Pub Date : 2026-01-01Epub Date: 2025-08-05DOI: 10.1016/j.expthermflusci.2025.111573
Yan Pan , Zhuoliang Yu , Leonardo P. Chamorro , Fei Ma , Tengfei Cai
Using high-speed imaging and three-dimensional surface morphology analysis, we examined the cavitation cloud dynamics and erosion characteristics of self-excited pulsating cavitating waterjets. Erosion experiments on aluminum specimens were conducted to evaluate the influence of varying outlet tube diameters and lengths on the waterjet’s performance. Mass loss measurements revealed that the erosion capability increased approximately threefold under the optimal outlet tube configuration. Proper Orthogonal Decomposition (POD) of high-speed snapshots identified distinct primary and secondary shedding modes driven by passive acoustic excitation. The presence of an outlet tube was found to enhance the volume and development of the primary cavitation cloud while facilitating the merging of secondary and primary modes. This mode-specific structural evolution leads to a synergistic amplification of cavitation cloud intensity, which governs the enhancement of erosion capacity.
{"title":"Outlet tube effects on cavitation cloud dynamics and erosion in self-excited waterjets","authors":"Yan Pan , Zhuoliang Yu , Leonardo P. Chamorro , Fei Ma , Tengfei Cai","doi":"10.1016/j.expthermflusci.2025.111573","DOIUrl":"10.1016/j.expthermflusci.2025.111573","url":null,"abstract":"<div><div>Using high-speed imaging and three-dimensional surface morphology analysis, we examined the cavitation cloud dynamics and erosion characteristics of self-excited pulsating cavitating waterjets. Erosion experiments on aluminum specimens were conducted to evaluate the influence of varying outlet tube diameters and lengths on the waterjet’s performance. Mass loss measurements revealed that the erosion capability increased approximately threefold under the optimal outlet tube configuration. Proper Orthogonal Decomposition (POD) of high-speed snapshots identified distinct primary and secondary shedding modes driven by passive acoustic excitation. The presence of an outlet tube was found to enhance the volume and development of the primary cavitation cloud while facilitating the merging of secondary and primary modes. This mode-specific structural evolution leads to a synergistic amplification of cavitation cloud intensity, which governs the enhancement of erosion capacity.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111573"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144771243","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 : 2026-01-01Epub Date: 2025-08-09DOI: 10.1016/j.expthermflusci.2025.111580
Xiao Liu , Xiaolei Zhang , Xiaoxin Yao , Zuohua Huang , Chenglong Tang
The application of ammonia in high-power marine engines has been receiving more attention on achieving zero-carbon emission goals. Due to the unique flashing boiling characteristics of ammonia, the influence of orifice diameter on its spray characteristics needs further research. Present study presents a comprehensive experimental analysis of liquid ammonia spray macroscopic characteristics using three injector orifice diameters (0.15 mm, 0.3 mm, and 0.45 mm) under high-pressure conditions (injection pressure up to 100 MPa, ambient pressure up to 6 MPa). The results show that ambient pressure exerts a more pronounced influence on spray characteristics than injection pressure. Notably, flash boiling significantly enhances radial spray expansion, particularly causing substantial axial momentum loss in sprays from larger orifice diameter. In non-flash boiling region, although the spray from small orifice diameter develops rapidly at the initial stage, the spray from large orifice diameter exhibits superior performance in penetration distance, velocity and area during later stages. Based on these experimental results, a developed prediction model on spray tip penetration is proposed and verified to be well applicable to different orifice diameters, which provides a reference for orifice diameter optimization. According to the predicted fuel–air mixing degree of spray analyzed through equivalent ratio calculation, present results indicate 0.3 mm orifice diameter is optimal for flash boiling conditions, whereas a 0.45 mm diameter proves more effective for non-flash boiling and high-pressure marine engine operations. These findings offer significant contributions to the design and optimization of ammonia-fueled marine propulsion systems, advancing the development of sustainable maritime technologies.
{"title":"Experimental analysis of liquid ammonia spray with different orifice diameter under marine engine conditions","authors":"Xiao Liu , Xiaolei Zhang , Xiaoxin Yao , Zuohua Huang , Chenglong Tang","doi":"10.1016/j.expthermflusci.2025.111580","DOIUrl":"10.1016/j.expthermflusci.2025.111580","url":null,"abstract":"<div><div>The application of ammonia in high-power marine engines has been receiving more attention on achieving zero-carbon emission goals. Due to the unique flashing boiling characteristics of ammonia, the influence of orifice diameter on its spray characteristics needs further research. Present study presents a comprehensive experimental analysis of liquid ammonia spray macroscopic characteristics using three injector orifice diameters (0.15 mm, 0.3 mm, and 0.45 mm) under high-pressure conditions (injection pressure up to 100 MPa, ambient pressure up to 6 MPa). The results show that ambient pressure exerts a more pronounced influence on spray characteristics than injection pressure. Notably, flash boiling significantly enhances radial spray expansion, particularly causing substantial axial momentum loss in sprays from larger orifice diameter. In non-flash boiling region, although the spray from small orifice diameter develops rapidly at the initial stage, the spray from large orifice diameter exhibits superior performance in penetration distance, velocity and area during later stages. Based on these experimental results, a developed prediction model on spray tip penetration is proposed and verified to be well applicable to different orifice diameters, which provides a reference for orifice diameter optimization. According to the predicted fuel–air mixing degree of spray analyzed through equivalent ratio calculation, present results indicate 0.3 mm orifice diameter is optimal for flash boiling conditions, whereas a 0.45 mm diameter proves more effective for non-flash boiling and high-pressure marine engine operations. These findings offer significant contributions to the design and optimization of ammonia-fueled marine propulsion systems, advancing the development of sustainable maritime technologies.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111580"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144827548","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 : 2026-01-01Epub Date: 2025-08-11DOI: 10.1016/j.expthermflusci.2025.111579
Senthil Kumar Parimalanathan , Pierre Colinet , Alexey Rednikov , Adam Chafai , Yannis Tsoumpas , Hosein Sadafi , Loucine Mekhitarian , Christophe Wylock , Benjamin Sobac , Sam Dehaeck
Mach–Zehnder interferometry is a powerful optical technique for investigating thermo-fluidic phenomena, particularly in experiments involving contact line and phase change measurements. This study presents a comprehensive experimental framework leveraging Mach–Zehnder interferometry to analyze liquid film thickness profiles, vapor concentration fields (vapor clouds), and concentration fields in a Hele-Shaw cell. The technique is applied to sessile droplet profilometry on transparent substrates, revealing wetting dynamics, contact angle evolution, and Marangoni-driven flows and instabilities in spreading and evaporating droplets. Apart from volatile pure droplets, where the thermal Marangoni effect may be essential on account of evaporative cooling, the study also explores the role of solutal Marangoni stresses in hygroscopic binary mixtures. Additionally, vapor interferometry is employed to quantify the concentration field above evaporating droplets and liquid pools, demonstrating the method’s capability for non-invasive measurement of evaporation rates. We also showcase the application of interferometry in dissolution studies within Hele-Shaw cells. The results highlight the versatility of Mach–Zehnder interferometry in capturing all those complex phenomena, offering valuable insights for the study of evaporation, wetting, and mass transport in confined geometries.
{"title":"Mach–Zehnder interferometry for fluid physics experiments involving contact lines and phase change","authors":"Senthil Kumar Parimalanathan , Pierre Colinet , Alexey Rednikov , Adam Chafai , Yannis Tsoumpas , Hosein Sadafi , Loucine Mekhitarian , Christophe Wylock , Benjamin Sobac , Sam Dehaeck","doi":"10.1016/j.expthermflusci.2025.111579","DOIUrl":"10.1016/j.expthermflusci.2025.111579","url":null,"abstract":"<div><div>Mach–Zehnder interferometry is a powerful optical technique for investigating thermo-fluidic phenomena, particularly in experiments involving contact line and phase change measurements. This study presents a comprehensive experimental framework leveraging Mach–Zehnder interferometry to analyze liquid film thickness profiles, vapor concentration fields (vapor clouds), and concentration fields in a Hele-Shaw cell. The technique is applied to sessile droplet profilometry on transparent substrates, revealing wetting dynamics, contact angle evolution, and Marangoni-driven flows and instabilities in spreading and evaporating droplets. Apart from volatile pure droplets, where the thermal Marangoni effect may be essential on account of evaporative cooling, the study also explores the role of solutal Marangoni stresses in hygroscopic binary mixtures. Additionally, vapor interferometry is employed to quantify the concentration field above evaporating droplets and liquid pools, demonstrating the method’s capability for non-invasive measurement of evaporation rates. We also showcase the application of interferometry in <span><math><msub><mrow><mi>CO</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> dissolution studies within Hele-Shaw cells. The results highlight the versatility of Mach–Zehnder interferometry in capturing all those complex phenomena, offering valuable insights for the study of evaporation, wetting, and mass transport in confined geometries.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111579"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144885777","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}
Clarifying the relationship between heat transfer and flow in energy devices is crucial. However, directly measuring heat transfer and flow is challenging. To address this issue, we apply a method for estimating the flow velocity near the wall based on wall thermal data, and we verify the physical meaning of the estimated velocity. Focusing on the channel turbulence at Reynolds numbers of 2,700, 3,300 and 3,800, the heat transfer coefficient was calculated from the wall temperature data experimentally obtained via infrared thermography. The advection velocity of the fluid was estimated based on the phase difference of the time-series fluctuations of the heat transfer coefficients at the upstream and downstream locations. The estimated advection velocity was compared with that obtained via particle image velocimetry (PIV). The time-averaged advection velocity reflects the increase in the mean flow velocity for each Reynolds number. Furthermore, the time-averaged advection velocity corresponded to the PIV results at y+= 14.5 ± 1.9, which was within the buffer layer (5 < y+ < 30). In addition, we confirm that the proposed method can capture instantaneous velocity to some extent.
{"title":"Physical meaning of advection velocity estimated from phase delay of heat transfer coefficients","authors":"Hiroki Nakajima, Kazuhito Dejima, Kiyoshi Kawasaki","doi":"10.1016/j.expthermflusci.2025.111597","DOIUrl":"10.1016/j.expthermflusci.2025.111597","url":null,"abstract":"<div><div>Clarifying the relationship between heat transfer and flow in energy devices is crucial. However, directly measuring heat transfer and flow is challenging. To address this issue, we apply a method for estimating the flow velocity near the wall based on wall thermal data, and we verify the physical meaning of the estimated velocity. Focusing on the channel turbulence at Reynolds numbers of 2,700, 3,300 and 3,800, the heat transfer coefficient was calculated from the wall temperature data experimentally obtained via infrared thermography. The advection velocity of the fluid was estimated based on the phase difference of the time-series fluctuations of the heat transfer coefficients at the upstream and downstream locations. The estimated advection velocity was compared with that obtained via particle image velocimetry (PIV). The time-averaged advection velocity reflects the increase in the mean flow velocity for each Reynolds number. Furthermore, the time-averaged advection velocity corresponded to the PIV results at <em>y</em><sup>+</sup>= 14.5 ± 1.9, which was within the buffer layer (5 < <em>y</em><sup>+</sup> < 30). In addition, we confirm that the proposed method can capture instantaneous velocity to some extent.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111597"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893748","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 : 2026-01-01Epub Date: 2025-08-27DOI: 10.1016/j.expthermflusci.2025.111599
Erfan Saeedian Sar , Azadeh Kebriaee , Ghader Olyaei
In this study, the droplet size and velocity distributions resulting from liquid jet and sheet injections into a cross-flow were investigated. Since previous research has provided limited insights into the effects of rectangular nozzles compared to circular ones, this study tested four different nozzles – two circular and two rectangular – each with distinct hydraulic diameters. This design aimed to explore the influence of nozzle geometry and hydraulic diameter on droplet size and velocity distributions. To assess the effects of liquid and gas flow conditions on the microscopic properties of droplets, the cross-flow Weber number ranged from 6 to 15, while the injection fluid Weber number varied from 90 to 1100. Additionally, measurements were conducted at varying distances and spatial positions relative to the spray nozzle, capturing three-dimensional spatial distributions of the studied parameters. An experimental methodology was employed to measure droplet size and velocity. The test setup was equipped with high-precision imaging capabilities and the shadowgraphy technique was utilized for droplet visualization. The collected data were analyzed using data analysis approaches, including analysis of covariance, multiple linear regression, and standard statistical tests. The investigation into the effects of flow conditions on droplet size revealed that the momentum ratio between the injected fluid and the cross-flow plays a critical role, with higher momentum ratios resulting in smaller droplet sizes. Furthermore, the study identified a critical gas Weber number and a universal critical momentum ratio, highlighting a dual-effect mechanism of the cross-flow on droplet diameter. This novel finding and its underlying physics, to the authors’ knowledge, have not been explicitly reported in prior research. The analysis also demonstrated that increasing the Weber number of either the injected fluid or the cross-flow increases the velocity of the produced droplets. A general inverse relationship between droplet size and velocity was observed. Regarding nozzle effects, the results indicate that rectangular nozzles produce smaller droplets, while larger hydraulic diameters yield larger droplet sizes. Finally, power-law relationships were developed to describe the distributions of droplet size and velocity as functions of flow conditions and spatial position for each nozzle type.
{"title":"Experimental investigation of momentum ratio and Weber number influence on droplets’ characteristics for jet in cross-flow","authors":"Erfan Saeedian Sar , Azadeh Kebriaee , Ghader Olyaei","doi":"10.1016/j.expthermflusci.2025.111599","DOIUrl":"10.1016/j.expthermflusci.2025.111599","url":null,"abstract":"<div><div>In this study, the droplet size and velocity distributions resulting from liquid jet and sheet injections into a cross-flow were investigated. Since previous research has provided limited insights into the effects of rectangular nozzles compared to circular ones, this study tested four different nozzles – two circular and two rectangular – each with distinct hydraulic diameters. This design aimed to explore the influence of nozzle geometry and hydraulic diameter on droplet size and velocity distributions. To assess the effects of liquid and gas flow conditions on the microscopic properties of droplets, the cross-flow Weber number ranged from 6 to 15, while the injection fluid Weber number varied from 90 to 1100. Additionally, measurements were conducted at varying distances and spatial positions relative to the spray nozzle, capturing three-dimensional spatial distributions of the studied parameters. An experimental methodology was employed to measure droplet size and velocity. The test setup was equipped with high-precision imaging capabilities and the shadowgraphy technique was utilized for droplet visualization. The collected data were analyzed using data analysis approaches, including analysis of covariance, multiple linear regression, and standard statistical tests. The investigation into the effects of flow conditions on droplet size revealed that the momentum ratio between the injected fluid and the cross-flow plays a critical role, with higher momentum ratios resulting in smaller droplet sizes. Furthermore, the study identified a critical gas Weber number and a universal critical momentum ratio, highlighting a dual-effect mechanism of the cross-flow on droplet diameter. This novel finding and its underlying physics, to the authors’ knowledge, have not been explicitly reported in prior research. The analysis also demonstrated that increasing the Weber number of either the injected fluid or the cross-flow increases the velocity of the produced droplets. A general inverse relationship between droplet size and velocity was observed. Regarding nozzle effects, the results indicate that rectangular nozzles produce smaller droplets, while larger hydraulic diameters yield larger droplet sizes. Finally, power-law relationships were developed to describe the distributions of droplet size and velocity as functions of flow conditions and spatial position for each nozzle type.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111599"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144922490","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 : 2026-01-01Epub Date: 2025-08-15DOI: 10.1016/j.expthermflusci.2025.111596
Xiangjun Zhou, Nian Xu, Xinyu Zhang, Huaqiang Chu
The impact behavior of the droplets was significantly influenced by the substrate temperature, surface hydrophobicity, and tilt angle. To elucidate the underlying interaction mechanisms between the droplet and the surface, this paper presents an experimental investigation of the interaction between droplets impacting various heated metallic surfaces. The study utilized three distinct hydrophobic aluminum substrates and employed 4 wt% glycerol aqueous solution as the test liquid. The temperature of the metallic substrates was maintained between 80 °C to 260 °C, while the droplet impact velocity was kept constant at 0.884 m/s. Under low-temperature conditions, droplets exhibit a sequence of spreading, receding, and oscillation. In contrast, elevated temperatures induce atomization and the Leidenfrost effect; these elevated temperatures promote spreading, accelerate receding, and enhance droplet rebound. Hydrophobic surfaces inhibit maximum spreading diameter while simultaneously increasing receding velocity and rebound amplitude; stronger hydrophobicity results in a more regular rebound morphology. As the tilt angle increases, droplet spreading and rebound tend to occur in the direction of the tilt, causing changes in the trajectory, displacement, and shape of the droplets. Furthermore, the synergistic effect of high temperature and strong hydrophobicity intensifies the coupling between receding and rebound. Adjustment of the tilt angle can amplify or qualitatively alter the interdependencies among other factors. Ultimately, the macroscopic spreading characteristics are determined by the dynamic balance between the intrinsic contact angle properties and the extrinsic tilt angle.
{"title":"Hydrophobic wettability effects on low-Weber-number droplets morphology evolution","authors":"Xiangjun Zhou, Nian Xu, Xinyu Zhang, Huaqiang Chu","doi":"10.1016/j.expthermflusci.2025.111596","DOIUrl":"10.1016/j.expthermflusci.2025.111596","url":null,"abstract":"<div><div>The impact behavior of the droplets was significantly influenced by the substrate temperature, surface hydrophobicity, and tilt angle. To elucidate the underlying interaction mechanisms between the droplet and the surface, this paper presents an experimental investigation of the interaction between droplets impacting various heated metallic surfaces. The study utilized three distinct hydrophobic aluminum substrates and employed 4 wt% glycerol aqueous solution as the test liquid. The temperature of the metallic substrates was maintained between 80 °C to 260 °C, while the droplet impact velocity was kept constant at 0.884 m/s. Under low-temperature conditions, droplets exhibit a sequence of spreading, receding, and oscillation. In contrast, elevated temperatures induce atomization and the Leidenfrost effect; these elevated temperatures promote spreading, accelerate receding, and enhance droplet rebound. Hydrophobic surfaces inhibit maximum spreading diameter while simultaneously increasing receding velocity and rebound amplitude; stronger hydrophobicity results in a more regular rebound morphology. As the tilt angle increases, droplet spreading and rebound tend to occur in the direction of the tilt, causing changes in the trajectory, displacement, and shape of the droplets. Furthermore, the synergistic effect of high temperature and strong hydrophobicity intensifies the coupling between receding and rebound. Adjustment of the tilt angle can amplify or qualitatively alter the interdependencies among other factors. Ultimately, the macroscopic spreading characteristics are determined by the dynamic balance between the intrinsic contact angle properties and the extrinsic tilt angle.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111596"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144878250","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 : 2025-12-01Epub Date: 2025-07-08DOI: 10.1016/j.expthermflusci.2025.111563
Feng Zhou , Weichen Sun , Qiang Chen , Haifeng Liu , Xiaobo Shen
This paper presents an experimental investigation of the liquid film resulting from jet impingement on a large-scale flat plate. A high-speed camera was used to capture direct footage of the liquid film, which was then analyzed using image processing techniques. The study focused on determining the thickness of the liquid film at various positions along the axial direction and examining the distribution and fluctuation characteristics of the falling liquid film under Reynolds number ranging from 4250 to 8500. Experiments were conducted at different angles of incidence to investigate the influence of the incidence angle on the thickness of the liquid film formed by the collision. The experimental results show that the development of liquid film thickness with increasing axial distance is divided into three stages. As the incident Reynolds number increases, both the average thickness and the degree of fluctuation of the liquid film increase, while the growth rate of the thickness decreases. Furthermore, it is evident that the surface of the liquid film will be disrupted during the flow process, and two modes of disruption have been distinguished.
{"title":"Experimental study of the characteristics and stability of liquid film formed by impinging of water jets on a large vertical plate","authors":"Feng Zhou , Weichen Sun , Qiang Chen , Haifeng Liu , Xiaobo Shen","doi":"10.1016/j.expthermflusci.2025.111563","DOIUrl":"10.1016/j.expthermflusci.2025.111563","url":null,"abstract":"<div><div>This paper presents an experimental investigation of the liquid film resulting from jet impingement on a large-scale flat plate. A high-speed camera was used to capture direct footage of the liquid film, which was then analyzed using image processing techniques. The study focused on determining the thickness of the liquid film at various positions along the axial direction and examining the distribution and fluctuation characteristics of the falling liquid film under Reynolds number ranging from 4250 to 8500. Experiments were conducted at different angles of incidence to investigate the influence of the incidence angle on the thickness of the liquid film formed by the collision. The experimental results show that the development of liquid film thickness with increasing axial distance is divided into three stages. As the incident Reynolds number increases, both the average thickness and the degree of fluctuation of the liquid film increase, while the growth rate of the thickness decreases. Furthermore, it is evident that the surface of the liquid film will be disrupted during the flow process, and two modes of disruption have been distinguished.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111563"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611723","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 : 2025-12-01Epub Date: 2025-07-03DOI: 10.1016/j.expthermflusci.2025.111552
P. Pirdavari, H. Tran, M. Upoma, M.Y. Pack
Viscous drop impacts occur in various modalities across numerous natural and commercial processes. In most practical applications, such as spray deposition, oblique impact is commonplace as well as the formation of a thin deposited film. In this study, impact dynamics of silicone oil drops on inclined ( = 30°) glass slides pre-wetted with the same liquid, both spanning a viscosity range of 4–10,000 were investigated. Using high-speed imaging techniques from both the side and bottom views, three distinct air entrainment dynamics were identified: single, double, and peripheral — governed by the viscous, capillary and inertial dynamics of the drop and the thin oil film. Additionally, the introduction of carbon black (0.005–0.1 wt.) particles significantly altered the wetting behavior by accelerating the air film rupture. Our results highlight the importance of drop and film viscosities and impact inertia in wetting dynamics and contact line propagation, and also underscores the need for multi-angle imaging to fully capture the transient wetting phenomena.
{"title":"Oil drop impact on inclined thin oil films","authors":"P. Pirdavari, H. Tran, M. Upoma, M.Y. Pack","doi":"10.1016/j.expthermflusci.2025.111552","DOIUrl":"10.1016/j.expthermflusci.2025.111552","url":null,"abstract":"<div><div>Viscous drop impacts occur in various modalities across numerous natural and commercial processes. In most practical applications, such as spray deposition, oblique impact is commonplace as well as the formation of a thin deposited film. In this study, impact dynamics of silicone oil drops on inclined (<span><math><mi>ϕ</mi></math></span> = 30°) glass slides pre-wetted with the same liquid, both spanning a viscosity range of 4–10,000 <span><math><mi>mPa s</mi></math></span> were investigated. Using high-speed imaging techniques from both the side and bottom views, three distinct air entrainment dynamics were identified: single, double, and peripheral — governed by the viscous, capillary and inertial dynamics of the drop and the thin oil film. Additionally, the introduction of carbon black (0.005–0.1 wt.<span><math><mtext>%</mtext></math></span>) particles significantly altered the wetting behavior by accelerating the air film rupture. Our results highlight the importance of drop and film viscosities and impact inertia in wetting dynamics and contact line propagation, and also underscores the need for multi-angle imaging to fully capture the transient wetting phenomena.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111552"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144556751","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 : 2025-12-01Epub Date: 2025-06-01DOI: 10.1016/j.expthermflusci.2025.111527
Artur Dróżdż , Vasyl Sokolenko , Witold Elsner
In this paper, the experimental study in flat-plate turbulent boundary layer (TBL) under various Reynolds number and adverse pressure gradient (APG) conditions was performed downstream of the wavy wall, which proved to be effective in delaying flow separation in Dróżdż et al. (2021). Three Reynolds numbers that reproduce the effect of slow changes in wind conditions on a large-scale pitch adjusted wind turbine (range of wind speed: ) and three pressure gradient evolutions that reproduce sudden changes in the relative inflow wind angle resulting from a rotation cycle and/or a blade torsional deflection cycle were analysed. The effect of Reynolds number was found to have a weak dependence on the performance of the method, since there was only about a 2% reduction in performance in the Reynolds number range studied, compared to the maximum efficiency of 15.5%. In contrast, for the maximum change in the pressure gradient, a decrease of 8.8% in the efficiency of the flow control method was reported. Assuming that a strong change in the pressure distribution occurs for at most a quarter of the blade deflection cycle, the rotor efficiency decreases by no more than 3.5%. Thus, the total efficiency of the method is not less than 10%. The results show that the chosen corrugation geometry works well under both nominal and off-design wind turbine rotor conditions. It was also shown that the method’s efficiency in postponing flow separation can be evaluated by increasing or maintaining total momentum, quantified by the changes in momentum-loss thickness due to wavy wall.
{"title":"Performance analysis of novel wavy-wall-based flow control method for wind turbine blade","authors":"Artur Dróżdż , Vasyl Sokolenko , Witold Elsner","doi":"10.1016/j.expthermflusci.2025.111527","DOIUrl":"10.1016/j.expthermflusci.2025.111527","url":null,"abstract":"<div><div>In this paper, the experimental study in flat-plate turbulent boundary layer (TBL) under various Reynolds number and adverse pressure gradient (APG) conditions was performed downstream of the wavy wall, which proved to be effective in delaying flow separation in Dróżdż et al. (2021). Three Reynolds numbers that reproduce the effect of slow changes in wind conditions on a large-scale pitch adjusted wind turbine (range of wind speed: <span><math><mrow><mn>5</mn><mo>−</mo><mn>40</mn><mspace></mspace><mi>m/s</mi></mrow></math></span>) and three pressure gradient evolutions that reproduce sudden changes in the relative inflow wind angle resulting from a rotation cycle and/or a blade torsional deflection cycle were analysed. The effect of Reynolds number was found to have a weak dependence on the performance of the method, since there was only about a 2% reduction in performance in the Reynolds number range studied, compared to the maximum efficiency of 15.5%. In contrast, for the maximum change in the pressure gradient, a decrease of 8.8% in the efficiency of the flow control method was reported. Assuming that a strong change in the pressure distribution occurs for at most a quarter of the blade deflection cycle, the rotor efficiency decreases by no more than 3.5%. Thus, the total efficiency of the method is not less than 10%. The results show that the chosen corrugation geometry works well under both nominal and off-design wind turbine rotor conditions. It was also shown that the method’s efficiency in postponing flow separation can be evaluated by increasing or maintaining total momentum, quantified by the changes in momentum-loss thickness due to wavy wall.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111527"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144221994","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 : 2025-12-01Epub Date: 2025-07-10DOI: 10.1016/j.expthermflusci.2025.111562
Xutun Wang, Yuchen Zhang, Zidong Li, Haocheng Wen, Bing Wang
This study presents a novel approach for quantificationally reconstructing density fields from shadowgraph images using physics-informed neural networks. The proposed method utilizes the shadowgraph technique visualizing the flow field, enabling reliable quantitative measurement of flow density fields. Compared to traditional methods, which obtain the distribution of physical quality in spatial coordinates case by case, our approach establishes an end-to-end neural network that directly maps shadowgraph images to physical fields. Besides, the model employs a self-supervised learning approach without any labeled data. Experimental validations across hot air jets, thermal plumes, and alcohol burner flames prove the model’s accuracy and universality. This approach offers a non-invasive, real-time surrogate model for flow diagnostics. It is believed that this technique could cover and become a reliable tool in various scientific and engineering disciplines.
{"title":"Physics-informed shadowgraph network: an end-to-end self-supervised density field reconstruction method","authors":"Xutun Wang, Yuchen Zhang, Zidong Li, Haocheng Wen, Bing Wang","doi":"10.1016/j.expthermflusci.2025.111562","DOIUrl":"10.1016/j.expthermflusci.2025.111562","url":null,"abstract":"<div><div>This study presents a novel approach for quantificationally reconstructing density fields from shadowgraph images using physics-informed neural networks. The proposed method utilizes the shadowgraph technique visualizing the flow field, enabling reliable quantitative measurement of flow density fields. Compared to traditional methods, which obtain the distribution of physical quality in spatial coordinates case by case, our approach establishes an end-to-end neural network that directly maps shadowgraph images to physical fields. Besides, the model employs a self-supervised learning approach without any labeled data. Experimental validations across hot air jets, thermal plumes, and alcohol burner flames prove the model’s accuracy and universality. This approach offers a non-invasive, real-time surrogate model for flow diagnostics. It is believed that this technique could cover and become a reliable tool in various scientific and engineering disciplines.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111562"},"PeriodicalIF":2.8,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144631677","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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