Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry.Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and acc...Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry.Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and accumulate to form slug flow, so it is necessary to remove the accumulated liquid by gas purging. In this paper, experiment is carried out in hilly terrain pipelines. Three flow patterns of stratified flow, slug flow and stratified entrained flow are observed. The process of gas purging accumulated liquid is divided into four stages, namely liquid accumulation, liquid rising, continuous outflow and tail outflow. At the same time, the flow pattern maps of each stage are drawn. The pressure drop signal is analyzed in time domain and frequency domain, and the contour map of pressure drop distribution is drawn. It is found that the ratio of range to average value can well distinguish the occurrence range of each flow pattern.Based on visualization, the transition process of slug flow to stratified flow and stratified entrained flow is studied, and the transition boundary prediction model is established. An image processing method is proposed to convert the image signal into a similarity curve, and PSD analysis is performed to calculate the slug frequency. The normal distribution is used to fit the slug frequency, and the predicted correlation is in good agreement with the experimental data.展开更多
The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle...The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle,initial position,aspect ratio,and size on the motion characteristics were investigated.The computational results indicate that the particle's motion undergoes two distinct stages:a starting stage that involves moving from the release position to a limit cycle,and a periodic stage that involves moving on the limit cycle.The initial orientation of the particle has a minimal impact on both stages of motion.In contrast,the time it takes for the particle to reach the limit cycle may vary depending on the release position.Furthermore,particles with a larger aspect ratio exhibit a greater maximum velocity magnitude;an increase in particle size causes the particle trajectory to contract more toward the center of the cavity,decreasing the centrifugal force experienced by the particle.展开更多
Flow boiling in open microchannels offers highly efficient heat transfer performance and has attracted increasing attention in the fields of heat transfer and thermalmanagement of electronic devices in recent years.Ho...Flow boiling in open microchannels offers highly efficient heat transfer performance and has attracted increasing attention in the fields of heat transfer and thermalmanagement of electronic devices in recent years.However,the continuous rise in power density of electronic components imposesmore stringent requirements on the heat transfer capability of microchannel flow boiling.HFE-7100,a dielectric coolant with favorable thermophysical properties,has become a focal point of research for enhancing flow boiling performance in open microchannels.The flow boiling heat transfer performance ofHFE-7100 was investigated in this study by fabricating micro-nano composite structures on the bottom surface of open microchannels using laser ablation technology.Based on visualization results,a comparative analysis was conducted on the bubble dynamics and flow pattern characteristics of HFE-7100 flow boiling in micronano structured open microchannels(MNSOMC)and smooth-surface open microchannels(SSOMC),to elucidate the enhancement mechanism of micro-nano structures on flow boiling heat transfer in open microchannels.The results indicate that the surface structures and strong wettability of MNSOMC accelerated bubble nucleation and departure.Moreover,bubbles in the channel tended to coalesce along the flow direction,forming elongated slug bubbles with high aspect ratios,which enabled efficient thin film evaporation in conjunction with intense nucleate boiling,thereby significantly enhancing flow boiling heat transfer.Under the experimental conditions of this study,the maximum enhancements in the heat transfer coefficient(HTC)and critical heat flux(CHF)of HFE-7100 inMNSOMC were 33.4%and 133.1%,respectively,with the CHF reaching up to 1542.3 kW⋅m^(−2).Furthermore,due to the superior wettability and capillary wicking capability of the micro-nano composite structures,the significant enhancement in flow boiling heat transfer was achieved without incurring a noticeable pressure drop penalty.展开更多
Buoyancy-driven flows are prevalent in a wide range of geophysical and astrophysical systems. In this review, we focus on threepivotal effects that significantly influence the dynamics and transport properties of buoy...Buoyancy-driven flows are prevalent in a wide range of geophysical and astrophysical systems. In this review, we focus on threepivotal effects that significantly influence the dynamics and transport properties of buoyancy-driven flows and may have impli-cations for natural systems. These effects pertain to the role of boundary conditions, the impact of rotation, and the effect offinite size. Boundary conditions represent how the fluid flow interacts with different kinds of surfaces. Rotation, as the Earth’srotation in geophysical systems or the whirling of astrophysical systems, introduces Coriolis and centrifugal forces, leading tothe profound vortical structure and distinct transport property. Finite size, representing geometrical constraints, influences thebehavior of buoyancy-driven flows across varying geometrical settings. This review aims to provide a holistic understanding ofthe intricate interplay of these factors, offering insights into the complex natural phenomena from the perspectives of the threeeffects.展开更多
Flow cytometry(FCM),characterized by its simplicity,rapid processing,multiparameter analysis,and high sen-sitivity,is widely used in the diagnosis,treatment,and prognosis of hematological malignancies.FCM testing of t...Flow cytometry(FCM),characterized by its simplicity,rapid processing,multiparameter analysis,and high sen-sitivity,is widely used in the diagnosis,treatment,and prognosis of hematological malignancies.FCM testing of tissue samples not only aids in diagnosing and classifying hematological cancers,but also enables the detection of solid tumors.Its ability to detect numerous marker parameters from small samples is particularly useful when dealing with limited cell quantities,such as in fine-needle biopsy samples.This attribute not only addresses the challenge posed by small sample sizes,but also boosts the sensitivity of tumor cell detection.The significance of FCM in clinical and pathological applications continues to grow.To standardize the use of FCM in detecting hematological malignant cells in tissue samples and to improve quality control during the detection process,experts from the Cell Analysis Professional Committee of the Chinese Society of Biotechnology jointly drafted and agreed upon this consensus.This consensus was formulated based on current literature and clinical practices of all experts across clinical,laboratory,and pathological fields in China.It outlines a comprehensive workflow of FCM-based assay for the detection of hematological malignancies in tissue samples,including report content,interpretation,quality control,and key considerations.Additionally,it provides recommendations on antibody panel designs and analytical approaches to enhancing FCM tests,particularly in cases with limited sample sizes.展开更多
Liquid film cooling as an advanced cooling technology is widely used in space vehicles.Stable operation of liquid film along the rocket combustion inner wall is crucial for thermal protection of rocket engines.The sta...Liquid film cooling as an advanced cooling technology is widely used in space vehicles.Stable operation of liquid film along the rocket combustion inner wall is crucial for thermal protection of rocket engines.The stability of liquid film is mainly determined by the characteristics of interfacial wave,which is rarely investigated right now.How to improve the stability of thin film has become a hot spot.In view of this,an advanced model based on the conventional Volume of Fluid(VOF)model is adopted to investigate the characteristics of interfacial wave in gas-liquid flow by using OpenFOAM,and the mechanism of formation and development of wave is revealed intuitively through numerical study.The effects from gas velocity,surface tension and dynamic viscosity of liquid(three factors)on the wave are studied respectively.It can be found that the gas velocity is critical to the formation and development of wave,and four modes of droplets generation are illustrated in this paper.Besides,a gas vortex near the gas-liquid interface can induce formation of wave easily,so changing the gas vortex state can regulate formation and development of wave.What’s more,the change rules of three factors influencing on the interfacial wave are obtained,and the surface tension has a negative effect on the formation and development of wave only when the surface tension coefficient is above the critical value,whereas the dynamic viscosity has a positive effect in this process.Lastly,the maximum height and maximum slope angle of wave will level off as the gas velocity increases.Meanwhile,the maximum slope angle of wave is usually no more than 38°,no matter what happens to the three factors.展开更多
Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to ...Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.展开更多
This paper gives an overview on nonlinear porous flow in low permeability porous media, reveals the microscopic mechanisms of flows, and clarifies properties of porous flow fluids. It shows that, deviating from Darcy...This paper gives an overview on nonlinear porous flow in low permeability porous media, reveals the microscopic mechanisms of flows, and clarifies properties of porous flow fluids. It shows that, deviating from Darcy＇s linear law, the porous flow characteristics obey a nonlinear law in a low-permeability porous medium, and the viscosity of the porous flow fluid and the permeability values of water and oil are not constants. Based on these characters, a new porous flow model, which can better describe low permeability reservoir~ is established. This model can describe various patterns of porous flow, as Darcy＇s linear law does. All the parameters involved in the model, having definite physical meanings, can be obtained directly from the experiments.展开更多
Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally s...Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally studied for supercritical fluids. Two types of flow excursion occur in a single tube. Type Ⅰ and Type Ⅱ excursions, and they are corresponding to decreasing and increasing flow rate respectively. They can trigger flow maldistribution between parallel tubes and the hysteresis phenomenon of flow distribution. The effects of system parameters, including inlet temperature,system pressure, and heat flux, on flow distribution were analyzed. In addition, the relationship between flow excursion and the pseudo-critical interval proposed in the literature was established according to the heated tube outlet temperature at the onset of flow instability. Finally, the flow excursion instability boundary was obtained using two dimensionless parameters. These experimental results can provide helpful insight on the mechanism of Scramjet regenerative cooling.展开更多
The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relev...The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relevant results anddata in the literature, in the present study, we concentrate on the experimental determination of the flow coefficientfor the annular orifice, the pressure distribution in the MCOP, and the characteristics of the choked flow itself. Asconfirmed by the experimental results, the Reynolds number, the orifice plate thickness, the plug taper, and theeccentricity have an obvious influence on the aforementioned flow coefficient. The pressure drop in the MCOPis mainly generated near the orifice plate, and the pressure upstream of the orifice plate is slightly reduced in theflow direction, while the pressure downstream of the orifice plate displays a recovery trend. The choked flow rateof the MCOP can be adjusted by replacing the spring with a maximum flow control deviation of 4.91%.展开更多
Machine learning combined with density functional theory(DFT)enables rapid exploration of catalyst descriptors space such as adsorption energy,facilitating rapid and effective catalyst screening.However,there is still...Machine learning combined with density functional theory(DFT)enables rapid exploration of catalyst descriptors space such as adsorption energy,facilitating rapid and effective catalyst screening.However,there is still a lack of models for predicting adsorption energies on oxides,due to the complexity of elemental species and the ambiguous coordination environment.This work proposes an active learning workflow(LeNN)founded on local electronic transfer features(e)and the principle of coordinate rotation invariance.By accurately characterizing the electron transfer to adsorption site atoms and their surrounding geometric structures,LeNN mitigates abrupt feature changes due to different element types and clarifies coordination environments.As a result,it enables the prediction of^(*)H adsorption energy on binary oxide surfaces with a mean absolute error(MAE)below 0.18 eV.Moreover,we incorporate local coverage(θ_(l))and leverage neutral network ensemble to establish an active learning workflow,attaining a prediction MAE below 0.2 eV for 5419 multi-^(*)H adsorption structures.These findings validate the universality and capability of the proposed features in predicting^(*)H adsorption energy on binary oxide surfaces.展开更多
The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed...The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed by conductivity probes to determine the liquid slug length distribution. The data covered both the slug and plug flow regimes. From experimental results, the mean liquid slug lengths were relatively insensitive to gas and liquid flow rates in the higher mixture velocity range. But in the lower mixture velocity range, the mean liquid slug length decreased and then increased with mixture velocity. It shows that the development length of slug flow was longer than x/D=1157. A slug tracking model was adapted to study the evolution of liquid slug length distribution in a horizontal pipeline. In the present model, the wake effect of elongated bubble and the pressure drop due to accel-eration are taken into account and random slug lengths are introduced at the entrance. The results of the model are compared with the measured slug length distributions of slug flow regime. It shows that the predicted mean and maximum slug lengths are in agreement with the experimental data at x/D=1157 and the form of the slug length distributions is also predicted well by the model.展开更多
The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe wi...The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40 mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superflcial velocity ranges of oil and water were: 0.04-1.2m·s-1 and 0.04-2.2m·s-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution of oil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.展开更多
The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug...The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.展开更多
The upward multiphase cross flow and heat transfer in the vertical tube may occur in oil production and chemical facilities. In this study, the local flow patterns of an upward gas-water two phase cross flow in a vert...The upward multiphase cross flow and heat transfer in the vertical tube may occur in oil production and chemical facilities. In this study, the local flow patterns of an upward gas-water two phase cross flow in a vertical tube with a horizontal rod have been investigated with an optical probe and the digital high speed video system. The local flow patterns are defined as the bubble, slug, churn and annular flow patterns. Optical probe signals are ana- lyzed in terms of probability density function, and it is proved that the local flow patterns can be recognized by this method. The transition mechanisms between the different flow patterns have been analyzed and the corresponding transitional models are proposed. Finally, local flow pattern maps of the upward gas-water two-phase flow in the vertical tube with a horizontal rod are constructed.展开更多
Infrasonic waves （frequency 〈 2o Hz） are generated during the formation and movement of debris flows, traveling in air with a speed far higher than that of the debris-flow movement. Infrasound monitoring and locali...Infrasonic waves （frequency 〈 2o Hz） are generated during the formation and movement of debris flows, traveling in air with a speed far higher than that of the debris-flow movement. Infrasound monitoring and localization of infrasonic waves can serve as warning properties for debris-flows. Based on the characteristics of infrasonic signals, this study presents a three-point array of infrasound sensors as time-synchronous multiple sensors for acquiring signals. In the meantime, the signals are sorted by mutual correlation of signals to figure out their latency, and by means of array coordinating to Locate the sound source to realize the monitoring and positioning of a debris-flows hazard. The method has been in situ tested and has been proven to be accurate in monitoring debris-flow occurrences and determining their positions, which is particularly effective for pre-event warning of debris-flow hazards.展开更多
Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theo...Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theory and natural closure approximation. Results of the stability analysis show attenuating effects of fibre additives to the flow instability. For the cases leading to transition, drag reduction rate increases with the characteristic parameter H of fibres. The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress. The theoretical results are qualitatively consistent with some typical experiments.展开更多
The focus of this paper is on the measurement and calculation model of void fraction for the vertical upward co-current air-water slug flow in a circular tube of 15 mm inner diameter. High-speed photography and optica...The focus of this paper is on the measurement and calculation model of void fraction for the vertical upward co-current air-water slug flow in a circular tube of 15 mm inner diameter. High-speed photography and optical probes were utilized, with water superficial velocity ranging from 0.089 to 0.65 m·s^(-1)and gas superficial velocity ranging from 0.049 to 0.65 m·s^(-1). A new void fraction model based on the local parameters was proposed, disposing the slug flow as a combination of Taylor bubbles and liquid slugs. In the Taylor bubble region, correction factors of liquid film thickness Cδand nose shape CZ*were proposed to calculate aTB. In the liquid slug region, the radial void fraction distribution profiles were obtained to calculate aLS, by employing the image processing technique based on supervised machine learning. Results showed that the void fraction proportion in Taylor bubbles occupied crucial contribution to the overall void fraction. Multiple types of void fraction predictive correlations were assessed using the present data. The performance of the Schmidt model was optimal, while some models for slug flow performed not outstanding. Additionally, a predictive correlation was correlated between the central local void fraction and the cross-sectional averaged void fraction, as a straightforward form of the void fraction calculation model. The predictive correlation showed a good agreement with the present experimental data, as well as the data of Olerni et al., indicating that the new model was effective and applicable under the slug flow conditions.展开更多
The modulation of turbulence by particles has been rigorously investigated in the literature yielding either a reduction or an enhancement of the turbulent kinetic energy at different spatial length scales.However,a g...The modulation of turbulence by particles has been rigorously investigated in the literature yielding either a reduction or an enhancement of the turbulent kinetic energy at different spatial length scales.However,a general description of the turbulence modulation in multiphase flows due to the presence of an interphase force has attracted less attention.In this paper,we investigate the turbulent modulation for interfacial and fluid-particle flows analytically and numerically,where surface tension and drag define the interphase coupling,respectively.It is shown that surface tension and drag appear as additional production/dissipation terms in the transport equations for the turbulent kinetic energies(TKE),which is of particular importance for the turbulence modelling of multiphase flows.Furthermore,we study the modulation of turbulence in decaying homogenous isotropic turbulence(HIT)for both types of multiphase flow.The results clearly unveil that in both cases the energy is reduced at large scales,while the small-scale energy is enhanced compared to single-phase flows.Particularly,at large scales surface tension works against the turbulent eddies and hinders the ejection of droplet from the corrugated interface.In contrast,at the small scales,the surface tension force and the velocity fluctuations are aligned leading to an enhancement of the energy.In the case of fluid-particle flows,particles retain their energy longer than the surrounding fluid increasing the energy at the small scales,while at the large scales the particles do not follow exactly the surrounding fluid reducing its energy.For the latter effect,a considerable dependence on the particle Stokes number is found.展开更多
Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inc...Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inclined and even vertical sections of gas wells.To grasp the flow law of slug flow and guide engineering practice,the flow law of slug flow at various inclination angles(30°~90°)is studied by means of the combination of laboratory experiments(including high frequency pressure data acquisition system)and finite element numerical simulation.The results reveal that because of the delay of pressure variation at the corresponding position of pipeline resulting from gas expansion,the highest point of pressure change curve corresponds not to the highest point of liquid holdup curve(pressure change lags behind 0.125 s of liquid holdup change).Thus,the delay of pressure should be highlighted in predicting slug flow using pressure parameter change;otherwise the accuracy of prediction will be affected when slug flow occurs.It is generally known that liquid holdup and pressure drop are the major factors affecting the pressure variation and stable operation of pipelines.Accordingly,the results of finite element numerical simulation and Beggs-Brill model calculation are compared with those of laboratory experiments.The numerical simulation method is applicable to predicting the pressure drop of the pipeline,while the Beggs-Brill model is more suitable for predicting the liquid holdup variation of the pipeline.The research conclusion helps reveal the slug flow law,and it is of a scientific guiding implication to the prediction method of flow parameters under slug flow pattern in the process of gas well exploitation.展开更多
基金supported by the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.52488201)the National Natural Science Foundation of China(No.52422606).
文摘Hilly terrain pipeline is a common form of pipeline in oil and gas storage and transportation industry.Due to the hilly terrain influence, the liquid at the elbow of the gathering pipeline is easy to flow back and accumulate to form slug flow, so it is necessary to remove the accumulated liquid by gas purging. In this paper, experiment is carried out in hilly terrain pipelines. Three flow patterns of stratified flow, slug flow and stratified entrained flow are observed. The process of gas purging accumulated liquid is divided into four stages, namely liquid accumulation, liquid rising, continuous outflow and tail outflow. At the same time, the flow pattern maps of each stage are drawn. The pressure drop signal is analyzed in time domain and frequency domain, and the contour map of pressure drop distribution is drawn. It is found that the ratio of range to average value can well distinguish the occurrence range of each flow pattern.Based on visualization, the transition process of slug flow to stratified flow and stratified entrained flow is studied, and the transition boundary prediction model is established. An image processing method is proposed to convert the image signal into a similarity curve, and PSD analysis is performed to calculate the slug frequency. The normal distribution is used to fit the slug frequency, and the predicted correlation is in good agreement with the experimental data.
文摘The motion of an elliptical rigid particle in a lid-driven cavity flow was numerically simulated using the immersed boundary lattice Boltzmann method(IB-LBM).The effects of the particle's initial orientation angle,initial position,aspect ratio,and size on the motion characteristics were investigated.The computational results indicate that the particle's motion undergoes two distinct stages:a starting stage that involves moving from the release position to a limit cycle,and a periodic stage that involves moving on the limit cycle.The initial orientation of the particle has a minimal impact on both stages of motion.In contrast,the time it takes for the particle to reach the limit cycle may vary depending on the release position.Furthermore,particles with a larger aspect ratio exhibit a greater maximum velocity magnitude;an increase in particle size causes the particle trajectory to contract more toward the center of the cavity,decreasing the centrifugal force experienced by the particle.
基金funded by the National Natural Science Foundation of China(Grant No.52276047)the Open Fund of NationalKey Laboratory of SpacecraftThermal Control(Grant No.NKLST-JJ-202401011)the Beijing Municipal Science&Technology Commission(Grant No.Z231100006123010).
文摘Flow boiling in open microchannels offers highly efficient heat transfer performance and has attracted increasing attention in the fields of heat transfer and thermalmanagement of electronic devices in recent years.However,the continuous rise in power density of electronic components imposesmore stringent requirements on the heat transfer capability of microchannel flow boiling.HFE-7100,a dielectric coolant with favorable thermophysical properties,has become a focal point of research for enhancing flow boiling performance in open microchannels.The flow boiling heat transfer performance ofHFE-7100 was investigated in this study by fabricating micro-nano composite structures on the bottom surface of open microchannels using laser ablation technology.Based on visualization results,a comparative analysis was conducted on the bubble dynamics and flow pattern characteristics of HFE-7100 flow boiling in micronano structured open microchannels(MNSOMC)and smooth-surface open microchannels(SSOMC),to elucidate the enhancement mechanism of micro-nano structures on flow boiling heat transfer in open microchannels.The results indicate that the surface structures and strong wettability of MNSOMC accelerated bubble nucleation and departure.Moreover,bubbles in the channel tended to coalesce along the flow direction,forming elongated slug bubbles with high aspect ratios,which enabled efficient thin film evaporation in conjunction with intense nucleate boiling,thereby significantly enhancing flow boiling heat transfer.Under the experimental conditions of this study,the maximum enhancements in the heat transfer coefficient(HTC)and critical heat flux(CHF)of HFE-7100 inMNSOMC were 33.4%and 133.1%,respectively,with the CHF reaching up to 1542.3 kW⋅m^(−2).Furthermore,due to the superior wettability and capillary wicking capability of the micro-nano composite structures,the significant enhancement in flow boiling heat transfer was achieved without incurring a noticeable pressure drop penalty.
基金supponted by the National Natural Science Foundation of China (Grant Nos 12202173,12072144,12232010,12372219,and 12302282).
文摘Buoyancy-driven flows are prevalent in a wide range of geophysical and astrophysical systems. In this review, we focus on threepivotal effects that significantly influence the dynamics and transport properties of buoyancy-driven flows and may have impli-cations for natural systems. These effects pertain to the role of boundary conditions, the impact of rotation, and the effect offinite size. Boundary conditions represent how the fluid flow interacts with different kinds of surfaces. Rotation, as the Earth’srotation in geophysical systems or the whirling of astrophysical systems, introduces Coriolis and centrifugal forces, leading tothe profound vortical structure and distinct transport property. Finite size, representing geometrical constraints, influences thebehavior of buoyancy-driven flows across varying geometrical settings. This review aims to provide a holistic understanding ofthe intricate interplay of these factors, offering insights into the complex natural phenomena from the perspectives of the threeeffects.
基金supported by grants from the National Natural Science Foundation of China(grant numbers:82370195,82270203,81770211)the Fundamental Research Funds for the Central Univer-sities(grant number:2022CDJYGRH-001)Chongqing Technology Innovation and Application Development Special Key Project(grant number:CSTB2024TIAD-KPX0031).
文摘Flow cytometry(FCM),characterized by its simplicity,rapid processing,multiparameter analysis,and high sen-sitivity,is widely used in the diagnosis,treatment,and prognosis of hematological malignancies.FCM testing of tissue samples not only aids in diagnosing and classifying hematological cancers,but also enables the detection of solid tumors.Its ability to detect numerous marker parameters from small samples is particularly useful when dealing with limited cell quantities,such as in fine-needle biopsy samples.This attribute not only addresses the challenge posed by small sample sizes,but also boosts the sensitivity of tumor cell detection.The significance of FCM in clinical and pathological applications continues to grow.To standardize the use of FCM in detecting hematological malignant cells in tissue samples and to improve quality control during the detection process,experts from the Cell Analysis Professional Committee of the Chinese Society of Biotechnology jointly drafted and agreed upon this consensus.This consensus was formulated based on current literature and clinical practices of all experts across clinical,laboratory,and pathological fields in China.It outlines a comprehensive workflow of FCM-based assay for the detection of hematological malignancies in tissue samples,including report content,interpretation,quality control,and key considerations.Additionally,it provides recommendations on antibody panel designs and analytical approaches to enhancing FCM tests,particularly in cases with limited sample sizes.
文摘Liquid film cooling as an advanced cooling technology is widely used in space vehicles.Stable operation of liquid film along the rocket combustion inner wall is crucial for thermal protection of rocket engines.The stability of liquid film is mainly determined by the characteristics of interfacial wave,which is rarely investigated right now.How to improve the stability of thin film has become a hot spot.In view of this,an advanced model based on the conventional Volume of Fluid(VOF)model is adopted to investigate the characteristics of interfacial wave in gas-liquid flow by using OpenFOAM,and the mechanism of formation and development of wave is revealed intuitively through numerical study.The effects from gas velocity,surface tension and dynamic viscosity of liquid(three factors)on the wave are studied respectively.It can be found that the gas velocity is critical to the formation and development of wave,and four modes of droplets generation are illustrated in this paper.Besides,a gas vortex near the gas-liquid interface can induce formation of wave easily,so changing the gas vortex state can regulate formation and development of wave.What’s more,the change rules of three factors influencing on the interfacial wave are obtained,and the surface tension has a negative effect on the formation and development of wave only when the surface tension coefficient is above the critical value,whereas the dynamic viscosity has a positive effect in this process.Lastly,the maximum height and maximum slope angle of wave will level off as the gas velocity increases.Meanwhile,the maximum slope angle of wave is usually no more than 38°,no matter what happens to the three factors.
基金the support of the Opening Fund of State Key Laboratory of Multiphase Flow in Power Engineering(SKLMF-KF-2102)。
文摘Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop.
文摘This paper gives an overview on nonlinear porous flow in low permeability porous media, reveals the microscopic mechanisms of flows, and clarifies properties of porous flow fluids. It shows that, deviating from Darcy＇s linear law, the porous flow characteristics obey a nonlinear law in a low-permeability porous medium, and the viscosity of the porous flow fluid and the permeability values of water and oil are not constants. Based on these characters, a new porous flow model, which can better describe low permeability reservoir~ is established. This model can describe various patterns of porous flow, as Darcy＇s linear law does. All the parameters involved in the model, having definite physical meanings, can be obtained directly from the experiments.
基金co-supported by the Open Fund of Key Laboratory of Power Research of China(No.2017-Ⅲ-0005-0029)the National Natural Science Foundation of China(No.51776167).
文摘Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally studied for supercritical fluids. Two types of flow excursion occur in a single tube. Type Ⅰ and Type Ⅱ excursions, and they are corresponding to decreasing and increasing flow rate respectively. They can trigger flow maldistribution between parallel tubes and the hysteresis phenomenon of flow distribution. The effects of system parameters, including inlet temperature,system pressure, and heat flux, on flow distribution were analyzed. In addition, the relationship between flow excursion and the pseudo-critical interval proposed in the literature was established according to the heated tube outlet temperature at the onset of flow instability. Finally, the flow excursion instability boundary was obtained using two dimensionless parameters. These experimental results can provide helpful insight on the mechanism of Scramjet regenerative cooling.
基金the Foundation of the Educational Commission of Hubei Province of China[Grant No.Q20191310]。
文摘The mechanically choked orifice plate (MCOP) is a new type of device for flow control by which choking conditionsfor incompressible fluids can be obtained with relatively small pressure losses. Given the lack of relevant results anddata in the literature, in the present study, we concentrate on the experimental determination of the flow coefficientfor the annular orifice, the pressure distribution in the MCOP, and the characteristics of the choked flow itself. Asconfirmed by the experimental results, the Reynolds number, the orifice plate thickness, the plug taper, and theeccentricity have an obvious influence on the aforementioned flow coefficient. The pressure drop in the MCOPis mainly generated near the orifice plate, and the pressure upstream of the orifice plate is slightly reduced in theflow direction, while the pressure downstream of the orifice plate displays a recovery trend. The choked flow rateof the MCOP can be adjusted by replacing the spring with a maximum flow control deviation of 4.91%.
基金supported by the National Natural Science Foundation of China(No.52488201)the Natural Science Basic Research Program of Shaanxi(No.2024JC-YBMS-284)+1 种基金the Key Research and Development Program of Shaanxi(No.2024GHYBXM-02)the Fundamental Research Funds for the Central Universities.
文摘Machine learning combined with density functional theory(DFT)enables rapid exploration of catalyst descriptors space such as adsorption energy,facilitating rapid and effective catalyst screening.However,there is still a lack of models for predicting adsorption energies on oxides,due to the complexity of elemental species and the ambiguous coordination environment.This work proposes an active learning workflow(LeNN)founded on local electronic transfer features(e)and the principle of coordinate rotation invariance.By accurately characterizing the electron transfer to adsorption site atoms and their surrounding geometric structures,LeNN mitigates abrupt feature changes due to different element types and clarifies coordination environments.As a result,it enables the prediction of^(*)H adsorption energy on binary oxide surfaces with a mean absolute error(MAE)below 0.18 eV.Moreover,we incorporate local coverage(θ_(l))and leverage neutral network ensemble to establish an active learning workflow,attaining a prediction MAE below 0.2 eV for 5419 multi-^(*)H adsorption structures.These findings validate the universality and capability of the proposed features in predicting^(*)H adsorption energy on binary oxide surfaces.
基金Supported by the National Natural Science Foundation of China (No.50536020 and 50323001).
文摘The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed by conductivity probes to determine the liquid slug length distribution. The data covered both the slug and plug flow regimes. From experimental results, the mean liquid slug lengths were relatively insensitive to gas and liquid flow rates in the higher mixture velocity range. But in the lower mixture velocity range, the mean liquid slug length decreased and then increased with mixture velocity. It shows that the development length of slug flow was longer than x/D=1157. A slug tracking model was adapted to study the evolution of liquid slug length distribution in a horizontal pipeline. In the present model, the wake effect of elongated bubble and the pressure drop due to accel-eration are taken into account and random slug lengths are introduced at the entrance. The results of the model are compared with the measured slug length distributions of slug flow regime. It shows that the predicted mean and maximum slug lengths are in agreement with the experimental data at x/D=1157 and the form of the slug length distributions is also predicted well by the model.
基金National Natural Science Foundation of China (No.59995462 and 10172069)
文摘The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40 mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superflcial velocity ranges of oil and water were: 0.04-1.2m·s-1 and 0.04-2.2m·s-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution of oil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.
基金National Natural Science Foundation of China(No.50206016)
文摘The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.
文摘The upward multiphase cross flow and heat transfer in the vertical tube may occur in oil production and chemical facilities. In this study, the local flow patterns of an upward gas-water two phase cross flow in a vertical tube with a horizontal rod have been investigated with an optical probe and the digital high speed video system. The local flow patterns are defined as the bubble, slug, churn and annular flow patterns. Optical probe signals are ana- lyzed in terms of probability density function, and it is proved that the local flow patterns can be recognized by this method. The transition mechanisms between the different flow patterns have been analyzed and the corresponding transitional models are proposed. Finally, local flow pattern maps of the upward gas-water two-phase flow in the vertical tube with a horizontal rod are constructed.
基金supported by the National Natural Science Foundation of China(Grant No.41501114)the General Project of Education Department in Sichuan Province(16ZB0104)the Science and Technology Service Network Initiative(No.KFJ-SW-STS-180)
文摘Infrasonic waves （frequency 〈 2o Hz） are generated during the formation and movement of debris flows, traveling in air with a speed far higher than that of the debris-flow movement. Infrasound monitoring and localization of infrasonic waves can serve as warning properties for debris-flows. Based on the characteristics of infrasonic signals, this study presents a three-point array of infrasound sensors as time-synchronous multiple sensors for acquiring signals. In the meantime, the signals are sorted by mutual correlation of signals to figure out their latency, and by means of array coordinating to Locate the sound source to realize the monitoring and positioning of a debris-flows hazard. The method has been in situ tested and has been proven to be accurate in monitoring debris-flow occurrences and determining their positions, which is particularly effective for pre-event warning of debris-flow hazards.
基金the National Natural Science Foundation of China (No. 10372090 and No. 10102017).
文摘Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theory and natural closure approximation. Results of the stability analysis show attenuating effects of fibre additives to the flow instability. For the cases leading to transition, drag reduction rate increases with the characteristic parameter H of fibres. The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress. The theoretical results are qualitatively consistent with some typical experiments.
基金supported by National Key Research and Development Program of China ( 2018YFE011061)。
文摘The focus of this paper is on the measurement and calculation model of void fraction for the vertical upward co-current air-water slug flow in a circular tube of 15 mm inner diameter. High-speed photography and optical probes were utilized, with water superficial velocity ranging from 0.089 to 0.65 m·s^(-1)and gas superficial velocity ranging from 0.049 to 0.65 m·s^(-1). A new void fraction model based on the local parameters was proposed, disposing the slug flow as a combination of Taylor bubbles and liquid slugs. In the Taylor bubble region, correction factors of liquid film thickness Cδand nose shape CZ*were proposed to calculate aTB. In the liquid slug region, the radial void fraction distribution profiles were obtained to calculate aLS, by employing the image processing technique based on supervised machine learning. Results showed that the void fraction proportion in Taylor bubbles occupied crucial contribution to the overall void fraction. Multiple types of void fraction predictive correlations were assessed using the present data. The performance of the Schmidt model was optimal, while some models for slug flow performed not outstanding. Additionally, a predictive correlation was correlated between the central local void fraction and the cross-sectional averaged void fraction, as a straightforward form of the void fraction calculation model. The predictive correlation showed a good agreement with the present experimental data, as well as the data of Olerni et al., indicating that the new model was effective and applicable under the slug flow conditions.
基金This work was supported by the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development. The authors further want to acknowledge the funding support of K1-MET GmbH, metallurgical competence center. The research programme of the K1-MET competence center is supported by COMET (Competence Center for Excellent Technologies), the Austrian programme for competence centers. COMET is funded by the Federal Ministry for Transport, Innovation and Technology, the Federal Ministry for Digital and Economic Affairs and the provinces of Upper Austria, Tyrol and Styria. Beside the public funding from COMET, this research project is partially financed by the industrial partners Primetals Technologies Austria GmbH, voestalpine Stahl Donawitz GmbH, RHI Magnesita GmbH and voestalpine Stahl GmbH.
文摘The modulation of turbulence by particles has been rigorously investigated in the literature yielding either a reduction or an enhancement of the turbulent kinetic energy at different spatial length scales.However,a general description of the turbulence modulation in multiphase flows due to the presence of an interphase force has attracted less attention.In this paper,we investigate the turbulent modulation for interfacial and fluid-particle flows analytically and numerically,where surface tension and drag define the interphase coupling,respectively.It is shown that surface tension and drag appear as additional production/dissipation terms in the transport equations for the turbulent kinetic energies(TKE),which is of particular importance for the turbulence modelling of multiphase flows.Furthermore,we study the modulation of turbulence in decaying homogenous isotropic turbulence(HIT)for both types of multiphase flow.The results clearly unveil that in both cases the energy is reduced at large scales,while the small-scale energy is enhanced compared to single-phase flows.Particularly,at large scales surface tension works against the turbulent eddies and hinders the ejection of droplet from the corrugated interface.In contrast,at the small scales,the surface tension force and the velocity fluctuations are aligned leading to an enhancement of the energy.In the case of fluid-particle flows,particles retain their energy longer than the surrounding fluid increasing the energy at the small scales,while at the large scales the particles do not follow exactly the surrounding fluid reducing its energy.For the latter effect,a considerable dependence on the particle Stokes number is found.
基金Gratitude is extended to Wei Luo,the corresponding author for the article.The authors would also like to acknowledge the support provided by the National Natural Science Fund Project(61572084)major national projects(2017ZX05030-005,2016ZX05056004-002,2016ZX05046004-003).
文摘Horizontal well production technology gradually occupies a dominant position in the petroleum field.With the rise in water production in the later stage of exploitation,slug flow phenomena will exist in horizontal,inclined and even vertical sections of gas wells.To grasp the flow law of slug flow and guide engineering practice,the flow law of slug flow at various inclination angles(30°~90°)is studied by means of the combination of laboratory experiments(including high frequency pressure data acquisition system)and finite element numerical simulation.The results reveal that because of the delay of pressure variation at the corresponding position of pipeline resulting from gas expansion,the highest point of pressure change curve corresponds not to the highest point of liquid holdup curve(pressure change lags behind 0.125 s of liquid holdup change).Thus,the delay of pressure should be highlighted in predicting slug flow using pressure parameter change;otherwise the accuracy of prediction will be affected when slug flow occurs.It is generally known that liquid holdup and pressure drop are the major factors affecting the pressure variation and stable operation of pipelines.Accordingly,the results of finite element numerical simulation and Beggs-Brill model calculation are compared with those of laboratory experiments.The numerical simulation method is applicable to predicting the pressure drop of the pipeline,while the Beggs-Brill model is more suitable for predicting the liquid holdup variation of the pipeline.The research conclusion helps reveal the slug flow law,and it is of a scientific guiding implication to the prediction method of flow parameters under slug flow pattern in the process of gas well exploitation.
