Experimental Thermal and Fluid Science最新文献

{"title":"Combustion of NH3/CH4 mixtures in a swirl burner: Study of non-premixed flames with radial fuel injection","authors":"Antoine Morel,&nbsp;Toufik Boushaki","doi":"10.1016/j.expthermflusci.2025.111630","DOIUrl":"10.1016/j.expthermflusci.2025.111630","url":null,"abstract":"<div><div>The transition to renewable energy is essential in addressing climate change. While natural gas plays a significant role in this transition, it still produces CO₂ emissions. Ammonia (NH₃) is being investigated as a promising alternative fuel. However, ammonia combustion presents several technical challenges, such as low flame velocity, limited calorific value, difficulties with flame stabilization, and high NOx emissions. This study examines the impact of ammonia addition to methane, equivalence ratio, and swirl number on pollutant emissions (NO, CO, CH₄, and CO₂), exhaust gas temperature, and flame stability. Experiments are carried out using a swirl burner with a radial fuel injection in a 1-meter high combustion chamber. The burner consists of two concentric tubes, with the inner tube supplying fuel and the outer tube supplying air. The fuel is injected radially through eight holes at the burner exit. The ammonia fraction ranges from 0 to 100 %, the equivalence ratio from 0.8 to 1.0, and the swirl number from 0.8 to 1.4, with a constant flame power of 10 kW. Emissions of NO, CO, CH₄, and CO₂ are measured in the dry exhaust gases using a multi-gas analyzer, inside chamber temperatures are measured and the flame structure is analyzed via OH* and NH₂* chemiluminescence and velocity measurements by LDA technique. The results show that both the swirl number and equivalence ratio significantly alter flame geometry, affecting combustion zones and flame height. Axial velocity measurements indicate that the recirculation zone shrinks with ammonia addition, while a high swirl number increases axial velocity, promoting ammonia combustion and upstream flame propagation. Up to 30 % ammonia, the flame remains stable, but higher ammonia levels lead to fluctuations in stabilization. High ammonia content in the fuel mixture results in reductions of NO, CO, and CO₂ emissions, though there is a potential increase in unburned gases. As expected, the inside chamber temperatures decrease as the ammonia fraction increases.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111630"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358722","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 stratification on thermoacoustic instability, emissions, and flame macrostructure in a swirl-stabilized dual annular burner: An experimental study","authors":"Qazi Talal ,&nbsp;Zubairu Abubakar ,&nbsp;Ahmed Gaber H. Saif ,&nbsp;ELSaeed Saad ELSihy ,&nbsp;M. Raghib Shakeel ,&nbsp;Esmail M.A. Mokheimer","doi":"10.1016/j.expthermflusci.2025.111620","DOIUrl":"10.1016/j.expthermflusci.2025.111620","url":null,"abstract":"<div><div>Stratified flames have attracted significant attention due to their superior resilience to turbulence and enhanced flame stability, enabling reduced NO_x and CO emissions. In this study, an innovative dual annular stratified burner was designed and experimentally investigated to characterize thermoacoustic instability, emissions and flame macrostructure in swirling and non-swirling (jet) methane-air flames. Experiments were systematically conducted across stratification ratios (SR = 1–3) and global equivalence ratios (Φ_g) ranging from lean blowoff to rich conditions (Φ_g = 1.2). Swirling flames exhibited consistently acceptable emissions (NO_x and CO &lt; 20 ppm) under stable lean operating conditions (Φ_g = 0.55–0.8) for all SRs tested. Jet flames showed no thermoacoustic instabilities irrespective of SR or Φ_g variations. Similarly, swirling flames remained stable for Φ_g &lt; 0.8; however, at Φ_g = 0.8, thermoacoustic instability initiated, characterized by coupled oscillations of acoustic pressure and heat release fluctuations. These oscillations were sustained until Φ_g = 1.1, beyond which decoupling occurred. Limit cycle oscillations with heightened sound pressure amplitudes were observed at lower stratification ratios (SR = 1–1.5), whereas no limit cycles were detected at higher SR values (&gt;1.5). Increasing SR significantly suppressed instability amplitudes, notably resulting in a 70 % reduction of oscillation amplitudes at Φ_g = 0.9 when SR increased from 1 to 3. Flame macrostructure analysis confirmed improved anchoring and mixing characteristics of swirling flames compared to jet flames, particularly at higher SR conditions. This work highlights that controlled stratification effectively enhances operational stability and produces more compact flames in swirling combustors, offering valuable insights for developing low-emission and high-efficiency combustion systems.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111620"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wake behavior and entrainment motion in the far-field stage of over-tripped boundary layer turbulence","authors":"Letian Chen ,&nbsp;Zhanqi Tang ,&nbsp;Zhenqing Li ,&nbsp;Nan Jiang","doi":"10.1016/j.expthermflusci.2025.111617","DOIUrl":"10.1016/j.expthermflusci.2025.111617","url":null,"abstract":"<div><div>This study investigates the far-field wake behavior and entrainment motions of the over-tripped boundary layer (OT-BL) turbulence induced by a family of wall-mounted tripwires with different wall blockage rate <span><math><mrow><msub><mi>σ</mi><mi>w</mi></msub></mrow></math></span>. Friction Reynolds number <span><math><mrow><msub><mrow><mi>Re</mi></mrow><mi>τ</mi></msub></mrow></math></span> is more than twice that of the unperturbed canonical turbulent boundary layer. Far-field streamwise development of the OT-BL is referred to as a cooperative action of wall-driven and wake-driven mechanisms. Spatial two-point correlation and intermittency factor are employed to quantify the wall-driven and wake-driven ranges. The wall driver shows a weak dependence on the tripwire configuration, whereas the wake driver is clearly related to the tripwire configuration. Along with downstream development, the wake-driven region exhibits an upward and spreading trend, which correlates positively with <span><math><mrow><msub><mi>σ</mi><mi>w</mi></msub></mrow></math></span> of tripwires. The wake dynamics in turbulent region and near-interface region are revealed from the turbulent/non-turbulent interface perspective. In the upstream stage, the wake is controlled by the tripwire-excited disturbed eddies, and then, in the downstream stage, the near-interface wake dynamics are gradually similar to canonical pattern. Further, entrainment is considered based on nibbling and engulfing motions. For OT-BL, tripwire-excited disturbed eddies enhance nibbling and engulfing entrainment. Nibbling entrainment is the main entrainment mode, although engulfing process is also a significant component. Finally, the study assesses the far-field recovery trend of the OT-BLs’ wake dynamics and entrainment motion. This research provides a reference for tripwire design to simulate higher-<span><math><mrow><msub><mrow><mi>Re</mi></mrow><mi>τ</mi></msub></mrow></math></span> OT-BL in a finite test section. Meanwhile, we discuss the evaluation scheme on the wake turbulence characteristics of OT-BL from multiple perspectives.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111617"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106733","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":"High-speed impact of water droplets on microtextured surfaces: Effect of roughness and wettability on corona splashing","authors":"Danila Verkhodanov ,&nbsp;Nikita Khomutov ,&nbsp;Maxim Piskunov ,&nbsp;Ivan Vozhakov ,&nbsp;Sergey Starinskiy ,&nbsp;Alexey Safonov ,&nbsp;Nikita Smirnov","doi":"10.1016/j.expthermflusci.2025.111618","DOIUrl":"10.1016/j.expthermflusci.2025.111618","url":null,"abstract":"<div><div>A study of the high-speed impact of water droplets on smooth and microtextured fluoropolymer-coated titanium surfaces is presented. The experimental samples had an average roughness <em>R_a</em> from 0.04 μm to 15.4 μm and a static contact angle <em>θ</em> from 74° to 164°. The 0.5–1.3-mm droplets were impacted on the surfaces at velocities <em>U₀</em> = 5–20 m/s (the Weber number <em>We</em> = 450–2,800). Using a high-speed video camera with a sample rate of 60,000 frames per second, the values of the opening angle <em>α</em>, the maximum diameter <em>D_cor</em>, and the lifetime of the corona were measured and analyzed. In addition, the mean splashing velocities of both large and small secondary fragments were captured. A dimensionless ratio, <em>α/θ</em>, which characterizes the predominance of inertial or adhesive forces, was proposed for the development of an empirical model for predicting <em>D_cor</em>. This model was validated using data from other authors, which proved its applicability in the ranges of <em>We</em> = 450–2,800, <em>R_a</em> = 1.05–38 µm, <em>θ</em> = 69–164° (water) and <em>θ</em> <span><math><mo>≈</mo></math></span> 0° (ethanol). The research elucidated that superhydrophobic microtextured surfaces provide greater symmetry in corona splash and a larger opening angle. However, these surfaces also delayed liquid removal during splashing, which has the potential to impact the effectiveness of their water-repellent properties.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111618"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106731","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":"Study on the microscopic characteristics of successive droplet clusters impacting on the wall","authors":"Feixiang Chang ,&nbsp;Mang Yan ,&nbsp;Hongliang Luo ,&nbsp;Wuli Hong ,&nbsp;Yewen Feng ,&nbsp;Fei Liu ,&nbsp;Chang Zhai ,&nbsp;Kang Yang ,&nbsp;Bo Song ,&nbsp;Jian Zhang ,&nbsp;Samir Chandra Ray","doi":"10.1016/j.expthermflusci.2025.111619","DOIUrl":"10.1016/j.expthermflusci.2025.111619","url":null,"abstract":"<div><div>In Direct Injection Spark Ignition (DISI) internal combustion engines, fuel droplets inevitably impact the cylinder walls, resulting in droplet adhesion and incomplete combustion, thereby increasing pollutant emissions. The injection strategy has been proven to significantly improve the droplet-wall interaction. Initially, the Refractive Index Matching (RIM) method was used to measure fuel adhesion under both single and double injection conditions, with results confirming that the double injection strategy significantly reduced the fuel adhesion mass. To investigate the mechanisms underlying the reduction in fuel adhesion with double injection, Particle image analysis (PIA) and a multiple droplets producer were employed to examine the micro-behavior of successive droplet clusters near the wall surface. Statistical analyses were conducted on droplet size and velocity. Results showed that, when the two successive droplet clusters impact the wall, the Sauter Mean Diameter (SMD) of the second cluster is greater than that of the first cluster. There are two reasons for this. First, this difference is attributed to the coalescence between the leading droplets of the second droplet cluster and the trailing droplets of the first droplet cluster. Second, when the second droplet cluster impacts the wall, the breakup of fuel adhesion can also lead to the formation of larger droplets. Moreover, the second droplet cluster exhibits a significantly higher penetration velocity than that of the first, which can be attributed to the interaction of the velocity fields between the trailing droplets of the first cluster and the leading droplets of the second cluster. Furthermore, analysis of the average minimum droplet distance shows that droplet number density near the wall is relatively high and decreases with increasing distance from the wall. Lastly, the Bai model was used to predict the probabilities of stick, rebound, spread, and splash of successive droplet clusters at various observation points.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111619"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106734","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 study of effect of physical properties on the impact of drop on a liquid pool for an immiscible reactive system","authors":"Vishal Kumar,&nbsp;Sumana Ghosh,&nbsp;Shabina Khanam","doi":"10.1016/j.expthermflusci.2025.111628","DOIUrl":"10.1016/j.expthermflusci.2025.111628","url":null,"abstract":"<div><div>Droplet impact on a liquid film or pool is a unique phenomenon that can be observed in different industrial applications and natural processes. The drop impact associated with chemical reaction with pool liquid is often utilized in the preparation of emulsions (single or double) for the encapsulation of various active reagents. The present study investigates the effects of viscosity on drop dynamics before and after impact on the liquid pool for an immiscible reactive system. The drop is made of various wt% of sodium alginate and calcium carbonate and the pool is comprised of soybean oil that contains acetic acid. In the present work, the impact process is studied for varying concentrations of sodium alginate and calcium carbonate drops at different impact heights. Two different situations are studied. In one case, the drop viscosity is lower than that of the pool and in the other two cases, the drop viscosities are much higher than that of the pool. It has been observed that maximum crater depth increases with impact height for the later cases. Also, the crater takes time to retract and thus, subsequent drop formation is delayed. However, the size of the drops is smaller and pinches-off quickly. The impact of a low viscous liquid on a high viscous pool produces a swallow crater that is closed quickly, while pinch-off is delayed in other cases. Different phenomena, such as jet and crater formation, crowning and drop fragmentation are captured using a high-speed camera. The images are processed using ImageJ software. Finally, a theoretical model based on energy conservation has been developed to predict the crater depth based on the physical properties of the liquids.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111628"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358721","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":"Influence of the velocity gradient of the carrier medium on the crushing characteristics of non-Newtonian liquid droplets on the example of a highly concentrated coal-water suspension","authors":"G.V. Kuznetsov,&nbsp;S.V. Syrodoy,&nbsp;R.R. Zamaltdinov,&nbsp;Zh.A. Kostoreva,&nbsp;B.V. Borisov,&nbsp;N.A. Nigay,&nbsp;N.Yu. Gutareva,&nbsp;M.S. Tamashevich","doi":"10.1016/j.expthermflusci.2025.111598","DOIUrl":"10.1016/j.expthermflusci.2025.111598","url":null,"abstract":"<div><div>The article presents the results of the experimental studies of the processes of fragmentation of coal-water slurry fuel (CWS) drops in an air flow. The directions of movement of the CWS drops and the air flow coincided. The effect of the velocity gradient (<span><math><mrow><mi>∇</mi><mi>V</mi></mrow></math></span>) of the carrier medium (air) on the characteristics and conditions of CWS drop fragmentation was analyzed based on the experimental results. It was found that the <span><math><mrow><mi>∇</mi><mi>V</mi></mrow></math></span> values have a significant effect on the characteristics and conditions of CWS drop fragmentation. An increase in the velocity gradient of the carrier gas medium leads to a significantly nonlinear and nonmonotonic change in the critical Weber numbers for CWS drops of typical sizes in the case of using highly concentrated suspensions (with a coal component concentration in the fuel of φ_coal = 50–55 %). The analysis of the effect of the coal type and its concentration in the water-coal suspension has shown that the characteristics and conditions of CWS drop fragmentation are significantly affected by the rheological properties of the water-coal fuel. It is shown that during fragmentation of drops of highly concentrated suspensions (at φ_coal = 50–55 %) the dependence of the critical Weber number on the velocity gradient of the carrier medium flow demonstrates significant non-monotonicity and non-linearity. With an increase in the velocity gradient from <span><math><mrow><mi>gradV</mi><mo>=</mo><mn>80</mn></mrow></math></span> s⁻¹ to <span><math><mrow><mi>gradV</mi><mo>=</mo><mn>160</mn></mrow></math></span> s⁻¹ the values of the critical Weber number decrease (by 20 %), while a further increase in the velocity gradient leads to an increase in the We_cry values by 40 %. The latter is due to a significantly non-linear relationship between the rheological characteristics of the CWS and the concentration of coal, as well as the degree of its metamorphism. The hypothesis describing this non-trivial result has been developed. The hypothesis has been substantiated that the nature of the process of fragmentation of typical CWS drops is greatly influenced by a complex of hydrodynamic processes occurring inside the drop in the time period immediately preceding the fragmentation.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"171 ","pages":"Article 111598"},"PeriodicalIF":3.3,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An experimental study on icing distribution and adhesion characteristics of wind turbine blades in saltwater Condition","authors":"He Shen ,&nbsp;Fupeng Zhang ,&nbsp;Yan Li ,&nbsp;Wenfeng Guo ,&nbsp;Fang Feng","doi":"10.1016/j.expthermflusci.2025.111575","DOIUrl":"10.1016/j.expthermflusci.2025.111575","url":null,"abstract":"<div><div>Icing on wind turbine blades reduces output power and poses operational risks due to cold, humid environments in high-latitude coastal regions. Despite increasing studies on offshore wind turbine icing, research in this field remains relatively scarce. This study investigates the temperature effects on ice distribution and adhesion strength of glass fiber-reinforced plastic (GFRP) blade surfaces under freshwater and saltwater (1 g/L) conditions through icing wind tunnel tests and ice adhesion measurements. Results show that at −4 ℃, the blade’s lower surface forms icicles through water runback effects, while saltwater significantly suppresses icicle growth. Decreasing temperatures induce ice-type transitions from glaze to mixed and then rime ice, with the ice profile evolving from irregular to quasi-aerodynamic shapes. Saltwater ice exhibits smoother surfaces than freshwater ice, but differences diminish at −16 ℃. Ice adhesion strength increases with decreasing temperature but shows decelerating growth rates. Freshwater ice demonstrates 2.5–––4.7 times higher adhesion strength than saltwater ice at equivalent temperatures. These findings provide critical insights into the icing research of coastal wind turbine blades.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111575"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144738025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Closed-loop rotary control of flow past a circular cylinder: An experimental study","authors":"Jian Song ,&nbsp;Zheng Zhang ,&nbsp;Yuanpu Zhao,&nbsp;Haibao Hu,&nbsp;Feng Ren","doi":"10.1016/j.expthermflusci.2025.111557","DOIUrl":"10.1016/j.expthermflusci.2025.111557","url":null,"abstract":"<div><div>An experimental investigation of closed-loop rotary control for flow past a circular cylinder has been conducted at a Reynolds number of <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>100</mn></mrow></math></span>. To support this study, an experimental platform is developed that integrates image pair acquisition, real-time particle image velocimetry (PIV) processing, and actuator driving, employing multithreading technology for enhanced performance. When the cylinder is towed in the water tank at a constant velocity, the downstream wake pattern is recorded to determine the feedback velocity signal via real-time PIV processing. Subsequently, the cylinder is driven to rotate by a motor, with the rotational velocity derived from proportional control. Experimental results for various proportional coefficients <span><math><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub></math></span> indicate that the closed-loop control significantly influences the flow field. When <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>&gt;</mo><mn>0</mn></mrow></math></span>, the downstream velocity fluctuations at the sensor location exhibit a reduction. The implementation of optimal control with <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>=</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></math></span> leads to a substantial decrease in the amplitude of transverse velocity fluctuations, reducing it to 52%. Additionally, this control strategy results in an elongation of both the recirculation region and the vortex formation region. The reduction in velocity fluctuations, as indicated by the normal Reynolds stress, suggests effective control of vortex shedding. However, in scenarios where <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>P</mi></mrow></msub><mo>&lt;</mo><mn>0</mn></mrow></math></span>, the downstream wake pattern transitions to the “C(2S)” mode, resulting in a significant increase in transverse velocity fluctuations. Local linear stability analysis demonstrates that control mechanisms can effectively affect the wake stability, elongating the absolutely unstable region by 38.6% for the most effective control parameter while reducing the sensitive disturbance frequency. In addition to presenting experimental evidence for closed-loop rotary control, the current study introduces a methodology for employing real-time PIV to generate velocity fields for the purpose of regulating flow around a bluff body.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111557"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144779802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of flow field structures induced by cavity geometry in supersonic Mach 2 conditions","authors":"Zhong-Xuan He,&nbsp;Zhi-Jun Liao,&nbsp;Ho-Tse Huang,&nbsp;Szu-I Yeh","doi":"10.1016/j.expthermflusci.2025.111594","DOIUrl":"10.1016/j.expthermflusci.2025.111594","url":null,"abstract":"<div><div>This study utilizes particle image velocimetry (PIV) to analyze the flow field dynamics in cavity flame holders with varying geometries, emphasizing the quantitative effects of shear layer impingement location and cavity geometry on recirculation zone behavior. Experimental findings reveal that reducing the aft ramp angle weakens high-speed reverse flow near the bottom of the cavity, promoting increased circulation values and a more stable flow structure through the suppression of small-scale vortices. Moreover, as the cavity length-to-depth ratio (L/D) increases, the shear layer impingement location shifts further toward the cavity bottom, causing the primary recirculation zone to diminish or vanish. Concurrently, the secondary recirculation zone expands, leading to a decrease in both average vorticity and circulation values. Enhanced positive axial flow is also observed within the cavity, attributed to the interaction between the shear layer and three-dimensional flow dynamics. This study offers new insights into the transient flow behavior within cavities under supersonic conditions, emphasizing the role of shear layer impingement and recirculation characteristics. The findings provide valuable guidance for the design of cavity-based flameholders, bridging the gap between fundamental flow understanding and practical scramjet combustor applications.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"170 ","pages":"Article 111594"},"PeriodicalIF":3.3,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852580","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}