Pub Date : 2025-12-17DOI: 10.1016/j.ijmultiphaseflow.2025.105567
Zhidian Yang, Bo Wang, Francesco Romanò
Cavitation near solid boundaries is a well-documented phenomenon due to its potential to damage surfaces and impair the performance of pumps, turbines, and similar machinery. This work numerically investigates the pressure exerted by a cavitation bubble collapsing near a rigid wall, with results compared against experimental measurements. The bubble is assumed to start from rest at its maximum equivalent radius. Simulations employ the All-Mach approach of Basilisk, using the VOF (Volume-of-Fluid) method to resolve interface dynamics. Our findings show that the maximum wall pressure during collapse depends strongly on the bubble stand-off ratio and the interior-to-exterior pressure ratio at maximum size. In contrast, the evolution of the equivalent radius shows a weak sensitivity to these parameters, despite significant effects on the detailed interface motion. Additional analyses assess the influence of viscosity, heat transfer, surface tension, and bubble sphericity, allowing identification of the leading-order mechanisms to reduce model complexity. Comparison with experiments and prior studies indicates that accounting for flow compressibility, while neglecting phase change during collapse, provides good agreement for interfacial dynamics, though notable discrepancies remain for the maximum wall pressure.
{"title":"Bubble collapse near a wall: A numerical study on the impact of physical mechanisms for a bubble initially at rest","authors":"Zhidian Yang, Bo Wang, Francesco Romanò","doi":"10.1016/j.ijmultiphaseflow.2025.105567","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105567","url":null,"abstract":"<div><div>Cavitation near solid boundaries is a well-documented phenomenon due to its potential to damage surfaces and impair the performance of pumps, turbines, and similar machinery. This work numerically investigates the pressure exerted by a cavitation bubble collapsing near a rigid wall, with results compared against experimental measurements. The bubble is assumed to start from rest at its maximum equivalent radius. Simulations employ the All-Mach approach of Basilisk, using the VOF (Volume-of-Fluid) method to resolve interface dynamics. Our findings show that the maximum wall pressure during collapse depends strongly on the bubble stand-off ratio and the interior-to-exterior pressure ratio at maximum size. In contrast, the evolution of the equivalent radius shows a weak sensitivity to these parameters, despite significant effects on the detailed interface motion. Additional analyses assess the influence of viscosity, heat transfer, surface tension, and bubble sphericity, allowing identification of the leading-order mechanisms to reduce model complexity. Comparison with experiments and prior studies indicates that accounting for flow compressibility, while neglecting phase change during collapse, provides good agreement for interfacial dynamics, though notable discrepancies remain for the maximum wall pressure.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105567"},"PeriodicalIF":3.8,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836920","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 : 2025-12-16DOI: 10.1016/j.ijmultiphaseflow.2025.105582
Ming Zhang , Pengcheng Li , Shengde Di , Jinghua Chen , Qi Xiang , Xiaoming Luo
Following the shutdown of deepwater oil–water multiphase pipelines, crude oil readily solidifies under low-temperature conditions, posing a serious risk of pipeline blockage. Diesel displacement is a critical technique for ensuring the safe shutdown and restart of subsea pipelines. However, the mechanisms governing the formation and evolution of the mixing zone and the reliable prediction of its length remain unclear. This study combines loop experiments with numerical simulations to systematically investigate the effects of flow velocity, water cut, pipe diameter, and pipeline inclination on the development of the mixing zone during diesel displacement of oil–water two-phase flow. The results demonstrate that flow velocity is the dominant factor controlling the mixing zone length, reducing the mixing zone length by 31–33% when the velocity increases from 0.5 to 1.0 m/s. Increasing velocity significantly enhances turbulence, accelerates diesel dissolution and scouring of wall-adhered crude oil, and strengthens water entrainment, thereby shortening the mixing zone and improving displacement efficiency. Larger pipe diameters and greater inclinations extend the mixing zone by approximately 20%, due to increased oil adhesion, water backflow in upward sections, and oil buoyancy or partial-flow effects in downward sections, while the impact of water cut is relatively minor. Meanwhile, numerical simulations can effectively reproduce the dynamic evolution of the mixing zone, but have difficulty in accurately characterizing crude oil adhesion effects, resulting in a MAPE of approximately 19.1% between the predicted and measured mixing zone lengths. This study elucidates the mechanisms underlying mixing zone formation and dynamic evolution, reveals the dissolution-scouring synergy governing the removal of wall-adhered crude oil and the roles of gravity-induced stratification and buoyancy, quantitatively assesses the effects of key parameters on mixing zone length, and provides a theoretical basis for optimizing shutdown displacement in deepwater multiphase pipelines.
{"title":"Dynamic evolution of the mixing zone during diesel displacement of oil-water two-phase flow in multiphase pipelines","authors":"Ming Zhang , Pengcheng Li , Shengde Di , Jinghua Chen , Qi Xiang , Xiaoming Luo","doi":"10.1016/j.ijmultiphaseflow.2025.105582","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105582","url":null,"abstract":"<div><div>Following the shutdown of deepwater oil–water multiphase pipelines, crude oil readily solidifies under low-temperature conditions, posing a serious risk of pipeline blockage. Diesel displacement is a critical technique for ensuring the safe shutdown and restart of subsea pipelines. However, the mechanisms governing the formation and evolution of the mixing zone and the reliable prediction of its length remain unclear. This study combines loop experiments with numerical simulations to systematically investigate the effects of flow velocity, water cut, pipe diameter, and pipeline inclination on the development of the mixing zone during diesel displacement of oil–water two-phase flow. The results demonstrate that flow velocity is the dominant factor controlling the mixing zone length, reducing the mixing zone length by 31–33% when the velocity increases from 0.5 to 1.0 m/s. Increasing velocity significantly enhances turbulence, accelerates diesel dissolution and scouring of wall-adhered crude oil, and strengthens water entrainment, thereby shortening the mixing zone and improving displacement efficiency. Larger pipe diameters and greater inclinations extend the mixing zone by approximately 20%, due to increased oil adhesion, water backflow in upward sections, and oil buoyancy or partial-flow effects in downward sections, while the impact of water cut is relatively minor. Meanwhile, numerical simulations can effectively reproduce the dynamic evolution of the mixing zone, but have difficulty in accurately characterizing crude oil adhesion effects, resulting in a MAPE of approximately 19.1% between the predicted and measured mixing zone lengths. This study elucidates the mechanisms underlying mixing zone formation and dynamic evolution, reveals the dissolution-scouring synergy governing the removal of wall-adhered crude oil and the roles of gravity-induced stratification and buoyancy, quantitatively assesses the effects of key parameters on mixing zone length, and provides a theoretical basis for optimizing shutdown displacement in deepwater multiphase pipelines.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105582"},"PeriodicalIF":3.8,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787065","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 : 2025-12-16DOI: 10.1016/j.ijmultiphaseflow.2025.105581
H.D. Haustein , E. Elias
This study examines the phenomenon of impact boiling in a uniformly heated liquid containing nucleation sites. This extreme phenomenon may occur in applications with intense heating, as is encountered in lasers and nuclear reactors. Present theoretical analysis couples the energy equation with a non-equilibrium vapor formation model, to describe the crucial competition between rapid volumetric heating and thermal relaxation by latent heat absorption. The pre-existence of nucleation sites limits the heat-up rates to 106 [K/s], and to the thermal bubble growth regime. This balance then yields a criterion for maximum achievable liquid superheat, expressed as a function of the ratio of heating rate to the density of existing vapor embryos. Exceeding this threshold triggers unwanted explosive boiling, characterized by intense vapor generation driven by homogeneous nucleation. The model’s dimensionless formulation allows for generalization to other liquids, beyond water and methanol examined here.
{"title":"Impact boiling in real liquids under intense heating rates","authors":"H.D. Haustein , E. Elias","doi":"10.1016/j.ijmultiphaseflow.2025.105581","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105581","url":null,"abstract":"<div><div>This study examines the phenomenon of impact boiling in a uniformly heated liquid containing nucleation sites. This extreme phenomenon may occur in applications with intense heating, as is encountered in lasers and nuclear reactors. Present theoretical analysis couples the energy equation with a non-equilibrium vapor formation model, to describe the crucial competition between rapid volumetric heating and thermal relaxation by latent heat absorption. The pre-existence of nucleation sites limits the heat-up rates to 10<sup>6</sup> [K/s], and to the thermal bubble growth regime. This balance then yields a criterion for maximum achievable liquid superheat, expressed as a function of the ratio of heating rate to the density of existing vapor embryos. Exceeding this threshold triggers unwanted <em>explosive</em> boiling, characterized by intense vapor generation driven by homogeneous nucleation. The model’s dimensionless formulation allows for generalization to other liquids, beyond water and methanol examined here.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105581"},"PeriodicalIF":3.8,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836919","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 : 2025-12-13DOI: 10.1016/j.ijmultiphaseflow.2025.105580
Xin Li , Yanshen Li
Bubbles at the air–liquid interface are important for many natural and industrial processes. Factors influencing the lifetime of such surface bubbles have been investigated extensively, yet the impact of dissolved gas concentration remains unexplored. Here we investigate how the lifetime of surface bubbles in volatile liquids depends on the dissolved gas concentration. The bubble lifetime is found to decrease with the dissolved gas concentration. Larger microbubbles at increased gas concentration are found to trigger bubble bursting at earlier times. Combined with the thinning rate of the bubble cap thickness, a scaling law of the bubble lifetime is developed. The scaling is also found to be independent of factors like container type, liquid pool depth and bubble size. Our findings may provide new insight on surface bubble lifetime and foam stability.
{"title":"Influence of dissolved gas concentration on the lifetime of surface bubbles in volatile liquids","authors":"Xin Li , Yanshen Li","doi":"10.1016/j.ijmultiphaseflow.2025.105580","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105580","url":null,"abstract":"<div><div>Bubbles at the air–liquid interface are important for many natural and industrial processes. Factors influencing the lifetime of such surface bubbles have been investigated extensively, yet the impact of dissolved gas concentration remains unexplored. Here we investigate how the lifetime of surface bubbles in volatile liquids depends on the dissolved gas concentration. The bubble lifetime is found to decrease with the dissolved gas concentration. Larger microbubbles at increased gas concentration are found to trigger bubble bursting at earlier times. Combined with the thinning rate of the bubble cap thickness, a scaling law of the bubble lifetime is developed. The scaling is also found to be independent of factors like container type, liquid pool depth and bubble size. Our findings may provide new insight on surface bubble lifetime and foam stability.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105580"},"PeriodicalIF":3.8,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145836916","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 : 2025-12-06DOI: 10.1016/j.ijmultiphaseflow.2025.105568
Mauricio Mani Marinheiro , Gustavo Matana Aguiar , Roman William Morse , Gherhardt Ribatski , Matteo Bucci
This experimental investigation leverages high-speed shadowgraphy and infrared thermography to provide a phenomenological description of heat transfer and boiling crisis in the churn flow regime. In churn flow, intermittent cycles of overheating and cooling occur on the heated surface. The surface is cooled down by nucleating bubbles, liquid slugs, and backflow and descending liquid films. However, backflow and descending liquid films are not observed at high mass flow rates. The surface overheats when the liquid film in contact with the channel wall stagnates. Under high imposed heat fluxes, the stagnant film dries out, forming a high-temperature region that prevents liquid slugs and descending liquid films from effectively cooling the surface, thereby triggering a boiling crisis. Since the macroscale characteristics of the churn flow govern the onset of a boiling crisis, mass flux has a more dominant influence on the critical heat flux than surface wettability.
{"title":"Phenomenological characterization of heat transfer and boiling crisis in churn liquid-vapor flows using high-resolution diagnostics","authors":"Mauricio Mani Marinheiro , Gustavo Matana Aguiar , Roman William Morse , Gherhardt Ribatski , Matteo Bucci","doi":"10.1016/j.ijmultiphaseflow.2025.105568","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105568","url":null,"abstract":"<div><div>This experimental investigation leverages high-speed shadowgraphy and infrared thermography to provide a phenomenological description of heat transfer and boiling crisis in the churn flow regime. In churn flow, intermittent cycles of overheating and cooling occur on the heated surface. The surface is cooled down by nucleating bubbles, liquid slugs, and backflow and descending liquid films. However, backflow and descending liquid films are not observed at high mass flow rates. The surface overheats when the liquid film in contact with the channel wall stagnates. Under high imposed heat fluxes, the stagnant film dries out, forming a high-temperature region that prevents liquid slugs and descending liquid films from effectively cooling the surface, thereby triggering a boiling crisis. Since the macroscale characteristics of the churn flow govern the onset of a boiling crisis, mass flux has a more dominant influence on the critical heat flux than surface wettability.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105568"},"PeriodicalIF":3.8,"publicationDate":"2025-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733885","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 : 2025-12-05DOI: 10.1016/j.ijmultiphaseflow.2025.105565
Niloy Laskar , Asmita Bhaumik , Sali Snigdha , Mihir K. Das
Engineered surfaces are widely recognized for enhancing pool boiling heat transfer (PBHT), yet the role of bubble dynamics across different fluids on a common platform has not been fully explored. This study presents a comprehensive experimental investigation of the coupled effects of surface morphology and fluid thermophysical properties on bubble dynamics and PBHT performance. Bare, copper-coated, DLC-coated, and micro-structure tubes were tested with distilled water, acetone, and isopropanol under PBHT conditions. Bubble dynamics parameters, including departure diameter, frequency, and nucleation site density, were quantified to understand their role in PBHT performance. The findings reveal a consistent trend across all fluids, with engineered surfaces producing smaller bubbles that depart more rapidly and exhibit a higher active nucleation sites compared to conventional bare surfaces. Among the tested surfaces, micro-structure tubes delivered the highest HTC and the lowest wall superheat, followed by copper- and DLC-coated surfaces. Fluid properties also significantly influenced PBHT performance, with isopropanol initiating the earliest onset of nucleate boiling, while water exhibited a delayed onset. Despite larger bubbles, lower frequency, and fewer nucleation sites, distilled water achieved the highest HTC due to its high latent heat and thermal conductivity. Additionally, the peak HTC enhancements observed on micro-structure surfaces were 96 % for distilled water, 134 % for acetone, and 161 % for isopropanol compared to bare tubes. The study highlights that optimal PBHT performance is achieved through a synergistic combination of surface engineering and appropriate fluid selection. The results provide actionable insights for designing next-generation heat exchangers that can achieve superior thermal performance.
{"title":"Engineered surface-fluid interactions: bubble dynamics and heat transfer with different fluid thermophysical properties","authors":"Niloy Laskar , Asmita Bhaumik , Sali Snigdha , Mihir K. Das","doi":"10.1016/j.ijmultiphaseflow.2025.105565","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105565","url":null,"abstract":"<div><div>Engineered surfaces are widely recognized for enhancing pool boiling heat transfer (PBHT), yet the role of bubble dynamics across different fluids on a common platform has not been fully explored. This study presents a comprehensive experimental investigation of the coupled effects of surface morphology and fluid thermophysical properties on bubble dynamics and PBHT performance. Bare, copper-coated, DLC-coated, and micro-structure tubes were tested with distilled water, acetone, and isopropanol under PBHT conditions. Bubble dynamics parameters, including departure diameter, frequency, and nucleation site density, were quantified to understand their role in PBHT performance. The findings reveal a consistent trend across all fluids, with engineered surfaces producing smaller bubbles that depart more rapidly and exhibit a higher active nucleation sites compared to conventional bare surfaces. Among the tested surfaces, micro-structure tubes delivered the highest HTC and the lowest wall superheat, followed by copper- and DLC-coated surfaces. Fluid properties also significantly influenced PBHT performance, with isopropanol initiating the earliest onset of nucleate boiling, while water exhibited a delayed onset. Despite larger bubbles, lower frequency, and fewer nucleation sites, distilled water achieved the highest HTC due to its high latent heat and thermal conductivity. Additionally, the peak HTC enhancements observed on micro-structure surfaces were 96 % for distilled water, 134 % for acetone, and 161 % for isopropanol compared to bare tubes. The study highlights that optimal PBHT performance is achieved through a synergistic combination of surface engineering and appropriate fluid selection. The results provide actionable insights for designing next-generation heat exchangers that can achieve superior thermal performance.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105565"},"PeriodicalIF":3.8,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733815","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}
Cavitating flows are characterized by multi-phase and multi-scale features, with evolutionary processes involving coupled interactions between the convection evolution of macroscale vapor structures and the growth and motion of microbubbles. The quantitative information and intrinsic physical mechanism are poorly understood, due to limitations of traditional methods in quantitatively measuring the three-dimensional distribution of microbubbles within cavity structures. In the present work, an experimental study integrating high-speed imaging of macroscale cavity convection evolution and quantitative digital in-line holography (DIH) measurement of microbubbles is conducted to investigate multiscale characteristics of cavitating flows. Results demonstrate that cavitation morphology progresses through inception, sheet, and cloud stages with decreasing cavitation numbers, accompanied by gradual increases in maximum attached cavity length and significant growth in discrete bubble quantities. Mesoscale bubbles are predominantly distributed at vapor-liquid interfaces of macroscale cavities, surrounding shedding cloud cavities, and within wake regions of turbulent cavitating flows. Meanwhile, the Sauter mean diameter of microbubbles progressively decreases along the streamwise direction. As the cavitation number decreases, within the cavity-shedding region, shed cavities gradually manifest as large scale cavities, the time-averaged number density of discrete microbubbles first increases and then paradoxically decreases. In contrast, within the wake flow region, shed cavities undergo complete fragmentation into discrete bubbles, resulting in a persistent increase in detectable mesoscale discrete bubbles with decreasing cavitation number. Across all cavitation regimes and the holographic measurement zone, the number of discrete bubbles initially increased then decreased with increasing bubble diameter, with spectral peaks in bubble size distribution (BSD) at 30-40 μm. Turbulent flow structures significantly affect bubble dynamic evolution. Consequently, dual power-law scaling governs the microbubble size distribution, relative to the Hinze scale at approximately 55–65 μm. Sub-Hinze-scale bubbles follow a − 4/3 scaling exponent, whereas super-Hinze-scale bubbles obey a − 10/3 scaling law.
{"title":"Experimental study on multi-scale characteristics of cavitating flows with holographic imaging measurement","authors":"Beichen Tian, Yuntian Wang, Biao Huang, Chao Liu, Yue Wu","doi":"10.1016/j.ijmultiphaseflow.2025.105569","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105569","url":null,"abstract":"<div><div>Cavitating flows are characterized by multi-phase and multi-scale features, with evolutionary processes involving coupled interactions between the convection evolution of macroscale vapor structures and the growth and motion of microbubbles. The quantitative information and intrinsic physical mechanism are poorly understood, due to limitations of traditional methods in quantitatively measuring the three-dimensional distribution of microbubbles within cavity structures. In the present work, an experimental study integrating high-speed imaging of macroscale cavity convection evolution and quantitative digital in-line holography (DIH) measurement of microbubbles is conducted to investigate multiscale characteristics of cavitating flows. Results demonstrate that cavitation morphology progresses through inception, sheet, and cloud stages with decreasing cavitation numbers, accompanied by gradual increases in maximum attached cavity length and significant growth in discrete bubble quantities. Mesoscale bubbles are predominantly distributed at vapor-liquid interfaces of macroscale cavities, surrounding shedding cloud cavities, and within wake regions of turbulent cavitating flows. Meanwhile, the Sauter mean diameter of microbubbles progressively decreases along the streamwise direction. As the cavitation number decreases, within the cavity-shedding region, shed cavities gradually manifest as large scale cavities, the time-averaged number density of discrete microbubbles first increases and then paradoxically decreases. In contrast, within the wake flow region, shed cavities undergo complete fragmentation into discrete bubbles, resulting in a persistent increase in detectable mesoscale discrete bubbles with decreasing cavitation number. Across all cavitation regimes and the holographic measurement zone, the number of discrete bubbles initially increased then decreased with increasing bubble diameter, with spectral peaks in bubble size distribution (BSD) at 30-40 μm. Turbulent flow structures significantly affect bubble dynamic evolution. Consequently, dual power-law scaling governs the microbubble size distribution, relative to the Hinze scale at approximately 55–65 μm. Sub-Hinze-scale bubbles follow <em>a</em> − 4/3 scaling exponent, whereas super-Hinze-scale bubbles obey <em>a</em> − 10/3 scaling law.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105569"},"PeriodicalIF":3.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733816","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 : 2025-12-04DOI: 10.1016/j.ijmultiphaseflow.2025.105562
Hao-Pin Lien , Rafael Clemente-Mallada , Meghna Dhanji , Roberto Torelli , Lyle M. Pickett
Methanol is considered a promising alternative fuel for internal combustion engines (ICEs) due to its high-octane number, fast laminar flame speed, and elevated latent heat of vaporization, all of which support higher compression ratios and improved thermal efficiency. However, its substantial latent heat of vaporization also poses cold-start challenges, such as misfire and fuel film deposition. This study aims to investigate methanol spray morphology and spray-wall interaction using the Spray M injector from the Engine Combustion Network within a constant-pressure flow vessel. A recently developed unified numerical framework capable of modeling both flash and non-flash boiling sprays is validated against experimental liquid volume fraction data acquired via 3-D computed tomography. The results reveal that flash boiling significantly alters the spray morphology, leading to smaller droplets and spray collapse due to enhanced air-entrainment-induced turbulence. Quantitative agreement between experiments and simulations confirms this behavior. Coupled 0-D equilibrium and 3-D computational fluid dynamics analyses show that flash boiling accelerates evaporation and reduces fuel residence time, while non-flash conditions maintain a persistent liquid core more susceptible to wall wetting. Wall temperature diagnostics reveal that spray collapse alters heat transfer patterns by shifting cooling effects. Mixture fraction analysis indicates that evaporation is primarily governed by shear-layer turbulence, though deviations from adiabatic equilibrium mixing emerge under low-turbulence conditions. Finally, increasing fuel, ambient, and wall temperatures reduces wall wetting and film thickness, mitigating cold-start risks. These findings enhance the understanding of methanol sprays’ behavior and support its adoption as a viable, alternative fuel for ICEs.
{"title":"Free-spray characteristics and spray-wall interactions of methanol on a gasoline direct injector under flash-boiling and non-flash-boiling conditions","authors":"Hao-Pin Lien , Rafael Clemente-Mallada , Meghna Dhanji , Roberto Torelli , Lyle M. Pickett","doi":"10.1016/j.ijmultiphaseflow.2025.105562","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105562","url":null,"abstract":"<div><div>Methanol is considered a promising alternative fuel for internal combustion engines (ICEs) due to its high-octane number, fast laminar flame speed, and elevated latent heat of vaporization, all of which support higher compression ratios and improved thermal efficiency. However, its substantial latent heat of vaporization also poses cold-start challenges, such as misfire and fuel film deposition. This study aims to investigate methanol spray morphology and spray-wall interaction using the Spray M injector from the Engine Combustion Network within a constant-pressure flow vessel. A recently developed unified numerical framework capable of modeling both flash and non-flash boiling sprays is validated against experimental liquid volume fraction data acquired via 3-D computed tomography. The results reveal that flash boiling significantly alters the spray morphology, leading to smaller droplets and spray collapse due to enhanced air-entrainment-induced turbulence. Quantitative agreement between experiments and simulations confirms this behavior. Coupled 0-D equilibrium and 3-D computational fluid dynamics analyses show that flash boiling accelerates evaporation and reduces fuel residence time, while non-flash conditions maintain a persistent liquid core more susceptible to wall wetting. Wall temperature diagnostics reveal that spray collapse alters heat transfer patterns by shifting cooling effects. Mixture fraction analysis indicates that evaporation is primarily governed by shear-layer turbulence, though deviations from adiabatic equilibrium mixing emerge under low-turbulence conditions. Finally, increasing fuel, ambient, and wall temperatures reduces wall wetting and film thickness, mitigating cold-start risks. These findings enhance the understanding of methanol sprays’ behavior and support its adoption as a viable, alternative fuel for ICEs.</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105562"},"PeriodicalIF":3.8,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733814","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 : 2025-12-03DOI: 10.1016/j.ijmultiphaseflow.2025.105566
Yating Wang , Yohei Sato
Three-dimensional direct numerical simulation (DNS) was performed to investigate mass transfer at high Schmidt numbers, focusing on a rising, dissolving gas bubble in a liquid. The objectives are (i) to develop a numerical method based on the volume-of-fluid (VOF) approach for simulating a dissolving gas bubble and (ii) to determine the mesh resolution required to accurately capture the underlying physical phenomena. A sharp-interface phase-change model is employed, in which the species concentration gradient at the gas–liquid interface is calculated using an irregular stencil that accounts for the local interface geometry. The method was first validated against benchmark cases at low Schmidt numbers, and then applied to a 9 mm CO₂ bubble rising in quiescent water. The simulation was performed on grids ranging from 128³ to 2048³, with the finest case using 8192 cores over 15 days. The total simulated physical time was 1.2 s, including the grid-refinement stages up to the finest resolution. The grid-dependence study indicates that the evaluated grid resolutions remain outside the fully asymptotic regime; nevertheless, the 2048³ grid result underestimates the Sherwood number by only about 7 % relative to the empirical correlation. The CO₂ concentration isosurface from the 2048³ case reveals a complex wake structure with elongated filaments and rolled-up sheets, indicative of shear-induced vortices and strong entrainment. The grid-dependence study suggests that even finer grids (e.g., 4096³) may be necessary, highlighting the need for future exascale computing to fully resolve mass transfer at a high Schmidt number (∼530).
{"title":"Direct numerical simulation of a rising CO2 bubble dissolving in quiescent water at high Schmidt number","authors":"Yating Wang , Yohei Sato","doi":"10.1016/j.ijmultiphaseflow.2025.105566","DOIUrl":"10.1016/j.ijmultiphaseflow.2025.105566","url":null,"abstract":"<div><div>Three-dimensional direct numerical simulation (DNS) was performed to investigate mass transfer at high Schmidt numbers, focusing on a rising, dissolving gas bubble in a liquid. The objectives are (i) to develop a numerical method based on the volume-of-fluid (VOF) approach for simulating a dissolving gas bubble and (ii) to determine the mesh resolution required to accurately capture the underlying physical phenomena. A sharp-interface phase-change model is employed, in which the species concentration gradient at the gas–liquid interface is calculated using an irregular stencil that accounts for the local interface geometry. The method was first validated against benchmark cases at low Schmidt numbers, and then applied to a 9 mm CO₂ bubble rising in quiescent water. The simulation was performed on grids ranging from 128³ to 2048³, with the finest case using 8192 cores over 15 days. The total simulated physical time was 1.2 s, including the grid-refinement stages up to the finest resolution. The grid-dependence study indicates that the evaluated grid resolutions remain outside the fully asymptotic regime; nevertheless, the 2048³ grid result underestimates the Sherwood number by only about 7 % relative to the empirical correlation. The CO₂ concentration isosurface from the 2048³ case reveals a complex wake structure with elongated filaments and rolled-up sheets, indicative of shear-induced vortices and strong entrainment. The grid-dependence study suggests that even finer grids (e.g., 4096³) may be necessary, highlighting the need for future exascale computing to fully resolve mass transfer at a high Schmidt number (∼530).</div></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":"196 ","pages":"Article 105566"},"PeriodicalIF":3.8,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787064","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 : 2025-11-28DOI: 10.1016/j.ijmultiphaseflow.2025.105556
Davide Picchi , Valentina Ciriello
The success of CCS technologies relies on the effectiveness and safety of the infrastructure for the transport of carbon dioxide in pressurized pipelines. Unlike natural gas networks, long-distance carbon dioxide transport presents critical design challenges, such as the need for repressurization to prevent two-phase flow conditions and potential freezing. To address this, we propose a comprehensive assessment framework that combines high-fidelity numerical simulations with a stochastic approach based on the Polynomial Chaos Expansion (PCE). Specifically, we employ the Homogeneous Equilibrium Model (HEM) to compute key quantities of interest (QoIs) — related to pressure drop and the maximum distance before repressurization is required — under a design scenario inspired by the Cortez pipeline (Colorado, USA). Based on PCE surrogates, we then perform global sensitivity analyses and uncertainty quantification to evaluate how variability in inlet parameters influences these QoIs, mapping results across a range of realistic operating conditions. Our results provide critical insight into the risks connected with CO2 transport and support the optimal design of operating conditions. Moreover, the proposed methodology is general and easily applicable to other CO2 transport facilities.
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