Experimental Thermal and Fluid Science最新文献

{"title":"An assessment of event-based imaging velocimetry for efficient estimation of low-dimensional coordinates in turbulent flows","authors":"Luca Franceschelli ,&nbsp;Christian E. Willert ,&nbsp;Marco Raiola ,&nbsp;Stefano Discetti","doi":"10.1016/j.expthermflusci.2025.111425","DOIUrl":"10.1016/j.expthermflusci.2025.111425","url":null,"abstract":"<div><div>This study explores the potential of neuromorphic Event-Based Vision (EBV) cameras for data-efficient representation of low-order model coordinates in turbulent flows. Unlike conventional imaging systems, EBV cameras asynchronously capture changes in temporal contrast at each pixel, delivering high-frequency output with reduced data bandwidth and enhanced sensitivity, particularly in low-light conditions. Pulsed Event-Based Imaging Velocimetry (EBIV) is assessed against traditional Particle Image Velocimetry (PIV) through two synchronized experiments: a submerged water jet and airflow around a square rib in a channel. The assessment includes a detailed comparison of flow statistics and spectral content, alongside an evaluation of reduced-order modeling capabilities using Proper Orthogonal Decomposition (POD). The event stream from the EBV camera is converted into pseudo-snapshots, from which velocity fields are computed using standard PIV processing techniques. These fields are then compared after interpolation onto a common grid. Modal analysis demonstrates that EBIV can successfully identify dominant flow structures, along with their energy and dynamics, accurately discerning singular values, spatial modes, and temporal modes. While noise contamination primarily affects higher modes – less critical for flow control applications – overall performance remains robust. Additionally, comparisons of Low-Order Reconstruction (LOR) validate EBIV’s capability to provide reliable reduced-order models of turbulent flows, essential for flow control purposes. These findings position EBV sensors as a promising technology for real-time, imaging-based closed-loop flow control systems.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"164 ","pages":"Article 111425"},"PeriodicalIF":2.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143227273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrigendum to “A study on the wake structure of an ascending submersible with silk flexible appendages using continuous wavelet transform and dynamic mode decomposition” [Exp. Therm. Fluid Sci. 160 (2025) 111323]","authors":"Fei Yan ,&nbsp;Gangqing Zhang ,&nbsp;Akira Rinoshika ,&nbsp;Bo Song ,&nbsp;Jian Zhang","doi":"10.1016/j.expthermflusci.2024.111354","DOIUrl":"10.1016/j.expthermflusci.2024.111354","url":null,"abstract":"","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"161 ","pages":"Article 111354"},"PeriodicalIF":2.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143175542","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":"Aerodynamic characterisation of isolated cycling wheels","authors":"Jiaqi Mao,&nbsp;Peng Zhou,&nbsp;Wei Yi,&nbsp;Xin Zhang","doi":"10.1016/j.expthermflusci.2025.111423","DOIUrl":"10.1016/j.expthermflusci.2025.111423","url":null,"abstract":"<div><div>This study evaluated the aerodynamic performance of isolated cycling wheels, including a 5-spoke wheel and a disc wheel, considering the effects of freestream velocity, wheel type, wheel rotation, and crosswinds. For the first time, the rotational torque of cycling wheels was characterised using a shaft-mounted torque transducer. Force and wake velocity measurements were conducted in a wind tunnel between <span><math><mrow><mn>10</mn><mspace></mspace><mtext>m/s</mtext></mrow></math></span> and <span><math><mrow><mn>22</mn><mspace></mspace><mtext>m/s</mtext></mrow></math></span>, where aerodynamics plays a dominant role in deciding overall resistance. The experimental results show that the wheel rotation has an opposite influence on the axial force of different wheels. A wake analysis effectively captured the influence of freestream velocity, wheel type, and wheel rotation on axial force. Results reveal that multiple vortical regions are formed in the lower wake of the rotating wheels, whereas the vortices in the upper wake are suppressed due to wheel rotation. When crosswinds are present, the disc wheel exhibits thirty times larger steering torque and generates much stronger vortical structures. This study offers valuable insights into the wake behaviour and drag generation around cycling wheels.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"164 ","pages":"Article 111423"},"PeriodicalIF":2.8,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143139228","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 shock train oscillation suppression by a plasma jet in a supersonic isolator","authors":"Fuhao Chen ,&nbsp;Zhaoyang Tian ,&nbsp;Chengzhi Zhang ,&nbsp;Lei Shi","doi":"10.1016/j.expthermflusci.2025.111428","DOIUrl":"10.1016/j.expthermflusci.2025.111428","url":null,"abstract":"<div><div>In a real ramjet engine, combustion instability gives rise to an unstable combustion pressure, which in turn disrupts the shock train in the inlet isolator, thereby introducing operational risks. This paper investigates the potential of the plasma jet (PJ) in supersonic flow control through a series of cold flow tests conducted at constant and incremental back pressure at <em>Mach</em> 2.5 freestream flow, respectively. As the pressure of the working material increases, the stable core region of the PJ expands, thereby demonstrating enhanced control capabilities. In the supersonic inlet isolator, the vertically injected PJ is compressed and induces a strong shock wave that dominates the downstream flow field. The shock wave induced by the PJ interacts with the leading-edge shock wave and results in a slight upstream movement of the shock train. The self-excited oscillation is suppressed with the implementation of the plasma actuator. The spatial FFT analysis indicates a reduction in both the oscillation frequency and the oscillation range of the leading-edge shock wave, with a suppression rate of 37.44% for the range. The PJ facilitates the momentum exchange near the shear layer and redistributes the oscillation energy. The dominant shock wave propagates the oscillation energy to the lower wall, thereby equalizing the energy distribution. Further studies on forced moving features demonstrate that the PJ effectively reduces low-frequency oscillation energy by at least 43.63% under incremental back pressure and achieves better control efficiency closer to the shock train. The high-frequency environment generated by the PJ and the shock wave induced by the PJ are considered the important factors in suppressing both self-excited and forced-excited oscillation of the shock train.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"163 ","pages":"Article 111428"},"PeriodicalIF":2.8,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134856","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":"Normalization of wettability and heat transfer coefficient curve prediction model on biphilic surfaces","authors":"Yindong Song ,&nbsp;Linfeng Xiang ,&nbsp;Xiuwei Cheng ,&nbsp;Dongshu Yang ,&nbsp;Kambiz Vafai","doi":"10.1016/j.expthermflusci.2025.111427","DOIUrl":"10.1016/j.expthermflusci.2025.111427","url":null,"abstract":"<div><div>The application of “biphilic surfaces” in boiling heat transfer has attracted widespread attention, and scholars have conducted numerous experimental studies in this field. Unfortunately, the relevant theoretical research is almost blank, especially in predicting essential parameters such as HTC. Therefore, it is necessary to develop a new correlation for the HTC of biphilic surfaces in boiling heat transfer. Firstly, in this study, biphilic surfaces composed of pure copper and Ag(S(CH₂)₁₇CH₃) were prepared using standard photolithography and chemical etching techniques. All of the surfaces feature 1000 μm square patterns, but there are variations in the contact angles (120.4°, 124.5°, 130.3°, 135°, 140°) of the hydrophobic surfaces. The maximum critical heat flux was 1203.5 kW/m², and the maximum heat transfer coefficient was 77.8 kW/m²K. Secondly, this study proposed the characteristic contact angle <em>θ_char</em>, which solves the issue of representing the wettability of biphilic surfaces with two contact angles. Next, the paper verified reliability of normalization process by combining the theory of homogeneous surfaces. Finally, this paper analyzed the undetermined coefficients in Rohsenow’s correlation by <em>θ_char</em>, enabling the prediction of HTC for biphilic surfaces. Compared with experimental data, the maximum prediction error does not exceed 24.13 %.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"164 ","pages":"Article 111427"},"PeriodicalIF":2.8,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143139227","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":"Transient freezing of water in a square channel: An experimental investigation","authors":"Bouke Johannes Kaaks,&nbsp;Danny Lathouwers,&nbsp;Jan-Leen Kloosterman,&nbsp;Martin Rohde","doi":"10.1016/j.expthermflusci.2025.111417","DOIUrl":"10.1016/j.expthermflusci.2025.111417","url":null,"abstract":"<div><div>This paper presents an experimental study for the transient growth of an ice layer in a square channel under laminar flow conditions and a mixed convection heat transfer regime. The ice layer was grown from a cold plate located at the bottom of the channel, capable of reaching temperatures between 0 and −20 °C. The onset of ice formation was marked by a sudden sharp increase of the cold plate temperature followed by a rapid spreading of the ice over the cold plate surface. This was attributed to subcooling effects within the thermal boundary layer of the flow. The flow field was measured using particle image velocimetry (PIV) and the ice profiles were measured at several instances of time after the onset of freezing by a visual tracing of the solid–liquid interface. In addition, a parametric study was performed regarding the effect of the cold plate temperature and the flow rate on the ice growth rate. Suitable approximations to the experimental boundary conditions were found after a detailed analysis of the cold plate’s transient temperature response, which could be readily implemented in numerical software. An important novelty of the present work is the measurement of the transient ice development of the ice-layer near the inlet of the channel, in addition to the centre of the channel where the flow is more developed. As such, a comprehensive and well-described experimental data set was generated for transient freezing in laminar internal flow. With this approach, a very good agreement was obtained between the experimental results and numerical simulations which were included to indicate the suitability of the current experimental campaign for numerical benchmarking purposes.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"163 ","pages":"Article 111417"},"PeriodicalIF":2.8,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of an advanced MEMS sensor for the simultaneous measurement of ion current and heat flux during flame–wall interactions","authors":"Kazuhito Dejima,&nbsp;Yoriaki Wakisaka,&nbsp;Tomoki Yokoyama,&nbsp;Kiyoshi Kawasaki,&nbsp;Koji Yamane","doi":"10.1016/j.expthermflusci.2025.111422","DOIUrl":"10.1016/j.expthermflusci.2025.111422","url":null,"abstract":"<div><div>Flame–wall interactions have been extensively investigated using optical diagnostic techniques or numerical simulations. However, these techniques tend to be costly and complex, making their application to actual combustor challenging. Therefore, a measurement technique that is easy to use and applicable to practical systems is required. In this study, a thin-film sensor for the simultaneous measurements of ion current and heat flux was developed using the micro-electro-mechanical systems (MEMS) technology. The MEMS sensor comprised two ion current sensors and a resistance temperature detector for evaluating flame behaviors and heat transfer during transient flame–wall interactions. The MEMS sensor was tested under a head-on quenching condition. Consequently, the ion current and heat flux were clearly measured. Compared with the flame images recorded by a high-speed camera, the ion current began to rise when the flame entered the flame-detectable zone (approximately 600 μm in this study) of the sensor and reached its peak when the flame was closest to the sensor. Subsequently, the ion current began to decrease and finally disappeared when the flame was completely quenched. In addition, the ion current and heat flux showed dispersions in their peak values and phases. Through the validation using simple numerical simulations, the reason for the dispersions was presumed to be the local heat release rate. The MEMS sensor detected the local ion current and heat flux. Therefore, it can be used to evaluate the near-wall characteristics of flame behaviors and heat transfer during flame–wall interactions.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"163 ","pages":"Article 111422"},"PeriodicalIF":2.8,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134855","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":"The regimes of drop vaporization in saturated conditions under low pressure","authors":"Antoine Courouble,&nbsp;Romuald Rullière,&nbsp;Jocelyn Bonjour","doi":"10.1016/j.expthermflusci.2025.111416","DOIUrl":"10.1016/j.expthermflusci.2025.111416","url":null,"abstract":"<div><div>This paper reports on a parametric study of the phenomenon of vaporization of drops deposited on a superheated wall in saturated low pressure conditions (i.e. close to the triple point pressure and in the absence of any non-condensable gas). The studied parameters were the surface temperature, the saturation pressure, the height of injection of the liquid forming the drop and the size of the injection needle. Three regimes of vaporization were observed : evaporation, rebound and boiling. The distinction between the regimes was based on the analysis of video sequences but also on the thermal signature of the process of vaporization as recorder by heat flux measurements performed by 25 heat flux sensors embedded in the heated wall.</div><div>The regime of evaporation is characterized by the progressive vaporization of the drop that keeps the shape of a spherical cap whose height and diameter decrease with time. The boiling regime may correspond to two different behaviors, both being characterized by the nucleation of a bubble inside the drop itself. In certain conditions, this bubble bursts in such a manner that the drop is atomized and many daughter drops are spread all over the heated wall (bursting bubble boiling behavior). Such burst is made possible by the large bubble diameters (up to several centimeters) that is typical of boiling at low pressure. In other conditions, the presence of the bubble slightly affects the overall phase change (soft bubble boiling) because the burst is not strong enough to disperse daughter drops. Lastly, the regime of rebound was observed only in a restricted range of operational conditions.</div><div>The time of vaporization obviously depends on the regime: the shorter times were recorded for the bursting bubble boiling behavior, owing to the dispersion of all small daughter drops that vaporize all over the surface. It was found to be longer for the behavior of soft bubble, and even longer for the regime of evaporation.</div><div>The conditions for the occurrence of the vaporization regimes were summarized on maps based on dimensionless parameters, namely the Weber number, the Ohnesorge number, a dimensionless heat flux and a dimensionless pressure.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"163 ","pages":"Article 111416"},"PeriodicalIF":2.8,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134918","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 characteristics of near-wall flow and instantaneous wall shear stress in front of wall-mounted cylinders","authors":"Qigang Chen (陈启刚) ,&nbsp;Dawei Zhang (张大伟) ,&nbsp;Zhongxiang Wang (王忠祥) ,&nbsp;Huilan Zhang (张会兰) ,&nbsp;Qiang Zhong (钟强)","doi":"10.1016/j.expthermflusci.2025.111424","DOIUrl":"10.1016/j.expthermflusci.2025.111424","url":null,"abstract":"<div><div>Characteristics of near-wall flow and instantaneous wall shear stress in front of wall-mounted cylinders are crucial for understanding the mechanism and correctly predicting the depth of local scour at piers. Here, the near-wall flow in front of circular and square cylinders mounted vertically in an open channel with Reynolds numbers from 9800 to 16,300 was measured via high-resolution particle tracking velocimetry (PTV). The instantaneous wall shear stress was obtained after determining the viscous sublayer thickness. The viscous sublayer, where the time-averaged streamwise velocity varies linearly along the wall-normal direction, is located below the downward flow, i.e., the turbulent horseshoe vortex, corner vortex, and jet-like reverse flow along the wall. Its thickness in the region below and away from the turbulent horseshoe vortices is thicker and thinner than that of uniform open channel flows, respectively. The instantaneous wall shear stress in the region dominated by the turbulent horseshoe vortex system exhibits a bimodal feature. The time-averaged wall shear stress is significantly amplified, with maximum magnification factors of approximately 2.5 and 4.0 in the flows upstream of the circular and square cylinders, respectively. Moreover, the corresponding turbulence intensities of the wall shear stress influenced by the turbulent horseshoe vortex in these two flows are approximately 2.0 and 5.5. The results indicate that the fluctuation of wall shear stress is crucial for correctly predicting the local scour at in-water cylinder structures such as bridge piers. However, the characteristics of wall shear stress are significantly different from those of turbulent open channel flows.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"163 ","pages":"Article 111424"},"PeriodicalIF":2.8,"publicationDate":"2025-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134857","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":"Coalescence position of two confined droplets with unequal lengths in microchannels","authors":"Wei Dong ,&nbsp;Yuqing Zhao ,&nbsp;Lei Tang ,&nbsp;Liangkang Xie ,&nbsp;Xiaoda Wang ,&nbsp;Wei Du","doi":"10.1016/j.expthermflusci.2025.111419","DOIUrl":"10.1016/j.expthermflusci.2025.111419","url":null,"abstract":"<div><div>The coalescence of two droplets with unequal lengths through a head-to-rear collision in the microchannel with a double T-junction is an important passive method to construct droplet reactors. However, the accurate prediction of the coalescence position is still not achievable. This work aimed to explore the coalescence position by analyzing the droplet dynamics. Firstly, the velocity variation of the paired droplets moving in a straight microchannel was analyzed to divide the whole process into several stages. Then, based on the experimental investigations, mathematical models were developed to describe the distances of the droplet-pairs moving in each stage to predict the coalescence position in the straight microchannel. In addition, the coalescence position, as well as the coalescence mechanism, was analyzed for the paired droplets in an expansion microchannel to explore the more possibilities of intensifying the construction of droplet reactors in microchannels.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"163 ","pages":"Article 111419"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134853","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}