Experimental Thermal and Fluid Science最新文献

{"title":"Flow field analysis of submerged oblique and normally impinging twin jets at varying impinging angles","authors":"C. Sandoval ,&nbsp;C. Treviño ,&nbsp;A. Alvarez ,&nbsp;D. Matuz ,&nbsp;J. Lizardi ,&nbsp;L. Martínez-Suástegui","doi":"10.1016/j.expthermflusci.2025.111491","DOIUrl":"10.1016/j.expthermflusci.2025.111491","url":null,"abstract":"<div><div>In this work, two-dimensional time-resolved particle image velocimetry (TR-PIV) measurements are carried out to study the flow structure and impinging interactions of two turbulent submerged isothermal circular impinging water jets. In this configuration, the uphill and downhill jets impinge obliquely and normally onto a flat target surface, respectively. A comprehensive parametric study is carried out for values of the jets’ exit Reynolds number of <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>j</mi></mrow></msub><mo>=</mo><mn>5000</mn></mrow></math></span> and 8000, jets’-to-surface target distances of <span><math><mrow><mi>H</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>3</mn></mrow></math></span> and 5, and inclination angles of the uphill oblique jet-to-impingement surface of (<span><math><mrow><msub><mrow><mi>θ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo></mrow></math></span>30°, 45°, 60°). For all the experiments, the jet-to-jet spacing distances were varied for each impingement angle of the oblique jet so that the impingement point of both jets coincide at the geometric intersection of the jets’ axes. Flow visualization images showing ensemble-averaged and instantaneous flow distributions and turbulent characteristics for equal and non-equal Reynolds numbers of the jets are presented. Velocity profiles and Reynolds shear stress distributions of the downhill wall jet development and its corresponding dimensionless shedding frequencies are also obtained. A proper orthogonal decomposition (POD) analysis reveals the spatial structure of the dominant fluctuation motions of the turbulent flow as well as their respective contributions to the total kinetic energy. Our results show that the jets’ exit Reynolds numbers, the oblique impingement angle of the uphill jet and the jets’-to-surface distance play a major role on the complex flow structure and dynamics, location of the stagnation point and entrainment characteristics of the turbulent flow field of the twin jets.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111491"},"PeriodicalIF":2.8,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833432","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":"Measurement of particulates formed during thermal protection system spallation in an arc-jet environment","authors":"K.J. Price,&nbsp;A. Martin,&nbsp;S.C.C. Bailey","doi":"10.1016/j.expthermflusci.2025.111487","DOIUrl":"10.1016/j.expthermflusci.2025.111487","url":null,"abstract":"<div><div>An arc-jet campaign conducted in the Aerodynamic Heating Facility at NASA Ames was conducted to investigate the spallation of thermal protection system materials by estimating the size of particles ejected from these materials, as well as the corresponding mass loss. Particle sizes were determined both from analysis of particle tracking velocimetry, utilizing a force balance on the particulates, and by direct measurement of particles captured through targeted design of the test articles. Analysis of the captured particles revealed that they took on different geometries consisting of fine particulates, individual fibers, and clumps of multiple fibers. Different methods were required for each particle sizing approach to determine particle quantities, and corresponding mass loss. However, similar values for mass loss were determined using both techniques. In addition, it was found that the particle size distributions were independent of surface heat flux, and whether the carbon preform contained additional phenolic resin. It was found, however, that the presence of phenolic resin caused a measurable reduction in the rate of particle production, potentially due to its pyrolysis reducing the diffusion of oxygen from the free stream into the sample.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111487"},"PeriodicalIF":2.8,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143821567","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 rotating detonation engine fueled by liquid ethanol and oxygen-enriched air","authors":"Jianghong Li ,&nbsp;Songbai Yao ,&nbsp;Ying Lei ,&nbsp;Jingtian Yu ,&nbsp;Yeqi Zhou ,&nbsp;Wenwu Zhang","doi":"10.1016/j.expthermflusci.2025.111494","DOIUrl":"10.1016/j.expthermflusci.2025.111494","url":null,"abstract":"<div><div>In this short communication, we explore the feasibility of using renewable ethanol fuel for the rotating detonation engine (RDE) and examine the behavior of the two-phase rotating detonation wave under varying working conditions. The liquid ethanol is injected at ambient temperature, while oxygen-enriched air (60 % oxygen by mass) is supplied at mass flow rates ranging from 90 to 200 g/s. The operation of the RDE is examined under fuel-lean conditions with equivalence ratios ranging from 0.4 to 0.9. At lower mass flow rates, the rotating detonation can still be initiated but remains highly unstable. As the mass flow rate increases, the stability of the ethanol-fueled RDE improves, premature extinction becomes less frequent, and the velocity deficit of the rotating detonation wave decreases.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111494"},"PeriodicalIF":2.8,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828237","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 wind load characteristics of high-rise buildings considering the aeroelastic effect of interference","authors":"Qiansen Wang ,&nbsp;Yunfei Zheng ,&nbsp;Shuochen Yang ,&nbsp;Xiongwei Yang ,&nbsp;Huimin Cui ,&nbsp;Qingkuan Liu","doi":"10.1016/j.expthermflusci.2025.111489","DOIUrl":"10.1016/j.expthermflusci.2025.111489","url":null,"abstract":"<div><div>To examine the impact of mutual interference between buildings on the wind loads acting on disturbed structures, a study was conducted using two identical square-section ultrahigh-rise buildings with a height-to-width ratio of 6:1. The wind tunnel pressure test considering aeroelastic effect was carried out. The results indicate that the influence of the aeroelastic effect is significant when the interfering building is positioned obliquely upstream or in a juxtaposed configuration. Then, the presence of upstream buildings reduces the mean pressure coefficient (<em>C_P</em>_{, mean}) of the disturbed building. However, when the interfering building is positioned directly upstream, the interference effect leads to an increase in the root mean square of the pressure coefficient (<em>C_P</em>_{, rms}) at most corner points of the disturbed building. Regardless of how the wind angle changes, except for some locations upstream of the interfering building, the extreme value of the wind pressure coefficient of the disturbed building often appears near the corner of the windward side of the building. The interference from different positions has varying effects on the mean aerodynamic force coefficients. Specifically, interference from an upstream oblique position increases the mean lift coefficient (<em>C_L</em>_{, mean}) of the disturbed building, whereas interference from a downstream oblique position increases the mean drag coefficient (<em>C_D</em>_{, mean}). The power spectrum of the aerodynamic force coefficients is most notably influenced by a building positioned directly upstream. Furthermore, as the wind direction angle increases, the changes in the power spectrum become more pronounced.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111489"},"PeriodicalIF":2.8,"publicationDate":"2025-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143821568","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":"Mitigating thermoacoustic instabilities in a Rijke tube burner using iron nanopowder additives","authors":"Xiaokang Liu ,&nbsp;Dongbin Wang ,&nbsp;Shen Fang ,&nbsp;Siyi Zhang ,&nbsp;Lijun Yang ,&nbsp;Jingxuan Li","doi":"10.1016/j.expthermflusci.2025.111472","DOIUrl":"10.1016/j.expthermflusci.2025.111472","url":null,"abstract":"<div><div>This study introduces a novel passive control method for mitigating thermoacoustic instabilities by adding iron nanopowder to the flame within a Rijke tube. A comprehensive experimental setup was designed to investigate how varying nanopowder concentrations influence self-excited oscillations at different Rijke tube lengths. Results show that even small amounts of iron nanopowder can suppress certain high-frequency instability modes or induce nonlinear behavior, such as mode switching from higher to lower modes. At higher concentrations, thermoacoustic instabilities can be almost entirely eliminated. Detailed analysis reveals that iron nanopowder mitigates thermoacoustic instabilities by extending the flame length, which reduces the heat release rate gain to the system, and by enhancing particle-induced acoustic damping.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111472"},"PeriodicalIF":2.8,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785893","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":"Falling film flow pattern transition of ionic liquid aqueous solution on horizontal tube bundles","authors":"Fangfang Zhang ,&nbsp;Shuyan Che ,&nbsp;Hao Yin ,&nbsp;Xiangyu Li ,&nbsp;Chuangyao Zhao","doi":"10.1016/j.expthermflusci.2025.111490","DOIUrl":"10.1016/j.expthermflusci.2025.111490","url":null,"abstract":"<div><div>The 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) ionic liquid aqueous solution is a promising absorbent used in absorption refrigeration technology. In this paper, the falling film flow pattern transition of the [EMIm]Ac ionic liquid aqueous solution was experimentally studied. The findings reveal that the critical Reynolds number for flow pattern transitions rises with increases in tube spacing, inlet liquid temperature, and circulating liquid temperature. In comparison to deionized water, the ionic liquid aqueous solution exhibits much smaller critical Reynolds numbers, and provides a more stable liquid film, and produces much smoother and clearer interfaces between liquid and gas. Additionally, hysteresis in flow pattern transitions is observed, and it generally increases with increasing tube spacing, inlet liquid temperature, and circulating liquid temperature. Criteria for flow pattern transitions are developed, and flow pattern maps are constructed for conditions with increasing and decreasing film flow rates, respectively.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111490"},"PeriodicalIF":2.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785854","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":"Gasoline direct injection spray-wall impingement: Macroscopic characterization and optical analysis","authors":"Jaime Gimeno,&nbsp;Pedro Martí-Aldaraví,&nbsp;Marcos Carreres,&nbsp;César Carvallo","doi":"10.1016/j.expthermflusci.2025.111476","DOIUrl":"10.1016/j.expthermflusci.2025.111476","url":null,"abstract":"<div><div>Spray-wall interaction (SWI) plays a crucial role in spray-based processes, influencing atomization, mixing, combustion efficiency, and pollutant formation. This study investigates SWI by analyzing spray morphology and key geometrical parameters, including spray penetration, spray area, spreading behavior on a quartz wall, and post-impingement spray thickness. Three optical visualization techniques were employed to study the effects of varying injection and ambient pressures, fuel and ambient temperatures, and injector tip-to-wall distance. The impact of cold-start and other evaporative engine conditions on spray morphology was analyzed. An increase in the injection pressure, an increase in wall-to-tip distance, and a decrease in ambient back-pressure delay the start of the spray-wall interaction. Higher injection pressure leads to greater spray spreading over the wall. Regarding extinction profiles, a higher injection pressure and ambient temperature result in lower liquid concentration in the spray.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111476"},"PeriodicalIF":2.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767705","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":"Investigation on aerodynamic force behavior and flow structure of Ahmed body under crosswind","authors":"Jinji Li,&nbsp;Yingchao Zhang,&nbsp;Ruizhuo Zhou,&nbsp;Zhe Zhang,&nbsp;Guohua Wang","doi":"10.1016/j.expthermflusci.2025.111488","DOIUrl":"10.1016/j.expthermflusci.2025.111488","url":null,"abstract":"<div><div>This study investigates the aerodynamic performance and the near wake of the Ahmed body under crosswind conditions experimentally at a length-based Reynolds number <span><math><msub><mrow><mi>Re</mi></mrow><mi>l</mi></msub></math></span> <span><math><mo>∈</mo></math></span>[0.11, 0.64] × 10⁶. The slant angle of the Ahmed body is 35°, and the yaw angle (β) ranges from 0° to 30°. Throughout the investigations, force, pressure, particle image velocimetry (PIV) and flow visualization measurements are conducted. The variation of drag coefficient <span><math><msub><mi>C</mi><mi>d</mi></msub></math></span> with yaw angle follows a parabolic curve, with a remarkable increase in <span><math><msub><mi>C</mi><mi>d</mi></msub></math></span> occurring at 6°&lt;β &lt; 16° yaw angle. Non-uniformity and asymmetry in pressure distribution are shown on the base and slant surfaces, which can be attributed to the asymmetry behavior of recirculation structures behind the body. As the yaw angle increases, the shrinking of recirculation structures and the movement of their foci toward the surface contribute to a significant reduction in pressure on the leeward side of rear surface, thereby increasing drag. The shear layer on the windward side is suppressed, while on the leeward side, it separates prematurely, corresponding to an increase in the side force. Based on the findings of the present study and previous literature, a conceptual model of the flow structure is proposed for the 35° slant angle Ahmed body under crosswind, aiming to explain the evolution of the behavior of forces, pressure distribution, and the flow structures.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111488"},"PeriodicalIF":2.8,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143777020","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":"2C-2D PIV/PTV measurements of high Reynolds number turbulent channel flow with sub-viscous-length wall-normal resolution","authors":"Bihai Sun,&nbsp;Callum Atkinson,&nbsp;Julio Soria","doi":"10.1016/j.expthermflusci.2025.111481","DOIUrl":"10.1016/j.expthermflusci.2025.111481","url":null,"abstract":"<div><div>This study presents a high spatial resolution hybrid particle image velocimetry/particle tracking velocimetry (PIV/PTV) methodology for investigating high Reynolds number turbulent channel flow. Utilising two 103-megapixel cameras, the experiment captures the entire channel height with a spatial resolution finer than the viscous length scale. To ensure accurate mapping of the PIV image pairs to a common coordinate system, a novel holography-based pixel-to-pixel imaging sensor registration technique is developed, which achieves an uncertainty of better than <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span>. At the same time, an efficient second calibration process accounts for lens distortion. The hybrid PIV/PTV analysis leverages PIV velocity vectors as predictors to identify particle pairs for PTV, with velocity vectors sorted into bins of 0.6 viscous length height in the wall-normal direction for statistical velocity analysis. The resulting first- and second-order velocity statistics and the streamwise velocity spectra agree with the equivalent results obtained from direct numerical simulations (DNS) of turbulent channel flow at similar friction Reynolds number, validating the effectiveness of the proposed methodology in capturing the structure of turbulent channel flow with resolution equivalent to DNS resolution.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111481"},"PeriodicalIF":2.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767889","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":"Morphology and dynamics scaling of water sheet jets generated by microfluidic convergent nozzles","authors":"Alexandros Peteinaris ,&nbsp;Priyanka Sinha ,&nbsp;Julian Schmid ,&nbsp;Alexandros Terzis","doi":"10.1016/j.expthermflusci.2025.111480","DOIUrl":"10.1016/j.expthermflusci.2025.111480","url":null,"abstract":"<div><div>The morphological dynamics of water sheet jets generated by microfluidic convergent nozzles represent a critical area of research with significant implications for advancing controlled spray formation. This study employs anodically bonded Silicon wafer chips with etched converging nozzle geometries to investigate the effects of geometric parameters under varying flow conditions. High-speed shadowgraph imaging is utilized to assess the influence of nozzle thickness, outlet width, converging angle, and flow rate on the size and stability of water sheet jets. Experimental results demonstrate that sheet size is primarily governed by flow rate, while stability is strongly affected by nozzle design. Scaling correlations are developed to quantitatively describe water sheet dimensions and transitions between jet breakup, stable sheets, and unstable sheet spray breakup. These findings advance the understanding of water sheet jet dynamics and provide a robust framework for designing microfluidic systems optimized for planar and controlled spray formation.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111480"},"PeriodicalIF":2.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767704","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}