By using two-parallel conductance probes,the instantaneous film thickness of gas-liquidtwo-phase flow within a horizontal plexiglass pipe of 50mm inner diameter was experimentallymeasured.The pipe was 6680mm long.Seve...By using two-parallel conductance probes,the instantaneous film thickness of gas-liquidtwo-phase flow within a horizontal plexiglass pipe of 50mm inner diameter was experimentallymeasured.The pipe was 6680mm long.Several wave patterns were distinguished through statisticalanalysis of signals of film thicknesses.Wave pattern maps were obtained and compared with resultsof former studies.The characteristics of the interfacial waves,such as time-averaged film thickness,wave height,wave propagation speed,wavelength and wave frequency,were systematically investigated.The effect of the exit structure of the test section on interfacial waves was experimentally examined.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
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
An experimental investigation on the behavior and characteristics of interfacial waves in downward inclined rectangular channel was conducted. The interfacial waves were traced and measured by us-ing conductance techn...An experimental investigation on the behavior and characteristics of interfacial waves in downward inclined rectangular channel was conducted. The interfacial waves were traced and measured by us-ing conductance technique. The wav patterns were distinguished and defined. The characteristics of the interfacial waves, such as time-averaged film thickness, wave height, wave propagation speed,wavlength and wave frequency, were systematically examined in terms of gas and liquid superficial volumetric fiuxes. The effect of the inclination and flow channel geometry of the test section on the interfacial wav was also investigated.展开更多
A double-sensor probe was used to measure local interfacial parameters of a gas-liquid bubbly flow in a horizontal tube. The parameters included void fraction, interfacial concentration, bubble size distribution, bubb...A double-sensor probe was used to measure local interfacial parameters of a gas-liquid bubbly flow in a horizontal tube. The parameters included void fraction, interfacial concentration, bubble size distribution, bubble frequency and bubble interface velocity. The authors paid special attention to the probe design and construction for minimizing measurement errors. Measures were also taken in the design of sensor ends for preventing corrosions in the flow. This is an effort to improve the current double-sensor probe technique to meet the ever-increasing needs to local parameter measurements in gas-liquid two-phase flows.展开更多
In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow...In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow in a 20 mm inner diameter pipe are measured by a novel conductance parallel-wire array probe(CPAP).It is found that,for flow conditions with low water holdup,there is a large deviation between the model-predicted interface shape and the experimentally measured one.Since the variation of pipe wetting characteristics in the process of fluid flow can lead to the changes of the contact angle between the fluid and the pipe wall,the models mentioned above are modified by considering dynamic contact angle.The results indicate that the interface shapes predicted by the modified models present a good consistence with the ones measured by CPAP.展开更多
基金Supported by the National Natural Science Foundation of China.
文摘By using two-parallel conductance probes,the instantaneous film thickness of gas-liquidtwo-phase flow within a horizontal plexiglass pipe of 50mm inner diameter was experimentallymeasured.The pipe was 6680mm long.Several wave patterns were distinguished through statisticalanalysis of signals of film thicknesses.Wave pattern maps were obtained and compared with resultsof former studies.The characteristics of the interfacial waves,such as time-averaged film thickness,wave height,wave propagation speed,wavelength and wave frequency,were systematically investigated.The effect of the exit structure of the test section on interfacial waves was experimentally examined.
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An experimental investigation on the behavior and characteristics of interfacial waves in downward inclined rectangular channel was conducted. The interfacial waves were traced and measured by us-ing conductance technique. The wav patterns were distinguished and defined. The characteristics of the interfacial waves, such as time-averaged film thickness, wave height, wave propagation speed,wavlength and wave frequency, were systematically examined in terms of gas and liquid superficial volumetric fiuxes. The effect of the inclination and flow channel geometry of the test section on the interfacial wav was also investigated.
基金Supported by the National Natural Science Foundation of China(No.59876032)and the Doctorate Foundation of Xi'an Jiaotong University(DFXJU-17).
文摘A double-sensor probe was used to measure local interfacial parameters of a gas-liquid bubbly flow in a horizontal tube. The parameters included void fraction, interfacial concentration, bubble size distribution, bubble frequency and bubble interface velocity. The authors paid special attention to the probe design and construction for minimizing measurement errors. Measures were also taken in the design of sensor ends for preventing corrosions in the flow. This is an effort to improve the current double-sensor probe technique to meet the ever-increasing needs to local parameter measurements in gas-liquid two-phase flows.
基金supported by the National Natural Science Foundation of China(Grant Nos.41974139,41504104,11572220,51527805)Natural Science Foundation of Tianjin,China(19JCYBJC18400)。
文摘In this study,interface shapes of horizontal oil–water two-phase flow are predicted by using Young-Laplace equation model and minimum energy model.Meanwhile,the interface shapes of horizontal oil–water twophase flow in a 20 mm inner diameter pipe are measured by a novel conductance parallel-wire array probe(CPAP).It is found that,for flow conditions with low water holdup,there is a large deviation between the model-predicted interface shape and the experimentally measured one.Since the variation of pipe wetting characteristics in the process of fluid flow can lead to the changes of the contact angle between the fluid and the pipe wall,the models mentioned above are modified by considering dynamic contact angle.The results indicate that the interface shapes predicted by the modified models present a good consistence with the ones measured by CPAP.
