Pub Date : 2024-11-28DOI: 10.1016/j.ijmultiphaseflow.2024.105070
Aadil Kureshee, S. Narayanan, Deepak Kumar Mandal
The present study aims to investigate the effect of an acoustic field on the internal circulation and evaporation of three distinct combinations of twin methanol drops. The drop combinations used for making twin drops are (i) methanol and water (i.e., 15% and 75% of methanol), (ii) pure methanol, (iii) one pure methanol, and methanol-water (15 % and 75 % of methanol). The studies are conducted for two different drop spacings of 0.5 and 1.5 cm. The results suggest that the higher spacing (i.e., 1.5 cm) produced a stronger acoustic streaming effect than the lower one (i.e., 0.5 cm) for all the twin drop combinations, which indicates higher internal circulation at a larger spacing of 1.5 cm. For all the spacings, the evaporation rate is observed to be proportional to the internal circulation at all twin drop combinations. Further, empirical correlations are developed to predict the evaporation rate and internal circulation for twin drops with different combinations. The study shows that the evaporation and internal circulation follow a universal behavior for all the combinations of twin drops at both the drop spacings, while the higher values are observed at a larger spacing of 1.5 cm compared to the smaller one of 0.5 cm. The paper clearly demonstrates the complex interplay of variables involved in the evaporation / internal circulation of twin methanol drops under the influence of an acoustic field, thus producing a universal behaviour that is independent of their composition for both the drop spacings.
{"title":"Acoustic-induced flow on the evaporation dynamics of twin drops","authors":"Aadil Kureshee, S. Narayanan, Deepak Kumar Mandal","doi":"10.1016/j.ijmultiphaseflow.2024.105070","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105070","url":null,"abstract":"<div><div>The present study aims to investigate the effect of an acoustic field on the internal circulation and evaporation of three distinct combinations of twin methanol drops. The drop combinations used for making twin drops are (i) methanol and water (i.e., 15% and 75% of methanol), (ii) pure methanol, (iii) one pure methanol, and methanol-water (15 % and 75 % of methanol). The studies are conducted for two different drop spacings of 0.5 and 1.5 cm. The results suggest that the higher spacing (i.e., 1.5 cm) produced a stronger acoustic streaming effect than the lower one (i.e., 0.5 cm) for all the twin drop combinations, which indicates higher internal circulation at a larger spacing of 1.5 cm. For all the spacings, the evaporation rate is observed to be proportional to the internal circulation at all twin drop combinations. Further, empirical correlations are developed to predict the evaporation rate and internal circulation for twin drops with different combinations. The study shows that the evaporation and internal circulation follow a universal behavior for all the combinations of twin drops at both the drop spacings, while the higher values are observed at a larger spacing of 1.5 cm compared to the smaller one of 0.5 cm. The paper clearly demonstrates the complex interplay of variables involved in the evaporation / internal circulation of twin methanol drops under the influence of an acoustic field, thus producing a universal behaviour that is independent of their composition for both the drop spacings.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105070"},"PeriodicalIF":3.6,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-28DOI: 10.1016/j.ijmultiphaseflow.2024.105064
Kelvin C.O. Barbosa , Edson J. Soares , Marcia C. Khalil , Osvaldo Karnitz Junior
Drag reduction by polymers is a critical issue, with several applications first reported more than 70 years ago. The number of related works is vast, but most are restricted to single-phase flow. The few available works treating two-phase flow use drag reducers only in the water phase. One goal of the present work is to study the role of polymer additives in both phases for a range of water fractions. We conduct the main tests by considering the pressure drop in a fully developed turbulent flow in a pipeline and fixing each phase flow rate. In our tests, the pressure drop depends on the water fraction, mixing viscosity, mean phase densities, polymer concentration, and molecular weight. It is worth mentioning that, in small concentrations, the water drops also work as a drag reducer. We conduct the tests to compare the role of polymers in single and two-phase flow, paying particular attention to mechanical polymer degradation. Our main conclusion is that drag reducers are effective only in the external phase. In our tests, the water drag reducer is effective for water fractions larger than 0.5, and the oil drag reducer for water fractions smaller than 0.5. When both phases contain additives, the pressure drops, relatively to the case in the absence of additives, for an entire range of water fractions.
{"title":"Polymer drag reduction in dispersed oil–water flow in tubes","authors":"Kelvin C.O. Barbosa , Edson J. Soares , Marcia C. Khalil , Osvaldo Karnitz Junior","doi":"10.1016/j.ijmultiphaseflow.2024.105064","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105064","url":null,"abstract":"<div><div>Drag reduction by polymers is a critical issue, with several applications first reported more than 70 years ago. The number of related works is vast, but most are restricted to single-phase flow. The few available works treating two-phase flow use drag reducers only in the water phase. One goal of the present work is to study the role of polymer additives in both phases for a range of water fractions. We conduct the main tests by considering the pressure drop in a fully developed turbulent flow in a pipeline and fixing each phase flow rate. In our tests, the pressure drop depends on the water fraction, mixing viscosity, mean phase densities, polymer concentration, and molecular weight. It is worth mentioning that, in small concentrations, the water drops also work as a drag reducer. We conduct the tests to compare the role of polymers in single and two-phase flow, paying particular attention to mechanical polymer degradation. Our main conclusion is that drag reducers are effective only in the external phase. In our tests, the water drag reducer is effective for water fractions larger than 0.5, and the oil drag reducer for water fractions smaller than 0.5. When both phases contain additives, the pressure drops, relatively to the case in the absence of additives, for an entire range of water fractions.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105064"},"PeriodicalIF":3.6,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study uses interface-resolved computational fluid dynamics simulations to investigate the dynamics of bubble growth on a horizontal solid surface, with a focus on the characteristics of the microlayer and the forces involved in the process. The simulations exclude phase change effects to concentrate on hydrodynamics and employ an external mass source for controlled bubble inflation. This mass source follows a time-dependent bubble radius growth law, , which is typical for heat-transfer-controlled growth of a vapour bubble during nucleate boiling of water at atmospheric pressure. The numerical framework is validated against recent experimental measurements of bubble shape and microlayer profile. The results of this work indicate that the rate of bubble growth significantly influences microlayer formation. Faster growth rates produce a near-hemispherical bubble shape with an extended radial microlayer on the solid, while slower rates yield a taller, more spherical bubble with a shorter microlayer. All microlayer profiles exhibit an outwardly-curved shape, with a maximum microlayer thickness increasing with the growth rate. The study also examines the force balance on the bubble, revealing that the net vertical force of the bubble does not equal zero even when the bubble remains attached to the solid surface. Our analysis of the bubble motion demonstrates that previous force balance models used for determining bubble detachment lack robustness. The microlayer profile obtained in this work is important for boiling heat transfer studies as the microlayer contributes significantly to local heat transfer. The force balance analysis shows the need for a new approach to determine bubble detachment behaviour, which is vital for predicting flow boiling rates.
{"title":"The microlayer and force balance of bubbles growing on solid in nucleate boiling","authors":"Xiaolong Zhang (张晓龙) , Ismail El Mellas , Nicola Andreini , Mirco Magnini","doi":"10.1016/j.ijmultiphaseflow.2024.105049","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105049","url":null,"abstract":"<div><div>This study uses interface-resolved computational fluid dynamics simulations to investigate the dynamics of bubble growth on a horizontal solid surface, with a focus on the characteristics of the microlayer and the forces involved in the process. The simulations exclude phase change effects to concentrate on hydrodynamics and employ an external mass source for controlled bubble inflation. This mass source follows a time-dependent bubble radius growth law, <span><math><mrow><mi>R</mi><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow><mo>∝</mo><msup><mrow><mi>t</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow></math></span>, which is typical for heat-transfer-controlled growth of a vapour bubble during nucleate boiling of water at atmospheric pressure. The numerical framework is validated against recent experimental measurements of bubble shape and microlayer profile. The results of this work indicate that the rate of bubble growth significantly influences microlayer formation. Faster growth rates produce a near-hemispherical bubble shape with an extended radial microlayer on the solid, while slower rates yield a taller, more spherical bubble with a shorter microlayer. All microlayer profiles exhibit an outwardly-curved shape, with a maximum microlayer thickness increasing with the growth rate. The study also examines the force balance on the bubble, revealing that the net vertical force of the bubble does not equal zero even when the bubble remains attached to the solid surface. Our analysis of the bubble motion demonstrates that previous force balance models used for determining bubble detachment lack robustness. The microlayer profile obtained in this work is important for boiling heat transfer studies as the microlayer contributes significantly to local heat transfer. The force balance analysis shows the need for a new approach to determine bubble detachment behaviour, which is vital for predicting flow boiling rates.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105049"},"PeriodicalIF":3.6,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1016/j.ijmultiphaseflow.2024.105067
Omid Tavakkoli , Mohammad Ebadi , Ying Da Wang , Peyman Mostaghimi , Ryan T. Armstrong
This study hypothesizes that a pore morphology method (PMM) can be used to accurately determine representative contact angles by effectively capturing fluid morphologies within porous media, thereby overcoming the challenges of accurate wettability characterization for porous materials. We introduce a methodology for the estimation of the wettability, along with measurements of capillary pressure and relative permeability, using a PMM. This approach employs morphological operations to model quasistatic drainage under different surface wetting conditions. To assess PMM, fluid morphologies resulting from the simulation were compared with experimentally derived geometric and thermodynamic contact angles, along with surface area, and Euler characteristic measurements. Based on fluid configurations under different wettability conditions, we find that PMM effectively captures realistic fluid morphologies. At lower capillary pressures, PMM exhibits superior adaptability to a wide range of wetting behaviors. However, at higher capillary pressures, PMM does not reflect the true morphologies of the fluid due to the interfaces that exist in the pendular state. The influence of these effects at higher capillary pressures introduces an inaccuracy in the simulated relative permeability of the wetting phase, though they do not affect the relative permeability of the nonwetting phase. Overall, these findings can significantly enhance the accuracy of wettability characterization in porous media, thereby advancing our understanding and prediction of fluid behavior in surface-based research of porous materials.
{"title":"Assessment of wetting conditions in quasistatic drainage modeling using a pore morphology method and J-function wettability estimator","authors":"Omid Tavakkoli , Mohammad Ebadi , Ying Da Wang , Peyman Mostaghimi , Ryan T. Armstrong","doi":"10.1016/j.ijmultiphaseflow.2024.105067","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105067","url":null,"abstract":"<div><div>This study hypothesizes that a pore morphology method (PMM) can be used to accurately determine representative contact angles by effectively capturing fluid morphologies within porous media, thereby overcoming the challenges of accurate wettability characterization for porous materials. We introduce a methodology for the estimation of the wettability, along with measurements of capillary pressure and relative permeability, using a PMM. This approach employs morphological operations to model quasistatic drainage under different surface wetting conditions. To assess PMM, fluid morphologies resulting from the simulation were compared with experimentally derived geometric and thermodynamic contact angles, along with surface area, and Euler characteristic measurements. Based on fluid configurations under different wettability conditions, we find that PMM effectively captures realistic fluid morphologies. At lower capillary pressures, PMM exhibits superior adaptability to a wide range of wetting behaviors. However, at higher capillary pressures, PMM does not reflect the true morphologies of the fluid due to the interfaces that exist in the pendular state. The influence of these effects at higher capillary pressures introduces an inaccuracy in the simulated relative permeability of the wetting phase, though they do not affect the relative permeability of the nonwetting phase. Overall, these findings can significantly enhance the accuracy of wettability characterization in porous media, thereby advancing our understanding and prediction of fluid behavior in surface-based research of porous materials.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105067"},"PeriodicalIF":3.6,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.ijmultiphaseflow.2024.105060
Ramakrishnan Thirumalaisamy, Amneet Pal Singh Bhalla
This work expands on our recently introduced low Mach enthalpy method (Thirumalaisamy and Bhalla 2023) for simulating the melting and solidification of a phase change material (PCM) alongside (or without) an ambient gas phase. The method captures PCM’s volume change (shrinkage or expansion) by accounting for density change-induced flows. We present several improvements to the original work. First, we introduce consistent time integration schemes for the mass, momentum, and enthalpy equations, which enhance the method stability. Demonstrating the effectiveness of this scheme, we show that a system free of external forces and heat sources can conserve its initial mass, momentum, enthalpy, and phase composition. This allows the system to transition from a non-isothermal, non-equilibrium, phase-changing state to an isothermal, equilibrium state without exhibiting unrealistic behavior. Furthermore, we show that the low Mach enthalpy method accurately simulates thermocapillary flows without introducing spurious phase changes. To reduce computational costs, we solve the governing equations on adaptively refined grids. We investigate two cell tagging/untagging criteria and find that a gradient-based approach is more effective. This approach ensures that the moving thin mushy region is always captured at fine grid levels, even when it temporarily falls within a subgrid level. We propose an analytical model to validate advanced computational fluid dynamics (CFD) codes used to simulate metal manufacturing processes (welding, 3D printing). These processes involve a heat source (like a laser) melting metal or its alloy in the presence of an ambient (inert) gas. Traditionally, studies relied on artificially manipulating material properties to match complex experiments for validation purposes. Leveraging the analytical solution to the Stefan problem with a density jump, this model offers a straightforward approach to validating multiphysics simulations involving heat sources and phase change phenomena in three-phase flows. Lastly, we demonstrate the practical utility of the method in modeling porosity defects (gas bubble trapping) during metal solidification. A field extension technique is used to accurately apply surface tension forces in a three-phase flow situation. This is where part of the bubble surface is trapped within the (moving) solidification front.
{"title":"A consistent, volume preserving, and adaptive mesh refinement-based framework for modeling non-isothermal gas–liquid–solid flows with phase change","authors":"Ramakrishnan Thirumalaisamy, Amneet Pal Singh Bhalla","doi":"10.1016/j.ijmultiphaseflow.2024.105060","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105060","url":null,"abstract":"<div><div>This work expands on our recently introduced low Mach enthalpy method (Thirumalaisamy and Bhalla 2023) for simulating the melting and solidification of a phase change material (PCM) alongside (or without) an ambient gas phase. The method captures PCM’s volume change (shrinkage or expansion) by accounting for density change-induced flows. We present several improvements to the original work. First, we introduce consistent time integration schemes for the mass, momentum, and enthalpy equations, which enhance the method stability. Demonstrating the effectiveness of this scheme, we show that a system free of external forces and heat sources can conserve its initial mass, momentum, enthalpy, and phase composition. This allows the system to transition from a non-isothermal, non-equilibrium, phase-changing state to an isothermal, equilibrium state without exhibiting unrealistic behavior. Furthermore, we show that the low Mach enthalpy method accurately simulates thermocapillary flows without introducing spurious phase changes. To reduce computational costs, we solve the governing equations on adaptively refined grids. We investigate two cell tagging/untagging criteria and find that a gradient-based approach is more effective. This approach ensures that the moving thin mushy region is always captured at fine grid levels, even when it temporarily falls within a subgrid level. We propose an analytical model to validate advanced computational fluid dynamics (CFD) codes used to simulate metal manufacturing processes (welding, 3D printing). These processes involve a heat source (like a laser) melting metal or its alloy in the presence of an ambient (inert) gas. Traditionally, studies relied on artificially manipulating material properties to match complex experiments for validation purposes. Leveraging the analytical solution to the Stefan problem with a density jump, this model offers a straightforward approach to validating multiphysics simulations involving heat sources and phase change phenomena in three-phase flows. Lastly, we demonstrate the practical utility of the method in modeling porosity defects (gas bubble trapping) during metal solidification. A field extension technique is used to accurately apply surface tension forces in a three-phase flow situation. This is where part of the bubble surface is trapped within the (moving) solidification front.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105060"},"PeriodicalIF":3.6,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.ijmultiphaseflow.2024.105063
Sang Ji Lee, Ji Yeop Kim, Mun Hee Lee, Jung Goo Hong
In this study, we experimentally investigate the effect of internal flow variation on the design characteristics of a Y-jet twin-fluid nozzle and its utilization for spray droplet size prediction. For this study, a laboratory-scale twin-fluid nozzle spray test system was constructed. Sauter mean diameter (SMD) measurements were made by a droplet measurement system using the laser diffraction principle, and spray images were obtained using a high-speed camera. The mass flow rate of the twin fluids under different spray conditions was expressed in terms of the gas-to-liquid mass flow rate ratio (GLR) and turn-down ratio. The GLR tended to decrease when the nozzle orifice diameter increased because the pressure of the supplied twin-fluid was the same. By contrast, increasing the nozzle mixing-tube length resulted in a negligible increase in GLR. This is because the nozzle design characteristics affect the internal pressure of the nozzle, which changes its spray characteristics. In general, the spray characteristics of Y-jet nozzles are most affected by GLR. However, in this study, a generalised GLR was devised to consider not only GLR but also the difference in the flow rate of the twin-fluid due to nozzle design factors. The generalised GLR has the advantage that it is constant under changes in twin-fluid pressure, unlike the GLR expressed by considering only the mass flow rate of the twin-fluid. Therefore, to estimate the SMD more accurately under different spray pressures for a constant GLR, we investigated the SMD estimation using the internal pressure ratio and generalised GLR.
{"title":"Experimental study of twin-fluid flow differences and Sauter mean diameter prediction according to Y-jet nozzle mixing-tube design","authors":"Sang Ji Lee, Ji Yeop Kim, Mun Hee Lee, Jung Goo Hong","doi":"10.1016/j.ijmultiphaseflow.2024.105063","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105063","url":null,"abstract":"<div><div>In this study, we experimentally investigate the effect of internal flow variation on the design characteristics of a Y-jet twin-fluid nozzle and its utilization for spray droplet size prediction. For this study, a laboratory-scale twin-fluid nozzle spray test system was constructed. Sauter mean diameter (SMD) measurements were made by a droplet measurement system using the laser diffraction principle, and spray images were obtained using a high-speed camera. The mass flow rate of the twin fluids under different spray conditions was expressed in terms of the gas-to-liquid mass flow rate ratio (GLR) and turn-down ratio. The GLR tended to decrease when the nozzle orifice diameter increased because the pressure of the supplied twin-fluid was the same. By contrast, increasing the nozzle mixing-tube length resulted in a negligible increase in GLR. This is because the nozzle design characteristics affect the internal pressure of the nozzle, which changes its spray characteristics. In general, the spray characteristics of Y-jet nozzles are most affected by GLR. However, in this study, a generalised GLR was devised to consider not only GLR but also the difference in the flow rate of the twin-fluid due to nozzle design factors. The generalised GLR has the advantage that it is constant under changes in twin-fluid pressure, unlike the GLR expressed by considering only the mass flow rate of the twin-fluid. Therefore, to estimate the SMD more accurately under different spray pressures for a constant GLR, we investigated the SMD estimation using the internal pressure ratio and generalised GLR.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105063"},"PeriodicalIF":3.6,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.ijmultiphaseflow.2024.105059
Byeong-Cheon Kim , Kyoungsik Chang , Sang-Wook Lee , Jaiyoung Ryu , Minjae Kim , Jaemoon Yoon
Over three decades, much research has proven the bubble drag reduction (BDR) technique. Recently, the improvement of computing performance has enabled the simulation of multi-phase flows. The present work simulated the microbubble-laden turbulent horizontal channel flow by Nek5000 code, which is based on the spectral element method. To resolve the microbubble dynamics, the 2-way coupling Euler–Lagrange approach was combined with Nek5000 code. Furthermore, for high accuracy, high-order Lagrange interpolation was adopted to track the microbubble's location and velocity in this code. All microbubbles were assumed as non-deformable, spherical, and immiscible. For the investigation of the drag reduction effect of microbubble size and the number of microbubbles, the uncertainty quantification (UQ) method was adopted with the non-intrusive polynomial chaos method. The Latin hypercube sampling method was used to obtain precision with lesser number of samples than the Monte Carlo method. The distribution of random variables was assumed to be Gaussian and generalized polynomial chaos expansion (gPC) was applied to build the surrogate model. The mean value (μ) of random variables was 110 µm, 6,345 each, while the standard deviation (σ) was ± 0.33 μ. As a result, the uncertainty propagation of velocity, second-order turbulence statistics, and drag reduction were achieved.
{"title":"Uncertainty quantification for the drag reduction of microbubble-laden fluid flow in a horizontal channel","authors":"Byeong-Cheon Kim , Kyoungsik Chang , Sang-Wook Lee , Jaiyoung Ryu , Minjae Kim , Jaemoon Yoon","doi":"10.1016/j.ijmultiphaseflow.2024.105059","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105059","url":null,"abstract":"<div><div>Over three decades, much research has proven the bubble drag reduction (BDR) technique. Recently, the improvement of computing performance has enabled the simulation of multi-phase flows. The present work simulated the microbubble-laden turbulent horizontal channel flow by Nek5000 code, which is based on the spectral element method. To resolve the microbubble dynamics, the 2-way coupling Euler–Lagrange approach was combined with Nek5000 code. Furthermore, for high accuracy, high-order Lagrange interpolation was adopted to track the microbubble's location and velocity in this code. All microbubbles were assumed as non-deformable, spherical, and immiscible. For the investigation of the drag reduction effect of microbubble size and the number of microbubbles, the uncertainty quantification (UQ) method was adopted with the non-intrusive polynomial chaos method. The Latin hypercube sampling method was used to obtain precision with lesser number of samples than the Monte Carlo method. The distribution of random variables was assumed to be Gaussian and generalized polynomial chaos expansion (gPC) was applied to build the surrogate model. The mean value (μ) of random variables was 110 µm, 6,345 each, while the standard deviation (σ) was ± 0.33 μ. As a result, the uncertainty propagation of velocity, second-order turbulence statistics, and drag reduction were achieved.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105059"},"PeriodicalIF":3.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142654152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-15DOI: 10.1016/j.ijmultiphaseflow.2024.105068
Vitor O.O. Machado , Marco G. Conte , Roel Belt , Chris Lawrence , Thierry Palermo , Eduardo N. dos Santos , Rigoberto E.M. Morales
In this work the existence of a bi-stable flow regime in a horizontal gas-liquid two-phase flow was experimentally confirmed. In this regime, both stratified and slug flows were found to be stable, and the occurrence of either regime depended on the inlet conditions imposed on the flow. When operating in the bi-stable flow condition, two types of slugs can occur. The first type was obtained by forcing a regular slug flow at the inlet of the horizontal pipe using an uphill section before the inlet. In this case, slugs in the uphill and horizontal sections have similar frequencies. The second type was obtained by forcing a stratified flow at the inlet, and then introducing a short pulse in the liquid flow rate. This triggered a solitary slug in the pipe, which grew linearly with the distance from the inlet. The behavior of the solitary slugs observed experimentally confirms the explanation and the model provided by Belt et al., 2024. The existence of such slugs can represent a threat in operations, since in long flowlines they can become extremely large and flood the downstream process installations. For instance, the experiments showed solitary slugs more than 200 pipe diameters long at a distance of 460 pipe diameters from the inlet. In order to evaluate the conditions under which the solitary slug phenomenon might occur, the extent of the bi-stable flow regime was experimentally determined. Its lower and upper boundaries match reasonably well with the stability conditions for slug flow and stratified flow, respectively, which were calculated within a 1D modeling framework.
在这项研究中，实验证实了水平气液两相流中存在一种双稳态流动机制。在这种流动状态下，分层流和蛞蝓流都是稳定的，而这两种流动状态的出现取决于对流动施加的入口条件。在双稳定流条件下运行时，会出现两种类型的蛞蝓。第一种类型是通过在水平管道的入口处利用入口前的上坡段强制形成有规律的蛞蝓流。在这种情况下，上坡段和水平段的蛞蝓具有相似的频率。第二种类型是在入口处强制形成分层流，然后在液体流速中引入一个短脉冲。这引发了管道中的孤流，孤流随距离入口的距离呈线性增长。实验中观察到的孤流的行为证实了 Belt 等人的解释和模型，2024。这种蛞蝓的存在可能会对运行造成威胁，因为在长的流水线上，它们可能会变得非常大，并淹没下游的工艺设备。例如，实验显示，在距离入口 460 管径的地方，单独的蛞蝓长度超过 200 管径。为了评估可能出现孤栓现象的条件，我们通过实验确定了双稳态流态的范围。其下界和上界分别与在一维建模框架内计算得出的蛞蝓流和分层流的稳定条件相当吻合。
{"title":"Experimental evaluation of solitary slugs in a horizontal pipe","authors":"Vitor O.O. Machado , Marco G. Conte , Roel Belt , Chris Lawrence , Thierry Palermo , Eduardo N. dos Santos , Rigoberto E.M. Morales","doi":"10.1016/j.ijmultiphaseflow.2024.105068","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105068","url":null,"abstract":"<div><div>In this work the existence of a bi-stable flow regime in a horizontal gas-liquid two-phase flow was experimentally confirmed. In this regime, both stratified and slug flows were found to be stable, and the occurrence of either regime depended on the inlet conditions imposed on the flow. When operating in the bi-stable flow condition, two types of slugs can occur. The first type was obtained by forcing a regular slug flow at the inlet of the horizontal pipe using an uphill section before the inlet. In this case, slugs in the uphill and horizontal sections have similar frequencies. The second type was obtained by forcing a stratified flow at the inlet, and then introducing a short pulse in the liquid flow rate. This triggered a solitary slug in the pipe, which grew linearly with the distance from the inlet. The behavior of the solitary slugs observed experimentally confirms the explanation and the model provided by Belt et al., 2024. The existence of such slugs can represent a threat in operations, since in long flowlines they can become extremely large and flood the downstream process installations. For instance, the experiments showed solitary slugs more than 200 pipe diameters long at a distance of 460 pipe diameters from the inlet. In order to evaluate the conditions under which the solitary slug phenomenon might occur, the extent of the bi-stable flow regime was experimentally determined. Its lower and upper boundaries match reasonably well with the stability conditions for slug flow and stratified flow, respectively, which were calculated within a 1D modeling framework.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105068"},"PeriodicalIF":3.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-15DOI: 10.1016/j.ijmultiphaseflow.2024.105066
F.J. Salvador , M. Carreres , F.X. Demoulin , A. Lozano
Reducing pollutants and carbon emissions is a main and commonplace concern nowadays. Improving liquid breakup efficiency in injection processes for combustion applications may lead to important benefits in that regard. In this work, the effect of varying the injection conditions in terms of their thermodynamic state is studied when injecting liquid fuel into quiescent air through a simplex pressure-swirl atomizer. For that purpose, high-fidelity DNS-like simulations are carried out. Results, validated by comparing the spray macroscopic shape with experimental pictures, show a realistic breakup mechanism already observed in previous studies. An improvement in breakup capabilities is observed when preheating both fuel and air. In this case, the injected liquid sheet is thinner and presents more instabilities, leading to an earlier breakup in the axial direction. Besides, the generated droplet population is larger and finer than that of the ambient temperature injection, indicating a better atomization efficiency. A size-growing trend is observed in the droplet population for both cases when getting far away from the nozzle, but is more noticeable in the low-temperature condition. This investigation helps to understand the first stage of the liquid breakup in pressure-swirl atomizers. Its results, complemented with those from simulating different operating conditions or fuels for the same atomizer, can be used to elaborate prediction models able to faithfully represent the primary atomization outcomes when using lower resolution methods more accessible from the computational standpoint. Besides, the importance of internal injector flow characteristics is also demonstrated, particularly when considering liquid film thickness, both mean and fluctuation. These findings indicate that a possible model based on internal injector flow studies may also be feasible for determining atomization efficiency.
{"title":"Computational study on the effect of thermodynamic operating conditions on primary atomization in pressure-swirl atomizers","authors":"F.J. Salvador , M. Carreres , F.X. Demoulin , A. Lozano","doi":"10.1016/j.ijmultiphaseflow.2024.105066","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105066","url":null,"abstract":"<div><div>Reducing pollutants and carbon emissions is a main and commonplace concern nowadays. Improving liquid breakup efficiency in injection processes for combustion applications may lead to important benefits in that regard. In this work, the effect of varying the injection conditions in terms of their thermodynamic state is studied when injecting liquid fuel into quiescent air through a simplex pressure-swirl atomizer. For that purpose, high-fidelity DNS-like simulations are carried out. Results, validated by comparing the spray macroscopic shape with experimental pictures, show a realistic breakup mechanism already observed in previous studies. An improvement in breakup capabilities is observed when preheating both fuel and air. In this case, the injected liquid sheet is thinner and presents more instabilities, leading to an earlier breakup in the axial direction. Besides, the generated droplet population is larger and finer than that of the ambient temperature injection, indicating a better atomization efficiency. A size-growing trend is observed in the droplet population for both cases when getting far away from the nozzle, but is more noticeable in the low-temperature condition. This investigation helps to understand the first stage of the liquid breakup in pressure-swirl atomizers. Its results, complemented with those from simulating different operating conditions or fuels for the same atomizer, can be used to elaborate prediction models able to faithfully represent the primary atomization outcomes when using lower resolution methods more accessible from the computational standpoint. Besides, the importance of internal injector flow characteristics is also demonstrated, particularly when considering liquid film thickness, both mean and fluctuation. These findings indicate that a possible model based on internal injector flow studies may also be feasible for determining atomization efficiency.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"183 ","pages":"Article 105066"},"PeriodicalIF":3.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1016/j.ijmultiphaseflow.2024.105062
F.J. Santos , L. Beckedorff , T.S. Possamai , K.V. Paiva , J. L.G. Oliveira
Air-water flows were assessed within Plate Heat Exchangers (PHE) with the aid of fast camera imaging. Tests occurred in transparent setups with three chevron angle arrangements (30o/30o, 30o/60o and 60o/60o), representative of low, in-between and high pressure drop channels. Evaluation upstream the PHE inlet happened with Electrical Capacitance Tomography. Three patterns were tested: bubbly, slug and stratified. The effects of flow direction, superficial fluid velocities, two-phase pattern, and chevron angle arrangement on air-water distributions were assessed. The PHE channel outlet is characterized by intense flow recirculation. Bubble entrapment occurs in the core of the recirculation zones. Energy dissipation processes along the PHE channel flow affect the inlet gaseous content, intensifying the mixing process of air and water phases, particularly at flow distribution areas owing to the occurrence of flow acceleration and deceleration. Bubble distribution is wide since the break-up process is rather heterogeneous. Prediction of the maximum bubble diameter was obtained with a modification to Hinze's model. Coalescence can occur with small liquid superficial velocities. At the exit manifold, the recirculation zones affect the two-phase pipe flow. In addition to swirling decay, two-phase flow features and gravitational forces need to be accounted to determine the necessary pipe length to attain stationary process.
{"title":"Two-phase flows downstream, upstream and within Plate Heat Exchangers","authors":"F.J. Santos , L. Beckedorff , T.S. Possamai , K.V. Paiva , J. L.G. Oliveira","doi":"10.1016/j.ijmultiphaseflow.2024.105062","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.105062","url":null,"abstract":"<div><div>Air-water flows were assessed within Plate Heat Exchangers (PHE) with the aid of fast camera imaging. Tests occurred in transparent setups with three chevron angle arrangements (30<sup>o</sup>/30<sup>o</sup>, 30<sup>o</sup>/60<sup>o</sup> and 60<sup>o</sup>/60<sup>o</sup>), representative of low, in-between and high pressure drop channels. Evaluation upstream the PHE inlet happened with Electrical Capacitance Tomography. Three patterns were tested: bubbly, slug and stratified. The effects of flow direction, superficial fluid velocities, two-phase pattern, and chevron angle arrangement on air-water distributions were assessed. The PHE channel outlet is characterized by intense flow recirculation. Bubble entrapment occurs in the core of the recirculation zones. Energy dissipation processes along the PHE channel flow affect the inlet gaseous content, intensifying the mixing process of air and water phases, particularly at flow distribution areas owing to the occurrence of flow acceleration and deceleration. Bubble distribution is wide since the break-up process is rather heterogeneous. Prediction of the maximum bubble diameter was obtained with a modification to Hinze's model. Coalescence can occur with small liquid superficial velocities. At the exit manifold, the recirculation zones affect the two-phase pipe flow. In addition to swirling decay, two-phase flow features and gravitational forces need to be accounted to determine the necessary pipe length to attain stationary process.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"182 ","pages":"Article 105062"},"PeriodicalIF":3.6,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142654153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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