Hot compression experiments were conducted on Ti 15 3 alloy specimens using Gleeble 1500 Thermal Simulator.These tests were focused to obtain the flow stress data under various conditions of strain,strain rate and tem...Hot compression experiments were conducted on Ti 15 3 alloy specimens using Gleeble 1500 Thermal Simulator.These tests were focused to obtain the flow stress data under various conditions of strain,strain rate and temperature. On the basis of these data, the predicting model for the nonlinear relation between flow stress and deformation strain,strain rate and temperature for Ti 15 3 alloy was developed with a back propagation artificial neural network method. Results show that the neural network can reproduce the flow stress in the sampled data and predict the nonsampled data well. Thus the neural network method has been verified to be used to tackle hot deformation problems of Ti 15 3 alloy. [展开更多
The thermodynamic system consists of the entropy flow and entropy product.This paper is to define the entropy flow and to apply it to determinig the minimal work in air-exhausting processes.It is found that the minimu...The thermodynamic system consists of the entropy flow and entropy product.This paper is to define the entropy flow and to apply it to determinig the minimal work in air-exhausting processes.It is found that the minimum work depends only on the pressure at the negative-pressure space.展开更多
In order to increase the effectiveness and the reliability of web services flow, the ~r-calculus formal method is introduced as a development language for web services flow. The π-calculus overcomes inabilities of we...In order to increase the effectiveness and the reliability of web services flow, the ~r-calculus formal method is introduced as a development language for web services flow. The π-calculus overcomes inabilities of web service flow languages in demonstrating the consistency, validating the correctness and so on. The π- calculus analysis and modeling of web services flow is presented, the dynamic actions and basic activities of WS-BPEL with π-calculus formally are described, and the mapping from π-calculus expression to WS-BPEL is built. The basic construction of web services flow with the π-calculus method after the analysis of the syntax of WS-BPEL and inter-description between WS-BPEL and π-calculus is expressed. Also discussed are the approaches to web services flow by modeling from different views, and the proposed approaches through the development and modeling of an e-commerce web service flow application are illustrated.展开更多
[目的]为Pleurotus eryngii—Co60-7木质素降解酶的分离纯化和综合利用提供试验依据。[方法]采用DEAE—Sepharose^TM Fast Flow离子交换介质，分别考察缓冲液pH值、流速和洗脱方式等对刺芹侧耳木质素降解酶分离纯化的影响，确定了最佳...[目的]为Pleurotus eryngii—Co60-7木质素降解酶的分离纯化和综合利用提供试验依据。[方法]采用DEAE—Sepharose^TM Fast Flow离子交换介质，分别考察缓冲液pH值、流速和洗脱方式等对刺芹侧耳木质素降解酶分离纯化的影响，确定了最佳分离纯化层析条件。[结果]DEAE-Sephalose^TM Fast Flow分离纯化Pleurotus eryngii-Co60-7木质素降解酶的最佳层析条件为：选择20mmol／L，pH值为5．0醋酸钠一醋酸缓冲体系，3ml／min的流速，进行分步洗脱（100、200～300和1000mmoL／L NaCl的三步洗脱），可较好地实现刺芹侧耳发酵液木质素降解酶初分，该纯化操作目标蛋白回收率达85％，纯化分离因素为2．71。[结论]该技术在分离纯化刺芹侧耳木质素降解酶上可行，具有潜在的工业应用价值。展开更多
Within the healthcare context is very important to foster the dynamics leading to positive experiences at work, in order to promote work motivation and well-being. This study investigated the influence of some persona...Within the healthcare context is very important to foster the dynamics leading to positive experiences at work, in order to promote work motivation and well-being. This study investigated the influence of some personal and job resources and of some job demands on the three dimensions (absorption, work enjoyment, intrinsic work motivation) of flow at work, on the basis of Job Demands-Resources Model. Flow at work is an inner experience arising during an activity in which people are immersed, feel motivated and enjoy it. Studies suggest that resources are the main antecedents of the flow experience. Respondents to the questionnaire were 197 nurses. Multiple regressions were performed to detect the resources and the demands that influence the three dimensions of flow at work. As expected, resources positively influenced the dimensions of flow at work, particularly work enjoyment. Job demands positively influenced absorption and negatively influenced the other two dimensions of flow at work. Human resources managers should promote flow at work supporting the availability of resources and monitoring the job demands.展开更多
半导体制冷箱的制冷效率是评价制冷箱性能的重要参数,因此提高制冷效率是设计的重点。对制冷装配体与制冷箱的耦合方式进行优化,并运用Solid Works Flow Simulation软件进行仿真分析。对比得出,在制冷装配体风扇外表面与制冷箱内壁重合...半导体制冷箱的制冷效率是评价制冷箱性能的重要参数,因此提高制冷效率是设计的重点。对制冷装配体与制冷箱的耦合方式进行优化,并运用Solid Works Flow Simulation软件进行仿真分析。对比得出,在制冷装配体风扇外表面与制冷箱内壁重合、所开槽尺寸为41.7mm×41.7mm×20mm、风扇为吸气时,制冷箱内温度最低。展开更多
Numerical simulation has been widely applied to the assessment of debris flow hazards. In East Asia and especially Taiwan, the most widely used numerical programs are FLO-2D and Debris-aD. Although these two programs ...Numerical simulation has been widely applied to the assessment of debris flow hazards. In East Asia and especially Taiwan, the most widely used numerical programs are FLO-2D and Debris-aD. Although these two programs are applied to the same engineering tasks, they are different in many aspects. These two programs were compared according to their fundamental theories, input and output data, computational algorithms and results. Using both programs, the simulations of a real debris flow with abundant granular material induced by landslides at Xinfa village in southern Taiwan are performed for comparison. The simulation results show that Debris- 2D gives better assessment in hazard area delineating and flow depth predicting. Therefore, Debris-2D is better for simulation of granular debris flows.展开更多
According to the necessity of flexible workflow management system, the solution to set up the visualized workflow modelling system based on B/S structure is put forward, which conforms to the relevant specifications o...According to the necessity of flexible workflow management system, the solution to set up the visualized workflow modelling system based on B/S structure is put forward, which conforms to the relevant specifications of WfMC and the workflow process definition meta-model. The design for system structure is presented in detail, and the key technologies for system implementation are also introduced. Additionally, an example is illustrated to demonstrate the validity of system.展开更多
The pressure-sensitive effect on the pore structure of sandstone was investigated using X-ray computed micro-tomography and QEMSCAN quantitative mineral analysis. In a physical simulation study, we extracted the pore ...The pressure-sensitive effect on the pore structure of sandstone was investigated using X-ray computed micro-tomography and QEMSCAN quantitative mineral analysis. In a physical simulation study, we extracted the pore network model from digital cores at different confining pressures and evaluated the effect of pressure sensitivity on the multiphase displacement process. In both the pore network model and QEMSCAN scanning, the pore structure was observed to be damaged under a high confining pressure. Due to their different scales, the pores and throats exhibited inhomogeneous changes; further, the throats exhibited a significant variation compared to that exhibited by the pores. Meanwhile, the heterogeneity of the pore structure under the two aforementioned activities was aggravated by the elastic-plastic deformation of the pore structure.The pressure-sensitive effect increased the proportion of mineral particles, such as quartz(the main component of the core skeleton), and reduced the proportion of clay minerals. The clay minerals were originally attached to the pore walls or interspersed in the pores; however, as the pressure increased, the clay minerals accumulated in the pores resulting in blockage of the pores. While simulating the multiphase displacement process, increasing the confining pressure was observed to severely restrict the flowability of oil and water. This study promises to improve the efficiency of reservoir development in terms of oil and gas exploitation.展开更多
随着信息化的发展,对企业的信息化管理系统的发展提出了更高的要求。本文从e Work Flow工作流出发,并以某公司的安全监控信息管理系统为例,阐述了e Work Flow工作流在信息化管理系统中的应用。通过e Work Flow工作流与此安全监控信息管...随着信息化的发展,对企业的信息化管理系统的发展提出了更高的要求。本文从e Work Flow工作流出发,并以某公司的安全监控信息管理系统为例,阐述了e Work Flow工作流在信息化管理系统中的应用。通过e Work Flow工作流与此安全监控信息管理系统的集成,实现了该企业信息化、电子化及无纸化的办公,且实现了此安全监控信息管理系统与公司的OA系统、资产管理等系统无缝结合。展开更多
Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to...Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance （gc） and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flowbased transpiration was measured to pararneterize Jarvistype models of gc and thus to simulate Ec of Populus cathayana using the Penman-Monteith equation. The results indicate that solar radiation （Rs） and vapor pressure deficit （VPD） are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind Rs and precedes VPD, and there is a 1-h time shift between Eo and sap flow in the 30-min interval data set. A parameterized Jarvis-type gc model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in go, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error （RMSEs） between the predicted and measured Ec were 1.91×10^-3 （with the time lag） and 3.12×10^-3cm h^-1 （without the time lag）. More importantly, Ec simulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error （MRE） of only 8.32% and the mean absolute error （MAE） of 1.48 × 10^-3 cm h^-1.展开更多
The instantaneous thermal expansion behavior of-two-phase heterogeneous materials subjected to a uniform temperature change is explored in the present study. The matrix phase is assumed to be a work-hardening ductile ...The instantaneous thermal expansion behavior of-two-phase heterogeneous materials subjected to a uniform temperature change is explored in the present study. The matrix phase is assumed to be a work-hardening ductile metal and the dispersive phase is assumed to consist of either aligned or randomly-oriented, elastic,, spheroidal inhomogeneities. The plastic flow and decreasing stiffness of the matrix during Eshelby's transformation strain of the equivalent inclusions are accounted for by using the deformation theory of plasticity. The explicit results of the instantaneous overall thermal expansion coefficients and the critical inelastic temperature changes are presented for aligned disc- and fiber-inclusions. For the spherical and randomly-oriented spheroidal inclusion, the present study demonstrates that when the yielding of the composites is governed by the average matrix stress, the overall response is always elastic in spite of the temperature change.展开更多
Most current lattice Boltzmann （LBM） models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular ...Most current lattice Boltzmann （LBM） models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular dynamics （MD） simulation and LBM to avoid such defect. The basic idea is to first construct a molecular model based on the actual components of the rock-fluid system, then to compute the interaction force between the rock and the fluid of different densities through the MD simulation. This calculated rock-fluid interaction force, combined with the fluid-fluid force determined from the equation of state, is then used in LBM modeling. Without parameter fitting, this study presents a new systematic approach for pore-scale modeling of multi-phase flow. We have validated this ap- proach by simulating a two-phase separation process and gas-liquid-solid three-phase contact angle. Based on an actual X-ray CT image of a reservoir core, we applied our workflow to calculate the absolute permeability of the core, vapor-liquid H20 relative permeability, and capillary pressure curves.展开更多
The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation （LES）. The sliding mesh method was used for the coupli...The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation （LES）. The sliding mesh method was used for the coupling between the rotating and the stationary frame of references. The calculations were carried out on the ＂Shengcao-21C＂ supercomputer using a computational fluid dynamics （CFD） code CFX5. The flow fields predicted by the LES simulation and the simulation using standard κ-ε model were compared to the results from particle image velocimetry （PIV） measurements. It is shown that the CFD simulations using the LES approach and the standard κ-ε model agree well with the PIV measurements. Fluctuations of the radial and axial velocity are predicted at different frequencies by the LES simulation. Velocity fluctuations of high frequencies are seen in the impeller region, while low frequencies velocity fluctuations are observed in the bulk flow. A low frequency velocity fluctuation with a nondimensional frequency of 0.027Hz is predicted by the LES simulation, which agrees with experimental investigations in the literature. Flow circulation patterns predicted by the LES simulation are asymmetric, stochastic and complex, spanning a large portion of the tanks and varying with time, while circulation patterns calculated by the simulation using the standard κ-ε model are symmetric. The results of the present work give better understanding to the flow instabilities in the mechanically agitated tank. However, further analysis of the LES calculated velocity series by means of fast Fourier transform （FFT） and/or spectra analysis are recommended in future work in order to gain more knowledge of the complicated flow phenomena.展开更多
The behavior of Taylor-Couette （TC） flow has been extensively studied. However, no suitable torque prediction models exist for high-capacity fluid machinery. The Eckhardt-Grossmann-Lohse （EGL） theory, derived base...The behavior of Taylor-Couette （TC） flow has been extensively studied. However, no suitable torque prediction models exist for high-capacity fluid machinery. The Eckhardt-Grossmann-Lohse （EGL） theory, derived based on the Navier-Stokes equations, is proposed to model torque behavior. This are the significant energy theory suggests that surfaces transfer interfaces between cylinders and annular flow. This study mainly focuses on the effects of surface texture on momentum transfer behavior through global torque measurement. First, a power-law torque behavior model is built to reveal the relationship between dimensionless torque and the Taylor number based on the EGL theory. Second, TC flow appa- ratus is designed and built based on the CNC machine tool to verify the torque behavior model. Third, four surface texture films are tested to check the effects of surface texture on momentum transfer. A stereo microscope and three-dimensional topography instrument are employed to analyze surface morphology. Global torque behavior is measured by rotating a multi component dynamometer, and the effects of surface texture on the annular flow behavior are observed via images obtained using a high-speed camera. Finally, torque behaviors under four differentsurface conditions are fitted and compared. The experi- mental results indicate that surface textures have a remarkable influence on torque behavior, and that the peak roughness of surface texture enhances the momentum transfer by strengthening the fluctuation in the TC flow.展开更多
Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate ...Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.展开更多
文摘Hot compression experiments were conducted on Ti 15 3 alloy specimens using Gleeble 1500 Thermal Simulator.These tests were focused to obtain the flow stress data under various conditions of strain,strain rate and temperature. On the basis of these data, the predicting model for the nonlinear relation between flow stress and deformation strain,strain rate and temperature for Ti 15 3 alloy was developed with a back propagation artificial neural network method. Results show that the neural network can reproduce the flow stress in the sampled data and predict the nonsampled data well. Thus the neural network method has been verified to be used to tackle hot deformation problems of Ti 15 3 alloy. [
文摘The thermodynamic system consists of the entropy flow and entropy product.This paper is to define the entropy flow and to apply it to determinig the minimal work in air-exhausting processes.It is found that the minimum work depends only on the pressure at the negative-pressure space.
文摘In order to increase the effectiveness and the reliability of web services flow, the ~r-calculus formal method is introduced as a development language for web services flow. The π-calculus overcomes inabilities of web service flow languages in demonstrating the consistency, validating the correctness and so on. The π- calculus analysis and modeling of web services flow is presented, the dynamic actions and basic activities of WS-BPEL with π-calculus formally are described, and the mapping from π-calculus expression to WS-BPEL is built. The basic construction of web services flow with the π-calculus method after the analysis of the syntax of WS-BPEL and inter-description between WS-BPEL and π-calculus is expressed. Also discussed are the approaches to web services flow by modeling from different views, and the proposed approaches through the development and modeling of an e-commerce web service flow application are illustrated.
文摘[目的]为Pleurotus eryngii—Co60-7木质素降解酶的分离纯化和综合利用提供试验依据。[方法]采用DEAE—Sepharose^TM Fast Flow离子交换介质，分别考察缓冲液pH值、流速和洗脱方式等对刺芹侧耳木质素降解酶分离纯化的影响，确定了最佳分离纯化层析条件。[结果]DEAE-Sephalose^TM Fast Flow分离纯化Pleurotus eryngii-Co60-7木质素降解酶的最佳层析条件为：选择20mmol／L，pH值为5．0醋酸钠一醋酸缓冲体系，3ml／min的流速，进行分步洗脱（100、200～300和1000mmoL／L NaCl的三步洗脱），可较好地实现刺芹侧耳发酵液木质素降解酶初分，该纯化操作目标蛋白回收率达85％，纯化分离因素为2．71。[结论]该技术在分离纯化刺芹侧耳木质素降解酶上可行，具有潜在的工业应用价值。
文摘Within the healthcare context is very important to foster the dynamics leading to positive experiences at work, in order to promote work motivation and well-being. This study investigated the influence of some personal and job resources and of some job demands on the three dimensions (absorption, work enjoyment, intrinsic work motivation) of flow at work, on the basis of Job Demands-Resources Model. Flow at work is an inner experience arising during an activity in which people are immersed, feel motivated and enjoy it. Studies suggest that resources are the main antecedents of the flow experience. Respondents to the questionnaire were 197 nurses. Multiple regressions were performed to detect the resources and the demands that influence the three dimensions of flow at work. As expected, resources positively influenced the dimensions of flow at work, particularly work enjoyment. Job demands positively influenced absorption and negatively influenced the other two dimensions of flow at work. Human resources managers should promote flow at work supporting the availability of resources and monitoring the job demands.
文摘半导体制冷箱的制冷效率是评价制冷箱性能的重要参数,因此提高制冷效率是设计的重点。对制冷装配体与制冷箱的耦合方式进行优化,并运用Solid Works Flow Simulation软件进行仿真分析。对比得出,在制冷装配体风扇外表面与制冷箱内壁重合、所开槽尺寸为41.7mm×41.7mm×20mm、风扇为吸气时,制冷箱内温度最低。
基金support from National Science Council of Chinese Taipei(Grant No.NSC 96-2625-Z-002-006-MY3)
文摘Numerical simulation has been widely applied to the assessment of debris flow hazards. In East Asia and especially Taiwan, the most widely used numerical programs are FLO-2D and Debris-aD. Although these two programs are applied to the same engineering tasks, they are different in many aspects. These two programs were compared according to their fundamental theories, input and output data, computational algorithms and results. Using both programs, the simulations of a real debris flow with abundant granular material induced by landslides at Xinfa village in southern Taiwan are performed for comparison. The simulation results show that Debris- 2D gives better assessment in hazard area delineating and flow depth predicting. Therefore, Debris-2D is better for simulation of granular debris flows.
基金Shanghai Municipal Science Committee key project(061612058,06JC14066,06DZ12001,061111006)Nationalscience and technology supporting project(2006BAF01A46)
文摘According to the necessity of flexible workflow management system, the solution to set up the visualized workflow modelling system based on B/S structure is put forward, which conforms to the relevant specifications of WfMC and the workflow process definition meta-model. The design for system structure is presented in detail, and the key technologies for system implementation are also introduced. Additionally, an example is illustrated to demonstrate the validity of system.
文摘The pressure-sensitive effect on the pore structure of sandstone was investigated using X-ray computed micro-tomography and QEMSCAN quantitative mineral analysis. In a physical simulation study, we extracted the pore network model from digital cores at different confining pressures and evaluated the effect of pressure sensitivity on the multiphase displacement process. In both the pore network model and QEMSCAN scanning, the pore structure was observed to be damaged under a high confining pressure. Due to their different scales, the pores and throats exhibited inhomogeneous changes; further, the throats exhibited a significant variation compared to that exhibited by the pores. Meanwhile, the heterogeneity of the pore structure under the two aforementioned activities was aggravated by the elastic-plastic deformation of the pore structure.The pressure-sensitive effect increased the proportion of mineral particles, such as quartz(the main component of the core skeleton), and reduced the proportion of clay minerals. The clay minerals were originally attached to the pore walls or interspersed in the pores; however, as the pressure increased, the clay minerals accumulated in the pores resulting in blockage of the pores. While simulating the multiphase displacement process, increasing the confining pressure was observed to severely restrict the flowability of oil and water. This study promises to improve the efficiency of reservoir development in terms of oil and gas exploitation.
文摘随着信息化的发展,对企业的信息化管理系统的发展提出了更高的要求。本文从e Work Flow工作流出发,并以某公司的安全监控信息管理系统为例,阐述了e Work Flow工作流在信息化管理系统中的应用。通过e Work Flow工作流与此安全监控信息管理系统的集成,实现了该企业信息化、电子化及无纸化的办公,且实现了此安全监控信息管理系统与公司的OA系统、资产管理等系统无缝结合。
基金supported by the Qinghai province natural science foundation project(2015-ZJ-902)the Qinghai province science and technology plan program(2014-NK-A4-4)
文摘Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance （gc） and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flowbased transpiration was measured to pararneterize Jarvistype models of gc and thus to simulate Ec of Populus cathayana using the Penman-Monteith equation. The results indicate that solar radiation （Rs） and vapor pressure deficit （VPD） are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind Rs and precedes VPD, and there is a 1-h time shift between Eo and sap flow in the 30-min interval data set. A parameterized Jarvis-type gc model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in go, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error （RMSEs） between the predicted and measured Ec were 1.91×10^-3 （with the time lag） and 3.12×10^-3cm h^-1 （without the time lag）. More importantly, Ec simulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error （MRE） of only 8.32% and the mean absolute error （MAE） of 1.48 × 10^-3 cm h^-1.
基金This work was supported by the National Science Foundation under the Grant 19302017 and 59472031
文摘The instantaneous thermal expansion behavior of-two-phase heterogeneous materials subjected to a uniform temperature change is explored in the present study. The matrix phase is assumed to be a work-hardening ductile metal and the dispersive phase is assumed to consist of either aligned or randomly-oriented, elastic,, spheroidal inhomogeneities. The plastic flow and decreasing stiffness of the matrix during Eshelby's transformation strain of the equivalent inclusions are accounted for by using the deformation theory of plasticity. The explicit results of the instantaneous overall thermal expansion coefficients and the critical inelastic temperature changes are presented for aligned disc- and fiber-inclusions. For the spherical and randomly-oriented spheroidal inclusion, the present study demonstrates that when the yielding of the composites is governed by the average matrix stress, the overall response is always elastic in spite of the temperature change.
文摘Most current lattice Boltzmann （LBM） models suffer from the deficiency that their parameters have to be obtained by fitting experimental results. In this paper, we propose a new method that integrates the molecular dynamics （MD） simulation and LBM to avoid such defect. The basic idea is to first construct a molecular model based on the actual components of the rock-fluid system, then to compute the interaction force between the rock and the fluid of different densities through the MD simulation. This calculated rock-fluid interaction force, combined with the fluid-fluid force determined from the equation of state, is then used in LBM modeling. Without parameter fitting, this study presents a new systematic approach for pore-scale modeling of multi-phase flow. We have validated this ap- proach by simulating a two-phase separation process and gas-liquid-solid three-phase contact angle. Based on an actual X-ray CT image of a reservoir core, we applied our workflow to calculate the absolute permeability of the core, vapor-liquid H20 relative permeability, and capillary pressure curves.
文摘The aim of this work is to investigate the flow instabilities in a baffled, stirred tank generated by a single Rushton turbine by means of large eddy simulation （LES）. The sliding mesh method was used for the coupling between the rotating and the stationary frame of references. The calculations were carried out on the ＂Shengcao-21C＂ supercomputer using a computational fluid dynamics （CFD） code CFX5. The flow fields predicted by the LES simulation and the simulation using standard κ-ε model were compared to the results from particle image velocimetry （PIV） measurements. It is shown that the CFD simulations using the LES approach and the standard κ-ε model agree well with the PIV measurements. Fluctuations of the radial and axial velocity are predicted at different frequencies by the LES simulation. Velocity fluctuations of high frequencies are seen in the impeller region, while low frequencies velocity fluctuations are observed in the bulk flow. A low frequency velocity fluctuation with a nondimensional frequency of 0.027Hz is predicted by the LES simulation, which agrees with experimental investigations in the literature. Flow circulation patterns predicted by the LES simulation are asymmetric, stochastic and complex, spanning a large portion of the tanks and varying with time, while circulation patterns calculated by the simulation using the standard κ-ε model are symmetric. The results of the present work give better understanding to the flow instabilities in the mechanically agitated tank. However, further analysis of the LES calculated velocity series by means of fast Fourier transform （FFT） and/or spectra analysis are recommended in future work in order to gain more knowledge of the complicated flow phenomena.
基金Supported by National Programs for Fundamental Research and Development of China(Grant Nos.2009CB724308,2015CB057302)National Science and Technology Major Project of China(Grant No.2013ZX06002002-017)
文摘The behavior of Taylor-Couette （TC） flow has been extensively studied. However, no suitable torque prediction models exist for high-capacity fluid machinery. The Eckhardt-Grossmann-Lohse （EGL） theory, derived based on the Navier-Stokes equations, is proposed to model torque behavior. This are the significant energy theory suggests that surfaces transfer interfaces between cylinders and annular flow. This study mainly focuses on the effects of surface texture on momentum transfer behavior through global torque measurement. First, a power-law torque behavior model is built to reveal the relationship between dimensionless torque and the Taylor number based on the EGL theory. Second, TC flow appa- ratus is designed and built based on the CNC machine tool to verify the torque behavior model. Third, four surface texture films are tested to check the effects of surface texture on momentum transfer. A stereo microscope and three-dimensional topography instrument are employed to analyze surface morphology. Global torque behavior is measured by rotating a multi component dynamometer, and the effects of surface texture on the annular flow behavior are observed via images obtained using a high-speed camera. Finally, torque behaviors under four differentsurface conditions are fitted and compared. The experi- mental results indicate that surface textures have a remarkable influence on torque behavior, and that the peak roughness of surface texture enhances the momentum transfer by strengthening the fluctuation in the TC flow.
基金supported by the National Natural Science Foundation of China (10872096)the Open Fund of State Key Laboratory of Explosion Science and Technology, Beijing University of Science and Technology (KFJJ09-13)
文摘Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.
