Experiments in Fluids最新文献

{"title":"Insights into the dynamics of full-scale sector combustor isothermal flow field","authors":"Darshan Rathod,&nbsp;Pratikash Panda,&nbsp;Saptarshi Basu","doi":"10.1007/s00348-024-03953-3","DOIUrl":"10.1007/s00348-024-03953-3","url":null,"abstract":"<div><p>An experimental investigation in a sector (<span>(20^circ)</span>) of a full-scale annular gas turbine combustor is performed. The sector combustor is optically accessible for the flow and flame visualization of the primary and exit zones of the combustor. The distinctive feature of the experimental setup is that it preserves the geometrical details of an annular combustor, which includes the casing, dome, and combustor liner. The combustor design features a series of primary and secondary dilution holes with multiple film cooling strips on the outer and inner liner. In the present study, the time-resolved particle image velocimetry (PIV) experiments are conducted on the central longitudinal plane and two azimuthal planes to gain insight into the dynamics of the sector combustor. Proper orthogonal decomposition (POD) is applied to the data to obtain the dominant dynamics of the combustor. The major coherent structures of the swirl flow field, the primary dilution jets flow field, and the dominant interaction of swirl and dilution jets are elucidated here. The azimuthal plane data provide a three-dimensional explanation of dilution jet dynamics. The dynamics of the exit zone is found to be influenced by the secondary dilution jet dynamics. The spectral properties of dynamics are illustrated from the recorded acoustic (<span>(p^prime)</span>) signal and the time coefficient of the POD eigenmodes. Further, the experiments are performed by blocking the dilution jets (without-DJ). These experimental data help to identify the source of the dominating frequency (<span>(f_textrm{d})</span>) within the combustor, which is found to be the swirl flow instabilities. Without-DJ data also showcases the role of dilution jets in convecting the swirl flow generated acoustics to the exit zone. The reconstructed flow field using POD provides physical insights into the dynamics occurring within the sector combustor.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142963109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Direct detection method for cusp thickness in wavy thin-film flow using an optical waveguide film","authors":"Kosuke Nakano,&nbsp;Hajime Furuichi,&nbsp;Yuki Mizushima","doi":"10.1007/s00348-024-03947-1","DOIUrl":"10.1007/s00348-024-03947-1","url":null,"abstract":"<div><p>The wave crest (cusp) of the disturbance wave in thin liquid film flow is an important factor contributing to heat/mass transfer, e.g., fuel rods in boiling water reactors, stator/rotor blades in steam turbines, and cleaning/drying wafer processes in semiconductor manufacturing. We developed a new technique for directly detecting the thickness of wave cusps using array-based sensing with an optical waveguide film (OWF). This technique, based on geometrical optics assumptions, simultaneously obtains information on liquid films’ thickness and their interfacial shape, i.e., whether or not the local interface is convex upward. We first performed a pseudo-film flow measurement using a metal specimen to confirm the basic principle. According to the results, a meaningful signal indicating the wave-cusp passage, along with a thickness signal, was detected simultaneously. The OWF signal processing for cusp thickness detection was newly established based on this fact. We then applied this technique to a wavy liquid film flow formed on a flat plate in the entry region. A series of experiments were performed over a wide range of air speeds (<i>j</i>_G = 20–70 m/s). As a result, the cusp thicknesses of relatively large waves on the wavy interface were successfully extracted from the OWF output signal. Further, the major thickness variables (i.e., base film thickness, median film thickness, and cusp thickness) were compared with those of conventional thickness estimation methods, which showed reasonable agreement. This paper provides a framework for wavy thin-film flow measurements via OWF that is specialized for directly detecting local thickness profiles.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 2","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03947-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Soft stereolithographic 3D printed phantoms for dual-modality particle image velocimetry (PIV)","authors":"Elnaz Hosseinzadeh,&nbsp;Hadi Mirgolbabaee,&nbsp;Lennart van de Velde,&nbsp;Michel Versluis,&nbsp;Erik Groot Jebbink,&nbsp;Alan Aguirre-Soto,&nbsp;Michel M. P. J. Reijnen","doi":"10.1007/s00348-024-03938-2","DOIUrl":"10.1007/s00348-024-03938-2","url":null,"abstract":"<div><p>The fabrication of arterial flow phantoms for fluid dynamics studies suitable for particle image velocimetry (PIV) techniques has presented challenges. Current 3D-printed blood flow phantoms with suitable transparency for optical PIV (laserPIV) are restricted to rigid materials far from those of arterial properties. Conversely, while soft 3D-printed phantoms demonstrate promise for sufficient acoustical transparency for ultrasound PIV (echoPIV), their optical translucency presents challenges for laserPIV applicability. This dual-modality approach leverages the high spatial resolution of laserPIV for in-vitro applications and the ability of echoPIV to quantify flow in both in-vivo and in-vitro application (also inside stents), providing a more comprehensive understanding of flow dynamics. In this study, we present a series of coated thin-walled 3D-printed compliant phantoms suitable for dual-modality PIV flow imaging (i.e., laserPIV and echoPIV) methods, overcoming current 3D-printable material limitations. Stereolithographic (SLA) 3D printing was used to fabricate pipe flow phantoms from a set of commercial soft resins (flexible and elastic) as vascular tissue surrogates. To overcome low transparency and poor surface finish of soft resins, we coated the 3D-printed flow phantoms with a soft, optically transparent, photo-activated polymeric coating. The feasibility of performing dual-modality PIV was tested in an in-vitro flow setup. Our results show that the average normalized root mean square errors obtained from comparing laserPIV and echoPIV velocity profiles against the analytical solutions were 3.2% and 5.1%, and 3.3% and 5.3% for the flexible and elastic phantoms, respectively. These results indicate that dual-modality PIV flow imaging is feasible in the 3D-printed coated phantoms, promoting its future use in fabricating clinically-relevant flow phantoms.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03938-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Particle shadow velocimetry and its potential applications, limitations and advantages vis-à-vis particle image velocimetry","authors":"Gauresh Raj Jassal,&nbsp;Maxwell Song,&nbsp;Bryan E. Schmidt","doi":"10.1007/s00348-024-03934-6","DOIUrl":"10.1007/s00348-024-03934-6","url":null,"abstract":"<div><p>Particle image velocimetry (PIV) is an established velocimetry technique in experimental fluid mechanics that involves determining a fluid flow velocity field from the motion of tracer particles illuminated by a laser sheet. The necessity of laser illumination poses challenges in certain applications and is a potential entry barrier due to its high cost and safety considerations. A laser-free alternative to PIV is particle shadow velocimetry (PSV), which uses images of the shadows cast by the particles on the camera sensor under back-illumination, instead of the Mie scattering signal produced by laser illumination. This study aims to compare various aspects of PSV such as depth of field, seeding density, type of illumination required, particle size, image filtering, cost-effectiveness and limitations with those of PIV. PSV and PIV measurements are taken in the wake of a flow past a cylinder and in a boundary layer developing over a flat plate. It is found that PSV is capable of achieving equivalent accuracy to PIV and is a viable alternative to PIV in certain applications where light sheet illumination creates experimental challenges.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extended particle streak velocimetry (E-PSV) for a comprehensive view of film flows","authors":"Sebastian Sold,&nbsp;Matthias Rädle,&nbsp;Jens-Uwe Repke","doi":"10.1007/s00348-024-03931-9","DOIUrl":"10.1007/s00348-024-03931-9","url":null,"abstract":"<div><p>Extended particle streak velocimetry (E-PSV) is a novel approach for comprehensive 2D flow measurement. It extends the measuring range of particle streak velocimetry (PSV) via particle tracking velocimetry (PTV). By using long camera exposure when recording moving tracer particles, streaks are created in areas of high flow velocities (PSV). In areas of low velocity, in contrast, particles are imaged point-shaped (PTV). E-PSV hereby offers the advantage of continuous measurement with PSV-typical setups, particularly when areas close to the wall and vortices require to be recorded simultaneously with areas of high velocity. For precise extraction of the flow information, a new model for the description of particle images is presented. It is based on the assumption that the intensity of a tracer can be modeled by a 2D Gaussian function. The temporal integral of the moving Gaussian is approximated by combining analytical calculation with values from a lookup table. We show that by this method even curved streaks can be reconstructed with subpixel accuracy under noise and quantization effects. The technique is demonstrated using a film flow in vicinity of a microstructure.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03931-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Spray interaction in adjacent GCSC injector elements: role of droplet collision and secondary droplet breakup","authors":"Surya Ghosh,&nbsp;Srikrishna Sahu","doi":"10.1007/s00348-024-03939-1","DOIUrl":"10.1007/s00348-024-03939-1","url":null,"abstract":"<p>This study investigates the evolution of spray characteristics in adjacent gas-centered swirl coaxial (GCSC) injectors, which finds application in liquid propellant rocket engines. The main objectives here are to measure the axial evolution of droplet characteristics in the spray interaction zone and understand the fundamental physics governing the spray interaction process. Experiments were conducted using air and water as the working fluids under atmospheric conditions. Utilizing the high-speed shadow imaging technique, the droplet images were captured at different axial and radial measurement stations for gas-to-liquid momentum flux ratio (<i>M</i>) ranging from 30 to 70. The images were processed to obtain droplet size, axial/radial components of droplet velocity, and droplet mass flux. The Mie-scattering images of the spray were acquired by laser sheet imaging to visualize the spray structure and spatial distribution of the droplets. Droplet measurements were also obtained by operating the injectors individually. Comparative analysis between the interacting and individual sprays highlighted the significant reduction in characteristic droplet size and an increase in the mean droplet velocity and local mass flux due to spray interaction. To elucidate the physical mechanisms behind the above observations, further analysis was carried out by evaluating the droplet collision, secondary atomization, and droplet dispersion in the interaction zone. Interestingly, the results highlight that, despite the intuitive notion that droplet collisions are the primary driver of the spray interaction process in the intersecting sprays, the improved secondary droplet atomization due to modification of airflow characteristics serves as the dominant factor in altering the droplet characteristics.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Holographic focusing schlieren imaging (HFSI) for three-dimensional flow visualization","authors":"Zhiming Lin,&nbsp;Yiqin Li,&nbsp;Aimin Xie,&nbsp;Kaihui Liu,&nbsp;Zhiliang Xue,&nbsp;Qiwen Jin,&nbsp;Yingchun Wu,&nbsp;Xuecheng Wu","doi":"10.1007/s00348-024-03951-5","DOIUrl":"10.1007/s00348-024-03951-5","url":null,"abstract":"<div><p>Flow field visualization techniques, e.g., schlieren and shadowgraphy, are indispensable in fluid mechanics research and application. In this paper, we present a novel technique, named holographic focusing schlieren imaging (HFSI), which takes only a single-camera and single-shot configuration to achieve three-dimensional (3D) flow visualization. The essence of this technique is that a coherent reference wave is introduced to interfere with the wavefront yielded by the traditional focusing schlieren (FS) method, forming a hologram. The reconstruction of the hologram directly yields the FS results along the test volume slice by slice with adjustable intervals, achieving 3D visualization. To demonstrate the capability of HFSI, a proof-of-concept setup was established, and experiments were performed using a compressed air jet, with a comparison to the FS method. The result shows that HFSI image reconstruction remarkably refocuses the out-of-focus jet flow, yielding similar schlieren effect observed in the FS images. The proposed HFSI holds significant practical value in some scenarios, such as in a wind tunnel, as it requires only one pair of parallel windows to achieve 3D flow visualization.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Supersonic discharge of cold gas inflators into rectangular ducts","authors":"Eduard Schnorr,&nbsp;Dennis Schütte,&nbsp;Peter Scholz,&nbsp;Rolf Radespiel","doi":"10.1007/s00348-024-03932-8","DOIUrl":"10.1007/s00348-024-03932-8","url":null,"abstract":"<p>We discuss the supersonic discharge of cold gas inflators into confined ducts typical of curtain airbag inflation. The medium discharged from the cold gas inflators is helium. For this purpose, two different generic duct geometries are chosen to obtain one case without and one with wall interaction of the underexpanded jet. In the latter case, a so-called shock train develops, which dominates the flow topology. To quantify the flow field, time-resolved pressure transducers measure the static pressure at the duct walls and time-resolved particle image velocimetry measures the velocity in the far field of the underexpanded jet. Schlieren images illustrate the topology of the flow field. A simplified numerical model is then created that drastically reduces the required resources. The numerical model is verified against the experimental data and provides deeper insight into the outflow process. In particular, the interaction of the underexpanded jet with the duct walls and thus the resulting shock train are found to be sensitive. The numerical model can reconstruct the flow topology, pressure and velocity within acceptable limits. The experimental data and numerical results may serve as a basis for subsequent studies on airbag inflation or physically similar processes, especially for the validation of numerical methods.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03932-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Tomo-PIV measurement of small-scale structures in Newtonian and polymeric turbulence","authors":"Feng Wang,&nbsp;Yi-Bao Zhang,&nbsp;Heng-Dong Xi","doi":"10.1007/s00348-024-03948-0","DOIUrl":"10.1007/s00348-024-03948-0","url":null,"abstract":"<div><p>The effects of polymer additives on turbulent fluid flows have attracted massive attention since the discovery of significant drag reduction by polymers in wall-bounded flows. Here we present an experimental study on the polymer–turbulence interaction at the center of the turbulent von Kármán swirling (VKS) flow system where the flow is far away from the boundary (bulk turbulence) with tomographic particle image velocimetry (Tomo-PIV). We used water–glycerol mixture to tune the viscosity of the working fluids, which facilitates us to resolve the dissipative scales and thus obtain all the nine components of the velocity gradient tensor directly. Our experiments demonstrate that at the center of the VKS flow, anisotropic properties extend from large scale to small scale, but gradually weaken with increasing Reynolds number. In polymeric turbulence, it is found that with increasing polymer concentration both the spatial averaged root mean square velocity and the average energy dissipation rate first decrease and then tend to stay at a constant value when concentration exceeds a critical value, implying that the effect of polymers saturates at high polymer concentration. We also find that the small scales become more anisotropic with the increasing concentration. The axisymmetry of small scales, however, is always retained, which can be employed to estimate the average energy dissipation rate from the planar PIV data. Moreover, we reveal that the number of the tube-like structures, the elementary structure in Newtonian turbulence, is strongly inhibited by the polymer additives, whereas the size of the tube-like structures is greatly enlarged.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 improved calibration methodology and uncertainty assessment in measurements of microbubble size and concentration","authors":"R. Stigter,&nbsp;D. Fiscaletti,&nbsp;G. E. Elsinga,&nbsp;T. van Terwisga,&nbsp;J. Westerweel","doi":"10.1007/s00348-024-03929-3","DOIUrl":"10.1007/s00348-024-03929-3","url":null,"abstract":"<div><p>Interferometric particle imaging (IPI) is used to measure both the size distribution and concentration of microbubbles (with a diameter less than 100 micron) in water. Using a new method for calibration makes it possible to obtain quantitative results for the concentration of microbubbles. The results are validated using imaging with a long-range microscope shadowgraph (LMS). Estimates of the size distribution and concentration from both IPI and LMS agree within uncertainty limits. The relative uncertainty in the IPI concentration estimation is about 10% and is mostly due to the finite number of detected bubbles. It is shown that the performance of the bubble-image detection algorithm needs to be quantified to obtain a reliable estimate of the concentration obtained with IPI.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03929-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142906122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}