Pub Date : 2024-04-15DOI: 10.1016/j.ijmultiphaseflow.2024.104824
Felix Schreiner, Tobias Gianfelice, Romuald Skoda
A model for the approximation of cavitation-induced air release in three-dimensional flow simulations is proposed. A cavitating orifice flow is investigated. It is assumed that vapor vanishes in the proximity of the orifice, and bubbles further downstream consist essentially of air. The model is based on a homogeneous mixture assumption and comprises one main parameter, which needs to be adjusted to the experimentally measured degassing fraction. Experimental validation is based on transmission light images downstream of the orifice. In the proximity of the orifice, the inclusion of air release in the CFD simulation yields a better agreement to experimentally measured cavitation intensity than the consideration of pure vapor only. It is concluded that a considerably larger amount of air is released than is dissolved in the evaporated amount of liquid. The simulation results suggest that the released air mass corresponds to about 1% of the evaporated liquid mass. These observations may be a good basis for purposeful future experiments, which are indispensable for the development of a more predictive approach of cavitation-induced air release in 3D CFD methods.
{"title":"Three-dimensional simulation of an orifice flow with cavitation-induced air release","authors":"Felix Schreiner, Tobias Gianfelice, Romuald Skoda","doi":"10.1016/j.ijmultiphaseflow.2024.104824","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104824","url":null,"abstract":"<div><p>A model for the approximation of cavitation-induced air release in three-dimensional flow simulations is proposed. A cavitating orifice flow is investigated. It is assumed that vapor vanishes in the proximity of the orifice, and bubbles further downstream consist essentially of air. The model is based on a homogeneous mixture assumption and comprises one main parameter, which needs to be adjusted to the experimentally measured degassing fraction. Experimental validation is based on transmission light images downstream of the orifice. In the proximity of the orifice, the inclusion of air release in the CFD simulation yields a better agreement to experimentally measured cavitation intensity than the consideration of pure vapor only. It is concluded that a considerably larger amount of air is released than is dissolved in the evaporated amount of liquid. The simulation results suggest that the released air mass corresponds to about 1% of the evaporated liquid mass. These observations may be a good basis for purposeful future experiments, which are indispensable for the development of a more predictive approach of cavitation-induced air release in 3D CFD methods.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301932224001034/pdfft?md5=21f39d793221fc434069e081ca1bcc4f&pid=1-s2.0-S0301932224001034-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140633146","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 : 2024-04-13DOI: 10.1016/j.ijmultiphaseflow.2024.104825
Daniely A. das Neves , Adriano T. Fabro , Saon C. Vieira , Juliana R. Cenzi , Marcelo S. Castro
Two-phase flow is typically found in several industrial applications, such as in the production and transportation of oil and gas in the petrochemical industry, in the catalytic cracking and microreactors in the chemical industry, and in nuclear reactor cooling pumps. Measurement of two-phase flow features is usually necessary and has been done in several ways, including pressure probes, resistive sensors, gamma-ray, wire-mesh sensor and many others. However, these are either intrusive or invasive techniques, which might be of challenging application in industrial environments, or rely on a hazardous radioactive source. Vibration-based measurement of two-phase flow in pipes stands out as a non-invasive/non-intrusive approach and, consequently, multiphase-flow induced vibration in pipes has receiving increasing attention in recent years. In this work, the dynamic behaviour of a horizontal tube conveying an intermittent two-phase gas-liquid flow is investigated based on indirect approaches. The phenomenon of fluid–structure coupling is investigated using acceleration and pressure measurement. Moreover, the bubble size distribution is estimated from high-speed camera images and a deep learning model for image segmentation, along with its spectral content and time modulation. Focus is given at frequency bands around the cut-on frequencies of the circumferential wave modes of the pipe. An approach based on the estimation of frequency response function of the pressure and vibration at the liquid slug and elongated bubble is proposed, such that the coherence function can be used as quantitative measure of the coupling. Two experimental conditions with intermittent flow are investigated as representative cases. It is shown that there is a great vibration amplification at the cut-on frequencies of circumferential wave modes in pipes due to the corresponding structural wave and pressure coupling. Consequently, the frequency of passage of bubble can be estimated from the demodulation of vibration response filtered at the cut-on modes. The experimental results pave the way for innovative vibration-based measurement approaches.
{"title":"An experimental investigation on the fluid–structure coupling in horizontal pipes conveying two-phase intermittent flow","authors":"Daniely A. das Neves , Adriano T. Fabro , Saon C. Vieira , Juliana R. Cenzi , Marcelo S. Castro","doi":"10.1016/j.ijmultiphaseflow.2024.104825","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104825","url":null,"abstract":"<div><p>Two-phase flow is typically found in several industrial applications, such as in the production and transportation of oil and gas in the petrochemical industry, in the catalytic cracking and microreactors in the chemical industry, and in nuclear reactor cooling pumps. Measurement of two-phase flow features is usually necessary and has been done in several ways, including pressure probes, resistive sensors, gamma-ray, wire-mesh sensor and many others. However, these are either intrusive or invasive techniques, which might be of challenging application in industrial environments, or rely on a hazardous radioactive source. Vibration-based measurement of two-phase flow in pipes stands out as a non-invasive/non-intrusive approach and, consequently, multiphase-flow induced vibration in pipes has receiving increasing attention in recent years. In this work, the dynamic behaviour of a horizontal tube conveying an intermittent two-phase gas-liquid flow is investigated based on indirect approaches. The phenomenon of fluid–structure coupling is investigated using acceleration and pressure measurement. Moreover, the bubble size distribution is estimated from high-speed camera images and a deep learning model for image segmentation, along with its spectral content and time modulation. Focus is given at frequency bands around the cut-on frequencies of the circumferential wave modes of the pipe. An approach based on the estimation of frequency response function of the pressure and vibration at the liquid slug and elongated bubble is proposed, such that the coherence function can be used as quantitative measure of the coupling. Two experimental conditions with intermittent flow are investigated as representative cases. It is shown that there is a great vibration amplification at the cut-on frequencies of circumferential wave modes in pipes due to the corresponding structural wave and pressure coupling. Consequently, the frequency of passage of bubble can be estimated from the demodulation of vibration response filtered at the cut-on modes. The experimental results pave the way for innovative vibration-based measurement approaches.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140604778","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}
We developed a Lagrangian sensor system capable of wirelessly measuring the 3D motions of objects and applied it to examine the floating and sinking behaviors in a gas–solid fluidized bed. The system consisted of a sensor particle, comprising a 9-axis sensor and a wireless module integrated into a spherical outer shell, and three pairs of magnetic coils. By utilizing this system, we can non-invasively measure the 3D motions of objects, which cannot be observed from the outside. In this study, we examined the motions of objects with various densities in the gas–solid fluidized bed. We found the similarity and dissimilarity between the float–sink motions of objects in fluidized beds and those in liquids. The experimental results revealed that the vertical motion of an object in the fluidized bed depends on its density and can be categorized into two distinct states: floating near the surface or settling down at the bottom. However, within a specific range of object densities close to the apparent density of the fluidized bed, the object exhibited complicated motions in the bed. In such cases, slight density variations induced unpredictable changes between the floating and sinking states. The results also suggested that the settling velocity of the objects in the fluidized bed varies with their vertical positions in the bed.
{"title":"Three-dimensional wireless measurement of float–sink object motions in a gas–solid fluidized bed","authors":"Tomoki Katayama , Yoko Otsuka , Shiori Saito , Shusaku Harada , Takuya Tsuji , Jun Oshitani","doi":"10.1016/j.ijmultiphaseflow.2024.104817","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104817","url":null,"abstract":"<div><p>We developed a Lagrangian sensor system capable of wirelessly measuring the 3D motions of objects and applied it to examine the floating and sinking behaviors in a gas–solid fluidized bed. The system consisted of a sensor particle, comprising a 9-axis sensor and a wireless module integrated into a spherical outer shell, and three pairs of magnetic coils. By utilizing this system, we can non-invasively measure the 3D motions of objects, which cannot be observed from the outside. In this study, we examined the motions of objects with various densities in the gas–solid fluidized bed. We found the similarity and dissimilarity between the float–sink motions of objects in fluidized beds and those in liquids. The experimental results revealed that the vertical motion of an object in the fluidized bed depends on its density and can be categorized into two distinct states: floating near the surface or settling down at the bottom. However, within a specific range of object densities close to the apparent density of the fluidized bed, the object exhibited complicated motions in the bed. In such cases, slight density variations induced unpredictable changes between the floating and sinking states. The results also suggested that the settling velocity of the objects in the fluidized bed varies with their vertical positions in the bed.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140649166","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 : 2024-04-10DOI: 10.1016/j.ijmultiphaseflow.2024.104820
Mingzhe Zhou , Ziyang Wang , Huaiyu Cheng , Bin Ji , Yantao Cao
Cavitation erosion is a long-standing issue, which plays a pivotal role in the material damage of much hydraulic machinery. However, despite abundant numerical research on cavitation erosion assessment, bubble dynamics has been commonly overlooked. Consequently, we develop an improved cavitation erosion model based on energy conversion and assess an ALE15 hydrofoil surface by its incorporation into a multiscale approach. Our erosion model stands out in considering the bubble behaviors throughout its entire lifespan to eliminate the influence of bubble oscillation on cavitation erosion. Using the bubble information in the well reproduced cavitating flow, we evaluate both the cumulative and instantaneous cavitation erosion, and the results show satisfactory agreement with the experimental pattern. Our findings demonstrate that frequent vapor-liquid alternations, induced by the collaborative effects of upstream pressure gradients and main flow, increase the potential for erosion risk at the hydrofoil leading edge. Downstream erosion primarily results from secondary shedding and the collapse of U-shaped cavities’ legs. By contrast, the acoustic energy emitted by the shedding cavities traveling farther and upwards away from the hydrofoil leads to negligible erosion on the surface.
气蚀是一个由来已久的问题,在许多液压机械的材料损坏中起着举足轻重的作用。然而,尽管有关气蚀评估的数值研究非常丰富,但气泡动力学却普遍被忽视。因此,我们开发了一种基于能量转换的改进型气蚀模型,并将其纳入多尺度方法,对 ALE15 水翼表面进行评估。我们的侵蚀模型突出地考虑了气泡在整个生命周期中的行为,消除了气泡振荡对空化侵蚀的影响。我们利用气泡在重现性良好的空化流中的信息,评估了累积空化侵蚀和瞬时空化侵蚀,结果显示与实验模式的一致性令人满意。我们的研究结果表明,在上游压力梯度和主流的共同作用下,频繁的汽液交替增加了水翼前缘潜在的侵蚀风险。下游侵蚀主要源于二次脱落和 U 形空腔支脚的坍塌。相比之下,脱落的空腔所发出的声能在远离水翼后向上传播,对表面的侵蚀可以忽略不计。
{"title":"Assessment of cavitation erosion on an asymmetric hydrofoil based on energy conversion via a multiscale approach","authors":"Mingzhe Zhou , Ziyang Wang , Huaiyu Cheng , Bin Ji , Yantao Cao","doi":"10.1016/j.ijmultiphaseflow.2024.104820","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104820","url":null,"abstract":"<div><p>Cavitation erosion is a long-standing issue, which plays a pivotal role in the material damage of much hydraulic machinery. However, despite abundant numerical research on cavitation erosion assessment, bubble dynamics has been commonly overlooked. Consequently, we develop an improved cavitation erosion model based on energy conversion and assess an ALE15 hydrofoil surface by its incorporation into a multiscale approach. Our erosion model stands out in considering the bubble behaviors throughout its entire lifespan to eliminate the influence of bubble oscillation on cavitation erosion. Using the bubble information in the well reproduced cavitating flow, we evaluate both the cumulative and instantaneous cavitation erosion, and the results show satisfactory agreement with the experimental pattern. Our findings demonstrate that frequent vapor-liquid alternations, induced by the collaborative effects of upstream pressure gradients and main flow, increase the potential for erosion risk at the hydrofoil leading edge. Downstream erosion primarily results from secondary shedding and the collapse of U-shaped cavities’ legs. By contrast, the acoustic energy emitted by the shedding cavities traveling farther and upwards away from the hydrofoil leads to negligible erosion on the surface.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140622492","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 : 2024-04-09DOI: 10.1016/j.ijmultiphaseflow.2024.104822
Hendrik Reese , Claus-Dieter Ohl , Juan Manuel Rosselló
We study the physical mechanisms behind the ejection of a liquid jet from a curved free surface, specifically a free-falling water drop. The jet is produced after a spherical shock wave emitted from a micro-explosion created by a focused laser pulse is refocused on the opposite side of its source. The analysis of high-speed videos of the liquid jet formation revealed that it originates from a larger, prolate cavitation bubble created by the strong tension produced after the reflection of the original wave on the air–liquid interface. The shock wave propagation and jet formation are modeled separately with finite volume simulations in OpenFOAM. Initially we study the pressure evolution inside the drop by comparing the numerical simulations with the distribution of bubbles nucleated after the passage of the negative pressure wave. The jet formation dynamics is explained by comparing the experiments with numerical results. The jet velocity is higher if the laser focus is closer to the drop surface.
{"title":"Cavitation and jetting from shock wave refocusing near convex liquid surfaces","authors":"Hendrik Reese , Claus-Dieter Ohl , Juan Manuel Rosselló","doi":"10.1016/j.ijmultiphaseflow.2024.104822","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104822","url":null,"abstract":"<div><p>We study the physical mechanisms behind the ejection of a liquid jet from a curved free surface, specifically a free-falling water drop. The jet is produced after a spherical shock wave emitted from a micro-explosion created by a focused laser pulse is refocused on the opposite side of its source. The analysis of high-speed videos of the liquid jet formation revealed that it originates from a larger, prolate cavitation bubble created by the strong tension produced after the reflection of the original wave on the air–liquid interface. The shock wave propagation and jet formation are modeled separately with finite volume simulations in OpenFOAM. Initially we study the pressure evolution inside the drop by comparing the numerical simulations with the distribution of bubbles nucleated after the passage of the negative pressure wave. The jet formation dynamics is explained by comparing the experiments with numerical results. The jet velocity is higher if the laser focus is closer to the drop surface.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301932224001022/pdfft?md5=b401bd03c5309675722f9960d9034244&pid=1-s2.0-S0301932224001022-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140540290","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 : 2024-04-04DOI: 10.1016/j.ijmultiphaseflow.2024.104821
Zhaolong Ge , Xiaotian Wang , Wenchuan Liu , Junhao Yan , Qi Liu , Chia-Fon Lee
Cavitation and flash boiling may coexist concurrently during depressurization conditions, and the interplay between cavitation and flash boiling remains incompletely understood. In this study, experiments and numerical studies were conducted to investigate cavitation evolution and its effects on flash boiling, and the jet width near the nozzle exit was extracted for quantitative analysis. The contributions of cavitation nucleation process to jet width were captured via a high-speed camera using the diffused back illumination method, with a focus on the near-field jet width. Simulation results and theoretical analysis were used to correlate the cavitation behavior and jet width. A correction in the exponent term in the nucleation barrier was achieved to account for the lower formation energy required for nucleation due to the presence of cavitation. Besides providing the nucleation sites, cavitation intensities and their fluctuation also contributed to the variations in jet width. Thermal effects on cavitation evolution began to manifest with the jet evolution. The modified cavitation number was proposed to account for the effects of injection pressure under non-flash and flashing stages. The deviation in the choked state induced by injection was not sufficient to account for the linear decrease in jet width, and thus a residence time term was introduced. Another pressure term was also introduced to account for the complicated role of ambient pressure in jet expansion. A comprehensive correlation containing the correction in nucleation barrier and aerodynamic instabilities was finally proposed and validated, providing guidance for the modulation of flash boiling based on cavitation evolution.
{"title":"The width correlation of flash boiling jet considering cavitation effects and aerodynamic instabilities","authors":"Zhaolong Ge , Xiaotian Wang , Wenchuan Liu , Junhao Yan , Qi Liu , Chia-Fon Lee","doi":"10.1016/j.ijmultiphaseflow.2024.104821","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104821","url":null,"abstract":"<div><p>Cavitation and flash boiling may coexist concurrently during depressurization conditions, and the interplay between cavitation and flash boiling remains incompletely understood. In this study, experiments and numerical studies were conducted to investigate cavitation evolution and its effects on flash boiling, and the jet width near the nozzle exit was extracted for quantitative analysis. The contributions of cavitation nucleation process to jet width were captured via a high-speed camera using the diffused back illumination method, with a focus on the near-field jet width. Simulation results and theoretical analysis were used to correlate the cavitation behavior and jet width. A correction in the exponent term in the nucleation barrier was achieved to account for the lower formation energy required for nucleation due to the presence of cavitation. Besides providing the nucleation sites, cavitation intensities and their fluctuation also contributed to the variations in jet width. Thermal effects on cavitation evolution began to manifest with the jet evolution. The modified cavitation number was proposed to account for the effects of injection pressure under non-flash and flashing stages. The deviation in the choked state induced by injection was not sufficient to account for the linear decrease in jet width, and thus a residence time term was introduced. Another pressure term was also introduced to account for the complicated role of ambient pressure in jet expansion. A comprehensive correlation containing the correction in nucleation barrier and aerodynamic instabilities was finally proposed and validated, providing guidance for the modulation of flash boiling based on cavitation evolution.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140535599","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 : 2024-04-01DOI: 10.1016/j.ijmultiphaseflow.2024.104815
Berend van Wachem, Hani Elmestikawy, Victor Chéron
In this work, we derive novel hydrodynamic force models to describe the interaction of a flow with particles in an assembly when only an averaged resolution of the flow is available. These force models are able to predict the average drag on the particle assembly, as well as the deviations from the average drag force and the lift force for each individual particle in the assembly. To achieve this, PR-DNS of various particle assemblies and flow regimes are carried out, varying the particle volume fraction up to 0.6, and the mean particle flow Reynolds number up to 300. To characterize the structure of the particles in the assembly, a Voronoi tessellation is carried out, and a number of scalars, vectors and tensors are defined based upon this tessellation. The microstructure informed hydrodynamic force models are based on symbolic regressions of these quantities derived from the Voronoi tessellation, the global particle volume fraction of the particle assembly and the flow regime represented by the Reynolds number, and the forces on the individual particles in the assembly.
The resulting hydrodynamic force models are single expressions and can be directly employed in a Lagrangian particle tracking (LPT) or computational fluid dynamics/discrete element model (CFD/DEM) framework. By comparing the results of the newly proposed hydrodynamic force models with an averaged force model, as is usually adopted in Lagrangian particle tracking simulations, we show that, potentially, a significant increase in accuracy can be achieved, with only a relatively small increase in computational cost, compared to the cost of the CFD/DEM simulation.
{"title":"Microstructure-based prediction of hydrodynamic forces in stationary particle assemblies","authors":"Berend van Wachem, Hani Elmestikawy, Victor Chéron","doi":"10.1016/j.ijmultiphaseflow.2024.104815","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104815","url":null,"abstract":"<div><p>In this work, we derive novel hydrodynamic force models to describe the interaction of a flow with particles in an assembly when only an averaged resolution of the flow is available. These force models are able to predict the average drag on the particle assembly, as well as the deviations from the average drag force and the lift force for each individual particle in the assembly. To achieve this, PR-DNS of various particle assemblies and flow regimes are carried out, varying the particle volume fraction up to 0.6, and the mean particle flow Reynolds number up to 300. To characterize the structure of the particles in the assembly, a Voronoi tessellation is carried out, and a number of scalars, vectors and tensors are defined based upon this tessellation. The microstructure informed hydrodynamic force models are based on symbolic regressions of these quantities derived from the Voronoi tessellation, the global particle volume fraction of the particle assembly and the flow regime represented by the Reynolds number, and the forces on the individual particles in the assembly.</p><p>The resulting hydrodynamic force models are single expressions and can be directly employed in a Lagrangian particle tracking (LPT) or computational fluid dynamics/discrete element model (CFD/DEM) framework. By comparing the results of the newly proposed hydrodynamic force models with an averaged force model, as is usually adopted in Lagrangian particle tracking simulations, we show that, potentially, a significant increase in accuracy can be achieved, with only a relatively small increase in computational cost, compared to the cost of the CFD/DEM simulation.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0301932224000958/pdfft?md5=6bcc0ea42e85666cb4b306cda2bb3a65&pid=1-s2.0-S0301932224000958-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140347883","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 : 2024-03-29DOI: 10.1016/j.ijmultiphaseflow.2024.104816
Ruoqing Gao (高若青) , Cheng Liu (刘成) , Yiding Hu (胡一丁) , Changhong Hu (胡长洪)
In this study, numerical simulations of bubbly flows in an infinitely long vertical channel were performed. Generally, the upper and lower boundaries of such channels are simplified as periodic boundary conditions. Unlike horizontal channel flows, the presence of gravity in the streamwise direction complicates the establishment of periodic boundary conditions. Therefore, a specialized treatment is required to prevent fluid acceleration. Here, we developed a novel treatment for the imposition of periodic boundaries and proposed a new microbubble model to consider the surface tension effect of microbubbles. To detect each bubble in the flow field, we implemented a bubble identification algorithm, which facilitates a thorough statistical analysis of bubble number, size, and spatial distribution. Validation tests were conducted, and good agreement was achieved between our results and reference data. We also confirmed that the results obtained with periodic boundaries are consistent with those achieved without them. Finally, we simulated the evolution of rising bubble swarms in a quiescent liquid. The method presented here contributes to the numerical simulations of bubbly flows in industrial systems, including oil-gas transportation, bubble columns, and nuclear reactors.
{"title":"Numerical simulations of bubbly flows in a vertical periodic channel","authors":"Ruoqing Gao (高若青) , Cheng Liu (刘成) , Yiding Hu (胡一丁) , Changhong Hu (胡长洪)","doi":"10.1016/j.ijmultiphaseflow.2024.104816","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104816","url":null,"abstract":"<div><p>In this study, numerical simulations of bubbly flows in an infinitely long vertical channel were performed. Generally, the upper and lower boundaries of such channels are simplified as periodic boundary conditions. Unlike horizontal channel flows, the presence of gravity in the streamwise direction complicates the establishment of periodic boundary conditions. Therefore, a specialized treatment is required to prevent fluid acceleration. Here, we developed a novel treatment for the imposition of periodic boundaries and proposed a new microbubble model to consider the surface tension effect of microbubbles. To detect each bubble in the flow field, we implemented a bubble identification algorithm, which facilitates a thorough statistical analysis of bubble number, size, and spatial distribution. Validation tests were conducted, and good agreement was achieved between our results and reference data. We also confirmed that the results obtained with periodic boundaries are consistent with those achieved without them. Finally, we simulated the evolution of rising bubble swarms in a quiescent liquid. The method presented here contributes to the numerical simulations of bubbly flows in industrial systems, including oil-gas transportation, bubble columns, and nuclear reactors.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140350266","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 : 2024-03-28DOI: 10.1016/j.ijmultiphaseflow.2024.104819
Jinyi Zhang , Baoshan Jia , Fangwei Han , Jingxue Yan , Deji Jing , Ruilin Li
The removal of respirable coal dust particles has been the focus of domestic and foreign research, and the spray dust suppression technology has been adopted for the prevention and control process; it is based on the mechanism whereby liquid droplets impact dust particles. To further study the wetting properties of microdroplets impacting respirable coal dust particles based on kinetics, this study focused on the droplet morphology, and mathematical and physical models of a microdroplet impacting a respirable coal dust particle were established to explore the variation laws of the droplet spreading and wetting under central and non-central impacts, for which the CLSVOF numerical simulation approach was adopted. The results showed the occurrence of gas retention at the phase interface, which affected the droplet wetting characteristics on the coal dust surface, after the contact between the liquid and dust particles. The influence of the impact velocity, particle size ratio, contact angle, and offset distance on the droplet spreading behavior was investigated by comparative analysis of 12 working conditions with different parameters. The droplets can completely wrap the coal dust particles under only one working condition parameter (V = 5m/s,Φ = 2,θ = 90°,L = 0 μm). The microdroplets are extremely difficult to wet respirable coal dust particles and the spreading behavior of the final droplet could be divided into three states: static adsorption, complete encapsulation and permanent escape. Our results can help better understand the wetting relationship between microdroplets and respirable coal dust particles, serving as a basis for dust prevention and control.
{"title":"Kinetics-based wetting properties of microdroplets impacting respirable coal dust particles","authors":"Jinyi Zhang , Baoshan Jia , Fangwei Han , Jingxue Yan , Deji Jing , Ruilin Li","doi":"10.1016/j.ijmultiphaseflow.2024.104819","DOIUrl":"https://doi.org/10.1016/j.ijmultiphaseflow.2024.104819","url":null,"abstract":"<div><p>The removal of respirable coal dust particles has been the focus of domestic and foreign research, and the spray dust suppression technology has been adopted for the prevention and control process; it is based on the mechanism whereby liquid droplets impact dust particles. To further study the wetting properties of microdroplets impacting respirable coal dust particles based on kinetics, this study focused on the droplet morphology, and mathematical and physical models of a microdroplet impacting a respirable coal dust particle were established to explore the variation laws of the droplet spreading and wetting under central and non-central impacts, for which the CLSVOF numerical simulation approach was adopted. The results showed the occurrence of gas retention at the phase interface, which affected the droplet wetting characteristics on the coal dust surface, after the contact between the liquid and dust particles. The influence of the impact velocity, particle size ratio, contact angle, and offset distance on the droplet spreading behavior was investigated by comparative analysis of 12 working conditions with different parameters. The droplets can completely wrap the coal dust particles under only one working condition parameter (<em>V</em> = 5m/s,Φ = 2,<em>θ</em> = 90°,<em>L</em> = 0 μm). The microdroplets are extremely difficult to wet respirable coal dust particles and the spreading behavior of the final droplet could be divided into three states: static adsorption, complete encapsulation and permanent escape. Our results can help better understand the wetting relationship between microdroplets and respirable coal dust particles, serving as a basis for dust prevention and control.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140345224","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 : 2024-03-28DOI: 10.1016/j.ijmultiphaseflow.2024.104814
Venkata Krisshna, Mark Owkes
Electrostatic rotary bell atomizers are commonly used in several engineering applications, including the automobile industry. A high-speed rotating nozzle operating in a strong background electric field atomizes paint into charged droplets that range from a few micrometers to tens of micrometers in diameter. The atomization process directly determines the droplet size and droplet charge distributions which subsequently control the transfer efficiency and the surface finish quality. We have previously developed a tool to perform high fidelity simulations of near-bell atomization with electrohydrodynamic effects. In this work, we perform simulations employed with a droplet ancestry extraction tool to analyze previously inaccessible information and understand the physical processes driving atomization. We find that the electric field accelerates breakup processes and enhances secondary atomization. The total number of droplets, the ratio of secondary to primary droplets, and the ratio of coalescence to breakup activity are all much higher when operating in an electric field. We analyze the droplet velocity, local Weber number and charge density statistics to understand the complex physics in electrically assisted breakup. The results of the study have helped us gain insights into the physics of atomization in electrostatic rotary sprays.
{"title":"Investigating atomization characteristics in an electrostatic rotary bell atomizer","authors":"Venkata Krisshna, Mark Owkes","doi":"10.1016/j.ijmultiphaseflow.2024.104814","DOIUrl":"10.1016/j.ijmultiphaseflow.2024.104814","url":null,"abstract":"<div><p>Electrostatic rotary bell atomizers are commonly used in several engineering applications, including the automobile industry. A high-speed rotating nozzle operating in a strong background electric field atomizes paint into charged droplets that range from a few micrometers to tens of micrometers in diameter. The atomization process directly determines the droplet size and droplet charge distributions which subsequently control the transfer efficiency and the surface finish quality. We have previously developed a tool to perform high fidelity simulations of near-bell atomization with electrohydrodynamic effects. In this work, we perform simulations employed with a droplet ancestry extraction tool to analyze previously inaccessible information and understand the physical processes driving atomization. We find that the electric field accelerates breakup processes and enhances secondary atomization. The total number of droplets, the ratio of secondary to primary droplets, and the ratio of coalescence to breakup activity are all much higher when operating in an electric field. We analyze the droplet velocity, local Weber number and charge density statistics to understand the complex physics in electrically assisted breakup. The results of the study have helped us gain insights into the physics of atomization in electrostatic rotary sprays.</p></div>","PeriodicalId":339,"journal":{"name":"International Journal of Multiphase Flow","volume":null,"pages":null},"PeriodicalIF":3.8,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140400802","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}