Experimental Thermal and Fluid Science最新文献

{"title":"Physics-informed shadowgraph network: an end-to-end self-supervised density field reconstruction method","authors":"Xutun Wang,&nbsp;Yuchen Zhang,&nbsp;Zidong Li,&nbsp;Haocheng Wen,&nbsp;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":"2025-07-10","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}

{"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":"Closed-loop rotary control of flow past a circular cylinder: An experimental study","authors":"Jian Song ,&nbsp;Zheng Zhang ,&nbsp;Yuanpu Zhao,&nbsp;Haibao Hu,&nbsp;Feng Ren","doi":"10.1016/j.expthermflusci.2025.111557","DOIUrl":"10.1016/j.expthermflusci.2025.111557","url":null,"abstract":"<div><div>An experimental investigation of closed-loop rotary control for flow past a circular cylinder has been conducted at a Reynolds number of <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>100</mn></mrow></math></span>. To support this study, an experimental platform is developed that integrates image pair acquisition, real-time particle image velocimetry (PIV) processing, and actuator driving, employing multithreading technology for enhanced performance. When the cylinder is towed in the water tank at a constant velocity, the downstream wake pattern is recorded to determine the feedback velocity signal via real-time PIV processing. Subsequently, the cylinder is driven to rotate by a motor, with the rotational velocity derived from proportional control. Experimental results for various proportional coefficients <span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> indicate that the closed-loop control significantly influences the flow field. When <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>&gt;</mo><mn>0</mn></mrow></math></span>, the downstream velocity fluctuations at the sensor location exhibit a reduction. The implementation of optimal control with <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>=</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></math></span> leads to a substantial decrease in the amplitude of transverse velocity fluctuations, reducing it to 52%. Additionally, this control strategy results in an elongation of both the recirculation region and the vortex formation region. The reduction in velocity fluctuations, as indicated by the normal Reynolds stress, suggests effective control of vortex shedding. However, in scenarios where <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>&lt;</mo><mn>0</mn></mrow></math></span>, the downstream wake pattern transitions to the “C(2S)” mode, resulting in a significant increase in transverse velocity fluctuations. Local linear stability analysis demonstrates that control mechanisms can effectively affect the wake stability, elongating the absolutely unstable region by 38.6% for the most effective control parameter while reducing the sensitive disturbance frequency. In addition to presenting experimental evidence for closed-loop rotary control, the current study introduces a methodology for employing real-time PIV to generate velocity fields for the purpose of regulating flow around a bluff body.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111557"},"PeriodicalIF":3.3,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144779802","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":"Wake asymmetry of a heated cylinder in a cross flow","authors":"Zhihao Zhang ,&nbsp;Yong Wang ,&nbsp;Ling Xiao ,&nbsp;Xueren Li ,&nbsp;Jiyuan Tu ,&nbsp;Shengjin Xu","doi":"10.1016/j.expthermflusci.2025.111560","DOIUrl":"10.1016/j.expthermflusci.2025.111560","url":null,"abstract":"<div><div>This paper investigates the flow and temperature distribution around a heated cylinder with an aspect ratio of 3.3 using 2D-PIV and thermocouples in a wind tunnel. The asymmetric wake and the influence of the free-stream turbulence intensity on the flow and temperature field were carefully examined under free-stream cross-flow conditions at a Reynolds number <em>Re_D</em> = 2.2 × 10⁴, with the flow being either laminar (<em>Tu =</em> 0.3 %) or turbulent (<em>Tu =</em> 5.9 %) after the artificial transition. Under laminar flow at a Richardson number <em>Ri</em> = 0.01, the heating from the cylinder increases the local air kinematic viscosity by approximately 1.47 times, which in turn, reduces the local Reynolds number to 1.5 × 10⁴. This causes the flow separation to occur earlier compared to the unheated scenario, with the width of the recirculation bubble and the length of vortex formation increasing up 16 % and 13 %, respectively. For heated scenario, geometrically asymmetric wake and surface temperature arise from slight differences in flow separation locations between the upper and lower surfaces, which is driven by local natural convection near the surface. When the free stream is turbulent, the asymmetry wake is weakened, and the surface temperature difference between the upper and lower surfaces decreases by 23 %, which is attributed to the attenuation of the natural convection near the cylinder surface. When comparing the temperature decay after the power to the heated cylinder is turned off, it is evident that temperature decreases more rapidly in the turbulent flow than that in the laminar flow, because of the enhanced forced convection in the turbulent flow.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111560"},"PeriodicalIF":2.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144653703","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}