During the exploitation of offshore oil and gas,it is easy to form severe slugging which can cause great harm in the riser connecting wellheads and offshore platform preprocessing system.The flow pattern and pressure ...During the exploitation of offshore oil and gas,it is easy to form severe slugging which can cause great harm in the riser connecting wellheads and offshore platform preprocessing system.The flow pattern and pressure fluctuation of severe slugging were studied in an experimental simulation system with inner diameter of 0.051 m.It is found that severe slugging can be divided into three severe slugging regimes：regime I at low gas and liquid flow rates with large pressure fluctuation,intermittent flow of liquid and gas in the riser,and apparent cutoff of liquid phase,regime II at high gas flow rate with non-periodic fluctuation and discontinuous liquid outflow and no gas cutoff,regime III at high liquid flow rate with degenerative pressure fluctuation in form of relatively stable bubbly or plug flow.The results indicate that severe slugging still occurs when the declination angle of pipeline is 0,and there are mainly two kinds of regimes：regime I and regime II.As the angle increases,the formation ranges of regime I and regime III increase slightly while that of regime II is not affected.With the increase of gas superficial velocity and liquid superficial velocity,the pressure fluctuation at the bottom of riser increases initially and then decreases.The maximum value of pressure fluctuation occurs at the transition boundary of regimes I and II.展开更多
Due to the special structure of offshore multiphase pipes, it is easy for severe slugging to occur in the riser at low gas-liquid velocity. Violent pressure fluctuations and dramatic changes of flow rate are the main ...Due to the special structure of offshore multiphase pipes, it is easy for severe slugging to occur in the riser at low gas-liquid velocity. Violent pressure fluctuations and dramatic changes of flow rate are the main characteristics of severe slugging, leading to the risk of serious damage. In this paper, the separator control is adopted to accurately control the separator liquid level and pressure under severe slugging flow conditions. This indicates that the separator liquid level control alone does not have a significant impact on the upstream flow, but it is beneficial for normal operation and pressure control of the separator. As the separator pressure increases, the peak pressure in the riser apparently diminishes, and the amplitude of pressure fluctuation gradually decreases, which means that severe slugging is inhibited. During the slug blowing out, the gas/liquid slipping in the riser intensifies. The long gas plug quickly flows through the riser, and then tends to morph into short and slowly flowing gas bubbles. The elimination effect of the pressure control strategy on severe slugging is related to the relative rate of the superficial gas/liquid flow.展开更多
Severe slugging can occur in a pipeline-riser system at relatively low liquid and gas flow rates during gas-oil transportation, possibly causing unexpected damage to the production facilities. Experiments with air and...Severe slugging can occur in a pipeline-riser system at relatively low liquid and gas flow rates during gas-oil transportation, possibly causing unexpected damage to the production facilities. Experiments with air and water are conducted in a horizontal and downward inclined pipeline followed by a catenary riser in order to investigate the mechanism and characteristics of severe slugging. A theoretical model is introduced to compare with the experiments. The results show that the formation mechanism of severe slugging in a catenary riser is different from that in a vertical riser due to the riser geometry and five flow patterns are obtained and analyzed. A gas-liquid mixture slug stage is observed at the beginning of one cycle of severe slugging, which is seldom noticed in previous studies. Based on both experiments and computations, the time period and variation of pressure amplitude of severe slugging are found closely related to the superficial gas velocity, implying that the gas velocity significantly influences the flow patterns in our experiments. Moreover, good agreements between the experimental data and the numerical results are shown in the stability curve and flow regime map, which can be a possible reference for design in an offshore oil-production system.展开更多
A mathematical model is presented to study the main characteristics of severe slugging in a downward inclined pipeline followed by a catenary riser. In this model, both simplified transient model and phase distributio...A mathematical model is presented to study the main characteristics of severe slugging in a downward inclined pipeline followed by a catenary riser. In this model, both simplified transient model and phase distribution model are included so that the flow characteristics of each stage for severe slugging can be accurately reproduced, especially for blowout stage. The results show that the flow features of severe slugging can be simulated by the proposed mathematical model. A good agreement between the experimental data and the numerical results is observed. The model can predict the transient fluctuation of many respects, such as the superficial gas velocity at the bottom of the riser and the average velocity at the outlet of the riser.展开更多
When using topside choking to eliminate severe slugging in offshore pipeline-riser systems,the resulting stability and effectiveness depend critically on the choice of variables in the associated control model.In this...When using topside choking to eliminate severe slugging in offshore pipeline-riser systems,the resulting stability and effectiveness depend critically on the choice of variables in the associated control model.In this study,both potential process variables and manipulated variables are investigated via manual choking experiments.Monotonicity and linearity are adopted as principles for selecting the optimal variables,and the availability of signals in an offshore field is also considered.Both amplitude-domain and time-domain variables are studied,of which five are recommended as the process variable,while the resistance factor of the choking valve is the optimal manipulated variable;other variables may act as auxiliary variables in the control model.How to determine the set value of the process variable is also discussed.Validation experiments with automatic control show that the optimized variables enable faster stabilization.This study offers a reference for the design of slugging control for offshore fields.展开更多
The supercritical-water fluidized bed(SCWFB)is a reactor for coal and biomass gasification without pollutant emission.We carried out a series of experiments in a SCWFB,and a dual-capacitance probe measurement system w...The supercritical-water fluidized bed(SCWFB)is a reactor for coal and biomass gasification without pollutant emission.We carried out a series of experiments in a SCWFB,and a dual-capacitance probe measurement system was applied to measure the hydrodynamics of slugs,such as the slug frequency,chord length,and rising velocity.Four groups of Geldart-B particles with different mean diameters were fluidized by supercritical water with a system pressure of 20-27MPa and at 410-570℃.The minimum slugging Reynolds number increases logarithmically with Archimedes number and a predicting correlation of the minimum slugging fluidization velocity in the SCWFB is presented:Rems=32908.84 ln(Ar^0.55+260376.65)-410361.90.The relative error of the above correlation was within ±15% and the averaged relative error was 7.5%.The effect of operating conditions on the minimum slugging fluidization velocity is discussed.This research provides useful guidance for scaling-up design and for determining the optimum range of operating conditions in the SCWFB.展开更多
Slugging represents one of the major regimes in fluidization,which occurs in small diameter beds with large bed height-to-diameter ratio or in large diameter beds with internals that resemble multiple small diameter f...Slugging represents one of the major regimes in fluidization,which occurs in small diameter beds with large bed height-to-diameter ratio or in large diameter beds with internals that resemble multiple small diameter fluidized beds.Slug types include round-nosed slug,wall slug and square nosed slug.Studies of the slugs have been mainly focused on round-nosed or wall slugs known as half slug.typically occurring in Geldart group A particle fuidization.The square-nosed slug typically occurring for Geldart group D particles appears to be regarded as simple in its structure.The Electrical Capacitance Volume Tomogra phy(ECVT)imaging of the square-nosed slugging phenomena conducted in this study reveals otherwise.That is the structure of the square nosed slug is,in fact,complex,particularly with respect to its dynamic variation in fluidization.More broadly.this study examines experimentally the hydrodynamic character-istics of the square-nosed fluidization regime.Specifically,simultaneous measurements from multiple ECVT sensors provide non-inv asive,continuous,3.dimensional imaging of the entire flow region of the slugging bed and hence enabling the dynamic characterization of the evolution of the slugs.The analysis of the 3D images reconstructed for real time gas-solid volume fraction profile of the slugging fluidized bed indicates that there are three different zones.namely.the bottom fluidization zone,the gas slug zone,and the solid slug zone,co-existing in the bed.The three zones present different hydrodynamic characteristics during the slug evolution.It is found that varying the gas velocity of the slugging bed mainly varies the maximum length of the gas slug zone,while it only has a minor effect on the lengths of the bottom fluidization zone and solid slug zone.It also has an insignificant efect on the solid volume fraction of the three zones.展开更多
This study examines the slug-induced vibration(SIV)response and fatigue behavior of offshore risers subjected to internal slug flow.A structural model incorporating internal slug flow dynamics is developed using the A...This study examines the slug-induced vibration(SIV)response and fatigue behavior of offshore risers subjected to internal slug flow.A structural model incorporating internal slug flow dynamics is developed using the Absolute Nodal Coordinate Formulation(ANCF)and a spatial-temporal density variation equation to analyze how slug flow parameters affect the SIV response of risers.Structural displacement,stress,and fatigue responses are systematically evaluated to characterize the structural behavior under SIV conditions.Longer slugs induce more pronounced traveling wave characteristics,while shorter slugs facilitate a mixed traveling-standing wave mode.Moreover,higher slug frequencies lead to increased fatigue accumulation,especially over an extended touchdown zone,thereby compromising the structural integrity of the riser.The findings yield valuable insights into the dynamic interactions between slug flow and riser response.This research advances the understanding of SIV mechanisms and provides a theoretical foundation for fatigue assessment and structural optimization,contributing to the safe and efficient design of offshore risers in deepwater environments.展开更多
An experimental analysis of the slug-induced vibration(SIV)of a flexible catenary riser with an aspect ratio of 130 is reported in this work.The vibration responses and internal slug flow details at different gas-liqu...An experimental analysis of the slug-induced vibration(SIV)of a flexible catenary riser with an aspect ratio of 130 is reported in this work.The vibration responses and internal slug flow details at different gas-liquid ratios(Q_(g)/Q_(l))and mixture velocities(vm)are non-intrusively and simultaneously captured by high-speed cameras.Both the in-plane and out-of-plane responses of the catenary riser are excited in all considered cases.The slug flow characteristics,including translational velocities,slug lengths,recurrence frequencies,and pressure variations,are analyzed and dis-cussed,as are the dynamic responses of the riser in terms of the amplitudes,space-varying frequency,and modal weight.The dominant modal response based on the root-mean-square amplitude profiles does not match that based on the dominant frequency.Three mode switching types are identified based on the RMS amplitude profiles and the dominant frequency.When vm is small,no mode switching(NMS)is observed in either the in-plane or out-of-plane responses.For mode switching I(MS I),the switching between the first and second modes in the in-plane response is induced by slug flow with different recurrence frequencies in cases of large Q_(g)/Q_(l).However,there is no mode switching in the out-of-plane response.The switching between the first and third modes for the in-plane response and the second and fourth modes for the out-of-plane response(MS II)occurs in cases of relatively high vm and low Q_(g)/Q_(l).展开更多
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
1 A rare and vibrant sea slug,a vision of beauty with its rainbow colors,has been discovered in the waters of Devon,a first⁃time occurrence that has sparked both awe and concern.Felix Lever and her father Ashley were ...1 A rare and vibrant sea slug,a vision of beauty with its rainbow colors,has been discovered in the waters of Devon,a first⁃time occurrence that has sparked both awe and concern.Felix Lever and her father Ashley were exploring the rock pools near Wembury,South Devon,when they came across this remarkable find.展开更多
In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,whi...In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.展开更多
Hydrate phase transition may pose risks in pipeline blockage and severe challenges for offshore natural gas hydrate pro-duction.The present work involves the development of a multiphase gas-liquid-solid vertical slug ...Hydrate phase transition may pose risks in pipeline blockage and severe challenges for offshore natural gas hydrate pro-duction.The present work involves the development of a multiphase gas-liquid-solid vertical slug flow hydrodynamic model consi-dering hydrate phase transition kinetics with heat and mass transfer behaviors.The varying gas physical properties due to pressure and temperature variations are also introduced to evaluate vertical slug flow characteristics.The proposed model is used to carry out a series of numerical simulations to examine the interactions between hydrate phase transition and vertical slug flow hydrodynamics.Furthermore,the hydrate volumetric fractions under different pressure and temperature conditions are predicted.The results reveal that hydrate formation and gas expansion cause the mixture superficial velocity,and the gas and liquid fractions,void fraction in liq-uid slug,and unit length tend to decrease.The increase in outlet pressure leads to an increased hydrate formation rate,which not only increases the hydrate volumetric fraction along the pipe but also causes the upward shift of the hydrate phase transition critical point.展开更多
基金Supported by the National High Technology Research and Development Program of China(2006AA09Z302)
文摘During the exploitation of offshore oil and gas,it is easy to form severe slugging which can cause great harm in the riser connecting wellheads and offshore platform preprocessing system.The flow pattern and pressure fluctuation of severe slugging were studied in an experimental simulation system with inner diameter of 0.051 m.It is found that severe slugging can be divided into three severe slugging regimes：regime I at low gas and liquid flow rates with large pressure fluctuation,intermittent flow of liquid and gas in the riser,and apparent cutoff of liquid phase,regime II at high gas flow rate with non-periodic fluctuation and discontinuous liquid outflow and no gas cutoff,regime III at high liquid flow rate with degenerative pressure fluctuation in form of relatively stable bubbly or plug flow.The results indicate that severe slugging still occurs when the declination angle of pipeline is 0,and there are mainly two kinds of regimes：regime I and regime II.As the angle increases,the formation ranges of regime I and regime III increase slightly while that of regime II is not affected.With the increase of gas superficial velocity and liquid superficial velocity,the pressure fluctuation at the bottom of riser increases initially and then decreases.The maximum value of pressure fluctuation occurs at the transition boundary of regimes I and II.
文摘Due to the special structure of offshore multiphase pipes, it is easy for severe slugging to occur in the riser at low gas-liquid velocity. Violent pressure fluctuations and dramatic changes of flow rate are the main characteristics of severe slugging, leading to the risk of serious damage. In this paper, the separator control is adopted to accurately control the separator liquid level and pressure under severe slugging flow conditions. This indicates that the separator liquid level control alone does not have a significant impact on the upstream flow, but it is beneficial for normal operation and pressure control of the separator. As the separator pressure increases, the peak pressure in the riser apparently diminishes, and the amplitude of pressure fluctuation gradually decreases, which means that severe slugging is inhibited. During the slug blowing out, the gas/liquid slipping in the riser intensifies. The long gas plug quickly flows through the riser, and then tends to morph into short and slowly flowing gas bubbles. The elimination effect of the pressure control strategy on severe slugging is related to the relative rate of the superficial gas/liquid flow.
基金financially supported by the National Natural Science Foundation of China(Grant No.11272211)the National Program on Key Basic Research Project of China(973 Program,Grant No.2015CB251203)
文摘Severe slugging can occur in a pipeline-riser system at relatively low liquid and gas flow rates during gas-oil transportation, possibly causing unexpected damage to the production facilities. Experiments with air and water are conducted in a horizontal and downward inclined pipeline followed by a catenary riser in order to investigate the mechanism and characteristics of severe slugging. A theoretical model is introduced to compare with the experiments. The results show that the formation mechanism of severe slugging in a catenary riser is different from that in a vertical riser due to the riser geometry and five flow patterns are obtained and analyzed. A gas-liquid mixture slug stage is observed at the beginning of one cycle of severe slugging, which is seldom noticed in previous studies. Based on both experiments and computations, the time period and variation of pressure amplitude of severe slugging are found closely related to the superficial gas velocity, implying that the gas velocity significantly influences the flow patterns in our experiments. Moreover, good agreements between the experimental data and the numerical results are shown in the stability curve and flow regime map, which can be a possible reference for design in an offshore oil-production system.
基金financially supported by the National Natural Science Foundation of China(Grant No.51979257)the Key Research and Development Program of Shandong Province(Grant No.2018GHY115045)
文摘A mathematical model is presented to study the main characteristics of severe slugging in a downward inclined pipeline followed by a catenary riser. In this model, both simplified transient model and phase distribution model are included so that the flow characteristics of each stage for severe slugging can be accurately reproduced, especially for blowout stage. The results show that the flow features of severe slugging can be simulated by the proposed mathematical model. A good agreement between the experimental data and the numerical results is observed. The model can predict the transient fluctuation of many respects, such as the superficial gas velocity at the bottom of the riser and the average velocity at the outlet of the riser.
基金the financial support received from the China National Key Research and Development Project(Grant No.2022YFC2806202)the Fundamental Research Funds for the Central Universities(Grant No.xtr042024002).
文摘When using topside choking to eliminate severe slugging in offshore pipeline-riser systems,the resulting stability and effectiveness depend critically on the choice of variables in the associated control model.In this study,both potential process variables and manipulated variables are investigated via manual choking experiments.Monotonicity and linearity are adopted as principles for selecting the optimal variables,and the availability of signals in an offshore field is also considered.Both amplitude-domain and time-domain variables are studied,of which five are recommended as the process variable,while the resistance factor of the choking valve is the optimal manipulated variable;other variables may act as auxiliary variables in the control model.How to determine the set value of the process variable is also discussed.Validation experiments with automatic control show that the optimized variables enable faster stabilization.This study offers a reference for the design of slugging control for offshore fields.
基金supported financially by the China National Funds for Distinguished Young Scientists(No.51925602)National Natural Science Foundation of China(No.91634109 and No.51676158)the National Key Research and Development Program of China(2016YFB0600102).
文摘The supercritical-water fluidized bed(SCWFB)is a reactor for coal and biomass gasification without pollutant emission.We carried out a series of experiments in a SCWFB,and a dual-capacitance probe measurement system was applied to measure the hydrodynamics of slugs,such as the slug frequency,chord length,and rising velocity.Four groups of Geldart-B particles with different mean diameters were fluidized by supercritical water with a system pressure of 20-27MPa and at 410-570℃.The minimum slugging Reynolds number increases logarithmically with Archimedes number and a predicting correlation of the minimum slugging fluidization velocity in the SCWFB is presented:Rems=32908.84 ln(Ar^0.55+260376.65)-410361.90.The relative error of the above correlation was within ±15% and the averaged relative error was 7.5%.The effect of operating conditions on the minimum slugging fluidization velocity is discussed.This research provides useful guidance for scaling-up design and for determining the optimum range of operating conditions in the SCWFB.
文摘Slugging represents one of the major regimes in fluidization,which occurs in small diameter beds with large bed height-to-diameter ratio or in large diameter beds with internals that resemble multiple small diameter fluidized beds.Slug types include round-nosed slug,wall slug and square nosed slug.Studies of the slugs have been mainly focused on round-nosed or wall slugs known as half slug.typically occurring in Geldart group A particle fuidization.The square-nosed slug typically occurring for Geldart group D particles appears to be regarded as simple in its structure.The Electrical Capacitance Volume Tomogra phy(ECVT)imaging of the square-nosed slugging phenomena conducted in this study reveals otherwise.That is the structure of the square nosed slug is,in fact,complex,particularly with respect to its dynamic variation in fluidization.More broadly.this study examines experimentally the hydrodynamic character-istics of the square-nosed fluidization regime.Specifically,simultaneous measurements from multiple ECVT sensors provide non-inv asive,continuous,3.dimensional imaging of the entire flow region of the slugging bed and hence enabling the dynamic characterization of the evolution of the slugs.The analysis of the 3D images reconstructed for real time gas-solid volume fraction profile of the slugging fluidized bed indicates that there are three different zones.namely.the bottom fluidization zone,the gas slug zone,and the solid slug zone,co-existing in the bed.The three zones present different hydrodynamic characteristics during the slug evolution.It is found that varying the gas velocity of the slugging bed mainly varies the maximum length of the gas slug zone,while it only has a minor effect on the lengths of the bottom fluidization zone and solid slug zone.It also has an insignificant efect on the solid volume fraction of the three zones.
基金financially supported by the National Natural Science Foundation of China(Grant No.52222111)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462025SZBH002)。
文摘This study examines the slug-induced vibration(SIV)response and fatigue behavior of offshore risers subjected to internal slug flow.A structural model incorporating internal slug flow dynamics is developed using the Absolute Nodal Coordinate Formulation(ANCF)and a spatial-temporal density variation equation to analyze how slug flow parameters affect the SIV response of risers.Structural displacement,stress,and fatigue responses are systematically evaluated to characterize the structural behavior under SIV conditions.Longer slugs induce more pronounced traveling wave characteristics,while shorter slugs facilitate a mixed traveling-standing wave mode.Moreover,higher slug frequencies lead to increased fatigue accumulation,especially over an extended touchdown zone,thereby compromising the structural integrity of the riser.The findings yield valuable insights into the dynamic interactions between slug flow and riser response.This research advances the understanding of SIV mechanisms and provides a theoretical foundation for fatigue assessment and structural optimization,contributing to the safe and efficient design of offshore risers in deepwater environments.
基金financially supported by the National Natural Science Foundation of China(Grant No.52301338)the Sichuan Science and Technology Program(Grant No.2024NSFSC0968).
文摘An experimental analysis of the slug-induced vibration(SIV)of a flexible catenary riser with an aspect ratio of 130 is reported in this work.The vibration responses and internal slug flow details at different gas-liquid ratios(Q_(g)/Q_(l))and mixture velocities(vm)are non-intrusively and simultaneously captured by high-speed cameras.Both the in-plane and out-of-plane responses of the catenary riser are excited in all considered cases.The slug flow characteristics,including translational velocities,slug lengths,recurrence frequencies,and pressure variations,are analyzed and dis-cussed,as are the dynamic responses of the riser in terms of the amplitudes,space-varying frequency,and modal weight.The dominant modal response based on the root-mean-square amplitude profiles does not match that based on the dominant frequency.Three mode switching types are identified based on the RMS amplitude profiles and the dominant frequency.When vm is small,no mode switching(NMS)is observed in either the in-plane or out-of-plane responses.For mode switching I(MS I),the switching between the first and second modes in the in-plane response is induced by slug flow with different recurrence frequencies in cases of large Q_(g)/Q_(l).However,there is no mode switching in the out-of-plane response.The switching between the first and third modes for the in-plane response and the second and fourth modes for the out-of-plane response(MS II)occurs in cases of relatively high vm and low Q_(g)/Q_(l).
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1 A rare and vibrant sea slug,a vision of beauty with its rainbow colors,has been discovered in the waters of Devon,a first⁃time occurrence that has sparked both awe and concern.Felix Lever and her father Ashley were exploring the rock pools near Wembury,South Devon,when they came across this remarkable find.
基金supported by the National Natural Science Foundation of China(Grant No.12202441).
文摘In this study,we numerically investigate the rise of a Taylor bubble in a vertically oscillating round tube.The results show that increasing the oscillation frequency and amplitude reduces the bubble rise velocity,which is consistent with previously reported experimental findings.Analysis of the flow in the annular film region indicates that the influence of tube wall oscillations is minimal.This suggests that the effect of tube oscillations is essentially equivalent to that of an oscillating piston above the bubble,leading to a similar mechanism for bubble deceleration.Using a theoretical formula from the literature,we demonstrate that at sufficiently high frequencies,the amplitude of the tube velocity oscillations becomes the sole control parameter affecting bubble deceleration.This study enhances our understanding of Taylor bubble behavior in mechanically oscillating environments and provides useful insights into the design of control strategies for Taylor bubble motion in vertical slug flows.
基金supported by the National Natural Science Foundation of China(No.52301355)the Natu-ral Science Foundation of Qingdao Municipality(No.23-2-1-108-zyyd-jch)the China University of Petroleum(East China)Independent Innovation Research Project(Science and Engineering)-Leading Talent Cultivation Fund(No.24CX07001A).
文摘Hydrate phase transition may pose risks in pipeline blockage and severe challenges for offshore natural gas hydrate pro-duction.The present work involves the development of a multiphase gas-liquid-solid vertical slug flow hydrodynamic model consi-dering hydrate phase transition kinetics with heat and mass transfer behaviors.The varying gas physical properties due to pressure and temperature variations are also introduced to evaluate vertical slug flow characteristics.The proposed model is used to carry out a series of numerical simulations to examine the interactions between hydrate phase transition and vertical slug flow hydrodynamics.Furthermore,the hydrate volumetric fractions under different pressure and temperature conditions are predicted.The results reveal that hydrate formation and gas expansion cause the mixture superficial velocity,and the gas and liquid fractions,void fraction in liq-uid slug,and unit length tend to decrease.The increase in outlet pressure leads to an increased hydrate formation rate,which not only increases the hydrate volumetric fraction along the pipe but also causes the upward shift of the hydrate phase transition critical point.
