Journal ArticleDOI
Twenty years of particle image velocimetry
TLDR
The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made.Abstract:
The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made. The current status of PIV is summarized, and some goals for future advances are addressed.read more
Citations
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Journal ArticleDOI
Dynamic Speckle Holography.
TL;DR: In this paper, the authors introduced dynamic speckle holography, a new technique that combines imaging and scattering to measure three-dimensional maps of displacements as small as ten nanometers over several centimeters.
Patent
Method and device for quantitative dynamic evaluation of skeletal muscles functionality
TL;DR: In this article, a method for quantitative dynamic evaluation of skeletal muscle functionality was proposed, which consists of two or more sequences of two-dimensional or three-dimensional echographic images of the muscle under investigation, transforming such sequence or sequences of images in sequences of measurements of deformations and/or strain rates in more spatial locations of the muscles or the muscles to evaluate.
DissertationDOI
Influence of rotational energy transfer on quantitative O2 laser-induced fluorescence measurements in flames
Abstract: Laser-induced fluorescence (LIF) is a widely used technique in combustion diagnostics due to its high detection sensitivity and its potential for 2-D and even 3-D applications. Commonly used diagnostic molecules are e.g. the OH radical for flame front detection or the NO radical for concentration or temperature measurements. Their spectroscopic properties and important collisional processes for quantitative LIF interpretation are well investigated. Despite of its predissociative nature, which is beneficial for high-pressure LIF as the signal is less affected by fluorescence quenching, the O2 molecule is not often used and collisional processes relevant in combustion environments are not investigated to the same detail. One of the possible reasons is that a saturation effect of the LIF signal was observed when employing high energy lasers, which is not quantitatively understood. This saturation is the result of the competition of laser excitation and ground state rotational energy transfer (RET). In this work, I introduce an experimental setup including a data acquisition routine and propose a kinetic model to investigate the saturation of O2 LIF. Concerning the modeling, I show that a relatively simple three-level model provides the best agreement with experimental data. A comparison of this model to others, including a more detailed description of RET population exchange indicates why the three-level model better represents the experimental data. Quantitative analysis with the three-level model at different pressures and for different flame gas compositions indicates that the saturation of the O2 LIF signal decreases with increasing pressure, although the dependence is not linear. In addition I found that the saturation depends on the flame gas composition, but not on the ro-vibronic transition in the investigated range. I show that the common O2 simulation tools can be expanded to predict the saturation effect. With respect to practical application of O2 LIF, I propose the use of 2-D O2 LIF to locate flame fronts in rich flames. The accuracy of this method is experimentally compared to traditionally used OH LIF and found to be identical. For quantitative spectral analysis I show that a non-negative matrix factorization method can successfully decompose an O2 spectrum into its different vibronic contributions. From this decomposition, I can estimate an upper bound of the quenching cross section of excited B-state O2 and show that quenching can be neglected for quantitative LIF investigations up to at least 10 bar.
References
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Book
Particle Image Velocimetry: A Practical Guide
TL;DR: In this paper, the authors present a practical guide for the planning, performance and understanding of experiments employing the PIV technique, which is primarily intended for engineers, scientists and students, who already have some basic knowledge of fluid mechanics and nonintrusive optical measurement techniques.
Journal ArticleDOI
Digital Particle Image Velocimetry
Christian Willert,Morteza Gharib +1 more
TL;DR: In this article, the directional ambiguity associated with PIV and LSV is resolved by implementing local spatial cross-correlations between two sequential single-exposed particle images, and the recovered velocity data are used to compute the spatial and temporal vorticity distribution and the circulation of the vortex ring.
Book ChapterDOI
Particle Image Velocimetry
TL;DR: In this paper, the authors use hot-wire (HW) or laser velocimetry (LV) to estimate the velocity, vorticity, and pressure fields of wake flows.
Journal ArticleDOI
Determination of displacements using an improved digital correlation method
TL;DR: An improved digital correlation method is presented for obtaining the full-field in-plane deformations of an object by numerically correlating a selected subset from the digitized intensity pattern of the undeformed object.
Journal ArticleDOI
Fundamentals of digital particle image velocimetry
TL;DR: In this paper, the measurement principle of digital particle image velocimetry (PIV) is described in terms of linear system theory and conditions for PIV correlation analysis as a valid interrogation method are determined.