Experiments in Fluids最新文献_第10页

A second-order polynomial kernel outperforms Gaussian kernels when smoothing Lagrangian particle trajectories 在平滑拉格朗日粒子轨迹时，二阶多项式核优于高斯核

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-07-03 DOI: 10.1007/s00348-024-03848-3

Tim Berk

{"title":"A second-order polynomial kernel outperforms Gaussian kernels when smoothing Lagrangian particle trajectories","authors":"Tim Berk","doi":"10.1007/s00348-024-03848-3","DOIUrl":"10.1007/s00348-024-03848-3","url":null,"abstract":"<div><p>Accurate reconstruction of particle acceleration requires post-processing of Lagrangian particle trajectories to limit noise amplification by differentiation. Over the past two decades, many studies have used a convolution filter based on a truncated Gaussian kernel. The present work evaluates the performance of Gaussian kernels truncated at varying standard deviations. It is shown that, compared to the truncation typically used in Lagrangian particle tracking, a stronger truncation has a similar frequency response, but is superior in terms of overall noise reduction. For kernels of equal width, particle accelerations calculated using a kernel with stronger truncation have up to 20% lower noise. Alternatively, for a specified reduction in noise a shorter kernel can often be used compared to a Gaussian kernel at the commonly used truncation, resulting in less loss of data at trajectory endpoints. It is shown that at the optimal truncation, a Gaussian kernel is mathematically approximated by a second-order polynomial. In this limit, the use of a polynomial kernel has equal results at reduced computational expense compared to the Gaussian kernel.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141525208","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}

引用次数: 0

Insights into bubble–droplet interactions in high-viscoelastic evaporating polymer droplets 高粘弹蒸发聚合物液滴中气泡与液滴相互作用的启示

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-07-03 DOI: 10.1007/s00348-024-03842-9

Gannena K. S. Raghuram, Durbar Roy, D. Chaitanya Kumar Rao, Aloke Kumar, Saptarshi Basu

{"title":"Insights into bubble–droplet interactions in high-viscoelastic evaporating polymer droplets","authors":"Gannena K. S. Raghuram, Durbar Roy, D. Chaitanya Kumar Rao, Aloke Kumar, Saptarshi Basu","doi":"10.1007/s00348-024-03842-9","DOIUrl":"10.1007/s00348-024-03842-9","url":null,"abstract":"<div><p>Polymer droplets subjected to a heated environment have significance in several fields ranging from spray drying, powder formation, and surface coating. In the current work, we study the evaporation of an acoustically levitated high-viscoelastic aqueous polymeric droplet under radiative heating. Depending on the irradiation intensity, we observe bubble nucleation in dilute regime of polymer concentration, contrary to previously observed nucleation in semi-dilute entangled regime for low-viscoelastic polymer droplets. After bubble nucleation, a quasi-steady bubble growth occurs depending on the irradiation intensity and polymer concentrations. Our scaling analysis reveals that initial bubble growth follows Plesset–Zwick criteria, independent of the viscoelastic properties of the polymer solution. Further, we establish that the onset of bubble growth has an inverse nonlinear dependence on the irradiation intensity. The droplet oscillations are primarily driven by the presence of multiple bubbles and, to some extent, by the rotational motion of the droplet. At high polymer concentrations and irradiation intensities, we report the expansion and collapse of polymer membrane without rupture, indicating the formation of an interfacial skin of significant strength. Finally, depending on the nature of bubble growth, different types of precipitate form contrary to the different modes of atomization observed in low-viscoelastic polymer droplets.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141552715","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}

引用次数: 0

Time-resolved phase-lock pressure-sensitive paint measurement of trailing edge noise dynamics 时间分辨锁相压敏涂料测量后缘噪声动态

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-07-02 DOI: 10.1007/s00348-024-03838-5

Masato Imai, Kohei Konishi, Keita Ogura, Kazuyuki Nakakita, Masaharu Kameda

{"title":"Time-resolved phase-lock pressure-sensitive paint measurement of trailing edge noise dynamics","authors":"Masato Imai, Kohei Konishi, Keita Ogura, Kazuyuki Nakakita, Masaharu Kameda","doi":"10.1007/s00348-024-03838-5","DOIUrl":"10.1007/s00348-024-03838-5","url":null,"abstract":"<p>Pressure-sensitive paint (PSP) was applied to the surface of a NACA0012 airfoil to investigate pressure fluctuations associated with trailing edge (TE) noise under low-velocity flow conditions. The primary focus is to assess the feasibility of employing laser pulses exposed at the airfoil surface to mitigate TE noise. However, the weak pressure fluctuations accompanying TE noise pose a challenge, as they are overshadowed by image sensor noise in high-speed cameras capturing PSP emission changes. To address this issue, a novel time-resolved phase-locking technique was introduced, utilizing the signal from a semiconductor pressure transducer at the trailing edge as a phase-lock trigger source. By repetitively conducting phase-locked measurements (1150 times), time series ensemble averaged data based on PSP emission images were obtained, enabling the capture of these subtle pressure fluctuations. Quantitatively, fluctuations with a dominant frequency of 679 Hz and an amplitude of 50 Pa are resolved within an accuracy of about 15 Pa, achieved at a recording rate of 19.2 kHz. Both the suppression and subsequent redevelopment of the pressure field with the TE noise offer valuable insights into the dynamics of TE noise and open avenues for targeted noise reduction strategies in aerodynamic applications.</p>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506633","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}

引用次数: 0

Influence of roughness-generated streaks on laminar separation bubbles 粗糙度产生的条纹对层流分离气泡的影响

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-07-02 DOI: 10.1007/s00348-024-03837-6

Tomek Jaroslawski, Maxime Forte, Olivier Vermeersch, Jean-Marc Moschetta, Erwin Gowree

{"title":"Influence of roughness-generated streaks on laminar separation bubbles","authors":"Tomek Jaroslawski, Maxime Forte, Olivier Vermeersch, Jean-Marc Moschetta, Erwin Gowree","doi":"10.1007/s00348-024-03837-6","DOIUrl":"10.1007/s00348-024-03837-6","url":null,"abstract":"<div><p>This experimental investigation studies the impact of streaks on two-dimensional laminar separation bubbles forming over an aerofoil. Streaks are introduced into the boundary layer using cylindrical roughness elements, and the resulting mean and unsteady flow fields are measured using hotwire anemometry. The observed streaks generated by roughness exhibit analogous behaviour to those generated by freestream turbulence, significantly altering the mean flow characteristics of the bubble, including reductions in its length, height, and the introduction of spanwise velocity gradients. These mean flow modifications have a damping effect on convective disturbance growth. The experiments suggest the coexistence of modal instability due to the laminar separation bubble and transient growth due to streaks. To investigate the combined effect of roughness and the presence of freestream turbulence, we increase the turbulence level from the baseline in the presence of a roughness forcing configuration. We find that increasing the turbulence intensity leads to an enhancement of transient growth, accompanied by distinctive chordwise disturbance growth compared to lower freestream turbulence intensity levels.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141525209","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}

引用次数: 0

Simultaneous velocity and concentration measurements over a rippled boundary subjected to oscillating fluid forcing 在受振荡流体强迫作用的波纹边界上同时测量速度和浓度

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-06-26 DOI: 10.1007/s00348-024-03840-x

Juan C. Vargas-Martinez, Sylvia Rodríguez-Abudo

引用次数: 0

High-speed two-color scanning volumetric laser-induced fluorescence 高速双色扫描体积激光诱导荧光技术

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-06-21 DOI: 10.1007/s00348-024-03831-y

Diego Tapia Silva, Cole J. Cooper, Tracy L. Mandel, Shilpa Khatri, Dustin Kleckner

{"title":"High-speed two-color scanning volumetric laser-induced fluorescence","authors":"Diego Tapia Silva, Cole J. Cooper, Tracy L. Mandel, Shilpa Khatri, Dustin Kleckner","doi":"10.1007/s00348-024-03831-y","DOIUrl":"10.1007/s00348-024-03831-y","url":null,"abstract":"<div><p>Many problems in fluid mechanics require single-shot 3D measurements of fluid flows, but are limited by available techniques. Here, we design and build a novel flexible high-speed two-color scanning volumetric laser-induced fluorescence (H2C-SVLIF) technique. The technique is readily adaptable to a range of temporal and spatial resolutions, rendering it easily applicable to a wide spectrum of experiments. The core equipment consists of a single monochrome high-speed camera and a pair of ND: YAG lasers pulsing at different wavelengths. The use of a single camera for direct 3D imaging eliminates the need for complex volume reconstruction algorithms and easily allows for the correction of distortion defects. Motivated by the large data loads that result from high-speed imaging techniques, we develop a custom, open-source, software package, which allows for real time playback with correction of perspective defects while simultaneously overlaying arbitrary 3D data. The technique is capable of simultaneous measurement of 3D velocity fields and a secondary tracer in the flow. To showcase the flexibility and adaptability of our technique, we present a set of experiments: (1) the flow past a sphere, and (2) vortices embedded in laminar pipe flow. In the first experiment, two channel measurements are taken at a resolution of 512 × 512 × 512 with volume rates of 65.1 Hz. In the second experiment, a single-color SVLIF system is integrated on a moving stage, providing imaging at 1280 × 304 × 256 with volume rates of 34.8 Hz. Although this second experiment is only single channel, it uses identical software and much of the same hardware to demonstrate the extraction of multiple information channels from single channel volumetric images.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03831-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141506634","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}

引用次数: 0

The interaction between turbulent separation bubble breathing and wall pressure on a 2D wing 二维机翼上湍流分离气泡呼吸与壁压之间的相互作用

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-06-14 DOI: 10.1007/s00348-024-03835-8

Sen Wang, Bradley Gibeau, Sina Ghaemi

{"title":"The interaction between turbulent separation bubble breathing and wall pressure on a 2D wing","authors":"Sen Wang, Bradley Gibeau, Sina Ghaemi","doi":"10.1007/s00348-024-03835-8","DOIUrl":"10.1007/s00348-024-03835-8","url":null,"abstract":"<div><p>This investigation characterized the relation between the breathing motion and wall-pressure fluctuations for a turbulent separation upstream of the trailing edge of a two-dimensional wing with NACA 4418 profile. The experiments were conducted at a freestream velocity <i>U</i><sub>∞</sub> = 10.2 m/s with a turbulent intensity of 0.4%. The wing had an aspect ratio of 1.2 and an angle of attack of 9.7°. The corresponding chord-based Reynolds number was 620,000. The measurements consisted of simultaneously acquired wall-pressure measurements at various streamwise locations and time-resolved particle image velocimetry (PIV) in a streamwise-wall-normal plane. Both measurements showed unsteadiness related to the breathing motion at low Strouhal number <i>St</i><sub><i>l</i></sub> ≈ 0.05. Here, <i>St</i><sub><i>l</i></sub> is defined based on the characteristic length, <i>l</i>, of the mean turbulent separation bubble (TSB). Cross-correlation between the measured wall pressures at different streamwise locations revealed that the breathing motion propagated at approximately 0.8<i>U</i><sub>∞</sub> downstream of the mean detachment (MD) point. The breathing motion was observed to establish a stronger correlation with the low-frequency wall-pressure fluctuations in the low-intermittency regions as opposed to the high-intermittency regions. Spectral proper orthogonal decomposition was performed using the combined PIV velocity fields and wall-pressure measurements. The results revealed that the expansion (or contraction) of TSB preceded a reduction (or increase) in wall pressure measured upstream of MD and an increase (or reduction) in wall pressure measured downstream of MD. The findings align with the fact that TSB expansion occurs when local adverse pressure gradient (APG) increases, whereas contraction corresponds to a decrease in APG.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 7","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141341504","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}

引用次数: 0

PIV-based fast pressure reconstruction and noise prediction of tandem cylinder configuration 基于 PIV 的串联气缸配置快速压力重建和噪声预测

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-06-09 DOI: 10.1007/s00348-024-03833-w

Langsheng Chen, Qingqing Ye

{"title":"PIV-based fast pressure reconstruction and noise prediction of tandem cylinder configuration","authors":"Langsheng Chen, Qingqing Ye","doi":"10.1007/s00348-024-03833-w","DOIUrl":"10.1007/s00348-024-03833-w","url":null,"abstract":"<div><p>The present work proposes a fast and optimized experimental approach for pressure reconstruction and far-field noise prediction for flow past tandem cylinders based on time-resolved particle image velocimetry (PIV). The low-order reconstruction of the velocity fields based on proper orthogonal decomposition (POD) is applied, which effectively mitigates the incoherent measurement noise by selecting the low-order modes representing the dominant coherent structures. The preprocessing of velocity fields significantly improves the accuracy of both field and surface pressure fluctuations estimated by solving the Poisson equation. The time-marching enhancement algorithm uses the pressure field from the preceding snapshot as the initial guess in the iterative process, which accelerates convergence and reduces the computational cost for solving the Poisson equation of the PIV database with a large ensemble size. The estimated surface pressure fluctuations are used to predict the far-field noise through Curle’s analogy with the correction based on the spanwise correlation length. Comparisons are performed with reference signals, yielding good agreement on both pressure and noise spectra.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 6","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141415514","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}

引用次数: 0

PIV analysis of wake characteristics of slanted-back Ahmed bodies: effect of leading-edge shape 斜背艾哈迈德天体尾流特性的 PIV 分析：前缘形状的影响

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-06-08 DOI: 10.1007/s00348-024-03834-9

Amir Sagharichi, Mark Francis Tachie

{"title":"PIV analysis of wake characteristics of slanted-back Ahmed bodies: effect of leading-edge shape","authors":"Amir Sagharichi, Mark Francis Tachie","doi":"10.1007/s00348-024-03834-9","DOIUrl":"10.1007/s00348-024-03834-9","url":null,"abstract":"<div><p>This study experimentally investigates turbulent flow separation around a slanted-back Ahmed body with different leading edge configurations [rounded (RL) and square (SL)] using the particle image velocimetry technique. The Reynolds number (based on freestream velocity and body height) is <span>({text{Re}}_{text{H}})</span> = 0.17 × 10<sup>5</sup>. Spatiotemporal flow characteristics, including mean flow, vorticity flux, two-point correlation, reverse flow area, frequency spectra, and proper orthogonal decomposition, are analyzed to elucidate the effects of leading edge shape on separated shear layer interactions over the roof, slanted surface, and the wake region. The results show that rounding the leading edge of the Ahmed body leads to the formation of smaller coherent structures with lower shedding frequency over the roof. While, the structures are still smaller over the slanted surface and the wake region of the RL body, the shedding frequency surpasses that of the SL ones. The results also show evidence of the identical shedding frequency over the roof, slanted surface, and wake region of the RL body. Detailed analyses, including convective velocities of vortices over the roof, slanted surface, and in the wake region, vary significantly between SL and RL cases, indicating distinct shedding mechanisms influenced by leading edge geometry.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 6","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141395454","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}

引用次数: 0

Optimization of SLIPI–polarization ratio imaging for droplets sizing in dense sprays 优化 SLIPI 偏振比成像，确定密集喷雾中的液滴大小

IF 2.3 3区工程技术

Experiments in Fluids Pub Date : 2024-06-07 DOI: 10.1007/s00348-024-03830-z

S. Garcia, M. Stiti, P. Doublet, C. Lempereur, M. Orain, E. Berrocal

{"title":"Optimization of SLIPI–polarization ratio imaging for droplets sizing in dense sprays","authors":"S. Garcia, M. Stiti, P. Doublet, C. Lempereur, M. Orain, E. Berrocal","doi":"10.1007/s00348-024-03830-z","DOIUrl":"10.1007/s00348-024-03830-z","url":null,"abstract":"<div><p>In this article, structured laser illumination planar imaging and polarization ratio techniques are successfully combined to size droplets in various optically dense sprays. The polarization ratio approach is based on the acquisition of the perpendicular and parallel polarized components of Lorenz–Mie scattered light, for which the ratio is proportional to the surface mean diameter, <i>D</i><sub>21</sub>. One of the main advantages of this technique, compared to some other laser imaging techniques for particle sizing, is that no fluorescent dye is required. This makes the technique suitable for characterizing sprays under evaporation conditions, such as combustion or spray drying applications. In addition, the SLIPI technique aims at suppressing the detection of multiple light scattering and at extracting the desirable single-light scattering signal. To test the reliability of this novel approach, an industrial hollow-cone nozzle is used, injecting at 50 bar water mixed with Glycerol (in the range of 0–60%). The first aim of this work is to study the experimental parameters that influence the reliability of the technique, such as the polarization orientation of the incident light, the refractive index of the injected liquid and the variation of the droplet size distribution. Using Phase Doppler Anemometry, the results show that a linear calibration is obtained for droplets ranging between 10 and 70 μm, when the incident illumination has a polarization set to 10° and 20°. In addition, this article demonstrates the feasibility of the technique for the measurement of liquids having a refractive index reaching 1.41. In the last stage of this work, after rotating the nozzle every 5°, a 3D tomographic reconstruction of <i>D</i><sub>21</sub> is performed. This demonstrates the robustness and efficiency of the technique for droplet sizing in 3D, under challenging conditions.</p></div>","PeriodicalId":554,"journal":{"name":"Experiments in Fluids","volume":"65 6","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00348-024-03830-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141404841","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}

引用次数: 0