Experimental Thermal and Fluid Science最新文献

{"title":"Experimental investigation on the evaporation dynamics of ethanol–water binary sessile droplets on a heated substrate","authors":"Du-Xin Zheng ,&nbsp;Xu-Ge Wang ,&nbsp;Lan Peng ,&nbsp;You-Rong Li","doi":"10.1016/j.expthermflusci.2026.111732","DOIUrl":"10.1016/j.expthermflusci.2026.111732","url":null,"abstract":"<div><div>To understand the coupled effect of substrate temperature and ethanol concentration on the evaporation characteristics of binary sessile droplets and their induced flow instability, we conducted an experimental study of the evaporation kinetics of ethanol–water binary sessile droplets on a heated substrate. The substrate temperature varies from 30 °C to 60 °C, while the ethanol volume concentration is from 0 to 90%. The distribution of the droplet surface temperature was observed using infrared thermography. Additionally, the evolutions in droplet surface thermal patterns and droplet morphology were examined. The results suggest that the evaporation of binary mixture droplets (BMD) is influenced by a combination of thermocapillary convection and solute capillary convection, resulting in pronounced flow instabilities, including hydrothermal waves (HTWs) and Bénard-Marangoni instabilities. The surface thermal pattern of BMD is closely related to the ethanol concentration. At low concentrations of ethanol, “three-convective cell” and “four-convective cell” structures are formed on the surface of the droplets, which are not observed at high ethanol concentrations. Increasing the substrate temperature enhances the droplet evaporation, leading to a higher BMD evaporation rate and an increase in the number of HTWs at the droplet surface. Furthermore, low concentration droplets exhibit a mixed evaporation mode, while high concentration droplets predominantly evaporate in a constant contact radius (CCR) mode.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"175 ","pages":"Article 111732"},"PeriodicalIF":3.3,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388209","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":"Turbulent drag reduction via interactions of deformable air films over super-hydrophobic surfaces","authors":"Minh Gia Nguyen ,&nbsp;Mohammad Mohammadzadeh Sanandaji ,&nbsp;Skinder Ali Dar ,&nbsp;Mohammad Ikram Haider ,&nbsp;Hongtao Ding ,&nbsp;Cong Wang","doi":"10.1016/j.expthermflusci.2026.111722","DOIUrl":"10.1016/j.expthermflusci.2026.111722","url":null,"abstract":"<div><div>Turbulent drag reduction remains a fundamental challenge for both aerial and ocean transportation. This study investigates the drag reduction effect of passively sustained deformable air-films or plastrons over patterned superhydrophobic surfaces (SHSs) in turbulent boundary layers (TBLs). SHSs with varied surface patterns and orientations, including uniform coating, streamwise strips, and transverse strips, were tested in TBLs over a Reynolds number range of <span><math><mrow><mn>3.2</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mn>5</mn></msup></mrow></math></span> to <span><math><mrow><mn>8.6</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mn>5</mn></msup></mrow></math></span>. These compliant air-films, characterized by high Weber numbers, exhibited dynamic deformations and strong coupling interactions with turbulent shear flows. These distinct effects are first qualitatively shown by a novel Lagrangian-type flow pathline visualization, which depicts suppressed or enhanced turbulence depending on the air-film pattern and orientations. High-fidelity time-resolved particle image velocimetry (PIV) was used to characterize such non-canonical TBLs and evaluate the associated drag reduction effects. The presence of deformable air-films led to reduced near-wall velocity and suppressed Reynolds shear stress (RSS), indicating effective drag reduction. Traditional wall shear stress estimation methods like the Charted Clauser method proved unreliable for these free-slip, deformable interfaces, due to the absence of log layer of canonical TBLs. The wall shear stress was instead estimated by extrapolating the total shear stress near the wall. The highest estimated drag reduction percentage was 28% for the streamwise strip pattern, 12% for the uniform surface, and −71% (drag increase) for transverse strip pattern, consistent with the flow visualization and PIV results. Additionally, an analysis of the total momentum flux across entire TBLs demonstrates a similar drag reduction trend, though the effect weakened at higher Reynolds numbers. The reported results contribute to a deeper understanding of turbulence control using non-canonical deformable boundaries, enabling sustainable drag reduction applications in hydrodynamic environments.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"175 ","pages":"Article 111722"},"PeriodicalIF":3.3,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388135","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 observation on flow pattern of thermal convection in eccentric annular deep-liquid pools","authors":"Chao Li ,&nbsp;Dong-Ming Mo ,&nbsp;Chun-Mei Wu ,&nbsp;You-Rong Li","doi":"10.1016/j.expthermflusci.2026.111720","DOIUrl":"10.1016/j.expthermflusci.2026.111720","url":null,"abstract":"<div><div>To clarify how eccentricity affects flow stability and the evolutionary process of thermal convection patterns, we conducted a sequence of experiments in deep-liquid pools with an eccentric annular structure. It is found that the bud-shaped flow pattern or straight spoke pattern will appear after the flow destabilization. In contrast to the flow structures appeared in concentric annular liquid pools, these patterns exhibit non-uniform distribution along the circumferential direction, that is, the spacing between adjacent flow modes is not uniform. Specifically, when the working fluid Prandtl (<em>Pr</em>) number is 6.7 and the liquid depth is fixed at 6 mm, the spoke-like patterns in the wide-slit area of the liquid pool will convert into bud-shaped structures with the increasing radial temperature difference, whereas they in the narrow-slit area start to oscillate. At <em>Pr</em> = 16.2 and 25.1, clear radial straight stripes are observed near the inner wall, and these radial straight stripes alternate with the straight spokes. The eccentricity also significantly reduces the critical value for flow destabilization. Notably, although buoyancy is increased in liquid layer depth, the eccentricity weakens the influence of buoyancy on flow stability.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"175 ","pages":"Article 111720"},"PeriodicalIF":3.3,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388207","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":"Quantitative analysis of droplet dynamics in ultrasonic atomization","authors":"Wenting Gu ,&nbsp;Shaoke Feng ,&nbsp;Xiuhong Chen ,&nbsp;Lutao Yan","doi":"10.1016/j.expthermflusci.2026.111757","DOIUrl":"10.1016/j.expthermflusci.2026.111757","url":null,"abstract":"<div><div>Ultrasonic atomization is widely used in engineering applications; however, the dynamic evolution of the atomization process still lacks effective quantitative characterization. This study proposes using the droplet area as a quantitative metric for characterizing the evolution of the ultrasonic atomization process. The results indicate that during atomization, the droplet area initially decreases, then rapidly increases, followed by a sharp decrease, and finally stabilizes. Moreover, higher ultrasonic input power and smaller initial droplet volume result in an earlier onset of atomization. Furthermore, the ultrasonic atomization process is identified as comprising two distinct stages: the spreading stage and the fragmentation stage. During the spreading stage, the evolution of key geometric parameters, namely droplet length, height, aspect ratio, and contact angle, is systematically analyzed under different ultrasonic input powers and initial droplet volumes. The results demonstrate that, during the spreading stage, droplet length and aspect ratio increase, whereas droplet height and contact angle decrease. Additionally, higher ultrasonic input power and smaller initial droplet volume increase the variation rates of these geometric parameters. Notably, the study reveals that ultrasonic atomization can achieve a droplet removal efficiency of up to 98.40% for adhered droplets. Therefore, this study provides useful guidance for parameter optimization in ultrasonic atomization applications and enhances the understanding of droplet morphological evolution during atomization.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"175 ","pages":"Article 111757"},"PeriodicalIF":3.3,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147797675","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":"Optical temperature measurements in superheated liquid droplets","authors":"M.Yu. Nichik ,&nbsp;R.E. Cherkasov ,&nbsp;D.V. Antonov ,&nbsp;P.A. Strizhak ,&nbsp;A.A. Zotyeva ,&nbsp;V.M. Dulin ,&nbsp;G. Castanet ,&nbsp;S.S. Sazhin","doi":"10.1016/j.expthermflusci.2026.111731","DOIUrl":"10.1016/j.expthermflusci.2026.111731","url":null,"abstract":"<div><div>A new laser-induced fluorescence (LIF) methodology, using a mixture of Kiton Red and Rhodamine 6G dyes (the 2cPLIF method), is developed and applied to the microscale liquid–liquid two-phase systems of oil and water. The results of the measurement of temperature fields for water–oil droplets, using this methodology and dyes with similar fluorescence spectra, are presented. Complex image processing, when dyes with similar emission peaks (585 nm and 550 nm) and threshold filters instead of bandpass filters are used, is required for this methodology. In the temperature range corresponding to the superheated state, the measurement error using this methodology is approximately <span><math><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mspace></mspace><mo>°</mo></mrow></math></span>C, which makes this approach more accurate than those used earlier. For complex objects with curvilinear interfaces (composite droplets), this approach is shown to effectively resolve their internal interfacial boundaries. The methodology, however, cannot properly compensate for the low intensity on the visible contour of the droplet and aberration effects. Potential applications of measurements of the temperature at the fuel/water interface, using the new methodology, could lead to an in-depth understanding of the underlying physics of puffing/micro-explosion in composite fuel/water droplets.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"175 ","pages":"Article 111731"},"PeriodicalIF":3.3,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388210","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":"Development of interferometric setup for studying transient fields during vapor–liquid absorption","authors":"Ane Errarte,&nbsp;Peru Fdez de Arroiabe,&nbsp;Aliaksandr Mialdun,&nbsp;Valentina Shevtsova,&nbsp;Mounir M. Bou-Ali","doi":"10.1016/j.expthermflusci.2026.111721","DOIUrl":"10.1016/j.expthermflusci.2026.111721","url":null,"abstract":"<div><div>A new interferometric setup has been developed and validated for investigation of vapor–liquid absorption in LiBr–H₂O systems. The system combines precise thermal control, multi-point temperature sensing, and high-resolution Mach–Zehnder interferometry, enabling simultaneous measurement of refractive index, temperature, and mass fraction fields. Validation experiments confirmed stable operation within a well-defined diffusion-dominated regime and demonstrated the capability to capture transient interfacial heating with high temporal and spatial resolution. Favorable agreement between interferometric and thermocouple data verifies the quantitative accuracy of the method and its sensitivity to small thermal gradients. The developed setup provides a versatile experimental platform for future studies of coupled heat and mass transfer across interfaces, including the influence of surfactants and Marangoni convection.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"175 ","pages":"Article 111721"},"PeriodicalIF":3.3,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388208","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":"2026-04-01","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":"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":"2026-04-01","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":"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":"2026-04-01","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":"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":"2026-04-01","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}