Experiments in Fluids最新文献

{"title":"Double refractive particle tracking and sizing","authors":"Jörg König,&nbsp;Christian Cierpka","doi":"10.1007/s00348-024-03894-x","DOIUrl":"10.1007/s00348-024-03894-x","url":null,"abstract":"<div><p>We present a novel bifocal imaging method enabling three-dimensional particle tracking and size determination employing a single camera only. The method is based on double refraction causing a particle to be imaged twice, each particle image of different blur. From these double images, a linear calibration function can be derived allowing to determine the three-dimensional particle position unambiguously over the entire depth of measurement volume. As this calibration function is independent of the particle size used, the particle size can be determined simultaneously by relating size of the double images and depth position of the particle. To prove the applicability, a co-laminar flow of two particle suspensions with particles of 1.14 <span>(upmu)</span>m and 2.47 <span>(upmu)</span>m in diameter was measured in a Y-shaped microchannel. While the laminar flow field was measured with very low uncertainty and independent of the particle size, the particle size distributions determined reproduced reliably the size distributions expected for the co-laminar flow applied, with a precision of about 98.6 <span>(%)</span> regarding the particle size discrimination. The progress for research is a new method readily to implement in common optical setups, promising, for example, valuable insights in polydisperse suspension flows—the vast majority of flows in fundamental research and applications.</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":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03894-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142540698","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":"Enhanced three-dimensional particle detection in microcirculation experiments with defocus particle tracking and ghost red blood cells","authors":"Gonçalo Coutinho,&nbsp;Philipp Warlitz,&nbsp;Ana R. Silva-Santos,&nbsp;Duarte M. Prazeres,&nbsp;Ana Moita,&nbsp;Jochen Kriegseis,&nbsp;António Moreira,&nbsp;Massimiliano Rossi","doi":"10.1007/s00348-024-03897-8","DOIUrl":"10.1007/s00348-024-03897-8","url":null,"abstract":"<div><p>Experimental investigations on the motion of rigid particles in microcirculation environments are still scarce owing to the three-dimensional (3D) motion of the particles and to the particle image masking due to the presence of the red blood cells (RBCs). Despite the recent progress on the 3D tracking of rigid particles in RBC flows with defocus particle tracking (DPT) methods, the problem of particle image masking remains to be solved. Here, we propose, test, and evaluate the use hemoglobin-free RBCs, also known as ghost RBCs, as a replacement for normal RBCs in experiments with rigid particles in microcirculation environments. We performed DPT measurements of a pressure-driven flow of normal and ghost RBC suspensions seeded with rigid particles at three different flow rates. We show that the quasi-transparent appearance of ghost RBCs, as a result of the lack of hemoglobin, eliminates the RBC-induced masking of the defocused particle images and allows to achieve the particle matching standards found in cell-free experiments. In fact, ghost RBC suspensions enable the tracking of the rigid particles across the entire height of the microchannel, which was not possible in normal RBC flows. On a fluid dynamic level, we show that ghost RBC suspensions provide similar conditions to normal RBCs in terms of the velocity of the rigid particles and the rigid particles exhibit similar lateral dynamics in both types of cell suspensions. In essence, the findings from this work demonstrate that ghost RBCs are a well-suited replacement for normal RBCs in experiments aiming at deciphering the motion of rigid particles in microcirculation environments.</p><h3>Graphical abstract</h3>\u0000<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03897-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142518773","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":"Development of a sensor for liquid film thickness measurements during annular flow in microchannels","authors":"Victor Eduardo Corte Baptistella,&nbsp;Zhaorui Guo,&nbsp;Minhyeok Lee,&nbsp;Gherhardt Ribatski,&nbsp;Yuji Suzuki","doi":"10.1007/s00348-024-03902-0","DOIUrl":"10.1007/s00348-024-03902-0","url":null,"abstract":"<div><p>A conductance-based sensor to measure liquid film thickness during annular two-phase flows in microchannels has been developed in the present study. The liquid film plays an important role on the characterization of two-phase annular flows. The mean thickness and the presence of interfacial waves influence the heat transfer rate, critical heat flux and pressure drop. The proposed sensor has a ring-shaped design and targets the measurement of films thinner than 50 µm in order to provide detailed information on the liquid film behavior during wall dryout events. It is fabricated on a TEMPAX wafer with micro-electro-mechanical systems (MEMS) technologies. The performance of the prototype device is assessed by using aqueous solutions of known conductivity and imposing liquid films with prescribed thicknesses above the sensor. The effects of the geometrical parameters on the sensor behavior are discussed with the aid of numerical simulation and experimental results. It is found that increasing the size of the electrodes increases the measured electrical signals, while increasing the spacing between the electrodes decreases the measured signal.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142524386","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":"Time resolution improvement of ultrasonic velocity profiler for flow over cylinder using EPOD method with optimally placed time-resolved sensors","authors":"Neetu Tiwari","doi":"10.1007/s00348-024-03903-z","DOIUrl":"10.1007/s00348-024-03903-z","url":null,"abstract":"<div><p>Ultrasonic velocity profiler (UVP) can be used for opaque and multiphase flows where particle image velocimetry (PIV) cannot be applied. The time resolution of PIV has greatly improved over the last few decades with the development of high-speed cameras and has been further improved using data-driven approaches. On the other hand, there have been very few works to improve the time resolution of UVP, which is already much lower than that of PIV. This study presents a proof of concept for time resolution improvement of UVP measurement, using an extended proper orthogonal decomposition (EPOD) method with optimized sensors. In this study, the EPOD method is improved by combining it with the sensor selection method, which eliminates the three-sigma (<span>(sigma)</span>) rule-based filtering introduced by Discetti et al. 2018 in the original work of Hosseini et al. 2015. In this study, sensor locations are optimized using sensor selection methods, and time-resolved flow fields are reconstructed using the EPOD method. The sensors’ locations along the line are optimized using non-time-resolved UVP velocity data by two sensor selection methods: determinant greedy (DG) and Bayesian determinant-based greedy (BDG). The performance of DG and BDG-optimized sensors is compared in reconstructing time-resolved flow fields. The technique is demonstrated with two sets of experimental data of flow over a cylinder: first, PIV data, which are down-sampled in the time domain and sampled along a line to mimic the UVP data, and second, actual UVP experimental data conducted in the wake of cylinder. The EPOD method’s time-resolved reconstruction capability was found to depend on the sensors’ location, and both sensor selection methods yielded similar results.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142518901","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":"Ultrasound imaging velocimetry in a dense two-phase swirling flow","authors":"Thomas Holemans,&nbsp;Willian Hogendoorn,&nbsp;Christian Poelma,&nbsp;Johan De Greef,&nbsp;Maarten Vanierschot","doi":"10.1007/s00348-024-03896-9","DOIUrl":"10.1007/s00348-024-03896-9","url":null,"abstract":"<div><p>Ultrasound imaging velocimetry (UIV) is a maturing technique for measuring the dispersed phase in two-phase flows. It enables measurements of dense suspensions when optical methods fail. This study explores UIV’s applicability to measure the flow field in a swirling flow reactor (SFR) for solid–liquid mixing of dense suspensions. Despite UIV’s historical focus on unidirectional flows like arteries and axisymmetric pipes, this research demonstrates its adaptation to an inherently complex 3D flow field, i.e., a swirling sudden expansion flow in an SFR. Using high-speed plane-wave imaging and correlation averaging techniques, satisfactory velocity profiles are achieved while preserving sufficient temporal information. Firstly, the applicability of UIV in this specific setup is demonstrated by comparing UIV with stereoscopic particle image velocimetry measurements of a single-phase flow in the SFR, both indicating a Coandă jet flow (CoJF). Secondly, several bulk velocities and volume concentrations (up to 50 vol%) are measured with UIV for a suspension of water and 2.3-mm glass beads. A transducer is installed in two orientations and captures all three velocity components when combining the two datasets. A timestep optimization process is implemented to avoid the need for manual finetuning of the acquisition frequency. A time-domain spectral analysis on the dispersed phase velocity fields in the SFR reveals dominant frequencies between 1.21 and 2.42 Hz, similar to those found in single-phase flow. The general flow structure of the dispersed phase in suspension is very similar to the latter; however, the addition of particles confines the central recirculation zone (CRZ) to the center. Finally, the implementation of swirl to keep solid–liquid mixtures in suspension in the SFR is experimentally confirmed by this study. Quantitative UIV measurements confirm favorable flow structures for mixing, specifically a CoJF that avoids sedimentation. The concentration of solids in an SFR can even be increased up to 50 vol% while still maintaining a uniform suspension.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142518432","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":"A particle-free stereo-video free-surface reconstruction method for wave-tank experiments","authors":"Sacha Le Page,&nbsp;Alan Tassin,&nbsp;Julien Caverne,&nbsp;Guillaume Ducrozet","doi":"10.1007/s00348-024-03887-w","DOIUrl":"10.1007/s00348-024-03887-w","url":null,"abstract":"<div><p>This paper introduces a new stereo-video-based free-surface reconstruction system developed for wave-tank experiments. The originality of the proposed approach relies on the use of short water waves and an adapted lighting system to create a fine texture suitable for the cross-correlation of the stereo image pairs. The feasibility of the approach is demonstrated experimentally in a wave flume. The accuracy of the stereo-video free-surface reconstruction method is assessed through comparisons with measurements performed with a servo-controlled wave gauge. The reconstruction of the free surface at rest and during different regular (periodic) long-crested wave experiments are considered for this purpose. The results demonstrate that, with a suitable free-surface roughness, the accuracy of the stereo-system can be similar to the accuracy of the wave gauge. The accuracy, the simplicity and the flexibility of the approach, which does not necessitate any seeding or dying of the water, nor the use of a laser light source, make it a promising measurement technique for water-wave experiments.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142451126","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":"Skin-friction from temperature and velocity data around a wall-mounted cube","authors":"Massimo Miozzi,&nbsp;Andreas Schröder,&nbsp;Daniel Schanz,&nbsp;Christian E. Willert,&nbsp;Christian Klein,&nbsp;Jonathan Lemarechal","doi":"10.1007/s00348-024-03881-2","DOIUrl":"10.1007/s00348-024-03881-2","url":null,"abstract":"<div><p>This paper reports an algorithm for measuring the time-averaged skin friction vector field <span>(overline{pmb {tau }}(pmb {X}))</span> starting from time-resolved temperature maps, acquired by a functional coating of temperature-sensitive paint. The algorithm is applied to a large area around a wall-mounted cube, immersed in the turbulent boundary layer over a flat plate. The method adopts a relaxed version of the Taylor Hypothesis operating on time-resolved maps of temperature fluctuations <span>(T')</span> measured on the slightly warmer bounding surface. The procedure extracts <span>({overline{U}}_T(pmb {X}))</span>, the celerity of displacement of <span>(T')</span>, as the best approximation of the forecasting provided by the frozen turbulence assumption near the wall, where its rigorous application is inappropriate. The <span>(overline{pmb {tau }}(pmb {X}))</span> estimation is based on the hypothesis of a linear relationship between <span>({overline{U}}_T(pmb {X}))</span> and <span>({overline{U}}_U(pmb {X}))</span>, chained to the one between <span>({overline{U}}_U(pmb {X}))</span> and <span>({overline{U}}_tau (pmb {X}))</span>. We assess the outcomes of the proposed algorithm against those derived by the 2D and 3D Lagrangian particle tracking (LPT) methodology ’Shake-The-Box’, whose advent has made available high-quality near-wall flow field information. Furthermore, data from high-density 2D time-resolved LPT allows exploring the suitability of the linear relationships chain between <span>({overline{U}}_T(pmb {X}))</span> and <span>({overline{U}}_tau (pmb {X}))</span> in the proposed context.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03881-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438816","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":"A fluorescent particle for PIV in gas phase flows","authors":"Mizuki Okada,&nbsp;Agastya Parikh,&nbsp;Jorge Pinho,&nbsp;Christian Kähler,&nbsp;Sergio Lavagnoli","doi":"10.1007/s00348-024-03889-8","DOIUrl":"10.1007/s00348-024-03889-8","url":null,"abstract":"<div><p>This paper presents the development of fluorescent tracer particles for use in gas flows as a countermeasure for undesired strong light reflections on surfaces of channel walls or obstacles and as a label for the discrimination of multi-constituent flows. The employment of fluorescent dye-doped tracer particles with a wavelength-specific optical filter enables the separation of the Stokes-shifted particle light emission from reflections on surfaces and Mie scattering from non-fluorescing particles. The fluorescent particles were made of Pyrromethene 567 (P567) and Di-Ethyl-Hexyl-Sebacate (DEHS), and the addition of P567 was not found to alter the characteristics of the particles generated. Investigations in a low-speed wind tunnel revealed that the intensity of fluorescent emission is proportional to the dye concentration at least up to <span>(2.0,hbox {g l}^{-1})</span>. The efficacy of reflection removal was investigated in a setup with a metal turbine blade placed in the flow and a laser sheet oriented to impinge the blade surface. With the installation of an appropriate optical filter, undesired light reflections were successfully removed, and reasonable vector calculations were enabled in proximity to the reflective blade surfaces. Finally, the performance of the modified DEHS was compared to conventional DEHS with the measurement of a canonical turbulent boundary layer (TBL). The flow was globally seeded with conventional DEHS and the TBL was locally seeded with fluorescing DEHS; simultaneous imaging with a notch filter confirmed that the flow is accurately tracked by the modified DEHS without additional bias. Furthermore, this indicated the possibility of using the newly developed particles to segregate portions of a flow with multiple constituents.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434944","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":"Three-dimensional dynamics of detonation cells in linearly diverging channels: experimental analysis of the cross-sectional shape and a detonation-shock dynamics interpretation","authors":"Vianney Monnier,&nbsp;Vincent Rodriguez,&nbsp;Pierre Vidal,&nbsp;Ratiba Zitoun","doi":"10.1007/s00348-024-03893-y","DOIUrl":"10.1007/s00348-024-03893-y","url":null,"abstract":"<div><p>We study the transient dynamics of three-dimensional detonation cells when the detonation front is subjected to weak expansion due to the diffraction from a straight channel to a diverging channel. We focus on the effect of the cross-sectional shape, namely square or round, using diverging channels with the same initial cross-sectional area of 16 cm <span>(^{2})</span> as the straight channels and the same expansion rate. The reactive mixture is <span>(2,hbox {H}_{2} + hbox {O}_{2} + 2,hbox {Ar})</span> at the initial pressure of 20 kPa and temperature of 294 K, and we use the sooted-foil technique to record the cellular dynamics. The mean cell widths first increase from different initial values, which depend on the cross-sectional shape and then decrease to stabilize at the same value independent of the shape but larger than the initial values. We use a relation of detonation dynamics between the velocity, total curvature and acceleration of the average detonation front to interpret successfully, albeit qualitatively, all the experimental trends. This sensitivity thus makes these experimental data a reliable basis for high-resolution numerical simulations capable of handling three-dimensionality and detailed chemical kinetics mechanisms. Defining a significative mean width of detonation cells requires constant cross-sectional tubes of size and length sufficiently large. Inductively, representing three-dimensional cells requires more statistical descriptors than a single mean width.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142410786","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":"Peak-CNN: improved particle image localization using single-stage CNNs","authors":"Philipp Godbersen,&nbsp;Daniel Schanz,&nbsp;Andreas Schröder","doi":"10.1007/s00348-024-03884-z","DOIUrl":"10.1007/s00348-024-03884-z","url":null,"abstract":"<div><p>An important step in the application of Lagrangian particle tracking (LPT) or in general for image-based single particle identification techniques is the detection of particle image locations on the measurement images and their sub-pixel accurate position estimation. In case of volumetric measurements, this constitutes the first step in the process of recovering 3D particle positions, which is usually performed by triangulation procedures. For two-component 2D measurements, the particle localization results directly serve as input to the tracking algorithm. Depending on the quality of the image, the shape and size of the particle images and the amount of particle image overlap, it can be difficult to find all, or even only the majority, of the projected particle locations in a measurement image. Advanced strategies for 3D particle position reconstruction, such as iterative particle reconstruction (IPR), are designed to work with incomplete 2D particle detection abilities but even they can greatly benefit from a more complete detection as ambiguities and position errors are reduced. We introduce a convolutional neural network (CNN) based particle image detection scheme that significantly outperforms current conventional approaches, both on synthetic and experimental data, and enables particle image localization with a vastly higher completeness even at high image densities.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 10","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03884-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142410712","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}