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Uwe Hampel - One of the best experts on this subject based on the ideXlab platform.
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do huge waves exist in horizontal gas liquid pipe Flow
International Journal of Multiphase Flow, 2017Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, B.j. Azzopardi, A Alsarkhi, Uwe HampelAbstract:Abstract Huge waves are periodic interfacial structures which are observed in vertical co-current gas-liquid two-phase Flow under Churn and the transition between Churn and annular Flows. Published data examining vertical gas-liquid Flow indicate that a huge wave has either a continuous gas core surrounded by a large-scale interfacial wave or a core with a highly-agitated mixture of gas and liquid. Employing a Wire-Mesh Sensor (WMS), the spatio/temporal investigation of high Flow rate horizontal air-water Flow divulged some recurrent liquid structures (one may call pseudo-slugs) analogous to huge waves of (vertical) Churn Flow. In both cases, the blow-through (penetration of gas into the liquid structure) was the most manifest feature. Different qualitative and quantitative methods were employed to compare the behavior of pseudo-slug to Churn Flow. The quantitative measures included Probability Density Function analysis (PDF), distribution coefficient in drift flux model, structural velocity, core average velocity, interfacial friction factor, and slippage number. Both Flow regimes demonstrated similar behavior.
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Assessment of a hybrid CFD model for simulation of complex vertical upward gas–liquid Churn Flow
Chemical Engineering Research and Design, 2016Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Madhusuden Agrawal, Vedanth Srinivasan, Uwe HampelAbstract:Abstract Gas–liquid multiphase Flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of Flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase Flow models are able to deliver a realistic solution for a complex Flow pattern like Churn Flow? And if yes, to what extent are the results accurate? To shed light on these issues, the Eulerian–Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015. 15.0 User's Guide, ANSYS Inc.) was used to simulate high Flow rate air–water multiphase Flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the Flow and delivering void fraction data which were in agreement with those of experiments.
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assessment of a hybrid cfd model for simulation of complex vertical upward gas liquid Churn Flow
Chemical Engineering Research & Design, 2016Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Madhusuden Agrawal, Vedanth Srinivasan, Uwe HampelAbstract:Abstract Gas–liquid multiphase Flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of Flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase Flow models are able to deliver a realistic solution for a complex Flow pattern like Churn Flow? And if yes, to what extent are the results accurate? To shed light on these issues, the Eulerian–Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015. 15.0 User's Guide, ANSYS Inc.) was used to simulate high Flow rate air–water multiphase Flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the Flow and delivering void fraction data which were in agreement with those of experiments.
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On the effect of liquid viscosity on interfacial structures within Churn Flow: Experimental study using wire mesh sensor
Chemical Engineering Science, 2015Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Uwe HampelAbstract:Abstract In the Churn Flow regime, periodical interfacial structures such as liquid slugs and huge waves can coexist and undoubtedly, a phase property such as liquid viscosity can dominate the behavior of these structures. Regrettably, neither are the characteristics of Churn Flow widely understood nor have the effects of liquid viscosity on gas–liquid Flow received enough attention. A Wire Mesh Sensor (WMS) with a 16×16 spatial resolution was employed to discover the effects of liquid viscosity on the behavior of Churn Flow in a vertical 76.2 mm pipe. Three liquid viscosities of 1, 10, and 40 cP, and superficial liquid velocities of 0.46, 0.61, and 0.76 m/s were employed; whereas, superficial gas velocity ranged from 10 to 27 m/s. Different techniques such as Probability Density Function (PDF), and 2-D and 3-D image reconstruction methods were applied to study the Flow. It was noticed that increasing liquid viscosity not only affected the Flow pattern but also the appearance frequencies of interfacial structures.
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Experimental investigation of interfacial structures within Churn Flow using a dual wire-mesh sensor
International Journal of Multiphase Flow, 2015Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Uwe HampelAbstract:Abstract A challenging area in the field of multiphase Flow is the study of Churn Flow. According to the multiphase Flow community, Churn Flow has not been widely investigated in intermediate and large diameter pipes at high gas and liquid Flow rates. The present work deals with an experimental study of upward vertical air–water Flow in a 76.2 mm I.D. pipe. Superficial gas velocities ranging from 10 to 38 m/s and four superficial liquid velocities (0.30, 0.46, 0.61 and 0.76 m/s) were employed. The experimental data points are mostly located in Churn Flow and at the transition between Churn and annular Flow. A dual 16 × 16 Wire Mesh Sensor (WMS) was used to obtain the temporal/spatial variations of phase distributions over the pipe cross-section at one specific axial location (L/D = 236). Sequences of phase distributions, axially sliced images, virtual 3-D images as well as void fraction time-series were used to distinguish between different interfacial structures such as slugs and huge waves. Results showed that huge waves occur with either a continuous gas core with a distinct boundary between two phases or a core with a gas–liquid mixture. Furthermore, velocities and frequencies of interfacial structures were obtained. Results are qualitatively and quantitatively consistent with the previous findings available in literature.
Mazdak Parsi - One of the best experts on this subject based on the ideXlab platform.
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Vertical upward and downward Churn Flow: Similarities and differences
Journal of Natural Gas Science and Engineering, 2020Co-Authors: Hiba Bouyahiaoui, Abdelwahid Azzi, Ammar Zeghloul, Abbas Hasan, Abdelsalam Al-sarkhi, Mazdak ParsiAbstract:Abstract Investigation of downward two-phase Flows received less attention compared to the vertical upward Flows. Downward Flows are found in many industries and facilities including; oil/gas production, nuclear industry and petroleum refinery/production facilities such as evaporators, chemical reactors and distillation towers. A thorough understanding of the Flow dynamic characteristics occur in such transportation lines, process plants and units is very crucial in terms of design, operation, production and safety. In the current work, air-water two-phase Churn Flow in a 34 mm I.D. pipe was investigated for two configurations of vertical upward (51 cases) and downward (48 cases). Several conductance probes and pressure transducers were used to measure cross-sectional averaged void fraction time series, and pressure drop along the pipe, respectively. The main objectives of the work were to investigate the similarities and dissimilarities between vertically upward and downward Churn Flow and specifically understand how gravity could affect the behavior of liquid structures present within the Flow. To quantify this, different parameters such as Probability Density Function, distribution coefficient in the drift-flux model, structural velocity, slippage number, dimensionless pressure gradient etc. were used. It was noticed that in both configurations, dimensionless pressure gradient and slippage number demonstrated a strong correlation with the mixture Froude number. There were, however, discrepancies in Probability Density Functions (PDFs) and structural velocities of Flow in the two orientations.
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do huge waves exist in horizontal gas liquid pipe Flow
International Journal of Multiphase Flow, 2017Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, B.j. Azzopardi, A Alsarkhi, Uwe HampelAbstract:Abstract Huge waves are periodic interfacial structures which are observed in vertical co-current gas-liquid two-phase Flow under Churn and the transition between Churn and annular Flows. Published data examining vertical gas-liquid Flow indicate that a huge wave has either a continuous gas core surrounded by a large-scale interfacial wave or a core with a highly-agitated mixture of gas and liquid. Employing a Wire-Mesh Sensor (WMS), the spatio/temporal investigation of high Flow rate horizontal air-water Flow divulged some recurrent liquid structures (one may call pseudo-slugs) analogous to huge waves of (vertical) Churn Flow. In both cases, the blow-through (penetration of gas into the liquid structure) was the most manifest feature. Different qualitative and quantitative methods were employed to compare the behavior of pseudo-slug to Churn Flow. The quantitative measures included Probability Density Function analysis (PDF), distribution coefficient in drift flux model, structural velocity, core average velocity, interfacial friction factor, and slippage number. Both Flow regimes demonstrated similar behavior.
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Assessment of a hybrid CFD model for simulation of complex vertical upward gas–liquid Churn Flow
Chemical Engineering Research and Design, 2016Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Madhusuden Agrawal, Vedanth Srinivasan, Uwe HampelAbstract:Abstract Gas–liquid multiphase Flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of Flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase Flow models are able to deliver a realistic solution for a complex Flow pattern like Churn Flow? And if yes, to what extent are the results accurate? To shed light on these issues, the Eulerian–Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015. 15.0 User's Guide, ANSYS Inc.) was used to simulate high Flow rate air–water multiphase Flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the Flow and delivering void fraction data which were in agreement with those of experiments.
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assessment of a hybrid cfd model for simulation of complex vertical upward gas liquid Churn Flow
Chemical Engineering Research & Design, 2016Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Madhusuden Agrawal, Vedanth Srinivasan, Uwe HampelAbstract:Abstract Gas–liquid multiphase Flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of Flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase Flow models are able to deliver a realistic solution for a complex Flow pattern like Churn Flow? And if yes, to what extent are the results accurate? To shed light on these issues, the Eulerian–Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015. 15.0 User's Guide, ANSYS Inc.) was used to simulate high Flow rate air–water multiphase Flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the Flow and delivering void fraction data which were in agreement with those of experiments.
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Ultrasonic measurements of sand particle erosion in gas dominant multiphase Churn Flow in vertical pipes
Wear, 2015Co-Authors: Mazdak Parsi, Ronald E. Vieira, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. ShiraziAbstract:Abstract Solid particle erosion can result in major pipeline failures, economic losses and more importantly safety and environmental issues. Erosion in multiphase Flow is not widely understood and previous work has mostly focused on cases where the carrier fluid is single phase. There are different multiphase Flow regimes, and amid them, Churn Flow appears frequently in piping systems such as risers, jumpers and Flow spools. Furthermore, elbows have broad applications in the oil and gas industry, and they are subject to sand particle erosion damage. Therefore, the study of erosion in elbows, while the superficial velocities of the carrier fluids are in the range so that the Flow pattern is Churn Flow, is of utmost importance. Experimental tests were carried out in order to investigate sand particle erosion in a 76.2 mm ID standard vertical–horizontal (V–H) elbow. A novel non-intrusive ultrasonic device was implemented to attain erosion patterns under different Flow conditions. The effects of superficial gas and liquid velocities, particle size and liquid viscosity on erosion rate were investigated. The results are compared to the available data of erosion rates in a horizontal–horizontal (H–H) elbow with the same size of the elbow employed here. The most striking outcome to emerge from the comparisons is that erosion rates in the V–H elbow are significantly higher than those in the H–H elbow.
Ruud Henkes - One of the best experts on this subject based on the ideXlab platform.
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Modelling of upwards gas-liquid annular and Churn Flow with surfactants in vertical pipes
International Journal of Multiphase Flow, 2018Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:Abstract Based on our earlier experimental work on the effect of surfactants on air-water Flow in vertical pipes with internal diameters of 34 mm, 50 mm, and 80 mm, we create a mechanistic annular Flow model for the pressure gradient. The mayor effect of the addition of surfactants is the formation of foam. We model the formation of foam and its impact on the Flow. In the model we consider a gas core and a film at the wall, which consists of a layer of liquid at the wall and a layer of foam between the liquid layer and the gas core. We do not consider entrainment in the model. We developed four closure relations in order to solve the model: (i) for the density of the foam, (ii) for the viscosity of the foam, (iii) for the interfacial friction between the gas and the film, and (iv) for the thickness of the liquid layer at the wall. Subsequently, we solve for the film thickness that yields the imposed liquid Flow rate. Comparing the experimental results for the pressure gradient to the results from the model, we observe that in most cases the model can predict the pressure gradient within 25%. Furthermore, the model is able to predict the onset of downwards Flow in the film. Therefore, it can predict the transition between annular Flow and Churn Flow. We show that the effect of five different surfactants on the Flow is equal, apart from a scaling factor of the concentration, which means that the model can be applied for many different types of surfactants. The scaling factor is an input parameter to the model, which needs to be determined in a small scale experiment.
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The effect of the diameter on air-water annular and Churn Flow in vertical pipes with and without surfactants
International Journal of Multiphase Flow, 2017Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:Abstract In this work, we present results of Flow visualisation, pressure gradient measurements, and liquid holdup measurements for air-water Flow without and with surfactants in vertical pipes with diameters of 34 mm, 50 mm, and 80 mm. The surfactants cause the formation of foam. This foam has a larger volume and a smaller density than the liquid. The larger volume results in a larger pressure gradient at large gas Flow rates. At small gas Flow rates, the lower density of the foam causes the transition between the regular annular Flow regime and the irregular Churn Flow regime to shift to lower gas Flow rates. As a result foam reduces the pressure gradient and the liquid holdup at small gas Flow rates. Surfactants reduce the pressure gradient more effectively for thinner liquid films at the wall; therefore, they are more effective for small pipe diameters and small liquid Flow rates.
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The effect of surfactants on air-water annular and Churn Flow in vertical pipes. Part 1: Morphology of the air-water interface
International Journal of Multiphase Flow, 2015Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:In this work, the influence of surfactants on air–water Flow was studied by performing experiments in a 12 metre long, 50 mm inner diameter, vertical pipe at ambient conditions. High-speed visualisation of the Flow shows that the morphology of the air–water interface determines the formation of foam. The foam subsequently alters the Flow morphology significantly. In annular Flow, the foam suppresses the roll waves, and a foamy crest is formed on the ripple waves. In the Churn Flow regime, the flooding waves and the downwards motion of the liquid film are suppressed by the foam. The foam is transported in foam waves moving upwards superposed on an almost stagnant foam substrate at the pipe wall. Foam thus effectively reduces the superficial gas velocity at which the transition from annular to Churn Flow occurs. These experiments make more clear how surfactants can postpone liquid loading in vertical pipes, such as in gas wells.
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The effect of surfactants on air–water annular and Churn Flow in vertical pipes. Part 2: Liquid holdup and pressure gradient dynamics
International Journal of Multiphase Flow, 2015Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:Abstract In this paper, we study the effect of surfactants on both the liquid holdup and the dynamics of the pressure gradient in annular and Churn Flow in vertical pipes. This effect is linked to the influence of the surfactants on the morphology of the air–water interface, which is studied in a related paper (van Nimwegen et al., 2014). The experimental results, obtained using a vertical Flow loop with a 5 cm internal diameter at ambient pressure, show three different effects of the surfactants on the measured quantities, depending on the air and water Flow rates. (i) At large air Flow rates, in the annular Flow regime for air–water Flow, the surfactants increase the pressure gradient; this is solely due to the increase of the frictional pressure gradient, caused by the larger interfacial stress between the foamy waves overlaying the foam substrate along the wall and the gas core. (ii) At low air Flow rates and low water Flow rates, in the Churn Flow regime for air–water Flow, the surfactants decrease significantly both the average pressure gradient and the pressure gradient fluctuations. While the frictional pressure gradient increases, the liquid holdup decreases by more than a factor of two; the foam suppresses the flooding waves, making the Flow much more regular, leading to the small pressure gradient fluctuations. Furthermore, there exists an optimum surfactant concentration for decreasing the average pressure gradient and the pressure gradient fluctuations. (iii) At low air and high water Flow rates, in the Churn Flow regime for air–water Flow, the average pressure gradient and the pressure gradient fluctuations are both somewhat decreased by the surfactants.
A.t. Van Nimwegen - One of the best experts on this subject based on the ideXlab platform.
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Modelling of upwards gas-liquid annular and Churn Flow with surfactants in vertical pipes
International Journal of Multiphase Flow, 2018Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:Abstract Based on our earlier experimental work on the effect of surfactants on air-water Flow in vertical pipes with internal diameters of 34 mm, 50 mm, and 80 mm, we create a mechanistic annular Flow model for the pressure gradient. The mayor effect of the addition of surfactants is the formation of foam. We model the formation of foam and its impact on the Flow. In the model we consider a gas core and a film at the wall, which consists of a layer of liquid at the wall and a layer of foam between the liquid layer and the gas core. We do not consider entrainment in the model. We developed four closure relations in order to solve the model: (i) for the density of the foam, (ii) for the viscosity of the foam, (iii) for the interfacial friction between the gas and the film, and (iv) for the thickness of the liquid layer at the wall. Subsequently, we solve for the film thickness that yields the imposed liquid Flow rate. Comparing the experimental results for the pressure gradient to the results from the model, we observe that in most cases the model can predict the pressure gradient within 25%. Furthermore, the model is able to predict the onset of downwards Flow in the film. Therefore, it can predict the transition between annular Flow and Churn Flow. We show that the effect of five different surfactants on the Flow is equal, apart from a scaling factor of the concentration, which means that the model can be applied for many different types of surfactants. The scaling factor is an input parameter to the model, which needs to be determined in a small scale experiment.
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The effect of the diameter on air-water annular and Churn Flow in vertical pipes with and without surfactants
International Journal of Multiphase Flow, 2017Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:Abstract In this work, we present results of Flow visualisation, pressure gradient measurements, and liquid holdup measurements for air-water Flow without and with surfactants in vertical pipes with diameters of 34 mm, 50 mm, and 80 mm. The surfactants cause the formation of foam. This foam has a larger volume and a smaller density than the liquid. The larger volume results in a larger pressure gradient at large gas Flow rates. At small gas Flow rates, the lower density of the foam causes the transition between the regular annular Flow regime and the irregular Churn Flow regime to shift to lower gas Flow rates. As a result foam reduces the pressure gradient and the liquid holdup at small gas Flow rates. Surfactants reduce the pressure gradient more effectively for thinner liquid films at the wall; therefore, they are more effective for small pipe diameters and small liquid Flow rates.
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the effect of surfactants on air water annular and Churn Flow in vertical pipes part 2 liquid holdup and pressure gradient dynamics
International Journal of Multiphase Flow, 2015Co-Authors: A.t. Van Nimwegen, L.m. Portela, R A W M HenkesAbstract:Abstract In this paper, we study the effect of surfactants on both the liquid holdup and the dynamics of the pressure gradient in annular and Churn Flow in vertical pipes. This effect is linked to the influence of the surfactants on the morphology of the air–water interface, which is studied in a related paper (van Nimwegen et al., 2014). The experimental results, obtained using a vertical Flow loop with a 5 cm internal diameter at ambient pressure, show three different effects of the surfactants on the measured quantities, depending on the air and water Flow rates. (i) At large air Flow rates, in the annular Flow regime for air–water Flow, the surfactants increase the pressure gradient; this is solely due to the increase of the frictional pressure gradient, caused by the larger interfacial stress between the foamy waves overlaying the foam substrate along the wall and the gas core. (ii) At low air Flow rates and low water Flow rates, in the Churn Flow regime for air–water Flow, the surfactants decrease significantly both the average pressure gradient and the pressure gradient fluctuations. While the frictional pressure gradient increases, the liquid holdup decreases by more than a factor of two; the foam suppresses the flooding waves, making the Flow much more regular, leading to the small pressure gradient fluctuations. Furthermore, there exists an optimum surfactant concentration for decreasing the average pressure gradient and the pressure gradient fluctuations. (iii) At low air and high water Flow rates, in the Churn Flow regime for air–water Flow, the average pressure gradient and the pressure gradient fluctuations are both somewhat decreased by the surfactants.
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The effect of surfactants on air-water annular and Churn Flow in vertical pipes. Part 1: Morphology of the air-water interface
International Journal of Multiphase Flow, 2015Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:In this work, the influence of surfactants on air–water Flow was studied by performing experiments in a 12 metre long, 50 mm inner diameter, vertical pipe at ambient conditions. High-speed visualisation of the Flow shows that the morphology of the air–water interface determines the formation of foam. The foam subsequently alters the Flow morphology significantly. In annular Flow, the foam suppresses the roll waves, and a foamy crest is formed on the ripple waves. In the Churn Flow regime, the flooding waves and the downwards motion of the liquid film are suppressed by the foam. The foam is transported in foam waves moving upwards superposed on an almost stagnant foam substrate at the pipe wall. Foam thus effectively reduces the superficial gas velocity at which the transition from annular to Churn Flow occurs. These experiments make more clear how surfactants can postpone liquid loading in vertical pipes, such as in gas wells.
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The effect of surfactants on air–water annular and Churn Flow in vertical pipes. Part 2: Liquid holdup and pressure gradient dynamics
International Journal of Multiphase Flow, 2015Co-Authors: A.t. Van Nimwegen, L.m. Portela, Ruud HenkesAbstract:Abstract In this paper, we study the effect of surfactants on both the liquid holdup and the dynamics of the pressure gradient in annular and Churn Flow in vertical pipes. This effect is linked to the influence of the surfactants on the morphology of the air–water interface, which is studied in a related paper (van Nimwegen et al., 2014). The experimental results, obtained using a vertical Flow loop with a 5 cm internal diameter at ambient pressure, show three different effects of the surfactants on the measured quantities, depending on the air and water Flow rates. (i) At large air Flow rates, in the annular Flow regime for air–water Flow, the surfactants increase the pressure gradient; this is solely due to the increase of the frictional pressure gradient, caused by the larger interfacial stress between the foamy waves overlaying the foam substrate along the wall and the gas core. (ii) At low air Flow rates and low water Flow rates, in the Churn Flow regime for air–water Flow, the surfactants decrease significantly both the average pressure gradient and the pressure gradient fluctuations. While the frictional pressure gradient increases, the liquid holdup decreases by more than a factor of two; the foam suppresses the flooding waves, making the Flow much more regular, leading to the small pressure gradient fluctuations. Furthermore, there exists an optimum surfactant concentration for decreasing the average pressure gradient and the pressure gradient fluctuations. (iii) At low air and high water Flow rates, in the Churn Flow regime for air–water Flow, the average pressure gradient and the pressure gradient fluctuations are both somewhat decreased by the surfactants.
Ronald E. Vieira - One of the best experts on this subject based on the ideXlab platform.
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A Mechanistic Model for Predicting Erosion in Churn Flow
Wear, 2021Co-Authors: Ronald E. Vieira, Siamack A. ShiraziAbstract:Abstract Sand particles, which are regularly entrained with the production fluids while transporting from a reservoir to surface facilities, can cause severe erosion and erosion-corrosion damage to production equipment. A crucial parameter for studying erosion in multiphase Flows is the Flow pattern. The particle motion characteristics will change drastically with changes in the Flow pattern in the pipelines. In vertical upward gas-liquid Flow, a widely accepted Flow pattern classification is bubble, slug, Churn and annular Flow. Churn Flow is a chaotic Flow pattern consisting of Taylor bubbles and liquid slugs that are distorted in shape and it is characterized by the presence of periodic large interfacial waves called flooding-type waves. Studying the erosion due to sand particles entrained in Churn Flows is extremely difficult, since the solid particle erosion magnitudes are coupled with several multiphase Flow parameters such as phase distribution and velocities. This work focuses on improvement of a multiphase Churn Flow erosion model for elbows in vertical pipes. In this investigation, a drift-flux model is proposed to better predict the Flow behavior and the characteristic initial particle velocity for Churn gas-liquid Flow. Based on the drift-flux model, the actual gas velocity is calculated as a function of mixture and drift velocities. The coefficients of the drift flux expression under Churn Flow conditions are determined from datasets available in literature. The model predictions are compared with the erosion data bank at the Erosion/Corrosion Research Center and other published papers. The data comprises effects of pipe diameter, particle characteristics, Flow velocities, and liquid viscosity. The results show that the new approach provides much better predictions for the maximum erosion in bends when compared with the original mixture based model and other models available in literature.
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do huge waves exist in horizontal gas liquid pipe Flow
International Journal of Multiphase Flow, 2017Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, B.j. Azzopardi, A Alsarkhi, Uwe HampelAbstract:Abstract Huge waves are periodic interfacial structures which are observed in vertical co-current gas-liquid two-phase Flow under Churn and the transition between Churn and annular Flows. Published data examining vertical gas-liquid Flow indicate that a huge wave has either a continuous gas core surrounded by a large-scale interfacial wave or a core with a highly-agitated mixture of gas and liquid. Employing a Wire-Mesh Sensor (WMS), the spatio/temporal investigation of high Flow rate horizontal air-water Flow divulged some recurrent liquid structures (one may call pseudo-slugs) analogous to huge waves of (vertical) Churn Flow. In both cases, the blow-through (penetration of gas into the liquid structure) was the most manifest feature. Different qualitative and quantitative methods were employed to compare the behavior of pseudo-slug to Churn Flow. The quantitative measures included Probability Density Function analysis (PDF), distribution coefficient in drift flux model, structural velocity, core average velocity, interfacial friction factor, and slippage number. Both Flow regimes demonstrated similar behavior.
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Assessment of a hybrid CFD model for simulation of complex vertical upward gas–liquid Churn Flow
Chemical Engineering Research and Design, 2016Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Madhusuden Agrawal, Vedanth Srinivasan, Uwe HampelAbstract:Abstract Gas–liquid multiphase Flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of Flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase Flow models are able to deliver a realistic solution for a complex Flow pattern like Churn Flow? And if yes, to what extent are the results accurate? To shed light on these issues, the Eulerian–Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015. 15.0 User's Guide, ANSYS Inc.) was used to simulate high Flow rate air–water multiphase Flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the Flow and delivering void fraction data which were in agreement with those of experiments.
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assessment of a hybrid cfd model for simulation of complex vertical upward gas liquid Churn Flow
Chemical Engineering Research & Design, 2016Co-Authors: Mazdak Parsi, Ronald E. Vieira, Carlos F. Torres, Brenton S. Mclaury, Siamack A. Shirazi, Eckhard Schleicher, Madhusuden Agrawal, Vedanth Srinivasan, Uwe HampelAbstract:Abstract Gas–liquid multiphase Flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of Flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase Flow models are able to deliver a realistic solution for a complex Flow pattern like Churn Flow? And if yes, to what extent are the results accurate? To shed light on these issues, the Eulerian–Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015. 15.0 User's Guide, ANSYS Inc.) was used to simulate high Flow rate air–water multiphase Flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the Flow and delivering void fraction data which were in agreement with those of experiments.
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Ultrasonic measurements of sand particle erosion in gas dominant multiphase Churn Flow in vertical pipes
Wear, 2015Co-Authors: Mazdak Parsi, Ronald E. Vieira, Netaji R. Kesana, Brenton S. Mclaury, Siamack A. ShiraziAbstract:Abstract Solid particle erosion can result in major pipeline failures, economic losses and more importantly safety and environmental issues. Erosion in multiphase Flow is not widely understood and previous work has mostly focused on cases where the carrier fluid is single phase. There are different multiphase Flow regimes, and amid them, Churn Flow appears frequently in piping systems such as risers, jumpers and Flow spools. Furthermore, elbows have broad applications in the oil and gas industry, and they are subject to sand particle erosion damage. Therefore, the study of erosion in elbows, while the superficial velocities of the carrier fluids are in the range so that the Flow pattern is Churn Flow, is of utmost importance. Experimental tests were carried out in order to investigate sand particle erosion in a 76.2 mm ID standard vertical–horizontal (V–H) elbow. A novel non-intrusive ultrasonic device was implemented to attain erosion patterns under different Flow conditions. The effects of superficial gas and liquid velocities, particle size and liquid viscosity on erosion rate were investigated. The results are compared to the available data of erosion rates in a horizontal–horizontal (H–H) elbow with the same size of the elbow employed here. The most striking outcome to emerge from the comparisons is that erosion rates in the V–H elbow are significantly higher than those in the H–H elbow.