Pasquale Borriello, E. Frosina, Pierpaolo Lucchesi, A. Senatore
This research conducts a comprehensive comparative analysis of simulation methodologies for spindle pumps, with a specific focus on steady-state CFD, transient-CFD, and lumped-parameter approaches. Spindle pumps, renowned for their reliability, efficiency, and low noise emission, play a pivotal role in Thermal Management for Battery Electric Vehicles, aligning with the automotive industry’s commitment to reducing pollutants and CO2 emissions. The study is motivated by the critical need to curtail energy consumption during on-the-road operations, particularly as the automotive industry strives for enhanced efficiency. While centrifugal pumps are commonly employed for such applications, their efficiency is highly contingent on rotational speed, leading to energy wastage in real-world scenarios despite high efficiency at the design point. Consequently, the adoption of precisely designed spindle pumps for thermal management systems emerges as a viable solution to meet evolving industry needs. Recognizing the profound impact of simulation tools on the design and optimization phases for pump manufacturers, this research emphasizes the significance of fast and accurate simulation tools. Transient-CFD emerges as a powerful Tool, enabling real-time monitoring of various performance indicators, while steady-CFD, with minimal simplifications, adeptly captures pressure distribution and machine leakages. Lumped-parameter approaches, though requiring effort in simulation setup and simplifying input geometry, offer rapid computational times and comprehensive predictions, including leakages, Torque, cavitation, and pressure ripple. Breaking new ground, this paper presents, for the first time in the literature, accurate simulation models for the same reference machine using the aforementioned methodologies. The results were rigorously validated against experiments spanning a wide range of pump speeds and pressure drops. The discussion encompasses predicted flow, Torque, cavitation, and pressure ripple, offering valuable insights into the strengths and limitations of each methodology.
{"title":"Comparative Analysis of Simulation Methodologies for Spindle Pumps","authors":"Pasquale Borriello, E. Frosina, Pierpaolo Lucchesi, A. Senatore","doi":"10.3390/fluids9020044","DOIUrl":"https://doi.org/10.3390/fluids9020044","url":null,"abstract":"This research conducts a comprehensive comparative analysis of simulation methodologies for spindle pumps, with a specific focus on steady-state CFD, transient-CFD, and lumped-parameter approaches. Spindle pumps, renowned for their reliability, efficiency, and low noise emission, play a pivotal role in Thermal Management for Battery Electric Vehicles, aligning with the automotive industry’s commitment to reducing pollutants and CO2 emissions. The study is motivated by the critical need to curtail energy consumption during on-the-road operations, particularly as the automotive industry strives for enhanced efficiency. While centrifugal pumps are commonly employed for such applications, their efficiency is highly contingent on rotational speed, leading to energy wastage in real-world scenarios despite high efficiency at the design point. Consequently, the adoption of precisely designed spindle pumps for thermal management systems emerges as a viable solution to meet evolving industry needs. Recognizing the profound impact of simulation tools on the design and optimization phases for pump manufacturers, this research emphasizes the significance of fast and accurate simulation tools. Transient-CFD emerges as a powerful Tool, enabling real-time monitoring of various performance indicators, while steady-CFD, with minimal simplifications, adeptly captures pressure distribution and machine leakages. Lumped-parameter approaches, though requiring effort in simulation setup and simplifying input geometry, offer rapid computational times and comprehensive predictions, including leakages, Torque, cavitation, and pressure ripple. Breaking new ground, this paper presents, for the first time in the literature, accurate simulation models for the same reference machine using the aforementioned methodologies. The results were rigorously validated against experiments spanning a wide range of pump speeds and pressure drops. The discussion encompasses predicted flow, Torque, cavitation, and pressure ripple, offering valuable insights into the strengths and limitations of each methodology.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"169 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139849778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pasquale Borriello, E. Frosina, Pierpaolo Lucchesi, A. Senatore
This research conducts a comprehensive comparative analysis of simulation methodologies for spindle pumps, with a specific focus on steady-state CFD, transient-CFD, and lumped-parameter approaches. Spindle pumps, renowned for their reliability, efficiency, and low noise emission, play a pivotal role in Thermal Management for Battery Electric Vehicles, aligning with the automotive industry’s commitment to reducing pollutants and CO2 emissions. The study is motivated by the critical need to curtail energy consumption during on-the-road operations, particularly as the automotive industry strives for enhanced efficiency. While centrifugal pumps are commonly employed for such applications, their efficiency is highly contingent on rotational speed, leading to energy wastage in real-world scenarios despite high efficiency at the design point. Consequently, the adoption of precisely designed spindle pumps for thermal management systems emerges as a viable solution to meet evolving industry needs. Recognizing the profound impact of simulation tools on the design and optimization phases for pump manufacturers, this research emphasizes the significance of fast and accurate simulation tools. Transient-CFD emerges as a powerful Tool, enabling real-time monitoring of various performance indicators, while steady-CFD, with minimal simplifications, adeptly captures pressure distribution and machine leakages. Lumped-parameter approaches, though requiring effort in simulation setup and simplifying input geometry, offer rapid computational times and comprehensive predictions, including leakages, Torque, cavitation, and pressure ripple. Breaking new ground, this paper presents, for the first time in the literature, accurate simulation models for the same reference machine using the aforementioned methodologies. The results were rigorously validated against experiments spanning a wide range of pump speeds and pressure drops. The discussion encompasses predicted flow, Torque, cavitation, and pressure ripple, offering valuable insights into the strengths and limitations of each methodology.
{"title":"Comparative Analysis of Simulation Methodologies for Spindle Pumps","authors":"Pasquale Borriello, E. Frosina, Pierpaolo Lucchesi, A. Senatore","doi":"10.3390/fluids9020044","DOIUrl":"https://doi.org/10.3390/fluids9020044","url":null,"abstract":"This research conducts a comprehensive comparative analysis of simulation methodologies for spindle pumps, with a specific focus on steady-state CFD, transient-CFD, and lumped-parameter approaches. Spindle pumps, renowned for their reliability, efficiency, and low noise emission, play a pivotal role in Thermal Management for Battery Electric Vehicles, aligning with the automotive industry’s commitment to reducing pollutants and CO2 emissions. The study is motivated by the critical need to curtail energy consumption during on-the-road operations, particularly as the automotive industry strives for enhanced efficiency. While centrifugal pumps are commonly employed for such applications, their efficiency is highly contingent on rotational speed, leading to energy wastage in real-world scenarios despite high efficiency at the design point. Consequently, the adoption of precisely designed spindle pumps for thermal management systems emerges as a viable solution to meet evolving industry needs. Recognizing the profound impact of simulation tools on the design and optimization phases for pump manufacturers, this research emphasizes the significance of fast and accurate simulation tools. Transient-CFD emerges as a powerful Tool, enabling real-time monitoring of various performance indicators, while steady-CFD, with minimal simplifications, adeptly captures pressure distribution and machine leakages. Lumped-parameter approaches, though requiring effort in simulation setup and simplifying input geometry, offer rapid computational times and comprehensive predictions, including leakages, Torque, cavitation, and pressure ripple. Breaking new ground, this paper presents, for the first time in the literature, accurate simulation models for the same reference machine using the aforementioned methodologies. The results were rigorously validated against experiments spanning a wide range of pump speeds and pressure drops. The discussion encompasses predicted flow, Torque, cavitation, and pressure ripple, offering valuable insights into the strengths and limitations of each methodology.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":" 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139789860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Julien Sirois, Marlène Sanjosé, Fabian Sanchez, V. Brailovski
The work presented here aims to provide design guidelines to create vortex-damping structures. A design of experiment was developed to investigate the individual and combined effects of the geometrical properties of planar regular grid structures, i.e., the wire diameter, the porosity, and the inter-grid spacing, on their vortex-breakdown performance. The simulations were carried out using a commercial unsteady RANS solver. The model relies on the Von Karman street effect to generate vortices in a pipe which are convected downstream, where they interact with an array of grids. The vortex-breakdown efficiency is characterized by the pressure drop, the residual turbulent kinetic energy, the flow homogeneity, and the size of the transmitted vortices. The wire diameter is shown to be an important design lever as it affects the level of distortion of the transmitted vortices. Increasing the number of grids augments the pressure loss, but their contribution to vortex breakdown is otherwise limited when the wire diameter is small. The influence of grid spacing strongly depends on the wire diameter and grid alignment. For instance, minimizing this gap reduces the pressure drop for the inline configurations, but increases the pressure drop for the offset configurations.
本文介绍的工作旨在为创建涡流阻尼结构提供设计指南。实验设计旨在研究平面规则网格结构的几何特性（即金属丝直径、孔隙率和网格间距）对其破涡性能的单独和综合影响。模拟使用商用非稳态 RANS 求解器进行。该模型依靠 Von Karman 街道效应在管道中产生涡流，涡流向下游对流，并与网格阵列相互作用。漩涡分解效率由压降、残余湍流动能、流动均匀性和传输漩涡的大小来表征。导线直径是一个重要的设计杠杆，因为它会影响传送涡流的扭曲程度。增加栅格的数量可以增加压力损失，但当导线直径较小时，栅格对涡流破坏的作用就会受到限制。网格间距的影响很大程度上取决于导线直径和网格排列。例如，尽量减小这一间隙可减少直列配置的压降，但会增加偏移配置的压降。
{"title":"Vortex-Breakdown Efficiency of Planar Regular Grid Structures—Towards the Development of Design Guidelines","authors":"Julien Sirois, Marlène Sanjosé, Fabian Sanchez, V. Brailovski","doi":"10.3390/fluids9020043","DOIUrl":"https://doi.org/10.3390/fluids9020043","url":null,"abstract":"The work presented here aims to provide design guidelines to create vortex-damping structures. A design of experiment was developed to investigate the individual and combined effects of the geometrical properties of planar regular grid structures, i.e., the wire diameter, the porosity, and the inter-grid spacing, on their vortex-breakdown performance. The simulations were carried out using a commercial unsteady RANS solver. The model relies on the Von Karman street effect to generate vortices in a pipe which are convected downstream, where they interact with an array of grids. The vortex-breakdown efficiency is characterized by the pressure drop, the residual turbulent kinetic energy, the flow homogeneity, and the size of the transmitted vortices. The wire diameter is shown to be an important design lever as it affects the level of distortion of the transmitted vortices. Increasing the number of grids augments the pressure loss, but their contribution to vortex breakdown is otherwise limited when the wire diameter is small. The influence of grid spacing strongly depends on the wire diameter and grid alignment. For instance, minimizing this gap reduces the pressure drop for the inline configurations, but increases the pressure drop for the offset configurations.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"112 1-3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139853925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Julien Sirois, Marlène Sanjosé, Fabian Sanchez, V. Brailovski
The work presented here aims to provide design guidelines to create vortex-damping structures. A design of experiment was developed to investigate the individual and combined effects of the geometrical properties of planar regular grid structures, i.e., the wire diameter, the porosity, and the inter-grid spacing, on their vortex-breakdown performance. The simulations were carried out using a commercial unsteady RANS solver. The model relies on the Von Karman street effect to generate vortices in a pipe which are convected downstream, where they interact with an array of grids. The vortex-breakdown efficiency is characterized by the pressure drop, the residual turbulent kinetic energy, the flow homogeneity, and the size of the transmitted vortices. The wire diameter is shown to be an important design lever as it affects the level of distortion of the transmitted vortices. Increasing the number of grids augments the pressure loss, but their contribution to vortex breakdown is otherwise limited when the wire diameter is small. The influence of grid spacing strongly depends on the wire diameter and grid alignment. For instance, minimizing this gap reduces the pressure drop for the inline configurations, but increases the pressure drop for the offset configurations.
本文介绍的工作旨在为创建涡流阻尼结构提供设计指南。实验设计旨在研究平面规则网格结构的几何特性（即金属丝直径、孔隙率和网格间距）对其破涡性能的单独和综合影响。模拟使用商用非稳态 RANS 求解器进行。该模型依靠 Von Karman 街道效应在管道中产生涡流，涡流向下游对流，并与网格阵列相互作用。漩涡分解效率由压降、残余湍流动能、流动均匀性和传输漩涡的大小来表征。导线直径是一个重要的设计杠杆，因为它会影响传送涡流的扭曲程度。增加栅格的数量可以增加压力损失，但当导线直径较小时，栅格对涡流破坏的作用就会受到限制。网格间距的影响很大程度上取决于导线直径和网格排列。例如，尽量减小这一间隙可减少直列配置的压降，但会增加偏移配置的压降。
{"title":"Vortex-Breakdown Efficiency of Planar Regular Grid Structures—Towards the Development of Design Guidelines","authors":"Julien Sirois, Marlène Sanjosé, Fabian Sanchez, V. Brailovski","doi":"10.3390/fluids9020043","DOIUrl":"https://doi.org/10.3390/fluids9020043","url":null,"abstract":"The work presented here aims to provide design guidelines to create vortex-damping structures. A design of experiment was developed to investigate the individual and combined effects of the geometrical properties of planar regular grid structures, i.e., the wire diameter, the porosity, and the inter-grid spacing, on their vortex-breakdown performance. The simulations were carried out using a commercial unsteady RANS solver. The model relies on the Von Karman street effect to generate vortices in a pipe which are convected downstream, where they interact with an array of grids. The vortex-breakdown efficiency is characterized by the pressure drop, the residual turbulent kinetic energy, the flow homogeneity, and the size of the transmitted vortices. The wire diameter is shown to be an important design lever as it affects the level of distortion of the transmitted vortices. Increasing the number of grids augments the pressure loss, but their contribution to vortex breakdown is otherwise limited when the wire diameter is small. The influence of grid spacing strongly depends on the wire diameter and grid alignment. For instance, minimizing this gap reduces the pressure drop for the inline configurations, but increases the pressure drop for the offset configurations.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"119 s438","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139794266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Turbulent heat transfer in channel flows is an important area of research due to its simple geometry and diverse industrial applications. Reynolds-Averaged Navier–Stokes (RANS) models are the most-affordable simulation methodology and are often the only viable choice for investigating industrial flows. However, accurate modelling of wall-bounded flows is challenging in RANS, and the assessment of the performance of RANS models for heated turbulent channel flow has not been sufficiently investigated for a wide range of Reynolds and Prandtl numbers. In this study, five RANS models are assessed for their ability to predict heat transfer in channel flows across a wide range of Reynolds and Prandtl numbers (Pr) by comparing the RANS results with respect to the corresponding Direct Numerical Simulation data. The models include three Eddy Viscosity Models (EVMs): standard k−ϵ, low Reynolds number k−ϵLS, and k−ωSST, as well as two Reynolds Stress Models (RSMs): Launder–Reece–Rodi and Speziale–Sarkar–Gatski models. The study analyses the Reynolds number effects on turbulent heat transfer in a channel flow at a Pr of 0.71 for friction Reynolds number values of 180,395,640, and 1020. The results show that all models accurately predict velocity across all Reynolds numbers, but the accuracy of mean temperature prediction drops with increasing Reynolds number for all models, except for the k−ωSST model. The study also analyses the Pr effects on turbulent heat transfer in a channel flow with Pr values between 0.025 and 10.0. An error analysis is performed on the results obtained from different turbulence models, and it is shown that the k−ωSST model has the smallest error for the predictions of the mean temperature and Nusselt number for high-Prandtl-number flows, while the low Reynolds number k−ϵLS model shows the smallest errors for low-Prandtl-number flows at different Reynolds numbers. An analytical solution is utilised to identify Pr effects on forced convection in a channel flow into three different regimes: analytical region, transitional region, and turbulent diffusion-dominated region. These regimes are helpful to discuss the validity of the models in relation to the Pr. The findings of this paper provide insights into the performance of different RANS models for heat transfer predictions in a channel flow.
{"title":"A Comprehensive Evaluation of Turbulence Models for Predicting Heat Transfer in Turbulent Channel Flow across Various Prandtl Number Regimes","authors":"Liyuan Liu, U. Ahmed, N. Chakraborty","doi":"10.3390/fluids9020042","DOIUrl":"https://doi.org/10.3390/fluids9020042","url":null,"abstract":"Turbulent heat transfer in channel flows is an important area of research due to its simple geometry and diverse industrial applications. Reynolds-Averaged Navier–Stokes (RANS) models are the most-affordable simulation methodology and are often the only viable choice for investigating industrial flows. However, accurate modelling of wall-bounded flows is challenging in RANS, and the assessment of the performance of RANS models for heated turbulent channel flow has not been sufficiently investigated for a wide range of Reynolds and Prandtl numbers. In this study, five RANS models are assessed for their ability to predict heat transfer in channel flows across a wide range of Reynolds and Prandtl numbers (Pr) by comparing the RANS results with respect to the corresponding Direct Numerical Simulation data. The models include three Eddy Viscosity Models (EVMs): standard k−ϵ, low Reynolds number k−ϵLS, and k−ωSST, as well as two Reynolds Stress Models (RSMs): Launder–Reece–Rodi and Speziale–Sarkar–Gatski models. The study analyses the Reynolds number effects on turbulent heat transfer in a channel flow at a Pr of 0.71 for friction Reynolds number values of 180,395,640, and 1020. The results show that all models accurately predict velocity across all Reynolds numbers, but the accuracy of mean temperature prediction drops with increasing Reynolds number for all models, except for the k−ωSST model. The study also analyses the Pr effects on turbulent heat transfer in a channel flow with Pr values between 0.025 and 10.0. An error analysis is performed on the results obtained from different turbulence models, and it is shown that the k−ωSST model has the smallest error for the predictions of the mean temperature and Nusselt number for high-Prandtl-number flows, while the low Reynolds number k−ϵLS model shows the smallest errors for low-Prandtl-number flows at different Reynolds numbers. An analytical solution is utilised to identify Pr effects on forced convection in a channel flow into three different regimes: analytical region, transitional region, and turbulent diffusion-dominated region. These regimes are helpful to discuss the validity of the models in relation to the Pr. The findings of this paper provide insights into the performance of different RANS models for heat transfer predictions in a channel flow.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"295 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139807887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Turbulent heat transfer in channel flows is an important area of research due to its simple geometry and diverse industrial applications. Reynolds-Averaged Navier–Stokes (RANS) models are the most-affordable simulation methodology and are often the only viable choice for investigating industrial flows. However, accurate modelling of wall-bounded flows is challenging in RANS, and the assessment of the performance of RANS models for heated turbulent channel flow has not been sufficiently investigated for a wide range of Reynolds and Prandtl numbers. In this study, five RANS models are assessed for their ability to predict heat transfer in channel flows across a wide range of Reynolds and Prandtl numbers (Pr) by comparing the RANS results with respect to the corresponding Direct Numerical Simulation data. The models include three Eddy Viscosity Models (EVMs): standard k−ϵ, low Reynolds number k−ϵLS, and k−ωSST, as well as two Reynolds Stress Models (RSMs): Launder–Reece–Rodi and Speziale–Sarkar–Gatski models. The study analyses the Reynolds number effects on turbulent heat transfer in a channel flow at a Pr of 0.71 for friction Reynolds number values of 180,395,640, and 1020. The results show that all models accurately predict velocity across all Reynolds numbers, but the accuracy of mean temperature prediction drops with increasing Reynolds number for all models, except for the k−ωSST model. The study also analyses the Pr effects on turbulent heat transfer in a channel flow with Pr values between 0.025 and 10.0. An error analysis is performed on the results obtained from different turbulence models, and it is shown that the k−ωSST model has the smallest error for the predictions of the mean temperature and Nusselt number for high-Prandtl-number flows, while the low Reynolds number k−ϵLS model shows the smallest errors for low-Prandtl-number flows at different Reynolds numbers. An analytical solution is utilised to identify Pr effects on forced convection in a channel flow into three different regimes: analytical region, transitional region, and turbulent diffusion-dominated region. These regimes are helpful to discuss the validity of the models in relation to the Pr. The findings of this paper provide insights into the performance of different RANS models for heat transfer predictions in a channel flow.
{"title":"A Comprehensive Evaluation of Turbulence Models for Predicting Heat Transfer in Turbulent Channel Flow across Various Prandtl Number Regimes","authors":"Liyuan Liu, U. Ahmed, N. Chakraborty","doi":"10.3390/fluids9020042","DOIUrl":"https://doi.org/10.3390/fluids9020042","url":null,"abstract":"Turbulent heat transfer in channel flows is an important area of research due to its simple geometry and diverse industrial applications. Reynolds-Averaged Navier–Stokes (RANS) models are the most-affordable simulation methodology and are often the only viable choice for investigating industrial flows. However, accurate modelling of wall-bounded flows is challenging in RANS, and the assessment of the performance of RANS models for heated turbulent channel flow has not been sufficiently investigated for a wide range of Reynolds and Prandtl numbers. In this study, five RANS models are assessed for their ability to predict heat transfer in channel flows across a wide range of Reynolds and Prandtl numbers (Pr) by comparing the RANS results with respect to the corresponding Direct Numerical Simulation data. The models include three Eddy Viscosity Models (EVMs): standard k−ϵ, low Reynolds number k−ϵLS, and k−ωSST, as well as two Reynolds Stress Models (RSMs): Launder–Reece–Rodi and Speziale–Sarkar–Gatski models. The study analyses the Reynolds number effects on turbulent heat transfer in a channel flow at a Pr of 0.71 for friction Reynolds number values of 180,395,640, and 1020. The results show that all models accurately predict velocity across all Reynolds numbers, but the accuracy of mean temperature prediction drops with increasing Reynolds number for all models, except for the k−ωSST model. The study also analyses the Pr effects on turbulent heat transfer in a channel flow with Pr values between 0.025 and 10.0. An error analysis is performed on the results obtained from different turbulence models, and it is shown that the k−ωSST model has the smallest error for the predictions of the mean temperature and Nusselt number for high-Prandtl-number flows, while the low Reynolds number k−ϵLS model shows the smallest errors for low-Prandtl-number flows at different Reynolds numbers. An analytical solution is utilised to identify Pr effects on forced convection in a channel flow into three different regimes: analytical region, transitional region, and turbulent diffusion-dominated region. These regimes are helpful to discuss the validity of the models in relation to the Pr. The findings of this paper provide insights into the performance of different RANS models for heat transfer predictions in a channel flow.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"43 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139867792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The atomization of liquid spray solutions through nozzles is a mechanism for delivering many pesticides to the target. The smallest drop sizes (<150 μm) are known as driftable fines and have a propensity for wind-induced convection. Many agricultural applications include oil-in-water formulations. The experimental metrics obtained from spray images of these formulations include the distance from the nozzle origin to the drop centroid once a drop has formed; the hole location and surface area for holes that form in the liquid sheet (all hole areas approximated as polygons); the angles formed between polygon segments (whose vertices are represented as boundary points); and the ligament dimensions that form from intersecting holes, such as the ligament aspect ratio (R/L), ligament length (L), and ligament radius (width), along with the number of drops a ligament breaks up into. These metrics were used in a principal component regression (PCR) analysis, and the results illustrated that 99% of the variability in the response variable (DT10) was addressed by 10 principal components. Angles formed by the colliding holes, hole distance from the nozzle, drop distance, hole number, ligament number, and drop number were negatively correlated to the atomization driftable fine fraction, while hole area, ligament distance, ligament area, and boundary area were positively correlated. Thus, to decrease/minimize driftable fines, one needs to increase the negatively correlated metrics.
{"title":"Interpreting Image Patterns for Agricultural Sprays Using Statistics and Machine Learning Techniques","authors":"Steven Cryer, John Raymond","doi":"10.3390/fluids9020040","DOIUrl":"https://doi.org/10.3390/fluids9020040","url":null,"abstract":"The atomization of liquid spray solutions through nozzles is a mechanism for delivering many pesticides to the target. The smallest drop sizes (<150 μm) are known as driftable fines and have a propensity for wind-induced convection. Many agricultural applications include oil-in-water formulations. The experimental metrics obtained from spray images of these formulations include the distance from the nozzle origin to the drop centroid once a drop has formed; the hole location and surface area for holes that form in the liquid sheet (all hole areas approximated as polygons); the angles formed between polygon segments (whose vertices are represented as boundary points); and the ligament dimensions that form from intersecting holes, such as the ligament aspect ratio (R/L), ligament length (L), and ligament radius (width), along with the number of drops a ligament breaks up into. These metrics were used in a principal component regression (PCR) analysis, and the results illustrated that 99% of the variability in the response variable (DT10) was addressed by 10 principal components. Angles formed by the colliding holes, hole distance from the nozzle, drop distance, hole number, ligament number, and drop number were negatively correlated to the atomization driftable fine fraction, while hole area, ligament distance, ligament area, and boundary area were positively correlated. Thus, to decrease/minimize driftable fines, one needs to increase the negatively correlated metrics.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"235 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139876989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A solvent in suspension often has non-Newtonian properties. To date, in order to determine these properties, many constitutive equations have been suggested. In particular, power-law fluid, which describes both dilatant and pseudoplastic fluids, has been used in many previous studies because of its simplicity. Then, the Herschel–Bulkley model is used, which describes fluid with yield stress. In this study, we considered how a non-Newtonian solvent affected the equilibrium position of a particle and relative viscosity using the regularized lattice Boltzmann method for fluid and a two-way coupling scheme for the particle. We focused on these methods so as to evaluate the non-Newtonian effects of a solvent. The equilibrium position in Bingham fluid was closer to the wall than that in Newtonian or power-law fluid. In contrast, the tendency of relative viscosity in Bingham fluid for each position was similar to that in power-law fluid.
{"title":"Numerical Analysis of Non-Newtonian Fluid Effects on the Equilibrium Position of a Suspended Particle and Relative Viscosity in Two-Dimensional Flow","authors":"Keiya Tomioka, Tomohiro Fukui","doi":"10.3390/fluids9020037","DOIUrl":"https://doi.org/10.3390/fluids9020037","url":null,"abstract":"A solvent in suspension often has non-Newtonian properties. To date, in order to determine these properties, many constitutive equations have been suggested. In particular, power-law fluid, which describes both dilatant and pseudoplastic fluids, has been used in many previous studies because of its simplicity. Then, the Herschel–Bulkley model is used, which describes fluid with yield stress. In this study, we considered how a non-Newtonian solvent affected the equilibrium position of a particle and relative viscosity using the regularized lattice Boltzmann method for fluid and a two-way coupling scheme for the particle. We focused on these methods so as to evaluate the non-Newtonian effects of a solvent. The equilibrium position in Bingham fluid was closer to the wall than that in Newtonian or power-law fluid. In contrast, the tendency of relative viscosity in Bingham fluid for each position was similar to that in power-law fluid.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"6 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139889193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we investigate the effect of dissolved gas concentration on cavitation inception and cavitation development in a transparent sharp-edged orifice, similar to that previously analyzed by Nurick in the context of liquid injectors. The working liquid is water, and carbon dioxide is employed as a non-condensable dissolved gas. Cavitation inception points are determined for different dissolved gas concentration levels by measuring wall-static pressures just downstream of the orifice contraction and visually observing the onset of a localized (vapor) bubble cloud formation and collapse. Cavitation onset correlates with a plateau in wall-static pressure measurements as a function of a cavitation number. An increase in the amount of dissolved carbon dioxide is found to increase the cavitation number at which the onset of cavitation occurs. The transition from cloud cavitation to extended-sheet or full cavitation along the entire orifice length occurs suddenly and is shifted to higher cavitation numbers with increasing dissolved gas content. Volume flow rate measurements are performed to determine the change in the discharge coefficient with the cavitation number and dissolved gas content for the investigated cases. CFD analyses are carried out based on the cavitation model by Zwart et al. and the model by Yang et al. to account for non-condensable gases. Discharge coefficients obtained from the numerical simulations are in good agreement with experimental values, although they are slightly higher in the cavitating case. The earlier onset of fluid cavitation (i.e., cavitation inception at higher cavitation numbers) with increasing dissolved carbon dioxide content is not predicted using the employed numerical model.
在这项工作中，我们研究了溶解气体浓度对透明尖角孔口中空化萌发和空化发展的影响，这与 Nurick 之前在液体喷射器中分析的情况类似。工作液体是水，二氧化碳是不可冷凝的溶解气体。通过测量孔口收缩下游的壁面静压力，并目测局部（蒸汽）气泡云的形成和崩溃，确定不同溶解气体浓度水平下的气蚀起始点。空化开始与壁面静压测量值的高低相关，是空化数的函数。研究发现，溶解二氧化碳量的增加会提高空化开始时的空化数。从云空化到沿整个孔口长度的扩展片状空化或完全空化的过渡是突然发生的，并且随着溶解气体含量的增加而转向更高的空化数。通过测量体积流量来确定排出系数随空化数和溶解气体含量的变化情况。根据 Zwart 等人的空化模型和 Yang 等人的模型进行 CFD 分析，以考虑不凝结气体。数值模拟得到的排流系数与实验值十分吻合，但空化情况下的排流系数略高。采用的数值模型没有预测到随着溶解二氧化碳含量的增加，流体空化开始得更早（即空化数越高，空化开始得越早）。
{"title":"Effect of Dissolved Carbon Dioxide on Cavitation in a Circular Orifice","authors":"Sina Safaei, Carsten Mehring","doi":"10.3390/fluids9020041","DOIUrl":"https://doi.org/10.3390/fluids9020041","url":null,"abstract":"In this work, we investigate the effect of dissolved gas concentration on cavitation inception and cavitation development in a transparent sharp-edged orifice, similar to that previously analyzed by Nurick in the context of liquid injectors. The working liquid is water, and carbon dioxide is employed as a non-condensable dissolved gas. Cavitation inception points are determined for different dissolved gas concentration levels by measuring wall-static pressures just downstream of the orifice contraction and visually observing the onset of a localized (vapor) bubble cloud formation and collapse. Cavitation onset correlates with a plateau in wall-static pressure measurements as a function of a cavitation number. An increase in the amount of dissolved carbon dioxide is found to increase the cavitation number at which the onset of cavitation occurs. The transition from cloud cavitation to extended-sheet or full cavitation along the entire orifice length occurs suddenly and is shifted to higher cavitation numbers with increasing dissolved gas content. Volume flow rate measurements are performed to determine the change in the discharge coefficient with the cavitation number and dissolved gas content for the investigated cases. CFD analyses are carried out based on the cavitation model by Zwart et al. and the model by Yang et al. to account for non-condensable gases. Discharge coefficients obtained from the numerical simulations are in good agreement with experimental values, although they are slightly higher in the cavitating case. The earlier onset of fluid cavitation (i.e., cavitation inception at higher cavitation numbers) with increasing dissolved carbon dioxide content is not predicted using the employed numerical model.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"66 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139825625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The atomization of liquid spray solutions through nozzles is a mechanism for delivering many pesticides to the target. The smallest drop sizes (<150 μm) are known as driftable fines and have a propensity for wind-induced convection. Many agricultural applications include oil-in-water formulations. The experimental metrics obtained from spray images of these formulations include the distance from the nozzle origin to the drop centroid once a drop has formed; the hole location and surface area for holes that form in the liquid sheet (all hole areas approximated as polygons); the angles formed between polygon segments (whose vertices are represented as boundary points); and the ligament dimensions that form from intersecting holes, such as the ligament aspect ratio (R/L), ligament length (L), and ligament radius (width), along with the number of drops a ligament breaks up into. These metrics were used in a principal component regression (PCR) analysis, and the results illustrated that 99% of the variability in the response variable (DT10) was addressed by 10 principal components. Angles formed by the colliding holes, hole distance from the nozzle, drop distance, hole number, ligament number, and drop number were negatively correlated to the atomization driftable fine fraction, while hole area, ligament distance, ligament area, and boundary area were positively correlated. Thus, to decrease/minimize driftable fines, one needs to increase the negatively correlated metrics.
{"title":"Interpreting Image Patterns for Agricultural Sprays Using Statistics and Machine Learning Techniques","authors":"Steven Cryer, John Raymond","doi":"10.3390/fluids9020040","DOIUrl":"https://doi.org/10.3390/fluids9020040","url":null,"abstract":"The atomization of liquid spray solutions through nozzles is a mechanism for delivering many pesticides to the target. The smallest drop sizes (<150 μm) are known as driftable fines and have a propensity for wind-induced convection. Many agricultural applications include oil-in-water formulations. The experimental metrics obtained from spray images of these formulations include the distance from the nozzle origin to the drop centroid once a drop has formed; the hole location and surface area for holes that form in the liquid sheet (all hole areas approximated as polygons); the angles formed between polygon segments (whose vertices are represented as boundary points); and the ligament dimensions that form from intersecting holes, such as the ligament aspect ratio (R/L), ligament length (L), and ligament radius (width), along with the number of drops a ligament breaks up into. These metrics were used in a principal component regression (PCR) analysis, and the results illustrated that 99% of the variability in the response variable (DT10) was addressed by 10 principal components. Angles formed by the colliding holes, hole distance from the nozzle, drop distance, hole number, ligament number, and drop number were negatively correlated to the atomization driftable fine fraction, while hole area, ligament distance, ligament area, and boundary area were positively correlated. Thus, to decrease/minimize driftable fines, one needs to increase the negatively correlated metrics.","PeriodicalId":510749,"journal":{"name":"Fluids","volume":"65 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139817357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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