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Flow Dynamics of a Spiral-groove Dry-gas Seal 被引量:20
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作者 WANG Bing ZHANG Huiqiang CAO Hongjun 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2013年第1期78-84,共7页
The dry-gas seal has been widely used in different industries. With increased spin speed of the rotator shaft, turbulence occurs in the gas film between the stator and rotor seal faces. For the micro-scale flow in the... The dry-gas seal has been widely used in different industries. With increased spin speed of the rotator shaft, turbulence occurs in the gas film between the stator and rotor seal faces. For the micro-scale flow in the gas film and grooves, turbulence can change the pressure distribution of the gas film. Hence, the seal performance is influenced. However, turbulence effects and methods for their evaluation are not considered in the existing industrial designs of dry-gas seal. The present paper numerically obtains the turbulent flow fields of a spiral-groove dry-gas seal to analyze turbulence effects on seal performance. The direct numerical simulation (DNS) and Reynolds-averaged Navier-Stokes (RANS) methods are utilized to predict the velocity field properties in the grooves and gas film. The key performance parameter, open force, is obtained by integrating the pressure distribution, and the obtained result is in good agreement with the experimental data of other researchers. Very large velocity gradients are found in the sealing gas film because of the geometrical effects of the grooves. Considering turbulence effects, the calculation results show that both the gas film pressure and open force decrease. The RANS method underestimates the performance, compared with the DNS. The solution of the conventional Reynolds lubrication equation without turbulence effects suffers from significant calculation errors and a small application scope. The present study helps elucidate the physical mechanism of the hydrodynamic effects of grooves for improving and optimizing the industrial design or seal face pattern of a dry-gas seal. 展开更多
关键词 flow dynamics spiral-groove dry-gas seal turbulence effects direct numerical simulation (DNS) Reynolds-averaged Navier-Stokes (RANS) method Reynolds lubrication equation
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Influence of core box vents distribution on flow dynamics of core shooting process based on experiment and numerical simulation 被引量:4
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作者 Chang-jiang Ni Gao-chun Lu +4 位作者 Qing-dong Zhang Tao Jing Jun-jiao Wu Lin-long Yang Qin-fang Wu 《China Foundry》 SCIE 2016年第1期22-29,共8页
Core shooting process plays a decisive role in the quality of sand cores, and core box vents distribution is one of the most important factor determining the effectiveness of core shooting process. In this paper, the ... Core shooting process plays a decisive role in the quality of sand cores, and core box vents distribution is one of the most important factor determining the effectiveness of core shooting process. In this paper, the influence of core box vents distribution on the flow dynamics of core shooting process was investigated based on in situ experimental observations with transparent core box, high-speed camera and pressure measuring system. Attention was focused on the variation of both the flow behavior of sand and pressure curves due to different vents distribution. Taking both kinetic and frictional stress into account, a kinetic-frictional constitutive model was established to describe the internal momentum transfer in the solid phase. Two-fluid model(TFM) simulation was then performed and good agreement was achieved between the experimental and simulated results on both the flow behavior of sand and the pressure curves. It was found that vents distribution has direct effect on the pressure difference of different locations in the core box, which determines the buoyancy force exerting on the sand particles and significantly influences the filling process of core sand. 展开更多
关键词 vents distribution flow dynamics pressure variation core shooting process kinetic-frictional model two-fluid model
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Influence of core sand properties on flow dynamics of core shooting process based on experiment and multiphase simulation 被引量:2
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作者 Chang-jiang Ni Gao-chun Lu +1 位作者 Tao Jing Jun-jiao Wu 《China Foundry》 SCIE 2017年第2期121-127,共7页
The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant t... The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant turbulence, the flow pattern of sand particles in the shooting head and core box was reproduced with colored core sands. By incorporating the kinetic theory of granular flow(KTGF), kinetic-frictional constitutive correlation and turbulence model, a two-fluid model(TFM) was established to study the flow dynamics of the core shooting process. Two-fluid model(TFM) simulations were then performed and a areasonable agreement was achieved between the simulation and experimental results. Based on the experimental and simulation results, the effects of turbulence, sand density, sand diameter and binder ratio were analyzed in terms of filling process, sand volume fraction(αs) and sand velocity(Vs). 展开更多
关键词 core shooting process sand property binder ratio two-fluid model flow dynamic turbulence
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Flow Dynamics around Two Side by Side Circular Cylinders with Alternating Movements
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作者 Alice Rosa da Silva 《World Journal of Mechanics》 2023年第1期1-19,共19页
The flow dynamics is analyzed through two-dimensional numerical simulations around two circular cylinders arranged side by side, with 4 combinations of alternating motions. All simulations are performed for Re = 1000,... The flow dynamics is analyzed through two-dimensional numerical simulations around two circular cylinders arranged side by side, with 4 combinations of alternating motions. All simulations are performed for Re = 1000, amplitude of oscillation (A) equal to 3, frequency ratio (f<sub>r</sub>) of 0.5, specific rotation (α) equal to 0.5 and different values of spacing ratio (L/D). It is verified that the combination of the type of movement, together with the position of one cylinder in relation to the other, exerts significant influence on the flow dynamics, as well as on the pressure distribution around the cylinder surface and on the average values of the fluid dynamics coefficients. The smallest value of the average pressure coefficient (C<sub>p</sub> = -3.3), is obtained for the oscillating cylinder when placed side by side with the clockwise rotation cylinder, case 3 and L/D = 1.5. On the other hand, the lowest mean drag coefficient (C<sub>d</sub> = 1.0788), is obtained for the cylinder with counterclockwise rotation, located in the lower position in relation to oscillating cylinder in the upper position, with spacing between them of 1.5. Furthermore, it is observed that the rotation movement is more effective in reducing drag than the rotation-oscillation movement, for the studied frequency ratio. 展开更多
关键词 ROTATION Rotation-Oscillation flow Dynamic Circular Cylinder
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Flow dynamics and contact efficiency in a novel fast-turbulent fluidized bed with ring-feeder internals 被引量:3
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作者 Qiang Geng Ping Wang +2 位作者 Xiaolin Zhu Xinghua You Chunyi Li 《Particuology》 SCIE EI CAS CSCD 2015年第4期203-211,共9页
The flow dynamics in a novel fast-turbulent fluidized bed (FTFB) with middle-upper expanding structure and two different ring-feeder internals (mixed and vortex ring-feeder) were studied to achieve a reduction in ... The flow dynamics in a novel fast-turbulent fluidized bed (FTFB) with middle-upper expanding structure and two different ring-feeder internals (mixed and vortex ring-feeder) were studied to achieve a reduction in gasoline olefin production, Compared with a conventional circulating fluidized bed, the novel FTFB displayed unique characteristics and advantages. A higher solids holdup and more uniform solids holdup distribution existed in the diameter-expanding region, especially for the FTFB with vortex ring-feeder structure, A probability density distribution analysis indicated that the novel fluidized bed could reduce gas-solids segregation and enhance gas-solids interaction. A constant carbon dioxide tracer system was used to simulate the reactant gas distribution. The gas-solids contact efficiency was defined according to the solid dispersibility and the amount of gas covering the solid surface. Novel FTFB risers, especially those with vortex ring-feeders, have a much higher gas-solids contact efficiency than that of traditional risers. 展开更多
关键词 flow dynamics Fast-turbulent fluidized bed Ring-feeder internal Carbon dioxide tracer Gas-solids contact efficiency
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Flow dynamics in low aspect ratio dump combustor
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作者 N.P.Yadav Abhjit Kushari 《Propulsion and Power Research》 SCIE 2014年第4期187-195,共9页
This paper repotts an experimental investigation of the flow field inside a low aspect ratio dump combustor.The length of the combustor studied was less than the reattachment length for the separated flow.The exit of ... This paper repotts an experimental investigation of the flow field inside a low aspect ratio dump combustor.The length of the combustor studied was less than the reattachment length for the separated flow.The exit of the combustor is tapered which supports the flow reversal from the exit section.The flow field behaviour in the combustor is evaluated from pressure and velocity measurement studies.The velocity,stream function and pressure distribution inside the combustor are used to elucidate the presence of recircu lation and flow reversal from the exit section of the combustor for different Reynolds numbers.A small variation in Ums velocity was observed in axial direction while in the radial direction it was quite high.Two recirculation zones are recognized and the strength of the recirculation was seen to increase with flow Reynolds number.The turbulence intensity in the recirculation and shear layer zone was seen to be higher than the potential core. 展开更多
关键词 Dump combustor flow dynamics CIRCULATION TURBULENCE Stream function
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Structural ensemble dynamics based closure model for wall-bounded turbulent flow 被引量:11
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作者 Zhen-Su She Ning Hu You Wu State Key Laboratory for Turbulence and Complex Systems and Dept Mechanical and Aerospace Engineering,College of Engineering, Peking University,100871 Beijing, China 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2009年第5期731-736,共6页
Wall-bounded turbulent flow involves the development of multi-scale turbulent eddies, as well as a sharply varying boundary layer. Its theoretical descriptions are yet phenomenological. We present here a new framework... Wall-bounded turbulent flow involves the development of multi-scale turbulent eddies, as well as a sharply varying boundary layer. Its theoretical descriptions are yet phenomenological. We present here a new framework called structural ensemble dynamics (SED), which aims at using systematically all relevant statistical properties of turbulent structures for a quantitative description of ensemble means. A new set of closure equations based on the SED approach for a turbulent channel flow is presented. SED order functions are defined, and numerically determined from data of direct numerical simulations (DNS). Computational results show that the new closure model reproduces accurately the solution of the original Navier-Stokes simulation, including the mean velocity profile, the kinetic energy of the streamwise velocity component, and every term in the energy budget equation. It is suggested that the SED-based studies of turbulent structure builds a bridge between the studies of physical mechanisms of turbulence and the development of accurate model equations for engineering predictions. 展开更多
关键词 TURBULENCE Closure equation Channel flow Structural ensemble dynamics
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From molecular dynamics to lattice Boltzmann:a new approach for pore-scale modeling of multi-phase flow 被引量:4
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作者 Xuan Liu Yong-Feng Zhu +2 位作者 Bin Gong Jia-Peng Yu Shi-Ti Cui 《Petroleum Science》 SCIE CAS CSCD 2015年第2期282-292,共11页
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
关键词 Molecular dynamics - Lattice BoltzmannMulti-phase flow Core simulation
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COMPUTATIONAL FLUID DYNAMICS RESEARCH ON PRESSURE LOSS OF CROSS-FLOW PERFORATED MUFFLER 被引量:15
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作者 HU Xiaodong ZHOU Yiqi +2 位作者 FANG Jianhua MAN Xiliang ZHAO Zhengxu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2007年第2期88-93,共6页
The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics (CFD) has been used to inv... The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics (CFD) has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design. 展开更多
关键词 Perforated muffler Pressure loss Computational fluid dynamics (CFD) Porosity flow velocity
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Continuum modeling for two-lane traffic flow with consideration of the traffic interruption probability 被引量:2
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作者 田川 孙棣华 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第12期51-59,共9页
Considering the effects that the probability of traffic interruption and the friction between two lanes have on the car-following behaviour, this paper establishes a new two-lane microscopic car-following model. Based... Considering the effects that the probability of traffic interruption and the friction between two lanes have on the car-following behaviour, this paper establishes a new two-lane microscopic car-following model. Based on this microscopic model, a new macroscopic model was deduced by the relevance relation of microscopic and macroscopic scale parameters for the two-lane traffic flow. Terms related to lane change are added into the continuity equations and velocity dynamic equations to investigate the lane change rate. Numerical results verify that the proposed model can be efficiently used to reflect the effect of the probability of traffic interruption on the shock, rarefaction wave and lane change behaviour on two-lane freeways. The model has also been applied in reproducing some complex traffic phenomena caused by traffic accident interruption. 展开更多
关键词 two lanes traffic interruption probability traffic flow dynamics model numerical simulation
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Computation of flow through the oesophagogastric junction 被引量:2
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作者 Barry P McMahon Karl D Odie +1 位作者 Kenneth W Moloney Hans Gregersen 《World Journal of Gastroenterology》 SCIE CAS CSCD 2007年第9期1360-1364,共5页
Whilst methods exist to indirectly measure the effects of increased flow or gastro-oesophageal refluxing, they cannot quantitatively measure the amount of acid travelling back up into the oesophagus during reflux, nor... Whilst methods exist to indirectly measure the effects of increased flow or gastro-oesophageal refluxing, they cannot quantitatively measure the amount of acid travelling back up into the oesophagus during reflux, nor can they indicate the flow rate through the oesophagogastric junction (OGJ). Since OGJ dysfunction affects flow it seems most appropriate to describe the geometry of the OGJ and its effect on the flow. A device known as the functional lumen imaging probe (FLIP) has been shown to reliably measure the geometry of and pressure changes in the OGJ. FLIP cannot directly measure flow but the data gathered from the probe can be used to model flow through the junction by using computational flow dynamics (CFD). CFD uses a set of equations known as the Navier-Stokes equations to predict flow patterns and is a technique widely used in engineering. These equations are complex and require appropriate assumptions to provide simplifications before useful data can be obtained. With the assumption that the cross-sectional areas obtained via FLIP are circular, the radii of these circles can be obtained. A cubic interpolation scheme can then be applied to give a high-resolution geometry for the OGJ. In the case of modelling a reflux scenario, it can be seen that at the narrowest section a jet of fluid squirts into the oesophagus at a higher velocity than the fluid surrounding it. This jet has a maximum velocity of almost 2 ms-1 that occurs where the OGJ is at its narrowest. This simple prediction of acid ‘squirting’ into the oesophagusillustrates how the use of numerical methods can be used to develop a better understanding of the OGJ. This initial work using CFD shows some considerable promise for the future. 展开更多
关键词 Computational flow dynamics model OESOPHAGUS
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Analysis of dynamic of two-phase flow in small channel based on phase space reconstruction combined with data reduction sub-frequency band wavelet 被引量:3
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作者 李洪伟 刘君鹏 +2 位作者 李涛 周云龙 孙斌 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2015年第6期1017-1026,共10页
A new method of nonlinear analysis is established by combining phase space reconstruction and data reduction sub-frequency band wavelet. This method is applied to two types of chaotic dynamic systems(Lorenz and Rssler... A new method of nonlinear analysis is established by combining phase space reconstruction and data reduction sub-frequency band wavelet. This method is applied to two types of chaotic dynamic systems(Lorenz and Rssler) to examine the anti-noise ability for complex systems. Results show that the nonlinear dynamic system analysis method resists noise and reveals the internal dynamics of a weak signal from noise pollution. On this basis, the vertical upward gas–liquid two-phase flow in a 2 mm × 0.81 mm small rectangular channel is investigated. The frequency and energy distributions of the main oscillation mode are revealed by analyzing the time–frequency spectra of the pressure signals of different flow patterns. The positive power spectral density of singular-value frequency entropy and the damping ratio are extracted to characterize the evolution of flow patterns and achieve accurate recognition of different vertical upward gas–liquid flow patterns(bubbly flow:100%, slug flow: 92%, churn flow: 96%, annular flow: 100%). The proposed analysis method will enrich the dynamics theory of multi-phase flow in small channel. 展开更多
关键词 Small channel two-phase flow flow pattern dynamics Phase space reconstruction Data reduction sub-frequency band wavelet
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Investigation of asphaltene deposition under dynamic flow conditions 被引量:2
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作者 Farhad Salimi Javad Salimi Mozafar Abdollahifar 《Petroleum Science》 SCIE CAS CSCD 2016年第2期340-346,共7页
Asphaltene deposition is one of the most seri- ous problems, which usually occurs in oil wells, petroleum production, oil processing, and transportation facilities. Deposition of heavy organic components, especially a... Asphaltene deposition is one of the most seri- ous problems, which usually occurs in oil wells, petroleum production, oil processing, and transportation facilities. Deposition of heavy organic components, especially asphaltene, can lead to wellbore blockage and impacts well economics due to reduction in oil production. Therefore, it is necessary to pay more attention to finding some solution to overcome this problem. In this study, a pipe-loop apparatus for investigation of oil stability was employed to measure deposition thickness using a thermal method. The effects of many factors such as oil type, oil temperature, oil velocity, inhibitors, and solvents on asphaltene deposition were investigated. The results showed that the deposition increased with the increasing value of the colloidal insta- bility index. Besides, the deposition thickness increased with the decreasing velocity of oil, but did not change with oil temperature. In addition, n-heptane could result in more deposition; however, toluene had no effect on the deposi- tion. Branched dodecyl benzene sulfonic acid (Branched DBSA) and Linear DBSA as inhibitors decreased the rate of asphaltene deposition. 展开更多
关键词 ASPHALTENE DEPOSITION Dynamic flow Pipe-loops INHIBITORS
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DCFl-Checker: Checking Kernel Dynamic Control Flow Integrity with Performance Monitoring Counter 被引量:2
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作者 SHI Wenchang ZHOU Hongwei +1 位作者 YUAN Jinhui LIANG Bin 《China Communications》 SCIE CSCD 2014年第9期31-46,共16页
It is a challenge to verify integrity of dynamic control flows due to their dynamic and volatile nature. To meet the challenge, existing solutions usually implant an "attachment" in each control transfer. However, t... It is a challenge to verify integrity of dynamic control flows due to their dynamic and volatile nature. To meet the challenge, existing solutions usually implant an "attachment" in each control transfer. However, the attachment introduces additional cost except performance penalty. For example, the attachment must be unique or restrictedly modified. In this paper, we propose a novel approach to detect integrity of dynamic control flows by counting executed branch instructions without involving any attachment. Our solution is based on the following observation. If a control flow is compromised, the number of executed branch instructions will be abnormally increased. The cause is that intruders usually hijack control flows for malicious execution which absolutely introduces additional branch instructions. Inspired by the above observation, in this paper, we devise a novel system named DCFI- Checker, which detect integrity corruption of dynamic control flows with the support of Performance Monitoring Counter (PMC). We have developed a proof-of-concept prototype system of DCFI-Checker on Linux fedora 5. Our experiments with existing kemel rootkits and buffer overflow attack show that DCFI- Checker is effective to detect compromised dynamic control transfer, and performance evaluations indicate that performance penaltyinduced by DCFI-Checker is acceptable. 展开更多
关键词 INTEGRITY dynamic control flow KERNEL branch performance monitoringcounter
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Arch structure effect of the coal gangue flow of the fully mechanized caving in special thick coal seam and its impact on the loss of top coal 被引量:9
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作者 Zhang Ningbo Liu Changyou 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2016年第4期593-599,共7页
Based on the characteristics of the top coal thickness of the fully mechanized caving in special thick coal seam,the long distance of coal gangue caving,as well as the different sizes of the coal gangue broken fragmen... Based on the characteristics of the top coal thickness of the fully mechanized caving in special thick coal seam,the long distance of coal gangue caving,as well as the different sizes of the coal gangue broken fragment dimension and spatial variation of drop flow,this paper uses laboratory dispersion simulation experiment and theoretical analysis to study the arch structure effect and its influence rule on the top coal loss in the process of coal gangue flow.Research shows that in the process of coal gangue flow,arch structure can be formed in three types:the lower arch structure,middle arch structure,and upper arch structure.Moreover,the arch structure has the characteristics of dynamic random arch,the formation probability of dynamic random arch with different layers is not the same,dynamic random arch caused the reduction of the top coal fluency;analyzing the dynamic random arch formation mechanism,influencing factors,and the conditions of instability;the formation probability of the lower arch structure is the highest,the whole coal arch and the coal gangue arch structure has the greatest impact on top coal loss.Therefore,to prevent or reduce the formation of lower whole coal arch structure,the lower coal gangue arch structure and the middle whole coal arch structure is the key to reduce the top coal loss.The research conclusion provides theoretical basis for the further improvement of the top coal recovery rate of the fully mechanized caving in extra thick coal seam. 展开更多
关键词 Extra thick coal seam Coalgangue flow Top coalloss Dynamic random arch effect
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Effects of a flexible net barrier on the dynamic behaviours and interception of debris flows in mountainous areas 被引量:4
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作者 HUO Miao ZHOU Jia-wen +1 位作者 YANG Xing-guo ZHOU Hong-wei 《Journal of Mountain Science》 SCIE CSCD 2017年第10期1903-1918,共16页
Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dyna... Flexible net barriers are a new type of effective mitigation measure against debris flows in valleys and can affect the kinematic energy and mass of debris flows. Here, ten flume tests were performed to study the dynamic behaviours of debris flows with differences in volumes, concentrations(solid volume fraction), and travel distances after interception by a uniform flexible net barrier. A high-speed camera was used to monitor the whole test process, and their dynamic behaviours were recorded. A preliminary computational framework on energy conversion is proposed according to the deposition mechanisms and outflow of debris flow under the effects of the flexible net barrier. The experimental results show that the dynamic interaction process between a debris flow and the flexible net barrier can be divided into two stages:(a) the two-phase impact of the leading edge of the debris flow with the net and(b) collision and friction between the body of the debris flow and intercepted debris material. The approach velocity of a debris flow decreases sharply(a maximum of 63%) after the interception by the net barrier, and the mass ratio of the debris material being intercepted and the kinetic energy ratio of the debris material being absorbed by the net barrier are close due to the limited interception efficiency of the flexible net barrier, which is believed to be related to the flexibility. The energy ratio of outflow is relative small despite the large permeability of the flexible net barrier. 展开更多
关键词 Debris flow Flexible net barrier Dynamic behaviours Interception efficiency Kinetic energy absorption High speed photography
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Applications and verification of a computational energy dynamics model for mine climate simulations 被引量:1
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作者 G.Danko D.Bahrami C.Stewart 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2020年第4期483-493,共11页
A complete thermodynamic model is described for temperature and heat flow distribution simulation for ventilation networks in underground mines.The method is called the Computational Energy Dynamics(CED)model of the h... A complete thermodynamic model is described for temperature and heat flow distribution simulation for ventilation networks in underground mines.The method is called the Computational Energy Dynamics(CED)model of the heat,mass,and energy transport.The Thermal and Humidity(TH)transport elements of the full model are described for advection,convection,and accumulation,encompassing heat capacity,radiation,latent heat for evaporation,and condensation in the airways,as well as variable heat conduction and accumulation in the rock strata.The thermal flywheel effect for time-dependent temperature field applications is included in the model solution.A CED model validation exercise is described,directly evaluating the iterated,minimized energy balance errors for the mechanical and thermal energy components for each network branch after a converged solution is determined.A simulation example relevant to mine safety and health is shown with the CED-TH model,demonstrating its capabilities in efficiency and accuracy in comparison with measurement results. 展开更多
关键词 Mine climate simulation Dynamic heat flow model Coupled heat and moisture transport Computational energy dynamics Mine safety and health
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Microfluidic-based single cell trapping using a combination of stagnation point flow and physical barrier 被引量:2
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作者 Miao Yu Zongzheng Chen +3 位作者 Cheng Xiang Bo Liu Handi Xie Kairong Qin 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第3期422-429,共8页
Single cell trapping in vitro by microfluidic device is an emerging approach for the study of the relationship between single cells and their dynamic biochemical microenvironments. In this paper, a hydrodynamic-based ... Single cell trapping in vitro by microfluidic device is an emerging approach for the study of the relationship between single cells and their dynamic biochemical microenvironments. In this paper, a hydrodynamic-based microfluidic device for single cell trapping is designed using a combination of stagnation point flow and physical barrier.The microfluidic device overcomes the weakness of the traditional ones, which have been only based upon either stagnation point flows or physical barriers, and can conveniently load dynamic biochemical signals to the trapped cell. In addition, it can connect with a programmable syringe pump and a microscope to constitute an integrated experimental system.It is experimentally verified that the microfluidic system can trap single cells in vitro even under flow disturbance and conveniently load biochemical signals to the trapped cell. The designed micro-device would provide a simple yet effective experimental platform for further study of the interactions between single cells and their microenvironments. 展开更多
关键词 Single cell trapping Microfluidics Stagnation point flow Physical barrier Hydrodynamic tweezers Dynamic biochemical signal
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Numerical simulation on rotordynamic characteristics of annular seal under uniform and non-uniform flows 被引量:4
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作者 吴大转 姜新阔 +2 位作者 初宁 武鹏 王乐勤 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第8期1889-1897,共9页
Currently, the flow field of annular seals disturbed by the circular whirl motion of rotors is usually solved using computational fluid dynamics(CFD) to evaluate the five rotordynamic coefficients. The simulations are... Currently, the flow field of annular seals disturbed by the circular whirl motion of rotors is usually solved using computational fluid dynamics(CFD) to evaluate the five rotordynamic coefficients. The simulations are based on the traditional quasi-steady method. In this work, an improved quasi-steady method along with the transient method was presented to compute the rotordynamic coefficients of a long seal. By comparisons with experimental data, the shortcomings of quasi-steady methods have been identified. Then, the effects of non-uniform incoming flow on seal dynamic coefficients were studied by transient simulations. Results indicate that the long seal has large cross stiffness k and direct mass M which are not good for rotor stability, while the transient method is more suitable for the long seal for its excellent performance in predicting M. When the incoming flow is non-uniform, the stiffness coefficients vary with the eccentric directions. Based on the rotordynamic coefficients under uniform incoming flow, the linearized fluid force formulas, which can consider the effects of non-uniform incoming flow, have been presented and can well explain the varying-stiffness phenomenon. 展开更多
关键词 long pump seal rotordynamic coefficients transient computational fluid dynamics(CFD) dynamic mesh non-uniform incoming flow
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Dynamic Flow Control Strategies of Vehicle SCR Urea Dosing System 被引量:1
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作者 LIN Wei ZHANG Youtong ASIF Malik 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2015年第2期276-284,共9页
Selective Catalyst Reduction(SCR)Urea Dosing System(UDS)directly affects the system accuracy and the dynamic response performance of a vehicle.However,the UDS dynamic response is hard to keep up with the changes o... Selective Catalyst Reduction(SCR)Urea Dosing System(UDS)directly affects the system accuracy and the dynamic response performance of a vehicle.However,the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions.That will lead to low NO_χconversion efficiency or NH_3 slip.In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions,an advanced control strategy based on an air-assisted volumetric UDS is presented.It covers the methods of flow compensation and switching working conditions.The strategy is authenticated on an UDS and tested in different dynamic conditions.The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS.The inject deviation range is improved from being between-8%and 10%to-4%and 2%and became more stable than before,and the dynamic response time was shortened from 200 ms to 150 ms.The ETC cycle result shows that after using the new strategy the NH_3 emission is reduced by 60%,and the NO_χemission remains almost unchanged.The trade-off between NO_χconversion efficiency and NH_3 slip is mitigated.The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly. 展开更多
关键词 select catalyst reduction(SCR) urea dosing system(UDS) dynamic flow control strategies
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