The flow behavior of molten steel in the thin slab mold under high casting speed conditions was investigated,with a focus on the multi-mode continuous casting and rolling mold.A steel-slag two-phase flow model was est...The flow behavior of molten steel in the thin slab mold under high casting speed conditions was investigated,with a focus on the multi-mode continuous casting and rolling mold.A steel-slag two-phase flow model was established using large eddy simulation,the volume of fluid,and magnetohydrodynamics methods through numerical simulation.The maximum flow velocity and wave height at the steel-slag interface within the mold are critical evaluation criteria for analyzing asymmetric flow under varying casting speeds and electromagnetic braking.The results indicate that the asymmetric flows within the mold do not occur synchronously.The severity of the asymmetric flow correlates with the velocity difference across the steel-slag interface.A greater biased flow prolongs the time required to revert to a steady state.When the magnetic field intensity is set to 0.24 T and the magnetic pole position is at 390 mm from the steel-slag interface,this configuration can reduce the velocity of the steel-slag interface,thereby mitigating the asymmetric flow.Additionally,it can diminish the velocity,impact depth,and impact intensity on the narrow face of the jet,thus improving the distribution of velocity and turbulent kinetic energy within the mold.This configuration prolongs the time required for the steel-slag interface to transition from a stable state to its maximum velocity and shortens the time for the interface to return to stability from an unstable state.Moreover,it ensures the positional stability of the steel-slag interface,confining its position within−3 mm.展开更多
A hierarchical model is developed to predict the streaming potential （SP） in the canaliculi of a loaded os teon. Canaliculi are assumed to run straight across the os teon annular cylinder wall, while disregarding th...A hierarchical model is developed to predict the streaming potential （SP） in the canaliculi of a loaded os teon. Canaliculi are assumed to run straight across the os teon annular cylinder wall, while disregarding the effect of lacuna. SP is generalized by the canalicular fluid flow. Ana lytical solutions are obtained for the canalicular fluid veloc ity, pressure, and SP. Results demonstrate that SP amplitude （SPA） is proportional to the pressure difference, strain am plitude, frequency, and strain rate amplitude. However, the key loading factor governing SP is the strain rate, which is a representative loading parameter under the specific phys iological state. Moreover, SPA is independent of canalicu lar length. This model links external loads to the canalicu lar fluid pressure, velocity, and SP, which can facilitate fur ther understanding of the mechanotransduction and electro mechanotransduction mechanisms of bones.展开更多
Oscillatory flow facilitates gas exchange in human respiration system. In the present study, both numerical calculation and PIV (Particle Image Velocimetry) measurement indicate that, under the application of HFOV (Hi...Oscillatory flow facilitates gas exchange in human respiration system. In the present study, both numerical calculation and PIV (Particle Image Velocimetry) measurement indicate that, under the application of HFOV (High Frequency Oscillatory Ventilation), apparent steady streaming is caused and augmented in distal airways by the continuous oscillation, i.e., the core air moves downwards and the peripheral air evacuates upwards within bronchioles. The net flow of steady streaming serves to overcome the lack of tidal volume in HFOV and delivers fresh air into deeper lung region. Also, numerical calculations reveal that the intensity of steady streaming is mainly influenced by the geometry of airways with provided oscillatory frequency and tidal volume, and it rises with Re and Wo up to a Re of about 124 and Wo of about 5. Steady streaming is considered as an important factor for the ventilation efficiency of HFOV.展开更多
Cleat serves as the primary flow pathway for coalbed methane(CBM)and water.However,few studies consider the impact of local contact on two-phase flow within cleats.A visual generalized model of endogenous cleats was c...Cleat serves as the primary flow pathway for coalbed methane(CBM)and water.However,few studies consider the impact of local contact on two-phase flow within cleats.A visual generalized model of endogenous cleats was constructed based on microfluidics.A microscopic and mesoscopic observation technique was proposed to simultaneously capture gas-liquid interface morphology of pores and throat and the two-phase flow characteristics in entire cleat system.The local contact characteristics of cleats reduced absolute permeability,which resulted in a sharp increase in the starting pressure.The reduced gas flow capacity narrowed the co-infiltration area and decreased water saturation at the isotonic point in a hydrophilic environment.The increased local contact area of cleats weakened gas phase flow capacity and narrowed the co-infiltration area.Jumping events occurred in methane-water flow due to altered porosity caused by local contact in cleats.The distribution of residual phases changed the jumping direction on the micro-scale as well as the dominant channel on the mesoscale.Besides,jumping events caused additional energy dissipation,which was ignored in traditional two-phase flow models.This might contribute to the overestimation of relative permeability.The work provides new methods and insights for investigating unsaturated flow in complex porous media.展开更多
The variable salinity in stored reservoirs connected by a long channel attracts the attention of scientists worldwide,having applications in environmental and geophysical engineering.This study explores the impact of ...The variable salinity in stored reservoirs connected by a long channel attracts the attention of scientists worldwide,having applications in environmental and geophysical engineering.This study explores the impact of Navier slip conditions on exchange flows within a long channel connecting two large reservoirs of differing salinity.These horizontal density gradients drive the flow.We modify the recent one-dimensional theory,developed to avoid runaway stratification,to account for the presence of uniform slip walls.By adjusting the parameters of the horizontal density gradient based on the slip factor,we resolve analytically various flow regimes ranging from high diffusion to transitional high advection.These regimes are governed by physical parameters like channel aspect ratio,slip factor,Schmidt number,and gravitational Reynolds number.Our solutions align perfectly with ones in the no-slip limit.More importantly,under the conditions of no net flow across the channel and high Schmidt number(where stratification is concentrated near the channel’s mid-layer),we derive a closed-form solution for the slip parameter,aspect ratio,and gravitational Reynolds number that describes the interface’s behavior as a sharp interface separating two distinct zones.This interface,arising from hydrostatic wall gradients,ultimately detaches the low-and high-density regimes throughout the channel when the gravitational Reynolds number is inversely proportional to the aspect ratio for a fixed slip parameter.This phenomenon,observed previously in 2D numerical simulations with no-slip walls in the literature,is thus confirmed by our theoretical results.Our findings further demonstrate that wall slip leads to distinct and diverse flow regimes.展开更多
It is common for the rotating pin largely plunging into lower sheet to break up lap interface of Friction Stir Lap Welding(FSLW)joint,but the unavoidable up-bending morphology of hook outside Nugget Zone(NZ)largely re...It is common for the rotating pin largely plunging into lower sheet to break up lap interface of Friction Stir Lap Welding(FSLW)joint,but the unavoidable up-bending morphology of hook outside Nugget Zone(NZ)largely reduces the joint bearing ability.Based on the novel Opposite-directions Flowing FSLW(OF-FSLW)by the self-developed rotating tool with an Xshaped right-left thread pin,the 2024 aluminum alloys lap joint was successfully welded in this study.The migration law of lap interface during welding was investigated by the experimental and numerical methods,and then how the rotating pin and its rotating velocity affect the formation and strength of OF-FSLW joint was further analyzed.The results show that the Material Concentrated Zone(MCZ)which formed above the original lap interface made the hook bend downward,the NZ greatly enlarged and the beginning part of cold lap compressed and thickened,thereby heightening the joint bearing ability.For the OF-FSLW joint,its maximum tensile strength was403 MPa,and the corresponding joint efficiency of 90.8%was an incredible and superb value for the 2000 series heat-treatment strengthened aluminum alloys friction stir welded joint.The OF-FSLW technology by the rotating tool with an X-shaped right-left thread pin is proven to be a greatly effective approach for manufacturing the aluminum alloys lap joint with superb strength.展开更多
In order to improve the precision of super point detection and control measurement resource consumption, this paper proposes a super point detection method based on sampling and data streaming algorithms （SDSD）, and...In order to improve the precision of super point detection and control measurement resource consumption, this paper proposes a super point detection method based on sampling and data streaming algorithms （SDSD）, and proves that only sources or destinations with a lot of flows can be sampled probabilistically using the SDSD algorithm. The SDSD algorithm uses both the IP table and the flow bloom filter （BF） data structures to maintain the IP and flow information. The IP table is used to judge whether an IP address has been recorded. If the IP exists, then all its subsequent flows will be recorded into the flow BF; otherwise, the IP flow is sampled. This paper also analyzes the accuracy and memory requirements of the SDSD algorithm , and tests them using the CERNET trace. The theoretical analysis and experimental tests demonstrate that the most relative errors of the super points estimated by the SDSD algorithm are less than 5%, whereas the results of other algorithms are about 10%. Because of the BF structure, the SDSD algorithm is also better than previous algorithms in terms of memory consumption.展开更多
A dynamical system of particle growth in the con vective undercooled melt driven by a biaxial straining flow is modeled. A uniformly valid asymptotic solution for the in terface evolution in particle growth is obtaine...A dynamical system of particle growth in the con vective undercooled melt driven by a biaxial straining flow is modeled. A uniformly valid asymptotic solution for the in terface evolution in particle growth is obtained by means of the multiple variable expansion method. The analytical so lution as a function of both azimuth angle and polar angle shows that the interface shape of particle growth in the bi axial straining flow is significantly deformed by the biaxial straining flow. The biaxial straining flow results in higher lo cal growth rate near the surface where the flow comes in and leads to lower local growth rate near the surface where the flow goes out. Due to the difference in local growth rate, an initially spherical particle will evolve into a prolate barrel like shape in the biaxial straining flow.展开更多
软件定义网络(software defined networking,SDN)分离的数据平面和控制平面,给网络管理带来了开放性和灵活性.但同时控制器与交换机之间的接口(控制器南向接口)需要更频繁的交互各种消息以实现对网络的控制.一方面,数据平面触发Table-M...软件定义网络(software defined networking,SDN)分离的数据平面和控制平面,给网络管理带来了开放性和灵活性.但同时控制器与交换机之间的接口(控制器南向接口)需要更频繁的交互各种消息以实现对网络的控制.一方面,数据平面触发Table-Miss的数据包需要通过Packet-In消息往返于交换机与控制器之间,时延增大的同时也给控制器南向接口带来繁重的通信开销,数据平面和控制平面之间的交互容易成为网络性能的瓶颈.另一方面,控制器在下发新的流表项时,由于缺乏新表项对应的数据流特征信息,易出现已有的大流表项被下发的小流表项替换的情况,造成冗余的Flow-Mod消息(流表更新消息)和Packet-In消息,进一步加重了南向接口的通信开销,降低了网络的整体性能.提出一种基于流量特征的OpenFlow南向接口开销优化技术uFlow,在控制器上通过对Packet-In消息中数据流量特征的识别以及对小流的直接转发,达到消除南向接口冗余开销的目的.对uFlow的原型系统进行了实现,并通过真实网络中的流量对uFlow优化效果进行了验证.实验结果显示:与传统的OpenFlow网络处理方式相比,uFlow消除了冗余的交换机流表项更新,显著地降低了OpenFlow南向接口的交互开销:在不同的网络负载和流表容量的情况下,uFlow平均能减少70%以上的Flow-Mod消息.展开更多
Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rule...Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rules of bubbles, which influence the mass transfer efficiency to a large extent, have received much less attention. In this paper, the volume of fluid method was used to calculate the bubble shapes, pressure, velocity distributions,and the flow patterns inside the bubbles. The rising behavior of the bubbles with four different initial diameters,i.e., 3 mm, 5 mm, 7 mm and 9 mm was investigated in four various liquids including water, 61.23% glycerol,86.73% glycerol and 100% glycerol. The results show that the liquid properties and bubble initial diameters have great impacts on bubble shapes. Moreover, flow patterns inside the bubbles with different initial diameters were analyzed and classified into three types under the condition of different bubble shapes. Three correlations for predicting the maximum internal circulation inside the bubbles in 86.73% glycerol were presented and the R-square values were all bigger than 0.98. Through analyzing the pressure and velocity distributions around the bubbles, four rules of bubble deformation were also obtained to explain and predict the shapes.展开更多
基金support from the National Natural Science Foundation of China(Grant Nos.52174313 and 52304350)thank all members of the Hebei High Quality Steel Continuous Casting Engineering Technology Research Center at North China University of Science and Technology,Tangshan,China.
文摘The flow behavior of molten steel in the thin slab mold under high casting speed conditions was investigated,with a focus on the multi-mode continuous casting and rolling mold.A steel-slag two-phase flow model was established using large eddy simulation,the volume of fluid,and magnetohydrodynamics methods through numerical simulation.The maximum flow velocity and wave height at the steel-slag interface within the mold are critical evaluation criteria for analyzing asymmetric flow under varying casting speeds and electromagnetic braking.The results indicate that the asymmetric flows within the mold do not occur synchronously.The severity of the asymmetric flow correlates with the velocity difference across the steel-slag interface.A greater biased flow prolongs the time required to revert to a steady state.When the magnetic field intensity is set to 0.24 T and the magnetic pole position is at 390 mm from the steel-slag interface,this configuration can reduce the velocity of the steel-slag interface,thereby mitigating the asymmetric flow.Additionally,it can diminish the velocity,impact depth,and impact intensity on the narrow face of the jet,thus improving the distribution of velocity and turbulent kinetic energy within the mold.This configuration prolongs the time required for the steel-slag interface to transition from a stable state to its maximum velocity and shortens the time for the interface to return to stability from an unstable state.Moreover,it ensures the positional stability of the steel-slag interface,confining its position within−3 mm.
基金supported by the OIT of Higher Learning Institutions of Shanxithe National Natural Science Foundation of China(11302143,11472185)Natural Science Fund of Shanxi(2014021013)
文摘A hierarchical model is developed to predict the streaming potential （SP） in the canaliculi of a loaded os teon. Canaliculi are assumed to run straight across the os teon annular cylinder wall, while disregarding the effect of lacuna. SP is generalized by the canalicular fluid flow. Ana lytical solutions are obtained for the canalicular fluid veloc ity, pressure, and SP. Results demonstrate that SP amplitude （SPA） is proportional to the pressure difference, strain am plitude, frequency, and strain rate amplitude. However, the key loading factor governing SP is the strain rate, which is a representative loading parameter under the specific phys iological state. Moreover, SPA is independent of canalicu lar length. This model links external loads to the canalicu lar fluid pressure, velocity, and SP, which can facilitate fur ther understanding of the mechanotransduction and electro mechanotransduction mechanisms of bones.
文摘Oscillatory flow facilitates gas exchange in human respiration system. In the present study, both numerical calculation and PIV (Particle Image Velocimetry) measurement indicate that, under the application of HFOV (High Frequency Oscillatory Ventilation), apparent steady streaming is caused and augmented in distal airways by the continuous oscillation, i.e., the core air moves downwards and the peripheral air evacuates upwards within bronchioles. The net flow of steady streaming serves to overcome the lack of tidal volume in HFOV and delivers fresh air into deeper lung region. Also, numerical calculations reveal that the intensity of steady streaming is mainly influenced by the geometry of airways with provided oscillatory frequency and tidal volume, and it rises with Re and Wo up to a Re of about 124 and Wo of about 5. Steady streaming is considered as an important factor for the ventilation efficiency of HFOV.
基金the financial support from the National Natural Science Foundation of China (No.42102127)the Postdoctoral Research Foundation of China (No.2024 M751860)。
文摘Cleat serves as the primary flow pathway for coalbed methane(CBM)and water.However,few studies consider the impact of local contact on two-phase flow within cleats.A visual generalized model of endogenous cleats was constructed based on microfluidics.A microscopic and mesoscopic observation technique was proposed to simultaneously capture gas-liquid interface morphology of pores and throat and the two-phase flow characteristics in entire cleat system.The local contact characteristics of cleats reduced absolute permeability,which resulted in a sharp increase in the starting pressure.The reduced gas flow capacity narrowed the co-infiltration area and decreased water saturation at the isotonic point in a hydrophilic environment.The increased local contact area of cleats weakened gas phase flow capacity and narrowed the co-infiltration area.Jumping events occurred in methane-water flow due to altered porosity caused by local contact in cleats.The distribution of residual phases changed the jumping direction on the micro-scale as well as the dominant channel on the mesoscale.Besides,jumping events caused additional energy dissipation,which was ignored in traditional two-phase flow models.This might contribute to the overestimation of relative permeability.The work provides new methods and insights for investigating unsaturated flow in complex porous media.
文摘The variable salinity in stored reservoirs connected by a long channel attracts the attention of scientists worldwide,having applications in environmental and geophysical engineering.This study explores the impact of Navier slip conditions on exchange flows within a long channel connecting two large reservoirs of differing salinity.These horizontal density gradients drive the flow.We modify the recent one-dimensional theory,developed to avoid runaway stratification,to account for the presence of uniform slip walls.By adjusting the parameters of the horizontal density gradient based on the slip factor,we resolve analytically various flow regimes ranging from high diffusion to transitional high advection.These regimes are governed by physical parameters like channel aspect ratio,slip factor,Schmidt number,and gravitational Reynolds number.Our solutions align perfectly with ones in the no-slip limit.More importantly,under the conditions of no net flow across the channel and high Schmidt number(where stratification is concentrated near the channel’s mid-layer),we derive a closed-form solution for the slip parameter,aspect ratio,and gravitational Reynolds number that describes the interface’s behavior as a sharp interface separating two distinct zones.This interface,arising from hydrostatic wall gradients,ultimately detaches the low-and high-density regimes throughout the channel when the gravitational Reynolds number is inversely proportional to the aspect ratio for a fixed slip parameter.This phenomenon,observed previously in 2D numerical simulations with no-slip walls in the literature,is thus confirmed by our theoretical results.Our findings further demonstrate that wall slip leads to distinct and diverse flow regimes.
基金supported by the National Natural Science Foundation of China(Nos.51874201 and 52074184)Natural Science Foundation project of Liaoning Province(2023-MS238)+1 种基金Liaoning Revitalization talents program(XLYC2203009)the Fundamental Research Funds for the Universities of Liaoning Province。
文摘It is common for the rotating pin largely plunging into lower sheet to break up lap interface of Friction Stir Lap Welding(FSLW)joint,but the unavoidable up-bending morphology of hook outside Nugget Zone(NZ)largely reduces the joint bearing ability.Based on the novel Opposite-directions Flowing FSLW(OF-FSLW)by the self-developed rotating tool with an Xshaped right-left thread pin,the 2024 aluminum alloys lap joint was successfully welded in this study.The migration law of lap interface during welding was investigated by the experimental and numerical methods,and then how the rotating pin and its rotating velocity affect the formation and strength of OF-FSLW joint was further analyzed.The results show that the Material Concentrated Zone(MCZ)which formed above the original lap interface made the hook bend downward,the NZ greatly enlarged and the beginning part of cold lap compressed and thickened,thereby heightening the joint bearing ability.For the OF-FSLW joint,its maximum tensile strength was403 MPa,and the corresponding joint efficiency of 90.8%was an incredible and superb value for the 2000 series heat-treatment strengthened aluminum alloys friction stir welded joint.The OF-FSLW technology by the rotating tool with an X-shaped right-left thread pin is proven to be a greatly effective approach for manufacturing the aluminum alloys lap joint with superb strength.
基金The National Basic Research Program of China(973Program)(No.2009CB320505)the Natural Science Foundation of Jiangsu Province(No. BK2008288)+1 种基金the Excellent Young Teachers Program of Southeast University(No.4009001018)the Open Research Program of Key Laboratory of Computer Network of Guangdong Province (No. CCNL200706)
文摘In order to improve the precision of super point detection and control measurement resource consumption, this paper proposes a super point detection method based on sampling and data streaming algorithms （SDSD）, and proves that only sources or destinations with a lot of flows can be sampled probabilistically using the SDSD algorithm. The SDSD algorithm uses both the IP table and the flow bloom filter （BF） data structures to maintain the IP and flow information. The IP table is used to judge whether an IP address has been recorded. If the IP exists, then all its subsequent flows will be recorded into the flow BF; otherwise, the IP flow is sampled. This paper also analyzes the accuracy and memory requirements of the SDSD algorithm , and tests them using the CERNET trace. The theoretical analysis and experimental tests demonstrate that the most relative errors of the super points estimated by the SDSD algorithm are less than 5%, whereas the results of other algorithms are about 10%. Because of the BF structure, the SDSD algorithm is also better than previous algorithms in terms of memory consumption.
基金supported by Overseas Distinguished Scholar Program by the Ministry of Chinese Education(MS2010BJKJ005)the National Natural Science Foundation of China(10972030)
文摘A dynamical system of particle growth in the con vective undercooled melt driven by a biaxial straining flow is modeled. A uniformly valid asymptotic solution for the in terface evolution in particle growth is obtained by means of the multiple variable expansion method. The analytical so lution as a function of both azimuth angle and polar angle shows that the interface shape of particle growth in the bi axial straining flow is significantly deformed by the biaxial straining flow. The biaxial straining flow results in higher lo cal growth rate near the surface where the flow comes in and leads to lower local growth rate near the surface where the flow goes out. Due to the difference in local growth rate, an initially spherical particle will evolve into a prolate barrel like shape in the biaxial straining flow.
文摘软件定义网络(software defined networking,SDN)分离的数据平面和控制平面,给网络管理带来了开放性和灵活性.但同时控制器与交换机之间的接口(控制器南向接口)需要更频繁的交互各种消息以实现对网络的控制.一方面,数据平面触发Table-Miss的数据包需要通过Packet-In消息往返于交换机与控制器之间,时延增大的同时也给控制器南向接口带来繁重的通信开销,数据平面和控制平面之间的交互容易成为网络性能的瓶颈.另一方面,控制器在下发新的流表项时,由于缺乏新表项对应的数据流特征信息,易出现已有的大流表项被下发的小流表项替换的情况,造成冗余的Flow-Mod消息(流表更新消息)和Packet-In消息,进一步加重了南向接口的通信开销,降低了网络的整体性能.提出一种基于流量特征的OpenFlow南向接口开销优化技术uFlow,在控制器上通过对Packet-In消息中数据流量特征的识别以及对小流的直接转发,达到消除南向接口冗余开销的目的.对uFlow的原型系统进行了实现,并通过真实网络中的流量对uFlow优化效果进行了验证.实验结果显示:与传统的OpenFlow网络处理方式相比,uFlow消除了冗余的交换机流表项更新,显著地降低了OpenFlow南向接口的交互开销:在不同的网络负载和流表容量的情况下,uFlow平均能减少70%以上的Flow-Mod消息.
基金Supported by the National Natural Science Foundation of China(21276132)the Transformation Project of Scientific and Technological Achievements of Qingdao(16-6-2-50-nsh)
文摘Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rules of bubbles, which influence the mass transfer efficiency to a large extent, have received much less attention. In this paper, the volume of fluid method was used to calculate the bubble shapes, pressure, velocity distributions,and the flow patterns inside the bubbles. The rising behavior of the bubbles with four different initial diameters,i.e., 3 mm, 5 mm, 7 mm and 9 mm was investigated in four various liquids including water, 61.23% glycerol,86.73% glycerol and 100% glycerol. The results show that the liquid properties and bubble initial diameters have great impacts on bubble shapes. Moreover, flow patterns inside the bubbles with different initial diameters were analyzed and classified into three types under the condition of different bubble shapes. Three correlations for predicting the maximum internal circulation inside the bubbles in 86.73% glycerol were presented and the R-square values were all bigger than 0.98. Through analyzing the pressure and velocity distributions around the bubbles, four rules of bubble deformation were also obtained to explain and predict the shapes.
