Experiments in Fluids最新文献

{"title":"Depth from defocus technique with convolutional neural networks for high particle concentrations","authors":"Rixin Xu,&nbsp;Zuojie Huang,&nbsp;Wu Zhou,&nbsp;Cameron Tropea,&nbsp;Tianyi Cai","doi":"10.1007/s00348-024-03933-7","DOIUrl":"10.1007/s00348-024-03933-7","url":null,"abstract":"<div><p>Recent advantages in the depth from defocus technique for the size and location determination of particles in dispersed two-phase flows have enabled the technique to detect and analyze spherical particle images in flow systems with high number concentrations. In the present study, the use of convolutional neural networks for this task will be explored, with comparisons to the conventional analyses in terms of accuracy, tolerable concentration limits and computational speed. This approach requires a large teaching dataset of images, which is only practical and feasible if the dataset can be synthetically generated. Thus, the first development to be presented is an image generation procedure for out-of-focus neighboring spherical particles resulting in a known blurred image overlap. This image generation procedure is validated using laboratory images of known particle size distribution, position and image overlap, before creating a teaching dataset. The trained processing scheme is then applied to both synthetic datasets and to experimental data. The synthetic datasets allow limits of image overlap and tolerable volume concentration limits of the technique to be evaluated as a function of particle size distribution.(https://github.com/xu200911/Generate-overlapping-out-of-focus-particles)</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142821448","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":"Impact of polarization and detection angle on Mie scattering signals for planar droplet sizing","authors":"B. W. Klevansky,&nbsp;Y. N. Mishra,&nbsp;B. L. Lehnert,&nbsp;M. Wensing,&nbsp;F. J. Bauer,&nbsp;S. Will","doi":"10.1007/s00348-024-03927-5","DOIUrl":"10.1007/s00348-024-03927-5","url":null,"abstract":"<p>The planar droplet sizing (PDS) method for determining the droplet diameter from the ratio of laser-induced fluorescence (LIF) and Mie scattering signal (Mie) has been extensively applied for right-angle scattering detection. The present work consists of a parametrical study of the Mie signal dependency on the scattering angle and polarization, as well as further experimental investigations in single droplets to ultimately improve the intensity fluctuation characteristics of the signal through a favorable experimental arrangement. Finally, we investigated how these findings impact droplet sizing in a spray on a shot-to-shot basis, as well as averaged across a dataset, via microscopic and macroscopic spray measurements. In the parametrical study, we found that horizontally polarized incident light results in a higher degree of Mie signal fluctuation than vertically polarized incident light at a scattering angle of <span>(Theta ={90}{^circ })</span>, whereas the reduction to <span>(Theta = {60}{^circ })</span> resulted in the exact opposite observation. Furthermore, the reduction from <span>(Theta = {90}{^circ })</span> to <span>(Theta = {60}{^circ })</span> resulted in an overall improvement to the <span>(D^2)</span>-dependency and signal fluctuation of the Mie signal. We observed the effects shown in the parametric study in the experimental droplet measurements. For instance, when observing single droplets, the change from <span>(Theta = {90}{^circ })</span> to <span>(Theta = {60}{^circ })</span> resulted in a reduction in signal fluctuation by 46.1% and 17.6% for horizontally and vertically polarized incident light, respectively. An implementation into a spray setup yielded reduced shot-to-shot sizing deviations and closer adherence to the microscopically measured diameter when averaged across the dataset.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03927-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142821446","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":"Volumetric supraglottal jet flow field analysis in synthetic multilayered self-oscillating vocal fold model","authors":"Jacob Michaud-Dorko,&nbsp;Charles Farbos de Luzan,&nbsp;Ephraim Gutmark,&nbsp;Liran Oren","doi":"10.1007/s00348-024-03936-4","DOIUrl":"10.1007/s00348-024-03936-4","url":null,"abstract":"<div><p>Recent research highlights the need for comprehensive three-dimensional (3D) analysis of laryngeal flow to better understand voice production, as traditional 2D methods fail to capture the full complexity of supraglottal jet dynamics. This study employed tomographic particle image velocimetry to capture the volume velocity flow fields in a synthetic multilayered vocal fold model. The impact of increased airway resistance from different vocal tract configurations was examined. Results indicated that adding a vocal tract reduced the maximum axial velocity and jet displacement, particularly at low subglottal pressure (Psg). Higher Psg increased both the maximum axial velocity and jet displacement. For all configurations, with and without a vocal tract, the vocal folds were observed to open at the posterior and anterior edges first, indicated by a double jet formation at the beginning of the opening phase, followed by an elongated jet during peak flow and a double jet at the posterior and anterior edges during the closing phase. Contrary to previous studies, the glottal flow waveforms became more symmetric between the opening and closing phases with higher Psg and the presence of a vocal tract. Additionally, vocal efficiency (VE) decreased while cepstral peak prominence increased with higher Psg. Overall, this study provides further insights into the influence of vocal tract configurations on the supraglottal jet and supports the correlation between glottal flow skewing and VE.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142821447","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":"Modified free-surface synthetic Schlieren method to adjust measurement sensitivity in high-strain waves","authors":"Hillel Mermelstein,&nbsp;Yuval Dagan","doi":"10.1007/s00348-024-03921-x","DOIUrl":"10.1007/s00348-024-03921-x","url":null,"abstract":"<div><p>This research revisits the free-surface synthetic Schlieren technique (FS-SS) (Moisy et al. in Exp Fluids 46(6):1021–1036, 2009) for the topographical measurement of the free surface of a liquid. In contrast to the aforementioned method, which utilizes the image refraction of a random dot pattern through a free surface to determine the surface gradients, this present study mathematically derives a method where the pattern may take an arbitrary three-dimensional shape. This is shown to be theoretically valid under a small pattern slope approximation. Our method is then verified against the previously mentioned, flat-pattern, free-surface synthetic Schlieren technique by resolving the free-surface elevation of plane waves across a channel, showing similar results in constant strain conditions, with improved results in variable strain conditions, particularly in cases where there is a very large difference in strain across the channel. The validation test cases investigated include a rectangular channel containing a transparent liquid with a random dot pattern placed below at a constant angle and a pattern placed on top of a cosine-shaped profile. Both of these setups are validated against the classical FS-SS technique involving a flat pattern. The new method involving an arbitrarily shaped pattern proposed here may increase the resolution in low-amplitude regions by increasing the surface–pattern distance below these regions and correspondingly reducing the sensitivity in high-strain regions by decreasing the surface–pattern distance. Geometries shown to produce advantageous results in waves that include both regions of very high strains and regions of very low amplitudes are explored, resolving the wave in both regions simultaneously. This shows promise in resolving multi-scale surface waves in highly viscous liquids, which may include very high-amplitude regions quickly followed by very low-amplitude regions due to damping effects.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03921-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142798419","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":"Wake Interactions of a Small Uncrewed Aerial System with a Moving Vehicle","authors":"David Lee,&nbsp;John Hrynuk","doi":"10.1007/s00348-024-03930-w","DOIUrl":"10.1007/s00348-024-03930-w","url":null,"abstract":"<div><p>This study presents an experimental investigation of the aerodynamics relevant to the landing of a small Uncrewed Aerial System on a fast-moving ground vehicle. A Representative Ground Vehicle and small Uncrewed Aerial System have been constructed for experimental measurements of the wake interactions in a low-speed, recirculating wind tunnel. Quantitative flow image techniques are employed to probe how the sUAS interacts with the wake structures shed by the ground vehicle when the two are in close proximity. Tools are developed for quantitative comparisons of flow fields and turbulence spectra. Using this tool, it is possible to identify regions of the flow and relative positions of the two vehicles where wake interactions are mostly linear in nature. This near-linear wake interaction was observed to extend to the wake spectra in regions where the time-averaged flow fields were also near-linear. Finally, it is shown that these observations of a near-linear wake interaction do not hold when the sUAS interacts with highly decelerated regions of the ground vehicle wake.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142798510","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":"On formation and breakup of jets during droplet impact on oscillating substrates","authors":"Aditya Potnis,&nbsp;Abhishek Saha","doi":"10.1007/s00348-024-03911-z","DOIUrl":"10.1007/s00348-024-03911-z","url":null,"abstract":"<div><p>Droplet impact on substrates is the cornerstone of several processes relevant to many industrial applications. Imposing substrate oscillation modifies the impact dynamics and can, therefore, be used to control the ensuing heat, mass, and energy transfer between the substrate and the impacting droplet. Previous research has shown that substrate oscillation strongly influences the spreading behavior of the droplet. In this study, we extend this understanding to examine how substrate oscillations can further modulate the retraction dynamics of the droplet, consequently affecting its long-term behavior, with a particular focus on induced jetting and subsequent breakup. We systematically examine the breakup of jets formed by the recoiling droplet through experimental investigations across a range of oscillation frequencies and amplitudes. Our findings reveal two distinct jet breakup modes: early and late, each governed by different time scales. Subsequently, we present a mechanistic description of the jetting process. Furthermore, we derive a simple scaling analysis based on energy balance to identify the critical condition required for jet breakup. Finally, we compare the experimental data with the scaling analyses to show its efficacy.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03911-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142789174","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":"Using unmanned aerial systems for observations of water wave characteristics","authors":"Vivek Bheeroo,&nbsp;Soo Bum Bae,&nbsp;Mu-Jung Lee,&nbsp;Scott A. Socolofsky,&nbsp;Kuang-An Chang","doi":"10.1007/s00348-024-03922-w","DOIUrl":"10.1007/s00348-024-03922-w","url":null,"abstract":"<div><p>Dominant wave components within a wavefield play key hydrodynamic and morphodynamic processes. Herein, we present a method to detect and measure the parameters of these waves, such as their wavelength, propagation angle and period. Image sequences of the free surface are captured with the use of a commercial unmanned aerial system. A snapshot proper orthogonal decomposition analysis is then applied to the image sequence, and a 2D autocorrelation is performed on the resulting modes. By extracting the mode that is representative of the dominant wave signal, it is then possible to infer the wave properties of the dominant wave. The outlined procedure is applied to ocean swells, wind waves, free surface undulations along a river and propagating ship wakes. Our results demonstrate an improvement in the signal-to-noise ratio of the peak wave signal to ambient noise over the more widely used fast Fourier transform approach.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"66 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03922-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142778292","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":"Experimental investigation on boundary-layer streaks induced by grid-generated free-stream turbulence in a water channel","authors":"Tristan M. Römer,&nbsp;Markus J. Kloker,&nbsp;Ulrich Rist,&nbsp;Christoph Wenzel","doi":"10.1007/s00348-024-03917-7","DOIUrl":"10.1007/s00348-024-03917-7","url":null,"abstract":"<div><p>In this study, the influence of various turbulence-grid configurations is analysed on both the induced free-stream turbulence (FST) and the resulting Klebanoff modes/streaks developing in a laminar flat-plate boundary layer downstream in a laminar water channel. All results are based on hot-film and particle image velocimetry measurements as well as visualizations. The grid design and installation has been done according to common grid installation recommendations to ensure homogeneous FST causing meandering Klebanoff modes inside the boundary layer. But it was found that (i) the Klebanoff modes do not meander for all grid configurations, (ii) not all configurations cause Klebanoff modes with the expected temporal and spatial behaviour, and (iii) for some configurations, the spanwise streak spacing is strictly locked to the grid spacing (mesh width). As these observations are unreported in the literature, this study is aimed at a thorough description of the influence of key grid parameters on the FST and the resulting streaks within the boundary layer. The investigation includes the grid parameters typically reported, such as the grid-bar diameters, the associated Reynolds numbers, or the streamwise placement of the grid, but now also the grid-orientation order (horizontal/vertical or vertical/horizontal order of grid bars of the dual-plane grid), the wall-normal position of the horizontal bars relative to the leading edge of the flat plate, and the existence of palpable imperfections in the manufactured grids. The Reynolds-number range covered lies well in the lower band of wind-tunnel experiments. Thus, this study suggests that the reliability and reproducibility of future experimental studies on FST would be greatly improved if they demonstrated homogeneity in the free-stream in both spanwise and wall-normal directions, documented the ongoing meandering and wavelengths of the generated Klebanoff modes and thus (implicitly) documented the spanwise independence of the results in the temporal mean. The latter is a prerequisite for the reliable investigation of FST/isolated-roughness interactions.</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 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03917-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142761922","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":"Impact of spanwise extent of transverse grooves on drag reduction in boat-tailed bluff bodies: an experimental study","authors":"Alessandro Mariotti,&nbsp;Gianmarco Lunghi,&nbsp;Elena Pasqualetto,&nbsp;Maria Vittoria Salvetti","doi":"10.1007/s00348-024-03924-8","DOIUrl":"10.1007/s00348-024-03924-8","url":null,"abstract":"<div><p>The paper describes the first experimental study on the application of small contoured grooves in boat-tailed bodies characterized by vortex shedding. In particular, we experimentally investigate the flow-separation delay and drag-reducing performance of spanwise-extruded and spanwise-discontinuous grooves. For this purpose, we consider groove geometries similar to those proposed and numerically investigated by Mariotti et al. (Eur J Mech B/Fluids 74:351–362, 2019) and Pasqualetto et al. (Fluids 7:121, 2022a). The Reynolds number, based on the freestream velocity and the model crossflow dimension, is <span>(mathrm Re=9.6cdot 10^4)</span>. In addition to serving as an experimental confirmation of previous numerical studies, an important difference is that the present experiments were conducted with a freestream turbulence intensity of 0.9%, whereas the simulations were carried out with a freestream without turbulence. This extends the applicability of this flow control device to a situation closer to real-world or industrial applications. In the experiments, we measure pressure-drag variations for different configurations and flow correlations in the spanwise direction through pressure and hot-wire measurements. The results confirm the good performance of the grooves as passive flow-control devices and the capability of grooves to delay flow separation even in a turbulent freestream. The experiments elucidate the physical mechanism leading to the enhanced performance, specifically the reduction of friction losses due to the local recirculation embedded in the groove region. However, the experiments reveal a different behavior in terms of vortex shedding correlation in the spanwise direction with the introduction of grooves of different spanwise extents. Interestingly, the spanwise-extruded grooves exhibit a weaker increase in spanwise correlation of vortex shedding in experiments compared to simulations. This difference is likely due to the presence of freestream turbulence in the wind tunnel, which is absent in simulations. As expected, the introduction of the spanwise-discontinuous groove reduces vortex shedding correlation. Consequently, in experiments the adoption of spanwise-discontinuous grooves yields fewer benefits than those previously found numerically.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142761753","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":"Estimation of local Mach number in compressible flows of dense organic vapors using Gabor filters and Radon transforms for the post-processing of schlieren images","authors":"Theodoros Michelis,&nbsp;Adam Head,&nbsp;Piero Colonna","doi":"10.1007/s00348-024-03925-7","DOIUrl":"10.1007/s00348-024-03925-7","url":null,"abstract":"<div><p>Images of compressible flows can be post-processed with digital imaging techniques to obtain accurate quantitative information about variables characterizing the flow. For example, the local flow Mach number can be obtained from the angle of Mach lines visualized with the schlieren method. These techniques were recently applied to supersonic flows of dense organic vapors, with the objective of obtaining accurate data to validate theory and CFD codes. Non-ideal compressible fluid dynamics (NICFD) is concerned with these flows, for which therefore the thermodynamic properties of the fluid can be modeled only with equations that are more complex than the ideal gas relations. NICFD flows are relevant, e.g., for applications in the power and chemical industry. However, currently employed image post-processing techniques used to obtain the local Mach number or shock wave angle from schlieren images, like the Hough transform, suffer from few drawbacks, namely a long computational time to obtain the relevant quantities and improvable accuracy. The investigation reported here concerns the application of known digital image processing methods to schlieren images, in this case Gabor filters and Radon transforms, to obtain the local Mach number and the shockwave angle of flows in NICFD conditions. The selected test case is the supersonic expansion of the dense vapor of hexamethyldisiloxane flowing through the nozzle test section of the ORCHID facility in operation at the Propulsion and Power laboratory of Delft University of Technology. The investigated digital image processing techniques provide values of the local Mach number with comparable uncertainty (within <span>(5%))</span> as the Hough transform approach. Moreover, Mach line orientations are computed for the whole field of view, together with Mach line wavelength. It was also proven that these methods are suitable for discerning Mach line orientation even in the case of very complex flow fields, with coexisting Mach waves and shock waves.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 12","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142737093","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}