182 results on '"Laser velocimetry"'
Search Results
2. 3D Fluid Flow Reconstruction Using A Compact Light Field Camera
- Author
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Yu Ji, Jingyi Yu, Jinwei Ye, Yuqi Ding, and Zhong Li
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Physics ,Laser velocimetry ,Light-field camera ,Optics ,Three dimensional imaging ,business.industry ,law ,Optical flow ,Fluid dynamics ,business ,law.invention - Abstract
We present a flexible and low-cost 3D PIV solution that uses a compact light field camera as acquisition device. Real experiments demonstrate that our method can volumetric 3D fluid flows of various types.
- Published
- 2021
- Full Text
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3. Visualization of exhaled breath by transmission electronic speckle pattern interferometry
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Thomas R. Moore
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Laser velocimetry ,Computer science ,business.industry ,Acoustics ,Object (computer science) ,Interference (wave propagation) ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Visualization ,010309 optics ,Optics ,Transmission (telecommunications) ,Electronic speckle pattern interferometry ,0103 physical sciences ,Speckle imaging ,Electrical and Electronic Engineering ,business ,Engineering (miscellaneous) ,Beam (structure) - Abstract
A method for visualizing the air flow from the mouths of vocalists and wind musical instruments is presented. The method is based on a modification of electronic speckle pattern interferometry that incorporates the interference of a transmitted object beam rather than the standard method using a reflected object beam. The resulting whole-field real-time images are a valuable resource for both scientific and pedagogical use.
- Published
- 2020
4. Cross-point calibration method for the Scheimpflug measurement system
- Author
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Fu Qinwei, Na Lv, Hui Zhao, Sun Hao, Cui Bin, and Wei Tao
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Laser velocimetry ,business.industry ,Computer science ,Calibration (statistics) ,System of measurement ,Coordinate system ,Scheimpflug principle ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Astrophysics::Instrumentation and Methods for Astrophysics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,Light intensity ,Optics ,Particle image velocimetry ,Feature (computer vision) ,0103 physical sciences ,Computer vision ,Artificial intelligence ,Electrical and Electronic Engineering ,business ,Engineering (miscellaneous) ,Camera resectioning - Abstract
The Scheimpflug measurement system has broad application prospects in the fields of tomographic particle image velocimetry (PIV), ophthalmology, and three-dimensional reconstruction. Additionally, its special imaging structure makes the theoretical model of other traditional calibration methods no longer applicable. A cross-point calibration method in which the real-world coordinate system is transferred from an in-kind calibrator to displacement, achieving great improvements in the quantity and accuracy of the feature points, is proposed. This method, which makes up for the defects introduced by the distorted imaging plane, also in turn simplifies the calibration process. Finally, the proposed method is tested via both simulation and calibration experiments. The high calibration accuracy verifies that the method is feasible.
- Published
- 2020
5. Combining laser-induced breakdown spectroscopy (LIBS) and particle imaging velocimetry (PIV) for flame diagnostics
- Author
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Andreas Fischer, Johannes Kiefer, and Christoph Vanselow
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Laser velocimetry ,Materials science ,business.industry ,Particle imaging velocimetry ,Flow field ,symbols.namesake ,Optics ,Particle imaging ,symbols ,Laser-induced breakdown spectroscopy ,business ,Spectroscopy ,Raman scattering ,Equivalence ratio - Abstract
We present quasi-simultaneous laser-induced breakdown spectroscopy (LIBS) and particle imaging velocimetiy (PIV) for sttrdying reacting flows. This allows a point measurement of the equivalence ratio and determining the flow field at the same time.
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- 2020
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6. 3D particle field reconstruction method based on convolutional neural network for SAPIV
- Author
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Yang Song, Zhenyan Guo, Ying Jin, Anzhi He, Xiangju Qu, and Zhenhua Li
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Synthetic aperture radar ,Laser velocimetry ,Artificial neural network ,Field (physics) ,business.industry ,Computer science ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Convolutional neural network ,Atomic and Molecular Physics, and Optics ,Image (mathematics) ,010309 optics ,Optics ,Particle image velocimetry ,Temporal resolution ,0103 physical sciences ,Computer vision ,Artificial intelligence ,0210 nano-technology ,business ,Image resolution - Abstract
Synthetic aperture particle image velocimetry (SAPIV) provides a non-invasive means of revealing the physics of complex flows using a compact camera array to resolve the 3D flow field with high temporal and spatial resolution. Intensity-threshold-based methods of reconstructing the flow field are unsatisfactory in nonuniform illuminated fluid flows. This article investigates the characteristics of the focused particles in re-projected image stacks, and presents a convolutional neural network (CNN)-based particle field reconstruction method. The CNN architecture determines the likelihood of each area containing focused particles in the re-projected 3D image stacks. The structural similarity between the images projected by the reconstructed particle field and the images captured from the cameras is then computed, allowing in-focus particles to be extracted. The feasibility of our method is investigated through synthetic simulations and experiments. The results show that the proposed technique achieves remarkable performance, paving the way for non-uniformly illuminated particle field applications in 3D velocity measurements.
- Published
- 2019
7. Development of a modular, high-speed plenoptic-camera for 3D flow-measurement
- Author
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Zu Puayen Tan, Brian S. Thurow, Christopher J. Clifford, and Kyle C. Johnson
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Microlens ,Laser velocimetry ,business.industry ,Computer science ,3D reconstruction ,Volume (computing) ,02 engineering and technology ,Modular design ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,law.invention ,010309 optics ,Lens (optics) ,Optics ,Particle image velocimetry ,law ,High-speed photography ,Component (UML) ,0103 physical sciences ,0210 nano-technology ,business - Abstract
This paper describes the development of a Modular Plenoptic Adaptor (MPA) for rapid and reversible conversion of high-speed cameras into plenoptic imaging systems, with the primary goal of enabling single-camera, time-resolved 3D flow-measurements. The MPA consists of a regular imaging lens, a microlens array, a tilt-adjustable microlens mount and an optical relay, which are collectively installed onto a high-speed camera through a standard lens mount. Each component within the system is swappable to optimize for specific imaging applications. In this study, multiple configurations of the MPA were tested and they demonstrated the ability to refocus and shift perspectives within high-speed scenes after capture. Additionally, the MPA demonstrated 3D reconstruction of captured scenes with
- Published
- 2019
8. Optical-numerical method based on a convolutional neural network for full-field subpixel displacement measurements
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Zhao Jian, Ren Qing, and Chaochen Ma
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Laser velocimetry ,Digital image correlation ,Artificial neural network ,business.industry ,Computer science ,Optical flow ,Image processing ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Convolutional neural network ,Subpixel rendering ,Atomic and Molecular Physics, and Optics ,Displacement (vector) ,010309 optics ,Digital image ,Speckle pattern ,Optics ,Computer Science::Computer Vision and Pattern Recognition ,0103 physical sciences ,Computer vision ,Artificial intelligence ,0210 nano-technology ,business - Abstract
The subpixel displacement estimation is an important step to calculation of the displacement between two digital images in optics and image processing. Digital image correlation (DIC) is an effective method for measuring displacement due to its high accuracy. Various DIC algorithms to compare images and to obtain displacement have been implemented. However, there are some drawbacks to DIC. It can be computationally expensive when processing a sequence of continuously deformed images. To simplify the subpixel displacement estimation and to explore a different measurement scheme, a convolutional neural network with a transfer learning based subpixel displacement measurement method (CNN-SDM) is proposed in this paper. The basic idea of the method is to compare images of an object decorated with speckle patterns before and after deformation by CNN, and thereby to achieve a coarse-to-fine subpixel displacement estimation. The proposed CNN is a classification model consisting of two convolutional neural networks in series. The results of simulated and real experiments are shown that the proposed CNN-SDM method is feasibly effective for subpixel displacement measurement due its high efficiency, robustness, simple structure and few parameters.
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- 2021
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9. Validation of the Gurney Model in Planar Geometry for a Conventional Explosive
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Andrew J. Higgins, William Georges, and Jason Loiseau
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Heterodyne ,020301 aerospace & aeronautics ,Laser velocimetry ,Materials science ,Terminal velocity ,Explosive material ,General Chemical Engineering ,02 engineering and technology ,General Chemistry ,Mechanics ,01 natural sciences ,010305 fluids & plasmas ,Acceleration ,Planar ,0203 mechanical engineering ,0103 physical sciences ,Range (statistics) ,Current (fluid) - Abstract
The analytical model developed by Gurney is a seminal tool for analyzing the acceleration of metal flyers driven by detonating high explosives. Despite the continued relevance of this model, relatively few experimental validations over a wide range of flyer-to-charge mass ratios exist in the open literature. The current study presents experimental results for planar aluminum flyers propelled by a conventional explosive over a range of mass ratios varying from 4.65 to 0.03. Flyer velocity was measured via Heterodyne Laser Velocimetry (PDV), permitting a continuous measurement of the acceleration process. Measured flyer velocities are compared to terminal velocity estimations from the Gurney model. Experimental terminal velocities are compared to the open face and asymmetric sandwich Gurney models. Excellent agreement is observed for terminal velocity predictions considering the gasdynamic simplifications inherent in the model formulation.
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- 2016
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10. Multimode Hollow-Core Anti-Resonant Optical Fibres
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William J. Wadsworth, Tim A. Birks, and Bartlomiej Winter
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Hollow core ,Laser velocimetry ,Materials science ,Fabrication ,Optical fiber ,Multi-mode optical fiber ,High power lasers ,business.industry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,010309 optics ,Core (optical fiber) ,law ,0103 physical sciences ,Optoelectronics ,Fiber fabrication ,0210 nano-technology ,business - Abstract
We report fabrication of a multimode hollow optical fibre with a core diameter of 164 μm guiding approximately 10 modes. The number of modes is found to scale more rapidly than the core area.
- Published
- 2019
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11. Complete plenoptic imaging using a single detector
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Yu Zhang, Liang Gao, Jie Lin, Peng Jin, and Shuaishuai Zhu
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Image fusion ,medicine.medical_specialty ,Laser velocimetry ,Computer science ,business.industry ,Detector ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Image processing ,02 engineering and technology ,01 natural sciences ,Ray ,Atomic and Molecular Physics, and Optics ,Spectral imaging ,010309 optics ,Imaging spectroscopy ,Compressed sensing ,Optics ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Medical imaging ,medicine ,020201 artificial intelligence & image processing ,Computer vision ,Artificial intelligence ,business - Abstract
Multi-dimensional imaging is a powerful technique for many applications, such as biological analysis, remote sensing, and object recognition. Most existing multi-dimensional imaging systems rely on scanning or camera array, which make the system bulky and unstable. To some extent, these problems can be mitigated by employing compressed sensing algorithms. However, they are computationally expensive and highly rely on the ill-posed assumption that the information is sparse in a given domain. Here, we propose a snapshot spectral-volumetric imaging (SSVI) system by introducing the paradigm of light-field imaging into Fourier transform imaging spectroscopy. We demonstrate that SSVI can reconstruct a complete plenoptic function, P(x,y,z,θ,φ,λ,t), of the incoming light rays using a single detector. Compared with other multidimensional imagers, SSVI features prominent advantages in compactness, robustness, and low cost.
- Published
- 2018
12. Quantification of tomographic PIV uncertainty using controlled experimental measurements
- Author
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Lin Ma, Ning Liu, and Yue Wu
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Laser velocimetry ,Computer science ,business.industry ,Published Erratum ,Listing (computer) ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010305 fluids & plasmas ,010309 optics ,Optics ,0103 physical sciences ,Electrical and Electronic Engineering ,business ,Engineering (miscellaneous) ,Image resolution ,Camera resectioning ,Remote sensing - Abstract
The goal of this work was to experimentally quantify the uncertainty of three-dimensional (3D) and three-component (3C) velocity measurements using tomographic particle image velocimetry (tomo-PIV). Controlled measurements were designed using tracer particles embedded in a solid sample, and tomo-PIV measurements were performed on the sample while it was moved both translationally and rotationally to simulate various known displacement fields, so the 3D3C displacements measured by tomo-PIV can be directly compared to the known displacements created by the sample. The results illustrated that (1) the tomo-PIV technique was able to reconstruct the 3D3C velocity with an averaged error of 0.8-1.4 voxels in terms of magnitude and 1.7°-1.9° in terms of orientation for the velocity fields tested; (2) view registration (VR) plays a significant role in tomo-PIV, and by reducing VR error from 0.6° to 0.1°, the 3D3C measurement accuracy can be improved by at least 2.5 times in terms of both magnitude and orientation; and (3) the use of additional cameras in tomo-PIV can extend the 3D3C velocity measurement to a larger volume, while maintaining acceptable accuracy. These results obtained from controlled tests are expected to aid the error analysis and the design of tomo-PIV measurements.
- Published
- 2018
13. Experimental investigation of the influence of natural convection and end-effects on Rayleigh streaming in a thermoacoustic engine
- Author
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Jean-Christophe Valière, Hélène Bailliet, Islam A. Ramadan, Institut Pprime (PPRIME), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS), Acoustique, Aérodynamique, Turbulence (2AT ), Département Fluides, Thermique et Combustion (FTC), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS)-Institut Pprime (PPRIME), Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers-ENSMA-Centre National de la Recherche Scientifique (CNRS), Université de technologie de Compiègne, CNRS, Roberval (Mechanics energy electricity), and Université de Technologie de Compiègne (UTC)
- Subjects
Convection ,Acoustics and Ultrasonics ,Flow (psychology) ,[PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph] ,Acoustic streaming ,Standing waves ,01 natural sciences ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,[SPI.AUTO]Engineering Sciences [physics]/Automatic ,Physics::Fluid Dynamics ,symbols.namesake ,Arts and Humanities (miscellaneous) ,[PHYS.QPHY]Physics [physics]/Quantum Physics [quant-ph] ,0103 physical sciences ,Computer Science::Multimedia ,Acoustical properties ,Mean flow ,Thermodynamic states and processes ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,Rayleigh scattering ,[PHYS.MECA.BIOM]Physics [physics]/Mechanics [physics]/Biomechanics [physics.med-ph] ,010306 general physics ,010301 acoustics ,Acoustic measurements and instrumentation ,ComputingMilieux_MISCELLANEOUS ,Physics ,[SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph] ,[PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph] ,Natural convection ,[SPI.FLUID]Engineering Sciences [physics]/Reactive fluid environment ,Laser velocimetry ,[SPI.NRJ]Engineering Sciences [physics]/Electric power ,Thermoacoustics ,[SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph] ,Mechanics ,[CHIM.MATE]Chemical Sciences/Material chemistry ,[PHYS.MECA.MSMECA]Physics [physics]/Mechanics [physics]/Materials and structures in mechanics [physics.class-ph] ,Electric power ,[PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph] ,[SPI.ELEC]Engineering Sciences [physics]/Electromagnetism ,[CHIM.POLY]Chemical Sciences/Polymers ,Particle image velocimetry ,Equations of fluid dynamics ,[SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph] ,symbols ,[PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph] ,Flow visualization - Abstract
International audience; The influence of both the natural convection and end-effects on Rayleigh streaming pattern in a simple standing-wave thermoacoustic engine is investigated experimentally at different acoustic levels. The axial mean velocity inside the engine is measured using both Laser Doppler Velocimetry and Particle Image Velocimetry. The mean flow patterns are categorized in three different regions referred to as “cold streaming” region, “hot streaming” region, and “end-effects” region. In the cold streaming region, the dominant phenomenon is Rayleigh streaming and the mean velocity measurements correspond well with the theoretical expectations of Rayleigh streaming at low acoustic levels. At higher acoustic levels, the measurements deviate from the theoretical expectations which complies with the literature. In the hot streaming region, temperature measurements reveal that the non-uniformity of the resonator wall temperature is the origin of natural convection flow. Velocity measurements show that natural convection flow superimposes on the Rayleigh streaming flow so that the measured mean velocity deviates from the theoretical expectations of Rayleigh streaming. In the last region, the measured mean velocity is very different from Rayleigh streaming due to the combined effects of both the flow disturbances generated near the extremity of the stack and the natural convection flow.ACKNOWLEDGMENTS
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- 2018
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14. Eruptions from UV to TIR: multispectral high-speed imaging of explosive volcanic activity
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Giancarlo Tamburello, Piergiorgio Scarlato, Elisabetta Del Bello, Jacopo Taddeucci, and Damien Gaudin
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Laser velocimetry ,geography ,geography.geographical_feature_category ,Thermal infrared ,Explosive material ,Multispectral image ,Mineralogy ,medicine.disease_cause ,Physics::Geophysics ,Volcano ,Physics::Space Physics ,Magma ,medicine ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Geology ,Ultraviolet - Abstract
Explosive volcanic eruptions eject a mixture of rock/magma fragments and gases. Ground-based eruption imaging, combining thermal infrared, high-speed visible, and ultraviolet videos, can parameterize ejection dynamics and gas/fragment ratios at the seconds and centimeter
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- 2018
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15. Novel Development for FMCW Lidar
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Jean-Pierre Schlotterbeck, Daniel Dolfi, Gregoire Pillet, J. Minet, Luc Leviandier, Patrick Feneyrou, Aude Martin, Xavier Lacondemine, T. Midavaine, A. Rieu, and Philippe Rondeau
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Laser velocimetry ,Signal processing ,Lidar ,law ,Environmental science ,Velocimetry ,Laser ,Range finding ,Remote sensing ,law.invention - Abstract
Frequency-modulated continuous-wave lidar is evaluated for laser anemometry for helicopter, range finding and velocimetry at long range. Optimized signal processing is described as well as demonstration of range-finding/velocimetry from a few meters up to 10 km.
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- 2018
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16. PIVOTS: A novel method of performing time gated particle image velocimetry
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Yi Chen, Kyle P. Lynch, Daniel R. Guildenbecher, and Megan Paciaroni
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Laser velocimetry ,Kerr effect ,Materials science ,Optics ,Backscatter ,Particle image velocimetry ,business.industry ,High-speed photography ,business - Abstract
Backscatter Particle Image Velocimetry via Optical Time-of-flight Sectioning (PIVOTS) is a novel method of performing PIV in situations where conventional PIV presents difficulties. The PIVOTS technique is introduced along with recent applications and results.
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- 2018
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17. Statistical model for speckle pattern optimization
- Author
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Yong Su, Qingchuan Zhang, and Zeren Gao
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Laser velocimetry ,Digital image correlation ,business.industry ,Computer science ,Image registration ,Speckle noise ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Metrology ,010309 optics ,Speckle pattern ,Optics ,Particle image velocimetry ,Motion estimation ,Electronic speckle pattern interferometry ,0103 physical sciences ,Speckle imaging ,0210 nano-technology ,business - Abstract
Image registration is the key technique of optical metrologies such as digital image correlation (DIC), particle image velocimetry (PIV), and speckle metrology. Its performance depends critically on the quality of image pattern, and thus pattern optimization attracts extensive attention. In this article, a statistical model is built to optimize speckle patterns that are composed of randomly positioned speckles. It is found that the process of speckle pattern generation is essentially a filtered Poisson process. The dependence of measurement errors (including systematic errors, random errors, and overall errors) upon speckle pattern generation parameters is characterized analytically. By minimizing the errors, formulas of the optimal speckle radius are presented. Although the primary motivation is from the field of DIC, we believed that scholars in other optical measurement communities, such as PIV and speckle metrology, will benefit from these discussions.
- Published
- 2017
18. Internal target reflections and line-imaging velocimetry
- Author
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Gilbert Collins, M. A. Barrios, T. R. Boehly, Dayne Fratanduono, and Jon Eggert
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Physics ,Nuclear and High Energy Physics ,Laser velocimetry ,Radiation ,Optics ,business.industry ,Velocimetry ,business ,Intensity modulation ,Intensity (physics) ,Line (formation) - Abstract
A commonly observed intensity modulation or “beating” in laser velocimetry (VISAR) data is examined and explained. It is found that internal target reflections between two surfaces moving relative to one another produces this intensity modulation in the VISAR steak record. The two partially reflecting surfaces define a Fabry–Perot cavity that creates an intensity interference pattern that is superimposed upon VISAR measurements. Experiments are conducted that demonstrate this phenomenon. Previous VISAR experiments that observe this beating pattern are presented and explained.
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- 2014
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19. Numerical and experimental validation of a single-camera 3D velocimetry based on endoscopic tomography
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Weiwei Cai, Hecong Liu, and Jianan Zhao
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Laser velocimetry ,Algebraic Reconstruction Technique ,Computer science ,Acoustics ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Optical flow ,Signal-To-Noise Ratio ,01 natural sciences ,010309 optics ,Imaging, Three-Dimensional ,Optics ,0103 physical sciences ,Photography ,Medical imaging ,Electrical and Electronic Engineering ,Tomography ,Engineering (miscellaneous) ,Probability ,Cross-correlation ,Computer simulation ,Phantoms, Imaging ,business.industry ,Endoscopy ,Numerical Analysis, Computer-Assisted ,Velocimetry ,Atomic and Molecular Physics, and Optics ,Particle image velocimetry ,Rheology ,business ,Algorithms - Abstract
Tomographic velocimetry as a 3D technique has attracted substantial research interests in recent years due to the pressing need for investigations of complex turbulent flows, which are inherently inhomogeneous. However, tomographic velocimetry usually suffers from high experimental costs, especially due to the formidable expenses of multiple high-speed cameras and the excitation laser source. To overcome this limitation, a cost-effective technique called endoscopic tomographic velocimetry has been developed in this work. As a single-camera system, nine projections of the target 3D luminous field at consecutive time instants can be registered from different orientations with one camera and customized fiber bundles, while this is possible only with the same number of cameras in a classical tomographic velocimetry system. Extensive numerical simulations were conducted with three inversion algorithms and two velocity calculation methods. According to RMS error analysis, it was found that the algebraic reconstruction technique outperformed the other two inversion algorithms, and the 3D optical flow method exhibited a better performance than cross correlation in terms of both accuracy and noise immunity. Proof-of-concept experiments were also performed to validate our developed system. The results suggested that an average reconstruction error of the artificially generated 3D velocity field was less than 6%, indicating good performance of the velocimetry system. Although this technique was demonstrated by reconstructing continuous luminous fields, it can be easily extended to discrete ones, which are typically adopted in particle image velocimetry. This technique is promising not only for flow diagnostics but other research areas such as biomedical imaging.
- Published
- 2019
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20. Volumetric calibration of a plenoptic camera
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Daniel R. Guildenbecher, Elise M. Hall, Timothy W. Fahringer, and Brian S. Thurow
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Polynomial ,Laser velocimetry ,Computer science ,Calibration (statistics) ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,010309 optics ,Optics ,law ,0103 physical sciences ,Computer vision ,Electrical and Electronic Engineering ,Image sensor ,Representation (mathematics) ,010306 general physics ,Engineering (miscellaneous) ,Image resolution ,business.industry ,Function (mathematics) ,Atomic and Molecular Physics, and Optics ,Lens (optics) ,Artificial intelligence ,business ,Camera resectioning - Abstract
The volumetric calibration of a plenoptic camera is explored to correct for inaccuracies due to real-world lens distortions and thin-lens assumptions in current processing methods. Two methods of volumetric calibration based on a polynomial mapping function that does not require knowledge of specific lens parameters are presented and compared to a calibration based on thin-lens assumptions. The first method, volumetric dewarping, is executed by creation of a volumetric representation of a scene using the thin-lens assumptions, which is then corrected in post-processing using a polynomial mapping function. The second method, direct light-field calibration, uses the polynomial mapping in creation of the initial volumetric representation to relate locations in object space directly to image sensor locations. The accuracy and feasibility of these methods is examined experimentally by capturing images of a known dot card at a variety of depths. Results suggest that use of a 3D polynomial mapping function provides a significant increase in reconstruction accuracy and that the achievable accuracy is similar using either polynomial-mapping-based method. Additionally, direct light-field calibration provides significant computational benefits by eliminating some intermediate processing steps found in other methods. Finally, the flexibility of this method is shown for a nonplanar calibration.
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- 2017
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21. E-1-3 Development of a New Calibration System for Laser Velocimetry towards the Establishment of Uncertainty Traceability in Measurement
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Jürgen Czarske, Katsuaki Shirai, and Lars Büttner
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Hydrology ,Laser velocimetry ,Traceability ,Calibration ,Environmental science ,Remote sensing - Published
- 2013
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22. Detection and counting of a submicrometer particle in liquid flow by self-mixing microchip Yb:YAG laser velocimetry
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Kenju Otsuka, Seiichi Sudo, and Takayuki Ohtomo
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Laser velocimetry ,Materials science ,Computer simulation ,business.industry ,Materials Science (miscellaneous) ,Mixing (process engineering) ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Signal ,Industrial and Manufacturing Engineering ,010309 optics ,Optics ,Modulation ,0103 physical sciences ,Chirp ,Physics::Accelerator Physics ,Particle ,Business and International Management ,0210 nano-technology ,business ,Beam (structure) - Abstract
We observed intermittent modulation by scattered light from a single submicrometer particle moving in the flow channel using a self-mixing microchip Yb:YAG laser Doppler velocimeter (LDV) under lateral beam access. The Doppler-shift frequency chirping (i.e., velocity change) was identified in accordance with a particle passage through the beam focus. Single particle counting, which obeys the Poisson distribution, was performed successfully over a long period of time. The experimental results have been reproduced by a numerical simulation. The LDV signal was increased over 20 dB for a 202-nm particle without chirping by collinear beam access with the laser beam axis aligned along the flow direction.
- Published
- 2016
23. Seeding in Laser Velocimetry
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Alain Boutier and Max Elena
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Laser velocimetry ,Optics ,Materials science ,Flow velocity ,business.industry ,Seeding ,business ,Particle control - Published
- 2012
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24. Assessment of plenoptic imaging for reconstruction of 3D discrete and continuous luminous fields
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Hecong Liu, Weiwei Cai, and Qianlong Wang
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Laser velocimetry ,Computer science ,business.industry ,Inversion (meteorology) ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Single camera ,Optics ,Three dimensional imaging ,Medical imaging ,Computer vision ,Computer Vision and Pattern Recognition ,Tomography ,Artificial intelligence ,business - Abstract
Volumetric tomography has become an indispensable tool for flow diagnostics. However, it usually suffers from high experimental costs as multiple cameras are required in a typical tomographic system. Plenoptic imaging (PI) is a promising alternative which can simultaneously record spatial and angular information using only one single camera. Although PI has been pioneered by a few groups for 3D flow imaging, this particular application is still at its early stage of development and there are some aspects that need further investigation. In this work, we will systematically assess three representative tomographic algorithms for PI via numerical studies. In addition, we show here how 3D PI inversion can be interpreted from a tomographic perspective and how to conveniently perform the calibration with an existing well-established method which can take into account the effect of lens distortion. A proof-of-concept experiment was also conducted, and the conclusions drawn were consistent with those from numerical studies. Although this work was discussed under the context of flow/flame imaging, the general conclusions are also applicable to other application fields, such as biomedical imaging.
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- 2019
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25. On the Stability of the Detonation Wave Front in the High Explosive Liquid Mixture Tetranitromethane/Nitrobenzene
- Author
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V. A. Davydov, A. V. Men’shikh, A. V. Fedorov, D. V. Nazarov, A. L. Mikhaylov, and S. A. Finyushin
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Wavefront ,Nitrobenzene ,Solvent ,Laser velocimetry ,chemistry.chemical_compound ,Physics and Astronomy (miscellaneous) ,chemistry ,Nitromethane ,Explosive material ,Analytical chemistry ,Detonation ,Tetranitromethane ,Photochemistry - Abstract
We performed experimental studies on the stability of the detonation wave front in mixtures of the liquids tetranitromethane (TNM) and nitrobenzene (NB). Tetranitromethane is an oxygen-rich explosive and nitrobenzene was used as a solvent or dilutant. (NB is not classed as an explosive but as an explosive would be oxygen poor and fuel rich.) The primary diagnostic was a laser velocimetry method with high temporal resolution. Data obtained were compared with the detonation parameters of the TNM/NB mixtures. In previous experimental work [1,2] it was shown that the detonation wave front in liquid explosives may be either smooth or rough. Rough detonation fronts have been reported in nitromethane, as well as nitromethane mixed with a solvent. Smooth detonation fronts have been reported in tetranitromethane. Previously, we conducted studies on the structure of the detonation wave front in liquid explosives containing tetranitromethane [3-5]. Smooth, stable fronts were recorded in pure tetranitromethane and in...
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- 2010
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26. Laser Doppler Vibrometry Measures of Physiological Function: Evaluation of Biometric Capabilities
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Sean D. Kristjansson, Alan D. Kaplan, Mei Chen, John W. Rohrbaugh, N Singla, Po-Hsiang Lai, Joseph A. O'Sullivan, and Erik J. Sirevaag
- Subjects
Laser velocimetry ,medicine.diagnostic_test ,Biometrics ,Computer Networks and Communications ,business.industry ,Computer science ,Carotid arteries ,Hemodynamics ,Ranging ,Laser Doppler velocimetry ,Sensor fusion ,Signal ,symbols.namesake ,symbols ,medicine ,Arterial wall ,Computer vision ,Artificial intelligence ,Time domain ,Safety, Risk, Reliability and Quality ,business ,Doppler effect ,Electrocardiography ,Statistical signal processing - Abstract
A novel approach for remotely sensing mechanical cardiovascular activity for use as a biometric marker is proposed. Laser Doppler Vibrometry (LDV) is employed to sense vibrations on the surface of the skin above the carotid artery related to arterial wall movements associated with the central blood pressure pulse. Carotid LDV signals are recorded using noncontact methods and the resulting unobtrusiveness is a major benefit of this technique. Several recognition methods are proposed that use the temporal and/or spectral information in the signal to assess biometric performance both on an intrasession basis, and on an intersession basis where LDV measurements were acquired from the same subjects after delays ranging from one week to six months. A waveform decomposition method that utilizes principal component analysis is used to model the signal in the time domain. Authentication testing for this approach produces an equal-error rate of 0.5% for intrasession testing. However, performance degrades substantially for intersession testing, requiring a more robust approach to modeling. Improved performance is obtained using techniques based on time-frequency decomposition, incorporating a method for extracting informative components. Biometric fusion methods including data fusion and information fusion are applied to train models using data from multiple sessions. As currently implemented, this approach yields an intersession equal-error rate of 6.3%.
- Published
- 2010
- Full Text
- View/download PDF
27. Calculation of light scattering of an elliptical Gaussian beam by a spherical particle
- Author
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Haitao Yu, Wei Wang, Xiang Liu, and Jianqi Shen
- Subjects
Physics ,Laser velocimetry ,010504 meteorology & atmospheric sciences ,business.industry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Light scattering ,Electronic, Optical and Magnetic Materials ,Quadrature (astronomy) ,010309 optics ,Angular spectrum method ,Optics ,0103 physical sciences ,Nyström method ,Beam shape ,Beam shaping ,Computer Vision and Pattern Recognition ,business ,0105 earth and related environmental sciences ,Gaussian beam - Abstract
The use of an elliptical Gaussian beam (EGB) for applications relying on light scattering depends much on the ability to evaluate the beam shape coefficients (BSC) effectively and accurately. Based on the angular spectrum decomposition (ASD) of the radial components of the beam field, we present the formulations of the BSCs for the EGB. Numerical calculations of the BSCs, the beam reconstruction, and light scattering are performed. The fidelity of the reconstructed field to the given one is discussed so as to examine the BSC calculation. A comparison of the ASD method with the quadrature and localized approximation methods leads to the conclusion that the ASD method is much faster than the quadrature method, and it is very powerful for acquiring reliable and accurate results of BSCs, even for far off-axis locations and high ellipticities of the EGB.
- Published
- 2018
- Full Text
- View/download PDF
28. A Compact Tunable Diode Laser Absorption Spectrometer to Monitor CO2 at 2.7 µm Wavelength in Hypersonic Flows
- Author
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Jacques Soutade, Jean-Luc Vérant, Sebastien Paris, A.K. Mohamed, Raphael Vallon, and Jason Meyers
- Subjects
Antimony ,Optical fiber ,Physics::Optics ,lcsh:Chemical technology ,Biochemistry ,gas sensor ,Analytical Chemistry ,law.invention ,distributed feedback (DFB) ,CO2 monitoring ,Mars atmosphere ,law ,07.07.Df ,Laser-Doppler Flowmetry ,lcsh:TP1-1185 ,47.40.Ki ,Ultrasonics ,Instrumentation ,Wind tunnel ,tunable diode laser absorption spectroscopy ,laser velocimetry ,hypersonic flow ,Distributed feedback laser ,42.55.Px ,Mars Exploration Program ,Atomic and Molecular Physics, and Optics ,07.57.Ty ,Physics::Space Physics ,Lasers, Semiconductor ,Environmental Monitoring ,Materials science ,Models, Biological ,Article ,Optics ,Computer Simulation ,42.62.Fi ,Electrical and Electronic Engineering ,Tunable diode laser absorption spectroscopy ,Spectrometer ,business.industry ,Spectrophotometry, Atomic ,42.79.Qx ,Carbon Dioxide ,Laser ,96.30.Gc ,Feasibility Studies ,business ,Tunable laser - Abstract
Since the beginning of the Mars planet exploration, the characterization of carbon dioxide hypersonic flows to simulate a spaceship’s Mars atmosphere entry conditions has been an important issue. We have developed a Tunable Diode Laser Absorption Spectrometer with a new room-temperature operating antimony-based distributed feedback laser (DFB) diode laser to characterize the velocity, the temperature and the density of such flows. This instrument has been tested during two measurement campaigns in a free piston tunnel cold hypersonic facility and in a high enthalpy arc jet wind tunnel. These tests also demonstrate the feasibility of mid-infrared fiber optics coupling of the spectrometer to a wind tunnel for integrated or local flow characterization with an optical probe placed in the flow.
- Published
- 2010
- Full Text
- View/download PDF
29. Three-Dimensional Imaging and Ranging in a Snapshot with an Extended Depth-of-Field
- Author
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Paul Zammit, Guillem Carles, and Andrew R. Harvey
- Subjects
Point spread function ,Laser velocimetry ,Optics ,Three dimensional imaging ,Computer science ,business.industry ,Image quality ,Data_FILES ,Snapshot (computer storage) ,Ranging ,Imaging technique ,Depth of field ,business - Abstract
We describe a unique single-snapshot three-dimensional imaging technique and experimentally demonstrate that it gives an image quality and depth information from a single snapshot comparable to that given by a focus-stack from tens of snapshots.
- Published
- 2016
- Full Text
- View/download PDF
30. 3D particle tracking in a micro-channel by means of helical wavefront shaping
- Author
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Jürgen Czarske, Martin Teich, Lars Büttner, and Jeremy Sturm
- Subjects
Point spread function ,Wavefront ,Physics ,Laser velocimetry ,Optics ,Flow (mathematics) ,business.industry ,Particle ,Beam expander ,Tracking (particle physics) ,business ,Communication channel - Abstract
We propose a technique for 3D measurements of flow fields. A double-helix point spread function (DH-PSF) is used to gain depth information on particles within a micro-channel. The technique allows robust axial localization of particles.
- Published
- 2016
- Full Text
- View/download PDF
31. High fidelity digital inline holographic method for 3D flow measurements
- Author
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Mostafa Toloui and Jiarong Hong
- Subjects
Laser velocimetry ,Microchannel ,business.industry ,Computer science ,Holography ,Optical flow ,Laminar flow ,Thresholding ,Atomic and Molecular Physics, and Optics ,law.invention ,Optics ,law ,Particle tracking velocimetry ,Particle diameter ,Particle ,Deconvolution ,business ,Image resolution ,Digital holography - Abstract
Among all the 3D optical flow diagnostic techniques, digital inline holographic particle tracking velocimetry (DIH-PTV) provides the highest spatial resolution with low cost, simple and compact optical setups. Despite these advantages, DIH-PTV suffers from major limitations including poor longitudinal resolution, human intervention (i.e. requirement for manually determined tuning parameters during tracer field reconstruction and extraction), limited tracer concentration, and expensive computations. These limitations prevent this technique from being widely used for high resolution 3D flow measurements. In this study, we present a novel holographic particle extraction method with the goal of overcoming all the major limitations of DIH-PTV. The proposed method consists of multiple steps involving 3D deconvolution, automatic signal-to-noise ratio enhancement and thresholding, and inverse iterative particle extraction. The entire method is implemented using GPU-based algorithm to increase the computational speed significantly. Validated with synthetic particle holograms, the proposed method can achieve particle extraction rate above 95% with fake particles less than 3% and maximum position error below 1.6 particle diameter for holograms with particle concentration above 3000 particles/mmsup3/sup. The applicability of the proposed method for DIH-PTV has been further validated using the experiment of laminar flow in a microchannel and the synthetic tracer flow fields generated using a DNS turbulent channel flow database. Such improvements will substantially enhance the implementation of DIH-PTV for 3D flow measurements and enable the potential commercialization of this technique.
- Published
- 2015
32. Recent Advancement of Laser Velocimetry
- Author
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Tomio Obogata
- Subjects
Laser velocimetry ,Optics ,Materials science ,business.industry ,business - Published
- 2005
- Full Text
- View/download PDF
33. Caractéristiques cinématiques et structurelles d'un jet d'air plan turbulent frappant une plaque plane placée à distance variable
- Author
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Stéphane Maurel, Michel Pavageau, Camille Solliec, and Claude Rey
- Subjects
Physics ,Laser velocimetry ,Mechanical Engineering ,General Materials Science ,Geomorphology ,Industrial and Manufacturing Engineering - Abstract
Le developpement du jet libre est relativement bien connu, ce n'est pas le cas du jet plan turbulent en presence d'un impact. En effet, selon la distance H de la paroi d'impact, et de l'epaisseur initiale e du jet, le developpement se fera de maniere relativement differente a cause du confinement qui conditionne l'expansion du jet. A la difference du jet libre, il n'existe pas a l'heure actuelle de base de donnees complete ni de modele global permettant de decrire analytiquement la decroissance de la vitesse moyenne dans le plan de symetrie des jets plans en impact. La litterature fait bien etat de lois semi-empiriques, mais les relations correspondantes ne concernent que quelques zones de la region de jet : le cone potentiel et la zone d'affinite principalement. Le travail presente concerne d'une part, l'etablissement d'une correlation generale capable de decrire l'evolution de la vitesse axiale quelles que soient l'epaisseur du jet et la distance a l'impact, et d'autre part, la description du champ de turbulence du jet et les lois d'epanouissement lateral. Les resultats du modele de decroissance de la vitesse axiale sont aussi compares et valides a l'aide de mesures experimentales obtenues par velocimetrie laser a effet Doppler.
- Published
- 2004
- Full Text
- View/download PDF
34. Instability and unsteadiness of aircraft wake vortices
- Author
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H. Vollmers, Denis Sipp, Vassilios Theofilis, Laurent Jacquin, and David Fabre
- Subjects
Physics ,Turbulence ,Laser velocimetry ,Aerospace Engineering ,Vorticity ,Wake ,Stability theory ,Particle image velocimetry ,Instability ,Vortex ,Physics::Fluid Dynamics ,Classical mechanics ,Hot wire velocimetry ,Aircraft wake ,Nonparallel global stability theory ,Vortex dynamics ,Unsteady flow ,Wind tunnel - Abstract
This paper presents a review of theoretical and experimental results on stability and other unsteady properties of aircraft wakes. The basic mechanisms responsible for the propagation and the amplification of perturbation along vortices, namely the Kelvin waves and the cooperative instabilities, are first detailed. These two generic unsteady mechanisms are described by considering asymptotic linear stability analysis of model flows such as vortex filaments or Lamb–Oseen vortices. Extension of the linear analysis to more representative flows, using a biglobal stability approach, is also described. Experimental results obtained using LDV, hot wire and PIV in wind tunnels are presented and they are commented upon the light of theory.
- Published
- 2003
- Full Text
- View/download PDF
35. Laser velocimetry for non-linear acoustics : An overview over two decades of research
- Author
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J.-Ch. Valière and H. Bailliet
- Subjects
Engineering ,Acoustic field ,Laser velocimetry ,Basis (linear algebra) ,business.industry ,Acoustics ,Laser Doppler velocimetry ,law.invention ,Nonlinear system ,Pressure measurement ,Nonlinear acoustics ,Optics ,Particle image velocimetry ,law ,business - Abstract
Since two decades, progresses in Laser velocimetry technics have allowed the latter to become competitive for the investigation of complex acoustic fields. These technics are of particular interest in situations where pressure measurements are not sufficient to entirely describe the acoustic fields, as is the case in nonlinear acoustics. In this paper, performances of Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV) are presented on the basis of results available in the literature. Then the benefit of these technics for a better understanding of certain nonlinear phenomena are highlighted based.
- Published
- 2015
- Full Text
- View/download PDF
36. Practical Single Snapshot 3D Imaging Method with an Extended Depth of Field
- Author
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Paul Zammit, Guillem Carles, and Andrew R. Harvey
- Subjects
Laser velocimetry ,Three dimensional imaging ,Kernel (image processing) ,Image quality ,business.industry ,Computer science ,Microscopy ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Snapshot (computer storage) ,Computer vision ,Depth of field ,Artificial intelligence ,business - Abstract
We propose a new, practical method of capturing extended depth-of-field, 3D images in a snapshot, based on hybrid-imaging and Complementary Kernel Matching. We demonstrate significantly improved image quality in microscopy compared to conventional hybrid-imaging.
- Published
- 2015
- Full Text
- View/download PDF
37. On the fundamental comparison between unfocused and focused light field cameras
- Author
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Shuaishuai Zhu, Katherine Eaton, Liang Gao, Andy Lai, and Peng Jin
- Subjects
Laser velocimetry ,Light-field camera ,business.industry ,Computer science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,02 engineering and technology ,Lateral resolution ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,law.invention ,010309 optics ,Computational photography ,Optics ,law ,0103 physical sciences ,Medical imaging ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Engineering (miscellaneous) ,Light field - Abstract
Light field cameras have been extensively used in a variety of applications, thanks to their snapshot three-dimensional imaging capability. However, little is known regarding their pros and cons for a given application. Herein we report a fundamental comparison between two types of light field cameras-focused and unfocused. Our results indicate that the unfocused light field camera outperforms its focused counterpart in depth range and number of resolvable depth steps, while the focused light field camera has an edge in lateral resolution and reconstruction accuracy.
- Published
- 2017
- Full Text
- View/download PDF
38. The cold gas-dynamic spray and characterization of microcrystalline austenitic stainless steel
- Author
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Schiel, Jonathan F., Brewer, Luke N., Menon, Sarath K., and Mechanical and Aerospace Engineering (MAE)
- Subjects
cold spray ,laser velocimetry ,stainless steel ,particle velocity - Abstract
This thesis presents research on the cold gas-dynamic spray process applied to the deposition of stainless steel coatings. Cold spray deposition is a relatively new process utilized to create corrosion protection coatings and to perform additive repair for large steel structures. This thesis aims to study the effectiveness of the low-pressure cold spray process on four, commercially available, austenitic stainless steel powders by characterizing both the powders and the resultant coatings. Particle velocimetry and fluid dynamics simulation were also utilized to study the in-flight characteristics of the powder. Notably, this thesis presents evidence that austenitic stainless steel can be successfully deposited via the low-pressure cold spray process. Substantial variability was observed in the commercially available austenitic stainless powders, particularly in the phase content, the particle size distribution, and the particle shape. These parameters had a large effect on the particle velocity and subsequent deposition characteristics. In fact, the PG-AMP- 10 powder, which possessed the highest ferrite fraction and had irregular particle shapes, achieved much higher velocities and greater deposition efficiency than the phase-pure and spherically-shaped S5001 powder. http://archive.org/details/thecoldgasdynami1094543994 Outstanding Thesis Lieutenant Commander, United States Navy Approved for public release; distribution is unlimited.
- Published
- 2014
39. Laser Velocimeter Measurements in the Pump of an Automotive Torque Converter Part II – Effect of Pump Speed and Oil Viscosity
- Author
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Klaus Brun, Ronald D. Flack, Leonard D. Whitehead, and Steven B. Ainley
- Subjects
Materials science ,Mechanical Engineering ,Reynolds number ,Rotational speed ,Mechanics ,Progressive cavity pump ,Pumps ,Industrial and Manufacturing Engineering ,Physics::Fluid Dynamics ,Laser velocimetry ,symbols.namesake ,Viscosity ,lcsh:TA1-2040 ,Rotodynamic pump ,symbols ,Torque ,lcsh:Engineering (General). Civil engineering (General) ,Torque converter ,Variable displacement pump ,Torque converters - Abstract
The velocity field inside a torque converter pump was studied for two separate effects: variable pump rotational speed and variable oil viscosity. Three-dimensional velocity measurements were taken using a laser velocimeter for both the pump mid- and exit planes. The effect ofvariable pump rotational speed was studied by running the pump at two different speeds and holding speed ratio (pump rotational speed]turbine rotational speed) constant. Similarly, the effect of viscosity on the pump flow field was studied by varying the temperature and]or using two different viscosity oils as the working fluid in the pump. Threedimensional velocity vector plots, through-flow contour plots, and secondary flow profiles were obtained for both pump planes and all test conditions. Results showed that torque converter mass flows increased approximately linearly with increasing pump rotational speed (and fixed speed ratio) but that the flow was not directly proportional to pump rotational speed. However, mass flows were seen to decrease as the oil viscosity was decreased with a resulting increased Reynolds number; for these conditions the high velocity regions were seen to decrease in size and low velocity regions were seen to increase in size. In the pump mid-plane strong counter-clockwise secondary flows and in the exit plane strong clockwise secondary flows were observed. The vorticities and slip factors were calculated from the experimental results and are presented. The torque core-to-shell and blade-to-blade torque distributions were calculated for both planes. Finally, the flow fields were seen to demonstrate similitude when Reynolds numbers were matched.
- Published
- 2000
- Full Text
- View/download PDF
40. Study of Several Jets Impinging on a Plane Wall: Visualizations and Laser Velocimetry Investigations
- Author
-
L.-E. Brizzi, A. Bernard, and J.-L. Bousgarbiès
- Subjects
Flow visualization ,Physics ,Laser velocimetry ,business.industry ,Mechanical Engineering ,Flow pattern ,Laser ,Vortex ,law.invention ,Physics::Fluid Dynamics ,Optics ,law ,Plane wall ,business ,Velocity measurement - Abstract
Different experimental techniques have been used in order to describe the flow pattern generated by fifteen jets impinging on a plane wall. The spreading over method revealed the jet influence on the impinged surface, particularly reattachment and detachment lines. The laser sheet visualizations show complex vortical structures such as the ground vortex and secondary rolling-ups near the target plate have been deduced. Velocity measurements have been realised to confirm these observations and to specify the flow pattern. A schema of the flow near the impinged wall is thus drawn.
- Published
- 1999
- Full Text
- View/download PDF
41. Validation of Turbomachinery Computational Fluid Dynamic Models Using Laser Velocimetry
- Author
-
T. Ferguson and R. McGlynn
- Subjects
Engineering ,Laser velocimetry ,Environmental Engineering ,Test facility ,business.industry ,Process (computing) ,Velocimetry ,Computational fluid dynamics ,Dynamic models ,Turbomachinery ,Environmental Chemistry ,Rocket engine ,Aerospace engineering ,Safety, Risk, Reliability and Quality ,business - Abstract
Computational fluid dynamic (CFD) codes are powerful tools for flow field modeling. The codes, however, must be calibrated with data from actual flows if the predictions of the analysis are to be applied with confidence. Laser velocimetry is one method whereby the predictions of the codes can be anchored with accurate, noninvasive flow-field data. This paper explores the process from initial CFD concerns to the application of the velocimeter in the test facility.
- Published
- 1999
- Full Text
- View/download PDF
42. Pipe-flow relaminarization by temporal acceleration
- Author
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E. A. Moss and David Greenblatt
- Subjects
Fluid Flow and Transfer Processes ,Physics ,Laser velocimetry ,Turbulence ,Mechanical Engineering ,Computational Mechanics ,Laminar flow ,Mechanics ,Condensed Matter Physics ,Pipe flow ,Physics::Fluid Dynamics ,Acceleration ,Classical mechanics ,Mechanics of Materials ,Mean flow ,Pressure gradient - Abstract
An experimental and computational study was conducted in temporally accelerated pipe flows under initially turbulent conditions. Relaminarization was identified when the imposed pressure gradient was of the same order as that required for relaminarization under steady conditions. Unlike the steady case, integral development of the mean flow does not characterize relaminarization. Rather, mean-flow effects were confined to the near-wall region, with significant departures from fully turbulent flow only evident at Y+⩽50. Streamwise turbulence fluctuations in the near-wall region initially decreased and then increased, and in the pipe core region the turbulence fluctuations were effectively frozen.
- Published
- 1999
- Full Text
- View/download PDF
43. The setting-up of an optical remote sensing system for target identification: a laboratory experiment
- Author
-
O.J. Dussarrat, D. F. Clark, and Tom Moir
- Subjects
Engineering ,Multipath interference ,Laser velocimetry ,business.industry ,Laser Doppler velocimetry ,Education ,Vibration measurement ,Electronic engineering ,Electrical and Electronic Engineering ,Laboratory experiment ,business ,Equivalence (measure theory) ,Computer Science::Databases ,Remote sensing - Abstract
The construction of an optical system for vibration measurement using laser doppler velocimetry (LDV) is presented, the basis of which can be used as a laboratory experiment for the classroom. LDV is an optical technique that can be used to determine an object's velocity by analyzing the frequency content of coherent light reflected from it. It can be used for vibration measurement, target identification, covert surveillance or studying the flow of fluids. The setting up of such a system in the laboratory can sometimes be difficult if it is performed in a nonsystematic way. This paper describes an approach to configuring a free-space optical system and also demonstrates the optical equivalence of cochannel and multipath interference.
- Published
- 1999
- Full Text
- View/download PDF
44. Velocity Measurements In an Automotive Torque Converter—Part II: Average Turbine and Stator Measurements
- Author
-
Ronald D. Flack and Leonard D. Whitehead
- Subjects
Laser velocimetry ,geography ,Engineering ,geography.geographical_feature_category ,business.industry ,Stator ,Mechanical Engineering ,Automotive industry ,Surfaces and Interfaces ,Mechanics ,Inlet ,Turbine ,Surfaces, Coatings and Films ,law.invention ,Mechanics of Materials ,Control theory ,law ,Gear ratio ,business ,Torque converter ,Wells turbine - Abstract
Laser velocimetry was used to measure the flow field in the turbine and stator of an automotive torque converter. The data complements that of data in a pump at the same operating conditions. Average velocities are presented and analyzed in this paper for three turbine/pump speed ratios (0.065, 0.600, and 0.800). Data presented in this paper embody the most detailed velocity measurements in torque converters available. At all speed ratios and in all turbine measurement planes the highest through flow velocities generally occurred at the pressure side of the channel. At the turbine inlet a velocity deficit near the core was observed. This is due to the velocity deficit at the pump exit that transmits to the turbine inlet. At the lowest speed ratio flow entered the turbine with significant “pre-swirl” causing the flow to separate on the suction surface between the inlet and the mid-plane, resulting in a separation region in the core-suction quadrant. Strong circulatory secondary flows were not observed in t...
- Published
- 1999
- Full Text
- View/download PDF
45. Velocity Measurements in an Automotive Torque Converter Part I—Average Pump Measurements
- Author
-
Leonard D. Whitehead and Ronald D. Flack
- Subjects
Laser velocimetry ,geography ,geography.geographical_feature_category ,Materials science ,business.industry ,Mechanical Engineering ,Automotive industry ,Surfaces and Interfaces ,Mechanics ,Secondary flow ,Inlet ,Turbine ,Surfaces, Coatings and Films ,Physics::Fluid Dynamics ,Mechanics of Materials ,Gear ratio ,Exit plane ,business ,Torque converter ,Simulation - Abstract
The flow field in the inlet, mid- and exit planes of the pump of an automotive torque converter was measured using laser velocimetry. Three turbine/pump speed ratios (0.065, 0.600, and 0.800) were tested and average velocities are presented and analyzed. Data presented in this paper embody the most detailed velocity measurements in torque converters available. The highest through flow velocities generally occurred at the shell side of the blades in all measurement planes and at all speed ratios. For all speed ratios the flow entered the pump inlet plane with a velocity deficit occurring at the core side. The flow was able to become more uniform before it reached the mid-plane at the speed ratio of 0.065, while at the higher speed ratios the flow field demonstrated a large separation region at the mid-plane in the suction side/core quadrant. The flow field was more uniform in the exit plane at all speed ratios and separation was not observed. The secondary flow in the pump mid-plane is counter-clockwise. O...
- Published
- 1999
- Full Text
- View/download PDF
46. Random Dots’ Parameters Optimization Study of Background for Background Oriented Schlieren (BOS) Environmental Research Application
- Author
-
Xiang Chen, Chenguang Yang, Zhenyu Xu, Ruifeng Kan, Jianguo Liu, and Lu Yao
- Subjects
Flow visualization ,Laser velocimetry ,Optics ,business.industry ,Computer science ,Schlieren ,Acoustics ,Environmental research ,Sensitivity (control systems) ,business - Abstract
BOS is a novel schlieren method, which has potential environmental application. In order to improve its sensitivity, the background parameters have been studied. And some flow visualization examples with the optimized background are shown.
- Published
- 2014
- Full Text
- View/download PDF
47. Basilar-membrane responses to tones at the base of the chinchilla cochlea
- Author
-
Mario A. Ruggero, Alberto Recio, Luis Robles, Nola C. Rich, and S. Shyamla Narayan
- Subjects
Laser velocimetry ,Cochlear amplifier ,Cell Death ,Acoustics and Ultrasonics ,Chemistry ,Acoustics ,Stimulus (physiology) ,Article ,Basilar Membrane ,Cochlea ,Basilar membrane ,Nuclear magnetic resonance ,Acoustic Stimulation ,Arts and Humanities (miscellaneous) ,Chinchilla ,Animals ,Relative phase - Abstract
Basilar-membrane responses to single tones were measured, using laser velocimetry, at a site of the chinchilla cochlea located 3.5 mm from its basal end. Responses to low-level (80 dB the largest responses are elicited by tones with frequency about 0.4–0.5 octave below CF. For stimulus frequencies well above CF, responses stop decreasing with increasing frequency: A plateau is reached. The compressive growth of responses to tones with frequency near CF is accompanied by intensity-dependent phase shifts. Death abolishes all nonlinearities, reduces sensitivity at CF by as much as 60–81 dB, and causes a relative phase lead at CF.
- Published
- 1997
- Full Text
- View/download PDF
48. MODERN HELICOPTER AERODYNAMICS
- Author
-
A. T. Conlisk
- Subjects
Laser velocimetry ,business.industry ,Computer science ,Computation ,Stall (fluid mechanics) ,Aerodynamics ,Computational fluid dynamics ,Wake ,Condensed Matter Physics ,law.invention ,Vortex ,law ,Helicopter rotor ,Aerospace engineering ,business - Abstract
▪ Abstract Modern helicopter aerodynamics is challenging because the flow field generated by a helicopter is extremely complicated and difficult to measure, model, and predict; moreover, experiments are expensive and difficult to conduct. In this article we discuss the basic principles of modern helicopter aerodynamics. Many sophisticated experimental and computational techniques have been employed in an effort to predict performance parameters. Of particular interest is the structure of the rotor wake, which is highly three-dimensional and unsteady, and the rotor-blade pressure distribution, which is significantly affected by the strength and position of the wake. We describe the various modern methods of computation and experiment which span the range from vortex techniques to full three-dimensional Navier-Stokes computations, and from classical probe methods to laser velocimetry techniques. Typical results for the structure of the wake and the blade pressure distribution in both hover and forward flight are presented Despite the complexity of the helicopter flow, significant progress has been made within the last ten years and the future will likely bring marked advances.
- Published
- 1997
- Full Text
- View/download PDF
49. Performance and Exit Flow Characteristics of Mixed-Flow Turbines
- Author
-
J. M. Nouri, C. Arcoumanis, C. C. Su, and R. F. Martinez-Botas
- Subjects
geography ,Degree of reaction ,Materials science ,geography.geographical_feature_category ,Rotor (electric) ,Mechanical Engineering ,Flow (psychology) ,laser velocimetry ,Mechanics ,Volute ,Inlet ,Turbochargers ,Turbine ,unsteady aerodynamics ,Industrial and Manufacturing Engineering ,law.invention ,pulsating flows ,lcsh:TA1-2040 ,law ,mixed flow turbines ,Velocity ratio ,lcsh:Engineering (General). Civil engineering (General) ,Constant (mathematics) - Abstract
The performance and exit flow characteristics of two mixed-flow turbines have been investigated under steady-state conditions. The two rotors differ mainly in their inlet angle geometry, one has a nominal constant incidence (rotor B) and the other has a constant blade angle (rotor C), but also in the number of blades. The results showed that the overall peak efficiency of rotor C is higher than that of rotor B. Two different volutes were also used for the tests, differing in their cross-sectional area, which confirm that the new larger area volute turbine has a higher efficiency than the old one, particularly at lower speeds, and a fairly uniform variation with velocity ratio.The flow exiting the blades has been quantified by laser Doppler velocimetry. A difference in the exit flow velocity for rotors B and C with the new volute was observed which is expected given their variation in geometry and performance. The tangential velocities near the shroud resemble a forced vortex flow structure, while a uniform tangential velocity component was measured near the hub. The exit flow angles for both rotor cases decreased rapidly from the shroud to a minimum value in the annular core region before increasing gradually towards the hub. In addition, the exit flow angles with both rotors were reduced with increasing rotational speeds. The magnitude of the absolute flow angle was reduced in the case of rotor C, which may explain the improved steady state performance with this rotor. The results also revealed a correlation between the exit flow angle and the performance of the turbines; a reduction in flow angle resulted in an increase in the overall turbine efficiency.
- Published
- 1997
- Full Text
- View/download PDF
50. Data processing of single burst signals from laser Doppler velocity sensors for turbulent flow measurements
- Author
-
Dishank Upadhyay
- Subjects
Laser velocimetry ,Signal processing ,Computer science ,Turbulence ,Acoustics ,Laser Doppler velocimetry ,Velocimetry ,Flow measurement ,Physics::Fluid Dynamics ,symbols.namesake ,Flow separation ,Data acquisition ,Particle image velocimetry ,Fluid dynamics ,symbols ,Acoustic Doppler velocimetry ,Laser Doppler vibrometer ,Image resolution ,Lorentz force ,Velocity measurement - Abstract
Flow separation and its control is a persistent topic of fluid dynamic research. The paper describes the development and implementation of a novel optical signal processing system to measure liquid flow velocities with a high spatial resolution in the order of 20 μm. The principles of Laser Doppler Anemometry coupled with signal processing algorithms are used to quantify the fluid flow velocities in the vicinity of a flow controlling device called Lorentz Force Actuator. The signal processing routines are tested on the bench using a Field Programmable Gate Array (FPGA) using LabVIEW from National Instruments. The LabVIEW code is ported to a PC based Data Acquisition Card for real time signal processing and correlation measurements in highly turbulent flows. The aim is to achieve the same performance as commercial systems, which are not applicable in conjunction with the novel laser Doppler sensors, while maintaining the high precision and flexibility of the propriety signal processing techniques.
- Published
- 2013
- Full Text
- View/download PDF
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