Experimental Thermal and Fluid Science最新文献

{"title":"Water droplet impact-freezing behaviors on cold superhydrophobic cylindrical surfaces","authors":"Qi Guo ,&nbsp;Jiaxiang Zheng ,&nbsp;Zunru Fu ,&nbsp;Hui Gao ,&nbsp;Dongsheng Wen","doi":"10.1016/j.expthermflusci.2025.111613","DOIUrl":"10.1016/j.expthermflusci.2025.111613","url":null,"abstract":"<div><div>The impact-freezing behavior of droplets on cold superhydrophobic cylinders was investigated using silica-based coating and a self-constructed low-temperature droplet impact experimental platform. The effects of surface temperature, droplet impact velocity, and surface curvature on droplet dynamics and freezing behavior were systematically investigated. Experimental results revealed that the surface temperature predominantly inhibited droplet retraction, with limited influence on the spreading stage. The effect of surface curvature was found to be more complicated. Droplets tended to freeze rather than rebound at smaller curvature diameters, highlighting the dominance of heat transfer. As the curvature diameter increased, fluid flow effects became more pronounced, leading to a larger circumferential spreading factor. Then, this factor gradually decreased with further increases in diameter and eventually stabilized. Experiment also showed that the circumferential maximum spreading factor was positively correlated with both the surface supercooling degree and the Weber number, but negatively correlated with the curvature diameters ratio. Notably, the influence of surface temperature on impact-freezing was highly related to surface curvature. These findings provided insights into optimizing structured superhydrophobic surfaces for anti-icing performance.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111613"},"PeriodicalIF":3.3,"publicationDate":"2025-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047490","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}

{"title":"Interfacial characteristics of a perturbed liquid jet in quiescent air","authors":"Tianyi Wang,&nbsp;Yannis Hardalupas","doi":"10.1016/j.expthermflusci.2025.111603","DOIUrl":"10.1016/j.expthermflusci.2025.111603","url":null,"abstract":"<div><div>The physical understanding of liquid jet breakup in quiescent air remains incomplete due to the complex interactions among influencing parameters and limitations in current measurement techniques. In this study, a needle pin was positioned at the nozzle exit of a liquid jet pressure atomiser to introduce an artificial perturbation of controlled magnitude, enabling an investigation on the influence of flow disturbances on the breakup process. This perturbation is introduced to model potential flow disturbances that may occur inside the nozzle of an atomiser, such as liquid flow separation or cavitation. The interfacial characteristics of the liquid jet, including surface morphology and interfacial motion, were analysed to assess the impact of the imposed perturbation on the breakup process. Optical Connectivity (OC), which transmits a laser beam through the intact liquid core, was employed to capture detailed interface geometry. The instantaneous interfacial characteristics were tracked in time using Optical Flow Velocimetry (OFV) to measure the interfacial velocity. Proper Orthogonal Decomposition (POD) was applied to extract the dominant interfacial wave structures, which were subsequently correlated with interfacial motion to provide a comprehensive assessment of the perturbation effects. The consistency between the dominant interfacial geometry extracted from POD and the measured interfacial velocity further validates the reliability of the OC-OFV technique. The findings reveal that introducing artificial perturbations and adjusting their amplitude can alter the interfacial motion and geometry of the liquid jet by modifying internal flow patterns, which in turn influence the liquid breakup process and the velocity of the resulting liquid fragments. This highlights the significant impact of nozzle disturbances, such as cavitation or manufacturing defects, on atomisation performance. Moreover, the results suggest that applying controlled artificial perturbations could serve as an effective strategy for controlling the breakup process and optimising the resulting spray droplet velocity.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111603"},"PeriodicalIF":3.3,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145007649","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}

{"title":"Aerodynamic performance analysis of a NACA 63(4)-421 airfoil equipped with a trailing edge slot at suction side","authors":"Himmet Erdi Tanürün ,&nbsp;Abdussamed Yıldız ,&nbsp;Mehmet Seyhan","doi":"10.1016/j.expthermflusci.2025.111604","DOIUrl":"10.1016/j.expthermflusci.2025.111604","url":null,"abstract":"<div><div>The present work addresses the aerodynamic penalties caused by laminar separation bubbles in low Reynolds number regimes, which are prevalent in UAVs and small wind turbines. The slot design, which has been subjected to experimental validation, offers a passive, cost-effective solution for enhancing aerodynamic efficiency in such critical applications. Therefore, this study investigates the aerodynamic performance of the NACA 63(4)-421 airfoil equipped with a Trailing Edge Slot (TES) at suction side, evaluated through Force Measurement Experiments (FMEs) and Surface Oil Flow Visualization (SOFV) techniques in suction type wind tunnel. To improve flow reattachment and aerodynamic efficiency, the TES slot geometry was designed taking into account the following parameters: slot width ratio, slot angle, slot inlet location, and Coanda radius (<em>r_c</em>), slot outlet suction side radius (<em>r_t</em>), and slot inlet pressure side radius (<em>r_p</em>). Among the four TES configurations tested in the 0° to 30° range; Model 2 (M2) demonstrated superior performance across the investigated angle of attack (AoA) range. The stall angle of M2 was delayed by 3°, reaching 17° compared to the baseline (B1), and the maximum lift coefficient (C_L,max) reached 1.51, corresponding to a 122% increase compared to B1. M2 model significantly reduces the undesired fluctuating lift via jet injection from the slot geometry as compared to the B1 at pre-stall region. At AoAs between 6° and 16°, the high-momentum slot flow effectively interacted with the main flow, re-energizing the boundary layer and enhancing surface attachment. This mechanism directly contributes to delaying the stall. Furthermore, NACA 63(4)-421 airfoil having TES has been demonstrated to re-energise the boundary layer, modify the position of the Laminar Separation Line (LSL), and Turbulent Reattachment Line (TRL) and expand the turbulent flow region. This, in turn, has been shown to enhance surface flow attachment and delay stall by controlling the laminer separation bubble (LSB). The combination of optimized slot geometry and effective flow interaction confirms that TES configurations significantly enhance aerodynamic performance in Re of 9x10⁴.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111604"},"PeriodicalIF":3.3,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145019317","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}

{"title":"Experimental study on the effects of fuel properties on spray macroscopic characteristics, particle size distribution, and velocity field in a constant volume chamber","authors":"Tangsong Guo ,&nbsp;Guoxiu Li ,&nbsp;Hongmeng Li ,&nbsp;Haobo Huo ,&nbsp;Xiaoqin Zhang ,&nbsp;Zhanguang Wang ,&nbsp;Honglin Bai","doi":"10.1016/j.expthermflusci.2025.111602","DOIUrl":"10.1016/j.expthermflusci.2025.111602","url":null,"abstract":"<div><div>With the growing energy crisis, clarifying the effects of fuel properties on the engine spray process is one of the critical researches to find new alternative fuels for engines. In this study, the spray macro characteristics, spray particle size distribution, and spray velocity field of various fuels (diesel/biodiesel/coal-to-liquids/aviation kerosene) in a constant volume chamber under different injection pressures and environmental conditions were studied using a spray visualization test platform. The effects of fuel properties such as density, kinematic viscosity, surface tension, and evaporation characteristics on spray parameters, particle size distributions, and velocity distributions were analyzed. The results showed that the physical properties of the fuels under different evaporation conditions affected the spray process to different degrees. The effect of kinematic viscosity was significant under low evaporation conditions. As the kinematic viscosity decreased, the fuel spread more easily, and the fuel spray velocity distribution was more uniform. The effect of fuel volatility on the spray process was enhanced in the presence of significant evaporation. The effects of spray conditions, environmental conditions, and fuel properties on the spray performance were synthesized, and the expression of <em>SMD</em> with respect to the dimensionless parameters <em>We</em> and <em>Re</em> was obtained. With the increase in <em>We</em> and <em>Re</em>, the kinetic energy of the fuel development increased, the jet was more easily broken, and the fuel was better atomized. The experimental analysis results provided in this study illustrate the influence mechanism of fuel physical properties on the fuel spray process, which can provide theoretical support for the improvement of engine fuel adaptability and can also provide ideas for the development of new fuels.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111602"},"PeriodicalIF":3.3,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047134","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}

{"title":"Experimental investigation of momentum ratio and Weber number influence on droplets’ characteristics for jet in cross-flow","authors":"Erfan Saeedian Sar ,&nbsp;Azadeh Kebriaee ,&nbsp;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":"2025-08-27","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}

{"title":"Combined polarization and electrophoretic influence on bubble dynamics in leaky dielectric fluids","authors":"Tianle Gu,&nbsp;Samuel Siedel","doi":"10.1016/j.expthermflusci.2025.111601","DOIUrl":"10.1016/j.expthermflusci.2025.111601","url":null,"abstract":"<div><div>Electrohydrodynamics (EHD) is a powerful tool for manipulating fluid interfaces. While many studies focus on polarization forces in ideal dielectrics, the behavior of modern leaky dielectric fluids, where free charges and Coulomb forces are significant, remains less understood. This study investigates the dynamics of air bubbles in HFE-7100, a representative leaky dielectric fluid, under DC, polarity-changing, and high-frequency (1 kHz) AC electric fields. High-speed imaging reveals that when the charge relaxation time (<span><math><msub><mrow><mi>τ</mi></mrow><mrow><mi>e</mi></mrow></msub></math></span>) is comparable to the bubble lifespan, complex dynamics emerge. Under DC fields, this leads to significant discrepancies in bubble lifespans and waiting times. During polarity reversal, Coulomb forces temporarily counteract buoyancy, pinning bubbles to the surface and creating unique triangular shapes. Conversely, high-frequency AC fields suppress these charge effects, leading to highly consistent, polarization-dominated dynamics, albeit with prolonged surface residence times. These findings demonstrate that free charges are critical in EHD phenomena in leaky dielectric fluids and highlight the limitations of quasi-electrostatic models. This work provides a foundation for refining theoretical models for EHD applications with modern fluids.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111601"},"PeriodicalIF":3.3,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144908317","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}

{"title":"Experimental study of flow characteristics on the Ahmed body covered by bio-inspired Convergent–Divergent riblets","authors":"Arash Mohammadikarachi,&nbsp;Mustafa Z. Yousif,&nbsp;Duy Dang Nguyen,&nbsp;Zhang Meng,&nbsp;Hee-Chang Lim","doi":"10.1016/j.expthermflusci.2025.111595","DOIUrl":"10.1016/j.expthermflusci.2025.111595","url":null,"abstract":"<div><div>The Ahmed body, which features a slanted rear surface, is a generic, simplified representation of ground vehicles. The present work aims to study the flow characteristics around the Ahmed body (with a 35° degree slanted surface) with a roof covered with novel bio-inspired convergent–divergent (C–D) riblets. For this purpose, various experimental measurements have been conducted using Particle Image Velocimetry (PIV) and Hot-Wire anemometry techniques. The findings of PIV measurements on the upper surface of the Ahmed body revealed a delay in detachment near the leading edge and suppression of the low-velocity recirculation region under the effect of C–D riblets, while also showing a reduction in the peak values of the time-averaged contours of Turbulent Kinetic Energy (TKE) and Reynolds shear stress in this region. In addition, the evaluation of the flow field on the slanted surface and in the wake region showed that the upper recirculation bubble behind the Ahmed body coated with C–D riblets moved vertically down (about 6.85%) and shifted upstream (about 22.7%) in the streamwise direction, while the lower recirculation bubble became thinner and more compact. The peak negative and positive values of Reynolds Shear Stress in the upper and lower shear layers behind the Ahmed body decreased with C–D riblets. Power spectrum analysis revealed that the dominant shedding frequency in the lower recirculation region increases (from <span><math><mrow><mi>S</mi><mi>t</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>23</mn></mrow></math></span> to 0.245) with the introduction of C–D riblets. Moreover, the Proper Orthogonal Decomposition analysis on the flow field over the roof and in the wake zone showed that the energy levels of the first two modes decreased when C–D riblets were applied.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111595"},"PeriodicalIF":3.3,"publicationDate":"2025-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895149","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}

{"title":"Experimental investigation of cooling and heat soak-back in inclined jet impingement liquid film","authors":"Bolin Hu ,&nbsp;Qingguo Lin ,&nbsp;Ting Li ,&nbsp;Weifeng Li ,&nbsp;Haifeng Liu ,&nbsp;Fuchen Wang","doi":"10.1016/j.expthermflusci.2025.111600","DOIUrl":"10.1016/j.expthermflusci.2025.111600","url":null,"abstract":"<div><div>Liquid film cooling plays a critical role in protecting the combustion chambers of liquid rocket engines from extreme thermal conditions. However, the heat soak-back effect remains a primary cause of engine overheating. This paper experimentally investigates the heat transfer characteristics during liquid film cooling and heat soak-back. The liquid film flow is visualized using a high-speed camera. The effects of liquid temperature, wall superheat, and input power are considered. The results indicate that the wall superheat exerts the strongest effect on the propagation of the wetting front, followed by liquid temperature and input power. The hindering effect of boiling decelerates the wetting front velocity. Thermal analysis reveals that the surface heat flux during liquid film cooling and heat soak-back exhibits a positive correlation with wall superheat and input power while being inversely proportional to liquid temperature. In addition, compared to the downstream of the liquid film, the wall temperature rise caused by the heat soak-back effect is more severe at the impingement point. Prolonged cooling durations amplify this divergence, with impingement point temperatures rising continuously while downstream of the liquid film exhibits sustained cooling. This is attributed to the combined effects of oblique jet impinging and the wall heat flux provided by the heater. The quantitative evaluation of cooling performance incorporates both the total heat removal and cooling efficiency. The cooling efficiency calculated through liquid film splashing rate demonstrates the coupling effect of liquid film flow and heat transfer.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111600"},"PeriodicalIF":3.3,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144893747","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}

{"title":"Influence of the velocity gradient of the carrier medium on the crushing characteristics of non-Newtonian liquid droplets on the example of a highly concentrated coal-water suspension","authors":"G.V. Kuznetsov,&nbsp;S.V. Syrodoy,&nbsp;R.R. Zamaltdinov,&nbsp;Zh.A. Kostoreva,&nbsp;B.V. Borisov,&nbsp;N.A. Nigay,&nbsp;N.Yu. Gutareva,&nbsp;M.S. Tamashevich","doi":"10.1016/j.expthermflusci.2025.111598","DOIUrl":"10.1016/j.expthermflusci.2025.111598","url":null,"abstract":"<div><div>The article presents the results of the experimental studies of the processes of fragmentation of coal-water slurry fuel (CWS) drops in an air flow. The directions of movement of the CWS drops and the air flow coincided. The effect of the velocity gradient (<span><math><mrow><mi>∇</mi><mi>V</mi></mrow></math></span>) of the carrier medium (air) on the characteristics and conditions of CWS drop fragmentation was analyzed based on the experimental results. It was found that the <span><math><mrow><mi>∇</mi><mi>V</mi></mrow></math></span> values have a significant effect on the characteristics and conditions of CWS drop fragmentation. An increase in the velocity gradient of the carrier gas medium leads to a significantly nonlinear and nonmonotonic change in the critical Weber numbers for CWS drops of typical sizes in the case of using highly concentrated suspensions (with a coal component concentration in the fuel of φ_coal = 50–55 %). The analysis of the effect of the coal type and its concentration in the water-coal suspension has shown that the characteristics and conditions of CWS drop fragmentation are significantly affected by the rheological properties of the water-coal fuel. It is shown that during fragmentation of drops of highly concentrated suspensions (at φ_coal = 50–55 %) the dependence of the critical Weber number on the velocity gradient of the carrier medium flow demonstrates significant non-monotonicity and non-linearity. With an increase in the velocity gradient from <span><math><mrow><mi>gradV</mi><mo>=</mo><mn>80</mn></mrow></math></span> s⁻¹ to <span><math><mrow><mi>gradV</mi><mo>=</mo><mn>160</mn></mrow></math></span> s⁻¹ the values of the critical Weber number decrease (by 20 %), while a further increase in the velocity gradient leads to an increase in the We_cry values by 40 %. The latter is due to a significantly non-linear relationship between the rheological characteristics of the CWS and the concentration of coal, as well as the degree of its metamorphism. The hypothesis describing this non-trivial result has been developed. The hypothesis has been substantiated that the nature of the process of fragmentation of typical CWS drops is greatly influenced by a complex of hydrodynamic processes occurring inside the drop in the time period immediately preceding the fragmentation.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111598"},"PeriodicalIF":3.3,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047491","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}

{"title":"A new method to measure hydrodynamic parameters of liquid–gas slug flow using ultrasound technique","authors":"Cáio César Silva Araújo ,&nbsp;Tiago Ferreira Souza ,&nbsp;Maurício de Melo Freire Figueiredo ,&nbsp;Flávio Vasconcelos da Silva ,&nbsp;Felipe de Castro Teixeira Carvalho ,&nbsp;Alberto Luiz Serpa ,&nbsp;Ana Maria Frattini Fileti","doi":"10.1016/j.expthermflusci.2025.111592","DOIUrl":"10.1016/j.expthermflusci.2025.111592","url":null,"abstract":"<div><div>The slug flow is a multiphase flow pattern widely found in many industries, like power generation, petrochemical, and oil and gas. Several experimental investigations have been done to estimate slug flow characteristics. Nevertheless, there is a lack of attention to assessing the gas velocity in the liquid slug and the evaluation of the applicability of the developed ultrasound techniques in media with different viscosity. In this context, this paper aims to show a new method, based only on ultrasound measurements, to estimate gas velocity in a liquid slug, Taylor bubble passage frequency, Taylor bubble length, and liquid slug length, as well as to analyze the effects of viscosity on slug flow characteristics assessed using ultrasound techniques. The experiments are carried out in a 2” vertical pipe with water–air or oil–air flows. The ultrasonic measurements were carried out using two piezoelectric transducers of 2.25 MHz central frequency in a pulse-echo mode. The raw echo signals acquired were processed to obtain the echo energy and time-of-flight signals to estimate the slug flow characteristics. The results indicate that the ultrasound method developed can estimate the slug flow characteristics in the water–air and oil–air two-phase flows.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111592"},"PeriodicalIF":3.3,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144878251","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}