Experimental Thermal and Fluid Science最新文献

{"title":"Comparative experimental study of the effect of loading rate on the typical mechanical properties of bubble and clear ice cubes","authors":"Keke Shao,&nbsp;Zekang Zhen,&nbsp;Runmiao Gao,&nbsp;Mengjie Song,&nbsp;Long Zhang,&nbsp;Xuan Zhang","doi":"10.1016/j.expthermflusci.2024.111264","DOIUrl":"10.1016/j.expthermflusci.2024.111264","url":null,"abstract":"<div><p>Icing is a common liquid–solid phase change process that usually has negative effects. Bubbles will form in ice since air is significantly less soluble in ice than it is in water and these bubbles will affect the mechanical properties of ice cubes. To quantitatively investigate the effect of air bubbles on the mechanical strength of ice cubes, an experimental setup is built to explore the mechanical strength and modulus of clear and bubble ice cubes at different loading rates. The results show that even a low volume fraction of air bubbles in the ice cubes as low as 1.98% can have a significant effect on their mechanical properties. The weakening of tensile, compressive and bending strengths by air bubbles is almost less than 20%, while the weakening of shear strength by air bubbles reaches almost 60%. The effect of air bubbles on the four typical mechanical moduli does not exceed 20%. This research helps to optimize the de-icing technique and also provides methods and ideas for preparing ice.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"159 ","pages":"Article 111264"},"PeriodicalIF":2.8,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141638645","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":"Boiling induced atomization of liquid film produced by oblique jet impingement on superheated wall","authors":"Noritaka Sako ,&nbsp;Jun Hayashi ,&nbsp;Chihiro Inoue ,&nbsp;Hiroshi Kawanabe ,&nbsp;Yu Daimon","doi":"10.1016/j.expthermflusci.2024.111262","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111262","url":null,"abstract":"<div><p>For the thermal management of industrial devices, a reduction in the net coolant flow rate by droplet dispersion from a liquid film is important because it can cause unexpected thermal failure. To understand the process of droplet dispersion from a liquid film better, we experimentally and theoretically evaluated the characteristics of boiling-induced atomization in a liquid film formed by oblique jet impingement on a superheated wall. Atomization processes were visualized using magnified high-speed imaging using a backlight technique. In this study, two types of droplets were observed using high-speed-magnification imaging. These were large droplets that disintegrated from the ligament formed on a relatively high-temperature wall, and small droplets from the ligament formed via bubble bursting in the nucleate boiling regime. For the atomization induced by nucleate boiling, larger droplets were produced via bubble bursting further downstream from the impingement point because the bubble size and liquid film thickness increased. Finally, the total volume of the droplets produced by nucleate boiling was estimated from the frequency of bubble bursting and droplet size measured from the visualization results. The estimation results suggest that the ratio of the total volume flow rate of the ejected droplets to the injection flow rate of the liquid was negligible (2%). Thus, most of the injected liquid eventually reached the wetting front of the sheet, separating it from the wall before drying out.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111262"},"PeriodicalIF":2.8,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141595949","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":"Analysis of stability and internal flow mechanisms in spiral annular flow with different swirlers","authors":"Haoyu Wang,&nbsp;Yang Yang,&nbsp;Bin Yang,&nbsp;Yu Tang,&nbsp;Wenjie Jing","doi":"10.1016/j.expthermflusci.2024.111263","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111263","url":null,"abstract":"<div><p>Spiral annular flow within ducts is widely utilized in modern industry, with the swirler serving as a critical component in generating such flow patterns. The structure of the swirler significantly influences the generation and stability of the spiral annular flow. This study selected four different swirler structures with outstanding performance from previous research and analyzed their characteristics through visual image processing combined with numerical simulations. By analyzing the amplitude information of the wave fluctuations in the annular swirling flow liquid film under different operating conditions using probability density functions, it was found that the swirler A(Flat-vane swirler) and swirler B(Flat-vane swirler with hub) produced smaller fluctuations in the annular swirling flow liquid film, indicating better stability compared to the swirler C(Arc-vane swirler) and swirler D(Spiral-vane swirler), which exhibited poor performance. Combining the numerical simulation results with the analysis of the internal mechanism of the swirlers, it was discovered that within the swirler A and swirler B, the fluid between the swirler vanes experienced a larger pressure gradient, resulting in phenomena such as “jump” and “pull” under this pressure gradient. This, in turn, contributed to the generation of greater tangential velocity and radial pressure gradient after the fluid exited the swirler. Due to the influence of the swirler structure, the swirler A and swirler B did not completely separate the fluid region into four independent spaces. Instead, in the central connection area of the rear section of the swirler, the gas phase components aggregated earlier, greatly promoting the downstream generation of spiral annular flow. This study analyzed the two-phase flow process and mechanism inside the swirler, filling a gap in previous research and providing important references for the optimization and selection of swirlers.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111263"},"PeriodicalIF":2.8,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141606781","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":"Effect of inlet flow turbulence on hydro–acoustic coupling and flame–vortex interactions in a premixed dump combustor","authors":"Pankaj Pancharia,&nbsp;Vikram Ramanan,&nbsp;S.R. Chakravarthy","doi":"10.1016/j.expthermflusci.2024.111260","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111260","url":null,"abstract":"<div><p>The present work examines the effect of inlet flow turbulence on the flame–vortex modulations, hydro–acoustic coupling and recirculation zone dynamics at the onset of instability. The flow turbulence intensity varied using a custom-designed turbulence generator with different slot-width blockage plates placed upstream to the nominal flame-stabilization zone. The high-speed recordings of the CH*/OH* chemiluminescence and particle image velocimetry are used to deduce the relation between the flame–acoustic, flame–vortex and hydrodynamic–acoustic features during the unsteady combustion. The bifurcation analysis map revealed the effect of high inlet flow turbulence on postponing the onset of instability to higher inlet flow parameters. The initial observations showed potential changes in the acoustic behaviour and dynamical state of premixed turbulent combustion with an increase in inlet flow turbulence. The spatial Rayleigh index map illustrates a significant change in the acoustic driving region at high inlet flow turbulence based on the flame stabilization, heat release zone and flame–acoustic modulation in the shear layer and recirculation zone. The velocity spectral analysis and dynamic mode decomposition (DMD) spectrum suggested a correlation between the acoustic modulation and hydrodynamic instabilities, resulting in higher heat release rate oscillations. The high inlet flow turbulence modulates the vertical flapping motion of the flame front and flame roll-up in the recirculation region as evident by DMD spectrum and spatial modes. The flame–vortex dynamics during the dynamic transition events showed that the high inlet flow turbulence influenced the vortex shedding along the shear layer and recirculation zone dynamics. At low turbulence intensity, the vortex, in turn, supports the bulk flame movement through the induced velocity, which interacts with the free stream to create regions of low velocity. In contrast, the vortex in the shear layer and flame resides along the shear layer at higher turbulence. The paper concludes that at higher inlet flow turbulence, the recirculating flame reduces the hydro–acoustically modulated flow velocity fluctuations, which significantly affect the upstream flame propagation propensity.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111260"},"PeriodicalIF":2.8,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141595951","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":"Flow periodicity in microchannels with fin arrays: Experimental validation","authors":"Pinar Eneren,&nbsp;Arthur Vangeffelen,&nbsp;Yunus Tansu Aksoy,&nbsp;Maria Rosaria Vetrano","doi":"10.1016/j.expthermflusci.2024.111261","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111261","url":null,"abstract":"<div><p>Investigation of the hydrodynamics within microfluidic chips is crucial for cutting-edge integrated liquid cooling systems due to the coupling between the temperature and velocity fields. Therefore, in this experimental work, we examine the spatial periodicity of the laminar velocity fields and pressure drops inside offset strip fin (OSF) and square pin fin (SPF) arrays at Reynolds numbers between 50 and 292 under isothermal conditions. The velocity fields are characterized using the <span><math><mi>μ</mi></math></span>PIV technique, and an advanced image stitching algorithm is applied to obtain the streamwise velocity fields. These stitched velocity fields serve two key purposes: evaluation of the flow development length and validation of the flow periodicity due to the periodic nature of the fin arrays. The velocity measurements are compared to the DNS results, and the friction factors acquired from pressure drop measurements are accurately predicted by the correlations based on the periodic flow assumption owing to the rapid flow development. For the first time, to the authors’ knowledge, the consistent monotonic decay of flow perturbations is experimentally evidenced to occur via a single exponential mode. Finally, based on our validation, we confirm the feasibility of using the unit-cell approach to significantly reduce the computational costs compared to simulations that resolve the entire geometry.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111261"},"PeriodicalIF":2.8,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141595952","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":"Comprehensive study on collision patterns of viscous droplets impacting on a heated particle","authors":"Zhiheng Fan,&nbsp;Daoyin Liu,&nbsp;Cai Liang,&nbsp;Xiaoping Chen","doi":"10.1016/j.expthermflusci.2024.111259","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111259","url":null,"abstract":"<div><p>The collision process involving droplets and heated particles has gained significant attention due to its wide industrial relevance. This study utilizes a high-speed photography to investigate the collision dynamics between viscous droplets and heated particles. The research identifies six distinct collision patterns. In the bubble-breakup mode, the particle experiences the greatest temperature drop, resulting in the most substantial heat transfer. The particle temperature plays a crucial role in determining collision behavior when the Reynolds number exceeds 100 and the Weber number exceeds 55. The maximum spreading area demonstrates a linear relationship with the Weber number, while it reaches a peak and stabilizes with Reynolds numbers in the deposition regime. Contact angle fluctuations are caused by the instability of the contact line. The liquid film thickness exhibits linear and power growth phases, followed by a rapid decrease in the bubble-breakup regime. While the branch-breakup pattern sees smaller fragmented droplet sizes, the atomization-breakup pattern sees flow velocity rise with both Reynolds and Weber numbers. The predicted wavelength of the disturbance in the atomization regime, based on Rayleigh-Taylor instability theory, aligns well with the experimental measurements. The residence time correlates positively with the Weber number.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111259"},"PeriodicalIF":2.8,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141482559","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":"Child droplet compositions produced by puffing and micro-explosion of two-liquid parent droplets","authors":"D.V. Antonov,&nbsp;R.M. Fedorenko,&nbsp;P.A. Strizhak","doi":"10.1016/j.expthermflusci.2024.111258","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111258","url":null,"abstract":"<div><p>The paper presents the experimental research findings on the compositions of child droplets produced by puffing and micro-explosion of parent two-liquid droplets. The droplets under study consisted of water and rapeseed oil. The research was carried out with varying concentrations of liquids in droplets, ambient temperatures, heating arrangements and initial sizes of two-liquid droplets. Parent droplets were heated in a flame, in a muffle furnace, and on a heated substrate. Child droplet compositions were identified using Laser Induced Fluorescence. Compositions were separated based on the difference in the fluorescence of liquids in child droplets exposed to laser radiation. Typical distributions of child droplets by size were obtained for water and rapeseed oil during parent droplet fragmentation when there was a group of contributing factors. The child droplet sizes were measured for water and rapeseed oil. Laser Induced Fluorescence was successfully used to identify different liquids in child droplets following the micro-explosive fragmentation of two-liquid droplets. The experimental data were processed to establish functional relationships between the main factors, parameters and integral characteristics of the investigated processes. Dimensionless criterion relationships and mathematical expressions were proposed for transferring the experimental results to different scales and conditions for heating two-liquid droplets. The applicability of this approach was described. Guidelines were provided on developing the proposed approach for heterogeneous compositions of parent droplets.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111258"},"PeriodicalIF":2.8,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141595950","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":"Film cooling performances of short fan-shaped-holes under oscillating freestream","authors":"Xin-yu Liu ,&nbsp;Jian Pu ,&nbsp;Jian-hua Wang ,&nbsp;Ran Yao","doi":"10.1016/j.expthermflusci.2024.111257","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111257","url":null,"abstract":"<div><p>Freestream oscillation presents a significant challenge in optimized design of short fan-shaped-hole, a good choice for more promising double-wall cooled blades. An experimental investigation was conducted to understand detailed effects of key geometrical parameters of the fan-shaped hole, freestream oscillating frequency and cooling air-to-mainstream blowing ratio on the unstable film cooling performances. The selected geometrical parameters included the length-to-diameter ratio, the lateral diffusion angle, and the length ratio of cylindrical section-to-diffusion section. Time-resolved planar quantitative light sheet technique was employed to visualize the temporal variations of jet trajectory and transported scalar concentrations. The experimental results indicated that freestream oscillation causes variations in jet mechanisms, changing the trend in film cooling with blowing ratio and reversing the universally-acknowledged harmful influence of non-fully development of cooling air in short tube. The optimized short-hole can achieve an increment up to 40% in film effectiveness under oscillating freestream, in comparison with the long-hole-jet. The primary principle of the optimized design of short shaped-hole is properly enlarging the lateral expansion angle, aiming at the higher steady film effectiveness while the lower unsteadiness due to the transient fluctuations. Further enlarging the length ratio can improve the stability of film cooling in an oscillating cycle.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111257"},"PeriodicalIF":2.8,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141444589","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":"Exploring thermal buoyant flow in urban street canyons: Influence of approaching turbulent boundary layer","authors":"Yunpeng Xue ,&nbsp;Yongling Zhao ,&nbsp;Shuo-Jun Mei ,&nbsp;Yuan Chao ,&nbsp;Jan Carmeliet","doi":"10.1016/j.expthermflusci.2024.111255","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111255","url":null,"abstract":"<div><p>Turbulent boundary layer inflow is a critical factor in urban climate research, shaping canyon flow dynamics, air ventilation patterns, and heat flux distribution. In numerical simulation studies, it serves as a fundamental inflow boundary condition, profoundly influencing overall results. In this study, simultaneous Particle Image Velocimetry and Laser-Induced Fluorescence (PIV-LIF) measurements are utilized within a large closed-circuit water tunnel. This approach allows comprehensive flow data to be gathered under varied flow and thermal conditions, encompassing a spectrum of Richardson numbers ranging from 0.01 to 1.34. The investigation aims to elucidate the effects of turbulent boundary layer flows on heat transfer mechanisms and flow behaviours within a two-dimensional street canyon model with a unit aspect ratio. The analysis reveals distinct heat and fluid flow characteristics, highlighting the interplay between thermal conditions and flow dynamics. The three chosen turbulent boundary layer flows demonstrate unique influences on flow characteristics and heat removal capacity. Significant variations in ventilation rates are observed, with a maximum difference of 80% among the tested boundary layer flows. Additionally, the most pronounced variation in heat removal capacity is approximately 45%. Thicker boundary layers with lower velocities near the canyon exhibit reduced ventilation and heat removal capabilities. Furthermore, the investigation reveals that varied turbulence inlet profiles result in diverse fluctuating features at the canyon roof level, with a comparatively lesser impact on the deeper regions of the canyon.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111255"},"PeriodicalIF":3.2,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0894177724001249/pdfft?md5=6ebe7db319c02e3c7d07c3e4c98e9f05&pid=1-s2.0-S0894177724001249-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141429266","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of the gap ratio on the flow field structures and the aerodynamic performance of an airfoil with ridge ice","authors":"Chengyi Zheng ,&nbsp;Zheyan Jin ,&nbsp;Zhigang Yang ,&nbsp;Lei Yu","doi":"10.1016/j.expthermflusci.2024.111256","DOIUrl":"https://doi.org/10.1016/j.expthermflusci.2024.111256","url":null,"abstract":"<div><p>Under SLD icing conditions, the ridge ice may appear on the surface of aircraft, which led to the significant aerodynamic deterioration and affected aircraft flight safety. The present study experimentally investigated the effects of the gap ratio on the flow field structures and aerodynamic performance of an airfoil with ridge ice. Detailed measurements were performed in a low-speed reflux wind tunnel by utilizing the Particle Image Velocimetry (PIV) technique and a high-sensitivity six-component balance. The results showed that the maximum lift coefficient, stall angle, and maximum pitch moment coefficient of the airfoil increased as the gap ratio enlarged. At AOA = 10 deg, the separation bubble length decreased by 77 % when the gap ratio changed from 0 to 0.1. Meanwhile, the separation bubble length decreased by 68 % when the gap ratio changed from 0.1 to 0.3. Besides, as the increase of the gap ratio, the average vorticity, turbulent kinetic energy, and Reynolds shear stress in the selected region above the airfoil decreased, while the average velocity increased. In addition, the gap ratio did not have an apparent effect on the transition onset positions and the maximum spanwise vorticity in the flow field.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"158 ","pages":"Article 111256"},"PeriodicalIF":3.2,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141429267","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}