved from the inside wall to the outside wall.This secondary flow could promote turbulence and mixing of particles and gas.In addition,when the particle volume fraction is reduced from 0.2 to 0.1,the accumulation at the bottom of the coil decreases,and the unevenness of the velocity distribution becomes larger.展开更多
A three-dimensional viscous code has been developed to solve Reynolds-averaged Navier-Stokes equations. The governing equations in finite volume form are solved by two-step Runge-Kutta scheme with implicit residual sm...A three-dimensional viscous code has been developed to solve Reynolds-averaged Navier-Stokes equations. The governing equations in finite volume form are solved by two-step Runge-Kutta scheme with implicit residual smoothing. The eddy viscous is obtained using the Baldwin-Lomax model. A prediction of the 3-D turbulent flow and the performance in the “all-over controlled vortex distribution” centrifugal impeller with a vaneless diffuser has been made for the compressor at design and off-design condition. The predicted effi-ciency is a little higher than the experiment data. These results suggest that the present calculation code is able to determine the flow development in the impeller and also the turbulence model in the centrifugal im-peller should be improved.展开更多
文摘In this article,the anaglyph video maker is employed for generating realistic 3-D flows and the software FlowAnimator is developed using that technology.Based on Microsoft Windows Presentation Foundation(WPF),the real 3-D scene is set up and marker particles are distributed in it randomly in order to create a more natural flow scenario.The trajectory of the particle motion is calculated with Lagrangian description in 3-D space.During the simulation,the viewport can be changed in order to focus on different parts of the model by panning,zooming,rotating and inclination variation etc.Marker particles may appear in different shapes:spheres,tracking-balls,cylinders and ribbons in order to fit different flows.It is the first time that the video anaglyph technology is employed in the 3-D hydrodynamic simulation,which removes the obstacles for 3-D scenes to be rendered on a flat-panel display.
基金supported by the National Natural Science Foundation of China(No.50675014).
文摘Basing on the analysis of the traits of the roll forging process, a system-model of computer simulation has been established. Three-dimensional rigid-plastic FEM has been used for the simulation of the deformation process in the oval and round pass rolling, including the entering, rolling, and separating stages. The analysis was conducted using the Deform-3D ver.5.0 code. The important information concerned with the deformation area characteristic, material flow, and velocity field has been presented. Otherwise, the location of the neutral plane in the deformation area was shown clearly.
文摘In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since river bends are not uniform-some are divergent and others convergent-in this study, after the SSIIM 3-D model was calibrated using the result of measurements along a uniform 180° bend with a width of 0.6 m, a similar but convergent 180v bend, 0.6 m to 0.45 m wide, was simulated using the SSI1M 3-D numerical model. Flow characteristics of the convergent 180° bend, including lengthwise and vertical velocity profiles, primary and secondary flows, lengthwise and widtbwise slopes of the water surface, and the helical flow strength, were compared with those of the uniform 180° bend. The verification results of the model show that the numerical model can effectively simulate the flow field in the uniform bend. In addition, this research indicates that, in a convergent channel, the maximum velocity path at a plane near the water surface crosses the channel's centerline at about a 30° to 40° cross-section, while in the uniform bend, this occurs at about the 50° cross-section. The varying range of the water surface elevation is wider in the convergent channel than in the uniform one, and the strength of the helical flow is generally greater in the uniform channel than in the convergent one. Also, unlike the uniform bend, the convergent bend exhibits no rotational cell against the main direction of secondary flow rotation at the 135° cross-section.
文摘A 3- D free surface flow in open channels based on the Reynolds equations with the k-ε turbulence closure model is presented in this paper. Insted of the 'rigid lid' approximation, the solution of the free surface equation is implemented in the velocity-pressure iterative procedure on the basis of the conventional SIMPLE method. This model was used to compute the flow in rectangular channels with trenches dredged across the bottom. The velocity, eddy viscosity coefficient, turbulent shear stress, turbulent kinetic energy and elevation of the free surface can be obtained. The computed results are in good agreement with previous experimental data.
基金The Specialized Research Fund for the Doctoral Programof Higher Education(No.20010610023) and the Sino-Finnish Scientific and TechnologicalCooperation Program
文摘The standard three dimensional(3D) k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch.
基金supported by the National Basic Research Program of China (973 Program, No. 2013CB035904)the Innovative Research Groups of the National Natural Science Foundation of China (No. 51321065)the National Natural Science Foundation of China (No. 51439005)
文摘Effectively and accurately modelling the spatial relation of fracture surfaces is crucial in the design and construction of large hydropower dams having a complex underlying geology. However, fracture surfaces are randomly formed and vary greatly with respect to their spatial distribution, which makes the construction of accurate 3-D models challenging. In this study, we use an optimal Monte Carlo simulation and dynamic conditioning to construct a fracture network model. We found the optimal Monte Carlo simulation to effectively reduce the error associated with the Monte Carlo method and use dynamic conditioning to ensure the consistency of the model with the actual distribution of fractures on the excavation faces and outcrops. We applied this novel approach to a hydropower station on the Jinshajiang River, China. The simulation results matched the real sampled values well, confirming that the model is capable of effectively and accurately simulating the spatial relations in a fracture network.
基金the Railways Research andDevelopment Project of the Ministry of Railways of the Peoples Republic of China(Grant No.Z2012-061)
文摘The anti-slide support structure is widely used in the anti-seismic reinforcement of bridge foundations,but related experimental research was processing slowly. Based on the prototype of the Jiuzhaigou bridge at the Chengdu-Lanzhou Railway,a 3-D simulation model was established on the basis of the shaking table model test,and the rationality of the dynamic analysis model was verified by indicators such as the bending moment of the bridge piles,peak soil pressure,and PGA amplification factors. The results show that the inertia force of the bridge pier has an important influence on the deformation of the pile foundation. The bending moment and shearing force are larger in lateral bridge piles,and the maximum value is near the pile top. The PGA amplification factor is stronger in the back of the rear anti-slide piles and so is it in front of the bridge pier,and the soil is prone to slip and damage. The bedrock is rigid and the dynamic response is maintained at a low level. The anti-slide piles in the rear row play a major role in the anti-seismic reinforcement design,and the anti-slide piles in the front row can be used as an auxiliary support structure.
文摘A 3-D finite-element numerical simulation model of temperature field for CIESC casting solidification process was developed with the aid of ANSYS software and a series of corresponding experiments were made. The results showed that the good agreement was obtained between the numerical simulation and the experiments. Based on the numerical simulation results, the characteristics of temperature distribution in the castings during CIESC solidification process were analyzed and summarized. According to the G/R-1/2 method and numerical simulation results, there is no any shrinkage defect in the CIESC casting and structure or casting is fine and compact.
文摘Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package POLYFLOW. Based on the velocity fields calculated, the particle trajectories in both machines are visualized using particle tracking technique. The numerical results indicate that the flow patterns in three-screw extruders are similar to those in twin-screw extruders. The triangularly-arranged three-screw extruder has the largest pumping capacity and also the highest extrusion stability in terms of flowrate fluctuation with screw rotation. The instantaneous mixing and cumulative residence time distribution (RTD) characteristics are also analyzed and compared with traditional intermeshing co-rotating twin-screw extruders. It is shown that the start section of the cumulative RTD curve for the triangularly-arranged machine has a small shoulder, which is attributed to the faster flow in the central region of this type of extruder.
基金the two referees for very helpful comments and suggestions to improve the quality of the paper.This work was partially supported by the Natural Science Foundation of Zhejiang province of China(LY21A010017)the National Natural Science Foundation of China(12071106,12171130).
文摘This paper concerns the sonic-supersonic structures of the transonic crossflow generated by the steady supersonic flow past an infinite cone of arbitrary cross section.Under the conical assumption,the three-dimensional(3-D)steady Euler equations can be projected onto the unit sphere and the state of fluid can be characterized by the polar and azimuthal angles.Given a segment smooth curve as a conical-sonic line in the polar-azimuthal angle plane,we construct a classical conical-supersonic solution near the curve under some reasonable assumptions.To overcome the difficulty caused by the parabolic degeneracy,we apply the characteristic decomposition technique to transform the Euler equations into a new degenerate hyperbolic system in a partial hodograph plane.The singular terms are isolated from the highly nonlinear complicated system and then can be handled successfully.We establish a smooth local solution to the new system in a suitable weighted metric space and then express the solution in terms of the original variables.
基金Project(51375498)supported by the National Natural Science Foundation of China
文摘Based on RNG k-ε turbulence model and sliding grid technique, solid-liquid two-phase three-dimensional(3-D) unsteady turbulence of full passage in slurry pump was simulated by means of Fluent software. The effects of unsteady flow characteristics on solid-liquid two-phase flow and pump performance were researched under design condition. The results show that clocking effect has a significant influence on the flow in pump, and the fluctuation of flow velocity and pressure is obvious, particularly near the volute tongue, at the position of small sections of volute and within diffuser. Clocking effect has a more influence on liquid-phase than on solid-phase, and the wake-jet structure of relative velocity of solid-phase is less obvious than liquid-phase near the volute tongue and the impeller passage outlet. The fluctuation of relative velocity of solid-phase flow is 7.6% smaller than liquid-phase flow at the impeller outlet on circular path. Head and radial forces of the impeller are 8.1% and 85.7% of fluctuation, respectively. The results provide a theoretical basis for further research for turbulence, improving efficient, reducing the hydraulic losses and wear. Finally, field tests were carried out to verify the operation and wear of slurry pump.
基金Supported by the National Natural Science Foundation of China (50905016)
文摘A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.
基金financially supported by the National Natural Science Foundation of China(51579113,51309111,51309113)
文摘Effective management of a river reach requires a sound understanding of flow and sediment transport generated by varying natural and artificial runoff conditions. Flow and sediment transport within the Ning-Meng reach of the Yellow River(NMRYR), northern China are controlled by a complex set of factors/processes, mainly including four sets of factors:(1) aeolian sediments from deserts bordering the main stream;(2) inflow of water and sediment from numerous tributaries;(3) impoundment of water by reservoir/hydro-junction; and(4) complex diversion and return of irrigation water. In this study, the 1-D flow & sediment transport model developed by the Yellow River Institute of Hydraulic Research was used to simulate the flow and sediment transport within the NMRYR from 2001 to 2012. All four sets of factors that primarily control the flow and sediment transport mentioned above were considered in this model. Compared to the measured data collected from the hydrological stations along the NMRYR, the simulated flow and sediment transport values were generally acceptable, with relative mean deviation between measured and simulated values of 〈15%. However, simulated sediment concentration and siltation values within two sub-reaches(i.e., Qingtongxia Reservoir to Bayan Gol Hydrological Station and Bayan Gol Hydrological Station to Toudaoguai Hydrological Station) for some periods exhibited relatively large errors(the relative mean deviations between measured and simulated values of 18% and 25%, respectively). These errors are presumably related to the inability to accurately determine the quantity of aeolian sediment influx to the river reach and the inflow of water from the ten ephemeral tributaries. This study may provide some valuable insights into the numerical simulations of flow and sediment transport in large watersheds and also provide a useful model for the effective management of the NMRYR.
基金Supported by the National Key Basic Research and Development Program(973 Program)(2014CB046405)
文摘In this paper a new spherical actuator is designed and its advantages are compared to an existing spherical actuator, which function is limited by several design bottlenecks. First the output torque is too small. Second, the attitude is difficult to be accurately detected. The new three-dimen- sional magnetic pole array can solve these major problems. The new actuator features an outer rotor with multiple permanent magnet (PM) poles. Using an analytical solution and the finite element so- lution simulation, the feasibility of the approach is verified. A prototype was developed, tested, and experiments were conducted to obtain the practical value of the magnetic flux density.
文摘According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200mm. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.
基金the financial support provided by Natural Science Foundation of Jiangsu Province (BK20180936)the Initial Funding of Scientific Research for the Introduction of Talents (YJ2021-41)
文摘According to environmental and energy issues,renewable energy has been vigorously promoted.Now solar power is widely used in many areas but it is limited by the weather conditions and cannot work continuously.Heat storage is a considerable solution for this problem and thermochemical energy storage is the most promising way because of its great energy density and stability.However,this technology is not mature enough to be applied to the industry.The reactor is an important component in the thermochemical energy storage system where the charging and discharging process happens.In this paper,a spiral coil is proposed and used as a reactor in the thermochemical energy storage system.The advantages of the spiral coil include simple structure,small volume,and so on.To investigate the flow characteristics,the simulation was carried out based on energy-minimization multi-scale model(EMMS)and Eulerian two-phase model.CaCO_(3) particles were chosen as the reactants.Particle distribution was shown in the results.The gas initial velocity was set to 2 m·s^(-1),3 m·s^(-1),and 4 m·s^(-1).When the particles flowed in the coil,gravity,centrifugal force and drag force influenced their flow.With the Reynold numbers increasing,centrifugal and drag force got larger.Accumulation phenomenon existed in the coil and results showed with the gas velocity increasing,accumulation moved from the bottom to the outer wall of the coil.Besides,the accumulation phenomenon was stabilized whenφ>720°.Also due to the centrifugal force,a secondary flow formed,which means solid particles moved from the inside wall to the outside wall.This secondary flow could promote turbulence and mixing of particles and gas.In addition,when the particle volume fraction is reduced from 0.2 to 0.1,the accumulation at the bottom of the coil decreases,and the unevenness of the velocity distribution becomes larger.
文摘A three-dimensional viscous code has been developed to solve Reynolds-averaged Navier-Stokes equations. The governing equations in finite volume form are solved by two-step Runge-Kutta scheme with implicit residual smoothing. The eddy viscous is obtained using the Baldwin-Lomax model. A prediction of the 3-D turbulent flow and the performance in the “all-over controlled vortex distribution” centrifugal impeller with a vaneless diffuser has been made for the compressor at design and off-design condition. The predicted effi-ciency is a little higher than the experiment data. These results suggest that the present calculation code is able to determine the flow development in the impeller and also the turbulence model in the centrifugal im-peller should be improved.