Experimental Thermal and Fluid Science最新文献

{"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 ,&nbsp;Weichen Sun ,&nbsp;Qiang Chen ,&nbsp;Haifeng Liu ,&nbsp;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":"2025-07-08","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}

{"title":"Time-resolved PIV measurements of an unsteady viscous oil flow in a centrifugal pump","authors":"Rodolfo M. Perissinotto ,&nbsp;William D.P. Fonseca ,&nbsp;Rafael F.L. Cerqueira ,&nbsp;Natan A.V. Bulgarelli ,&nbsp;William Monte Verde ,&nbsp;Erick M. Franklin ,&nbsp;Marcelo S. Castro","doi":"10.1016/j.expthermflusci.2025.111558","DOIUrl":"10.1016/j.expthermflusci.2025.111558","url":null,"abstract":"<div><div>Centrifugal pumps are essential for many human activities, accounting for a considerable portion of the global electricity consumption. However, despite decades of study, the flow within the pump’s impeller and its effects on the performance are far from being fully understood, particularly when the flow involves fluids more viscous than water. In this context, this paper reports experiments using time-resolved particle image velocimetry (TR-PIV) for investigating the flow of a 14-cP-viscosity mineral oil in a transparent pump with radial impeller. We found that: (i) at low flow rates, the positions of vortices depend on the fluid properties; (ii) at higher flow rates, the oil flows aligned in the radial direction, while the water flows following closely the blade curvature; (iii) the velocity profiles for the oil are approximately parabolic, whereas those for water are flatter; (iv) the average deflection angle of the velocity vectors relative to the blade curvature changes significantly with viscosity; (v) contrary to common expectation, the turbulent kinetic energy is up to four times higher for oil than for water; (vi) vortices are periodically formed and dissipated with a frequency proportional to the rotational speed. Our results provide new insights into the flow of viscous fluids in pumps, with valuable information for their design and installation.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111558"},"PeriodicalIF":2.8,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595979","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":"Dynamic characteristics of pilot injection: Spray evaporation, mixture formation, and combustion under engine-like conditions","authors":"Shiyan Li ,&nbsp;Yijie Wei ,&nbsp;Ning Wang ,&nbsp;Shuai Huang ,&nbsp;Xinyi Zhou ,&nbsp;Jiale Cao ,&nbsp;Run Chen ,&nbsp;Tie Li","doi":"10.1016/j.expthermflusci.2025.111564","DOIUrl":"10.1016/j.expthermflusci.2025.111564","url":null,"abstract":"<div><div>In dual-fuel engines, pilot diesel injection critically influences combustion dynamics by initiating alternative fuel ignition, yet excessive replacement ratios may introduce disturbances within the nozzle, impacting external jet atomization and subsequent combustion processes. This study employs high-speed UV-LAS and OH* chemiluminescence imaging techniques to resolve transient mixture formation and flame development, comparing pilot injection (simulated with minimal needle valve activation) against main injection under varied injection pressures and ambient temperatures. Results demonstrate that pilot injection dominates liquid length control—surpassing ambient temperature effects and showing negligible pressure influence—where internal nozzle flow variations emerge as the primary driver of enhanced atomization when ambient enthalpy suffices for evaporation. Auto-ignition timing exhibits strong sensitivity to ambient temperature but minimal pilot-main differences due to comparable stoichiometric mixtures at ignition sites. Flame propagation dynamically self-regulates by targeting vapor-phase penetration, transitioning from entrainment-controlled to combustion-driven expansion. Quantitative analysis confirms pilot injection strategically modulates spatial mixture distribution: enriching near-stoichiometric/fuel-rich zones (φ &gt; 0.8) to enhance low-reactivity fuel (e.g., ammonia) ignition, while rapid post-injection homogenization establishes &gt;90 % lean mixtures (φ ≤ 0.8) within 0.5 <!--> <!-->ms after EOF. These findings establish pilot injection as a precision tool for in-cylinder equivalence ratio control, providing actionable strategies to optimize nozzle dynamics and combustion phasing in advanced dual-fuel systems.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111564"},"PeriodicalIF":2.8,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595978","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":"Crossflow induced vibrations of isosceles triangular cross-sections and related energy transfer at confined flow","authors":"E. Morales ,&nbsp;J. Corral ,&nbsp;E. Duñabeitia ,&nbsp;A. Barrero-Gil","doi":"10.1016/j.expthermflusci.2025.111555","DOIUrl":"10.1016/j.expthermflusci.2025.111555","url":null,"abstract":"<div><div>Experimental investigations on cross-flow induced vibrations of rigid prisms with isosceles triangle cross-sections, elastically supported in a free-surface recirculating water channel at a large blockage ratio of 0.4, are presented. The experiments revealed that the oscillatory response differed markedly from that observed in unbounded flows. Notably, sustained oscillations at very low reduced velocities and pronounced hysteretic effects were observed. From an energy transfer perspective, the isosceles triangle with a vertex angle of 150°was identified as the optimal geometry, exhibiting superior efficiency in transferring flow energy compared to previously reported geometries.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111555"},"PeriodicalIF":2.8,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144571961","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 novel event-based ensemble particle tracking velocimetry for single-pixel turbulence statistics","authors":"Jiajun Cao,&nbsp;Xin Zeng,&nbsp;Sen Li,&nbsp;Chuangxin He,&nbsp;Xin Wen,&nbsp;Yingzheng Liu","doi":"10.1016/j.expthermflusci.2025.111554","DOIUrl":"10.1016/j.expthermflusci.2025.111554","url":null,"abstract":"<div><div>This paper presents a long-duration event-based ensemble particle tracking velocimetry (EEPTV) method for single-pixel turbulence statistics; toward this end, a turbulent annular jet at a Reynolds number of 7,500 is used for demonstration. Leveraging the low-data-redundancy, high-temporal-resolution capabilities of an event-based camera, the EEPTV system complemented with grayscale correction from a low-speed frame-based camera successfully recovers 2.8 × 10⁶ image frames of the flow at 2,000 Hz. The EEPTV accurately captures the high velocity gradient in the shear layers, and the mean absolute velocity discrepancy is only 0.09 pixels/frame. This method also demonstrates superior performance in resolving Reynolds stresses compared to conventional window-based PIV, which suffers from an underestimation of up to 52 % due to the spatial smoothing effect. A detailed analysis of sampling errors using the bootstrap resampling method reveals that the widths of statistical confidence intervals follow a power-law relationship with respect to both the frame count and the bin size, highlighting the necessity of long-duration acquisition for accurate single-pixel turbulence measurements. In this way, an efficient framework for high-resolution turbulence statistics is established, overcoming the long-standing trade-off between the spatial resolution and statistical fidelity. This work has the potential to provide reliable and spatially resolved turbulence statistics for turbulence modelling and data-driven algorithms.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111554"},"PeriodicalIF":2.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144571960","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":"Oil drop impact on inclined thin oil films","authors":"P. Pirdavari,&nbsp;H. Tran,&nbsp;M. Upoma,&nbsp;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":"2025-07-03","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}

{"title":"An experimental investigation of air, mist/air, and steam film cooling on a flat plate with single- and double-row holes","authors":"Tianyi Huo ,&nbsp;Penglei Su ,&nbsp;Xiaoze Du ,&nbsp;Li Li ,&nbsp;Runsheng Zhang ,&nbsp;Leping Zhou ,&nbsp;Hui Zhang","doi":"10.1016/j.expthermflusci.2025.111559","DOIUrl":"10.1016/j.expthermflusci.2025.111559","url":null,"abstract":"<div><div>Mist/air cooling, a novel technology proposed to enhance conventional air cooling, has been extensively studied. However, previous experimental studies have been limited to relatively low mainstream temperatures, resulting in incomplete mist evaporation. This study presents the first experimental investigation of mist/air film cooling under high-temperature mainstream conditions up to 460 K, focusing on the effects of blowing ratios (0.5–1.5) and row arrangements (single, in-line, and staggered-row). Comparative analyses are also performed using air-only and steam cooling results to provide a comprehensive evaluation of cooling performance. The results indicate that inline hole film cooling demonstrates improved performance along the centerline, though its effectiveness (<em>η</em>) diminishes between adjacent holes compared to single-row holes. In contrast, the staggered hole arrangement enhances cooling performance and results in more pronounced jet lift-off followed by reattachment to the wall. As the blowing ratio (<em>M</em>) increases, both single-row and inline hole arrangements experience a decrease in <em>η</em>, with mist cooling for single rows being an exception. Conversely, the staggered holes exhibit increased effectiveness. Additionally, both mist and steam cooling outperform conventional air film cooling in terms of <em>η</em>. Specifically, steam cooling increases the area-averaged effectiveness by up to 65.5 % at <em>M</em> = 1.5 with single-row holes, while mist cooling increases the effectiveness by 22.7 % at <em>M</em> = 1.0 for the staggered-row, with minimal water usage (6 % of coolant mass flow).</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111559"},"PeriodicalIF":2.8,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518736","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":"The spraying characteristics of electrohydrodynamic atomization under different nozzle heights and diameters","authors":"Yin Guan ,&nbsp;Yanxiu Sha ,&nbsp;Hao Wu ,&nbsp;Jingze Zheng ,&nbsp;Bin He ,&nbsp;Yang Liu ,&nbsp;Yihang Lei ,&nbsp;YongAn Huang","doi":"10.1016/j.expthermflusci.2025.111551","DOIUrl":"10.1016/j.expthermflusci.2025.111551","url":null,"abstract":"<div><div>Electrohydrodynamic atomization (EHDA), the atomization mode of variable electrohydrodynamic (EHD) spraying process, has been extensively studied and widely applied in assorted micro/nanoscopic engineering applications in recent years. However, many aspects of the rapidly changing liquid atomization behavior are not fully understood, especially that the impacts of nozzle height and diameter on the spraying characteristics of EHDA are quite lacking in the literature. In view of this, we performed an experimental work on EHDA under four most fundamental operating parameters including electric voltage, liquid flow rate, nozzle height, and nozzle diameter. Eight distinct spraying modes, namely Spindle, Pulsating Jet, Rotating Atomization, Pulsating Atomization, Stable Atomization, Tilted Atomization, Oscillating Jet, and Multi-jet were observed. The variations of spraying mode, Taylor cone length and angle, liquid jet breakup length, liquid jet rotating and pulsating frequency, atomization angle, and atomization area are analyzed in terms of electric Bond number and dimensionless flow rate, which are two most frequently used dimensionless variables in EHD spraying studies. Meanwhile, the influences of nozzle height and diameter on liquid spraying characteristics are also discussed. The Rotating Atomization and Pulsating Atomization modes are two newly discovered spraying modes that have not been reported in previous EHDA articles. The spraying characteristics of these two modes are examined in detail, which are also compared with those of the Stable Atomization mode obtained in this work, for the purpose of exploring their potential applications in the future.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111551"},"PeriodicalIF":2.8,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144501086","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":"Heat transfer augmentation using collapsible tube-induced pulsating flow","authors":"Aashish Ranjan,&nbsp;P. Deepu,&nbsp;Subrata Kumar","doi":"10.1016/j.expthermflusci.2025.111543","DOIUrl":"10.1016/j.expthermflusci.2025.111543","url":null,"abstract":"<div><div>This study investigates the enhancement of heat transfer rates using a simple passive pulsation mechanism facilitated by a collapsible tube (CT). A comparative analysis between the collapsible tube and a rigid tube is conducted at various Reynolds numbers (<span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>) to understand the impact of pulsation on the thermal and flow characteristics. The results show that the CT-induced pulsation significantly enhances the heat transfer rate, with an observed increase ranging from 70% to 50% at lower <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> (581 to 1597) with a corresponding Strouhal number (<span><math><mrow><mi>S</mi><mi>r</mi><mo>⪆</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>). However, the enhancement diminishes at higher <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> beyond 1597, characterized by a lower pulsation frequency (<span><math><mrow><mi>S</mi><mi>r</mi><mo>⪅</mo><mn>0</mn><mo>.</mo><mn>15</mn></mrow></math></span>), reducing from 44% at <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> = 1742 to 23% at <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> = 2323, as compared to the rigid tube case. Additionally, the thermohydraulic performance index (TPI) is assessed to quantify the efficiency of heat transfer rate relative to pressure losses in the collapsible tube system. Proper Orthogonal Decomposition (POD) analysis is employed to extract key flow structures and characterize the pulsation dynamics. The POD results reveal that the dynamic behaviour of the collapsible tube introduces energetic intermittent coherent structures in the flow field, which are absent in the rigid tube case, contributing to enhanced mixing and more efficient heat transfer. These findings suggest that employing a collapsible tube offers a practical strategy for significantly improving the heat transfer rate in various engineering applications without the need for complex active control systems.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111543"},"PeriodicalIF":2.8,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471479","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":"Impact of electrode surface texturing on hydrogen bubble dynamics during proton exchange membrane water electrolysis","authors":"Jakob Raeymaekers ,&nbsp;Klara Arhar ,&nbsp;Matic Može ,&nbsp;Pierre Colinet ,&nbsp;Iztok Golobič ,&nbsp;Johan Steelant ,&nbsp;Maria Rosaria Vetrano","doi":"10.1016/j.expthermflusci.2025.111538","DOIUrl":"10.1016/j.expthermflusci.2025.111538","url":null,"abstract":"<div><div>Water electrolysis systems are vital for sustaining human life during long-term space exploration missions. The main obstacle to the in-space operation of a water electrolysis system is the near-absence of buoyancy forces, impeding the detachment of hydrogen and oxygen bubbles from the electrodes and further complicating gas management, a crucial factor for efficient operation even in terrestrial applications. One of the most promising approaches to mitigate this problem is the micro- or nanostructuring of the electrode surfaces. Via surface structuring, the electrochemically active surface area can be enlarged and hydrophilicity increased, leading to easier detachment of gas bubbles. Additionally, bubble nucleation can be improved and bubble coalescence reduced. In this study, five pairs of laser-textured electrodes are manufactured, characterized and analyzed in terms of their performance and their influence on the bubble dynamics of the produced hydrogen gas. All textured electrodes achieve a performance enhancement over the unmodified surface (10% to 45% increase in current density for the same supply voltage). Gas production experiments prove that an increase in current density at a given voltage directly corresponds to a rise in production rate and, hence, in electrolysis performance. Significant differences in the bubble size distribution are observed on the different surfaces, as well as at different supply voltages. Distribution shapes and parameters (mean and standard deviation) remain mostly constant over time. Bubble rise velocities are significantly influenced by the entrainment of flow by the rising bubble plumes. Bubble growth after detachment is proven to be diffusion-controlled, and mainly determined by the degree of supersaturation close to the electrodes. This study proves that modification of the electrode surface morphology influences the performance of PEM systems by alteration of the bubble behavior during operation.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111538"},"PeriodicalIF":2.8,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471480","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}