Experimental Thermal and Fluid Science最新文献

{"title":"A multi-scale experimental investigation on the interfacial drag characteristic in porous media through capillary forces and capillary bridge dynamics","authors":"Aimad Bouloudenine ,&nbsp;Liangxing Li ,&nbsp;Salah Chikh ,&nbsp;Kailin Wang ,&nbsp;Faiza Bibi ,&nbsp;Ahmed Yasiry","doi":"10.1016/j.expthermflusci.2026.111710","DOIUrl":"10.1016/j.expthermflusci.2026.111710","url":null,"abstract":"<div><div>Two-phase flow through porous media is a foundational phenomenon critical to industrial and natural processes. The flow resistances in such systems are particularly crucial for applications such as debris bed coolability during nuclear severe accidents, where interfacial drag between phases constitutes a significant but poorly understood portion of the total pressure drop, especially in large particle systems where conventional models fail. This study conducts a multi-scale experimental investigation that links macroscale flow resistance to its microscale physical origin. At the macroscale, a Flow Characteristics in Porous Media (FCPM) test system measured pressure drop and interfacial drag in adiabatic air–water two-phase flow through packed beds of 1.5 mm and 6 mm spheres. Results revealed that in the 6 mm bed, interfacial drag contributes up to 35% of the total pressure drop and creates a distinctive non-monotonic pressure gradient profile, a behavior absent in fine particle systems. At the microscale, a dedicated Capillary Force Analysis in Porous Media (CFAPM) test system directly measured capillary bridge forces between particles, finding a maximum tensile force of only 0.85 mN between two 6 mm spheres. This weak microscale adhesion (compared to gas inertial forces) enables highly mobile liquid interfaces that generate substantial interfacial drag at the macroscale. Existing two-phase flow models failed to reproduce these phenomena, revealing fundamental limitations in their physical basis. This work demonstrates that weak capillary forces at the pore-scale enable highly deformable, mobile interfaces that generate disproportionately strong interfacial drag, providing new physical insights for modeling two-phase transport in coarse porous media.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111710"},"PeriodicalIF":3.3,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074490","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 Weber number and impact angle on solidification behaviour of a molten droplet on an inclined surface","authors":"Raju Chowdhury ,&nbsp;Geoffrey Evans ,&nbsp;Tom Honeyands ,&nbsp;Brian J Monaghan ,&nbsp;David Scimone ,&nbsp;Subhasish Mitra","doi":"10.1016/j.expthermflusci.2026.111707","DOIUrl":"10.1016/j.expthermflusci.2026.111707","url":null,"abstract":"<div><div>Molten droplet impingement on an inclined surface and subsequent solidification occurs widely in various industrial applications. While the interaction behaviour of a molten droplet on a solid flat surface is well understood, understanding the interaction and subsequent solidification behaviour on an inclined surface is very limited. In the present study, high-speed imaging was used to determine interaction dynamics and solidification behaviour of a molten droplet of three different compositions onto an inclined solid surface over a range of normal Weber number (<em>We_n</em> &lt; 135) and impact angle (ϕ ≥ 45°). Five major interaction outcomes − (1) rebound, (2) disintegration, (3) partial rebound, (4) rivulet, and (5) combined effect of spreading and detachment were observed. Upon impingement, each droplet deforms asymmetrically on an inclined surface. The maximum spread ratio was shown to increase with the increase in normal Weber number and decrease with the decrease in impact angle. The spreading time was found to follow a power law form. It was found that at higher impact angles, the entire mass of the initial droplet solidified on the surface, whereas at lower impact angles only a portion of the droplet mass solidified. The solidification time of the impinged droplet was highly dependent on the amount of droplet mass that remained on the surface. A recovery type exponential profile was used to describe the droplet spreading kinetics. Finally, two regime maps were developed based on the Weber number and impact angle.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111707"},"PeriodicalIF":3.3,"publicationDate":"2026-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074613","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 influence of multi-row vortex generators on static hydrofoil","authors":"Pengzhong Wang ,&nbsp;Zhenyu Su ,&nbsp;Lan Ding ,&nbsp;Lu Wang ,&nbsp;Hongyang Zhao ,&nbsp;Bin Huang","doi":"10.1016/j.expthermflusci.2026.111703","DOIUrl":"10.1016/j.expthermflusci.2026.111703","url":null,"abstract":"<div><div>Vortex generators (VGs) suppress flow separation by introducing high-momentum fluid into the boundary layer, a technique that has been successfully implemented in aircraft and wind turbines. In hydraulic applications, VGs have also demonstrated effectiveness in controlling cloud cavitation. Previous research has primarily focused on single-row VG configurations, with limited studies on dual-row arrangements in wind turbines. Investigations into the effects of multi-row VGs (exceeding two rows) on flow field characteristics remain notably scarce. This study experimentally examines the cavitation and non-cavitation characteristics of a NACA63820 hydrofoil equipped with five-row micro vortex generators (mVGs), with particular emphasis on their influence on the hydrodynamic performance of stationary hydrofoils under both cavitating and non-cavitating conditions. The results reveal three key findings. First, regarding hydrodynamic torque, the multi-row mVGs exhibit negligible effects on the torque coefficient under non-cavitating conditions. However, under cavitating conditions, they significantly reduce the torque at angles of attack (AoA) below 6° compared to a smooth hydrofoil, while inducing higher torque at AoA exceeding 6°. Second, for cavitation-induced flow noise, the multi-row VGs effectively reduce the total sound pressure level (TSPL) at AoA below 6°, but substantially amplify hydrofoil-generated noise at higher AoA. Third, concerning cavitation patterns, the multi-row VGs modify the spatial distribution of surface cavitation, resulting in more uniform coverage while simultaneously increasing the frequency of cavitation shedding.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111703"},"PeriodicalIF":3.3,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074489","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":"Near field of a synthetic jet-controlled sweeping jet","authors":"Antonio D’Onofrio,&nbsp;Gerardo Paolillo,&nbsp;Carlo Salvatore Greco","doi":"10.1016/j.expthermflusci.2026.111705","DOIUrl":"10.1016/j.expthermflusci.2026.111705","url":null,"abstract":"<div><div>In the present study, the free flow field generated by a synthetic jet-controlled jet is experimentally investigated. The device under examination consists of two synthetic jets, which, being driven with a phase shift of <span><math><mrow><mn>180</mn></mrow></math></span>°, force a main steady jet emitted by a square exit nozzle to sweep. Besides the baseline configuration (i.e. without control), nine control configurations are studied by varying frequency and momentum of the synthetic jets, resulting in different values of the Strouhal number <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span> and momentum coefficient <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>μ</mi></mrow></msub></math></span>. For each tested configuration, the main jet Reynolds number is set at <span><math><mrow><mn>5</mn><mo>.</mo><mn>79</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>3</mn></mrow></msup></mrow></math></span>. The external flow field is measured by employing the planar Particle Image Velocimetry (PIV) technique. The triple decomposition technique is used to analyse the time- and phase-averaged mean and turbulent statistics of the controlled sweeping jet. It is observed that the main jet sweeps a wider angle when the synthetic jet control parameters, above all the momentum coefficient, are increased. The configurations characterized by the largest values of the actuation parameters feature also a faster streamwise decay of the centreline velocity. On the other hand, the increase of <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>μ</mi></mrow></msub></math></span> and <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span> leads to higher spreading rate. Furthermore, by fixing <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span>, the increase of <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>μ</mi></mrow></msub></math></span> leads to the increase of the values of phase-correlated kinetic energy in correspondence of the jet most deflected positions and to the reduction of the potential core-like region. Conversely, by fixing <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>μ</mi></mrow></msub></math></span> and increasing <span><math><mrow><mi>S</mi><mi>t</mi></mrow></math></span>, the highest values of turbulent kinetic energy are attained nearby the jet centreline. For the highest <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>μ</mi></mrow></msub></math></span>, it can be also noticed that the extent of the region marked by high values of phase-correlated kinetic energy reduces in the streamwise direction. Such a behaviour is explained through the phase-average analysis, which reveals that the Strouhal number strongly affects the jet oscillating pattern, specifically its curvature, thus reducing coherent fluctuations and promoting the increase of turbulent activity.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111705"},"PeriodicalIF":3.3,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074487","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":"Mixing and combustion of methanol and ethanol high-pressure sprays","authors":"Kevin Wan ,&nbsp;Junghwa Yi ,&nbsp;Lyle Pickett ,&nbsp;Julien Manin","doi":"10.1016/j.expthermflusci.2026.111704","DOIUrl":"10.1016/j.expthermflusci.2026.111704","url":null,"abstract":"<div><div>Time-resolved liquid and vapor mixing and combustion of methanol and ethanol from high-pressure sprays are measured by employing simultaneous high-speed diffuse-back illumination extinction imaging (DBI-EI), Rayleigh scattering, and OH* chemiluminescence. The experiments are performed in a constant-volume vessel at 22.8 kg/m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> and 800–1200 K. Methanol exhibits a longer liquid length and slightly faster vapor penetration than ethanol. Methanol liquid droplets suspected to be nanometer-scale, invisible to the DBI-EI diagnostic, are observed via scattering several millimeters downstream of the extinction-measured liquid length. On the other hand, the DBI-EI technique appears suitable for measuring ethanol liquid length at these conditions. A 1-D adiabatic jet mixing model and vapor–liquid equilibrium approximations shed insights on differences in mixing and evaporation. Methanol is shown to be the most sensitive to perturbations from equilibrium. The alcohols require relatively little mixing to approach near-stoichiometric conditions and are thus weakly sensitive to ambient oxygen levels, but fail to ignite below 1000 K ambient temperature, at least 200 K higher than needed for typical diesel-representative hydrocarbons such as n-dodecane. Instead, they require strong mixing to reach sufficient temperatures for ignition to counteract the strong evaporative cooling effects. The effect of 5% EHN is mild under these conditions, as it was estimated to lower the ignition temperature threshold by 40 K at most.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111704"},"PeriodicalIF":3.3,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036004","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 heat transfer and axis switching in multiple rectangular free surface jets with streamwise and spanwise orientations","authors":"Abhijit Madhav Date,&nbsp;Janani Srree Murallidharan,&nbsp;S.V. Prabhu","doi":"10.1016/j.expthermflusci.2026.111700","DOIUrl":"10.1016/j.expthermflusci.2026.111700","url":null,"abstract":"<div><div>This work presents an experimental investigation on the heat transfer characteristics and flow behaviour of multiple free surface rectangular water jets arranged in streamwise and spanwise orientations. The jets are configured in a 3 <span><math><mo>×</mo></math></span> 3 symmetric array with a uniform pitch of <span><math><mn>4</mn><mi>d</mi></math></span> and a hydraulic diameter of 3 mm. Experiments are conducted for Reynolds numbers from 1500 to 7500 and orifice-to-plate spacings (<span><math><mrow><mi>z</mi><mo>/</mo><mi>d</mi></mrow></math></span>) between 2 and 10. A 0.06 mm thick stainless steel foil serves as the target surface and infrared thermography records detailed surface temperature fields over a 37 mm <span><math><mo>×</mo></math></span> 37 mm area, providing about 63,000 data points for evaluating local, spanwise and overall average Nusselt numbers.</div><div>The results confirm that rectangular jets exhibit Reynolds number dependent axis switching, where the jet alternates its major axis orientation as it develops downstream. At low Reynolds numbers, multiple switching events occur with changing <span><math><mrow><mi>z</mi><mo>/</mo><mi>d</mi></mrow></math></span>, while at higher Reynolds numbers <span><math><mrow><mo>(</mo><mo>≥</mo><mn>4500</mn><mo>)</mo></mrow></math></span> a single stable switch forms near the orifice and remains unchanged. With increasing Reynolds number, the overall heat transfer nearly doubles across the studied range, showing a strong influence of jet momentum on convective performance. The two orientations show similar behaviour with a 90° phase difference and to the best of the authors’ knowledge, this is the first experimental demonstration of axis switching in multiple rectangular free surface jets.</div><div>Compared to circular jets from literature, rectangular jets achieve 30–40 % higher stagnation values and 40–45 % stronger off-centre cooling. The overall average Nusselt number increases by 60–100 % at low <span><math><mrow><mi>Re</mi></mrow></math></span> and by 45–50 % at higher <span><math><mrow><mi>Re</mi></mrow></math></span>, making rectangular jets highly effective for wide area cooling applications. Cosine based correlations predict 95 % of the data within 20 %, validating the proposed models for practical jet impingement applications.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111700"},"PeriodicalIF":3.3,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combined effects of fine particles and surfactant on bubble and bubbly flow characteristics in a narrow rectangular column","authors":"Ryo Kurimoto ,&nbsp;Soichiro Horita ,&nbsp;Kota Haruna ,&nbsp;Kosuke Hayashi","doi":"10.1016/j.expthermflusci.2026.111702","DOIUrl":"10.1016/j.expthermflusci.2026.111702","url":null,"abstract":"<div><div>Combined effects of fine particles and surfactant on bubbles and overall bubbly flows were investigated using image processing techniques. The distribution of bubble diameter <em>d</em> in the particle-laden surfactant solution shifted to larger diameter region with increasing measurement heights <em>z</em> due to bubble coalescence and lay between that in water and that in the particle-laden water. The distribution of the bubble aspect ratio <em>E</em> in the particle-laden surfactant solution did not vary with increasing <em>z</em> in contrast to that in the surfactant solution. The surfactant concentration available for adsorption onto the bubble interface was estimated by measuring the surface tension and was much lower than the setting value in the particle-laden surfactant solution due to surfactant adsorption onto particle surfaces. Additional measurements of <em>d</em> confirmed that the estimated concentration was adequate to inhibit bubble coalescence, while being inadequate to affect <em>E</em>. The distributions of the bubble velocity and gas holdup were also measured. In the particle-laden surfactant solution, the bubble velocity decreased while the gas holdup increased compared with those in the particle-laden water. This was attributed to the ratio of large <em>d</em> bubbles.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111702"},"PeriodicalIF":3.3,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074488","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":"Wind tunnel experimental study on drag reduction characteristics and mechanism of a wing with porous surface integrated with micro-blowing","authors":"Hai Du ,&nbsp;Yuhang Wei ,&nbsp;Yang Zhao ,&nbsp;Jiang Xu ,&nbsp;Dongsheng Gong ,&nbsp;Qiushi Li ,&nbsp;Yunao He","doi":"10.1016/j.expthermflusci.2026.111699","DOIUrl":"10.1016/j.expthermflusci.2026.111699","url":null,"abstract":"<div><div>Approximately 50% of the aerodynamic drag of an aircraft originates from viscous drag, within which skin-friction drag is the dominant component. Therefore, research on turbulent drag reduction holds both substantial economic value and scientific significance. In this study, the NASA SC (2)-0714 airfoil is selected as the research model, with porous media installed at the trailing edge. A combination of static force measurements and PIV experiments is employed to investigate the drag-reduction mechanism of a passive–active hybrid control strategy that integrates porous media with micro-blowing. Experimental results show that when only porous media are applied, the total drag of the airfoil decreases by 17.6% and the lift-to-drag ratio increases by 18.1%. With the addition of micro-blowing, the total drag reduction further reaches 20.1% and the lift-to-drag ratio improves by 20.8%. The local maximum drag reduction on the porous-wall surface of the airfoil reaches 33.4%, and is further enhanced to 40.2% under the influence of micro-blowing. Flow-field analysis reveals that the proposed passive–active hybrid control not only significantly reduces skin-friction drag, but also thickens the shear layer and decreases wall shear stress. Specifically, the average shear-layer thickness on the airfoil surface increases by 36.8% with porous media and further rises to 47.3% when combined with micro-blowing. In addition, this control strategy is capable of breaking up and lifting the vortex structures within the separation region, thereby substantially improving the overall aerodynamic performance.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111699"},"PeriodicalIF":3.3,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036052","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":"Droplet impact dynamics of spray coated superhydrophobic metal surfaces at various inclinations","authors":"B.V.R. Sai Krishna ,&nbsp;Manas Kumar Pal","doi":"10.1016/j.expthermflusci.2026.111697","DOIUrl":"10.1016/j.expthermflusci.2026.111697","url":null,"abstract":"<div><div>The wetting dynamics and impact behavior of water droplets on super hydrophobic (SHB) surfaces play a crucial role across wide range of applications. Hence several methods are developed for manufacturing of SHB surfaces. Among them, spray coating technique is quick, efficient and cost effective. In this study, three metal substrates are modified to exhibit superhydrophobic (SHB) properties via a unique spray coating. Droplet impact dynamics are investigated on both normal and SHB surfaces at various impact velocities (0.44–0.99 m/s) and surface inclinations (0°–60°). Key parameters including sliding length, maximum spreading factor (<span><math><msub><mrow><mi>β</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span>), rebound height, contact time, coefficient of restitution (CR), and droplet detachment time are systematically analyzed.</div><div>Results show a notable reduction in <span><math><msub><mrow><mi>β</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span> on SHB surfaces compared to normal ones, with <span><math><msub><mrow><mi>β</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span> increasing with higher impact velocity and decreasing with increasing surface inclination. Empirical correlations for <span><math><msub><mrow><mi>β</mi></mrow><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span> as a function of Weber number are developed for both surface types, achieving prediction accuracies within <span><math><mrow><mo>±</mo><mn>7</mn><mtext>%</mtext></mrow></math></span>. On SHB surfaces, droplet rebound is observed, where rebound height increases and CR decreases with increase in impact velocity. Correlations for dimensionless contact time are also proposed, with similar predictive accuracy.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111697"},"PeriodicalIF":3.3,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036053","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":"Effects of hydrogen and ammonia substitution on morphological and optical parameters of soot aggregates in ethylene/air laminar coflow diffusion flames","authors":"Raul Serrano-Bayona ,&nbsp;Felipe Campuzano ,&nbsp;Faruk Aydin ,&nbsp;Tirthankar Mitra ,&nbsp;Peng Liu ,&nbsp;William L. Roberts","doi":"10.1016/j.expthermflusci.2026.111698","DOIUrl":"10.1016/j.expthermflusci.2026.111698","url":null,"abstract":"<div><div>This study investigates the morphological and optical properties of soot aggregates in ethylene/air laminar coflow diffusion flames under partial substitution by hydrogen (H₂) and ammonia (NH₃), using the non-intrusive multi-angle light scattering (MALS) technique. A vertically-polarized 514.5 nm beam was focused on the flame centerline, and the scattering signal was collected between 25°-155°. A reference flame (Fuel: 60 vol% ethylene, 40 vol% nitrogen) was compared with cases where nitrogen (N₂) is substituted with H₂ and NH₃, maintaining a constant exit flow velocity. Measurements were carried out at three heights to assess the influence of residence time. Soot properties, including scattering-to-absorption ratio (<span><math><msub><mi>ρ</mi><mrow><mi>SA</mi></mrow></msub></math></span>), single-scatter albedo (<span><math><msub><mi>ω</mi><mi>A</mi></msub></math></span>), mean aggregate radius of gyration (<span><math><msub><mi>R</mi><mrow><mi>gm</mi></mrow></msub></math></span>), fractal dimension (<span><math><msub><mi>D</mi><mi>f</mi></msub></math></span>), and primary particle diameter (<span><math><msub><mi>d</mi><mi>p</mi></msub></math></span>), were characterized using the Rayleigh-Debye-Gans theory for fractal aggregates (RDG-FA). H₂ substitution increased <span><math><msub><mi>R</mi><mrow><mi>gm</mi></mrow></msub></math></span> and <span><math><msub><mi>D</mi><mi>f</mi></msub></math></span>, and displayed a more pronounced decrease in <span><math><msub><mi>d</mi><mi>p</mi></msub></math></span>, indicating enhanced aggregation and restructuring driven by elevated temperatures. Conversely, NH₃ substitution reduced <span><math><msub><mi>R</mi><mrow><mi>gm</mi></mrow></msub></math></span>, possibly due to inhibition in soot nucleation rates and surface growth by reducing H-radical concentrations and carbon-based precursors. <span><math><msub><mi>d</mi><mi>p</mi></msub></math></span> decreased with height, possibly due to enhanced graphitization and surface oxidation. Higher flame temperature increased <span><math><msub><mi>ρ</mi><mrow><mi>SA</mi></mrow></msub></math></span> and <span><math><msub><mi>ω</mi><mi>A</mi></msub></math></span>, and these ratios decreased with a reduction in carbon flux. These results offer a more integrated understanding of the links between aggregate structure, growth dynamics, and radiative behavior of soot formed under different fuel substitution conditions.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"174 ","pages":"Article 111698"},"PeriodicalIF":3.3,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145941149","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}