scholarly journals A novel streak velocimetry technique based on 2D fits of decaying phosphor particle images

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Luming Fan ◽  
Patrizio Vena ◽  
Bruno Savard ◽  
Guangtao Xuan ◽  
Benoît Fond
Keyword(s):  
Particle Tracking ◽  
Particle Tracking Velocimetry ◽  
Particle Image ◽  
Uv Light ◽  
Light Sheet ◽  
Luminescence Decay ◽  
Phosphor Particle ◽  
Pulsed Uv Light ◽  
Velocity Information ◽  
Particle Images

A new 2D velocimetry technique based on streaks formed by individual phosphor particles, which are moving during their luminescence decay following pulsed excitation is proposed in this study. Tin-doped phosphor particles (Sr,Mg)3(PO4)2:Sn2+ are dispersed into flows and excited by a pulsed UV light sheet. During the phosphor decay time (~27 µs), the emission streaks due to particle motion are recorded. A 2D fitting is then applied on each particle streak against the analytical expression of intensity distribution, to obtain the velocity information for each particle. Unlike Particle Tracking Velocimetry (PTV) this technique does not rely on any particle image searching procedure.

Three-Dimensional Particle Tracking Velocimetry With Laser-Light Sheet Scannings

1996 ◽  
Vol 118 (2) ◽  
pp. 352-357 ◽  
Author(s):  
Satoru Ushijima ◽  
Nobukazu Tanaka
Keyword(s):  
Particle Tracking ◽  
High Speed ◽  
Particle Tracking Velocimetry ◽  
Laser Light ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Light Sheet ◽  
Optical Scanners ◽  
Particle Images

This paper describes three-dimensional particle tracking velocimetry (3D PTV), which enables us to obtain remarkably larger number of velocity vectors than previous techniques. Instead of the usual stereoscopic image recordings, the present 3D PTV visualizes an entire three-dimensional flow with the scanning laser-light sheets generated from a pair of optical scanners and the images are taken by a high-speed video system synchronized with the scannings. The digital image analyses to derive velocity components are based on the numerical procedure (Ushijima and Tanaka, 1994), in which several improvements have been made on the extraction of particle images, the determination of their positions, the derivation of velocity components and others. The present 3D PTV was applied to the rotating fluids, accompanied by Ekman boundary layers, and their complicated secondary flow patterns, as well as the primary circulations, are quantitatively captured.

Poor-Contrast Particle Image Processing in Microscale Mixing

2010 ◽  
Author(s):  
F. Go¨khan Ergin ◽  
Bo Beltoft Watz ◽  
Kaspars Erglis ◽  
Andrejs Cebers
Keyword(s):  
Particle Image ◽  
Strong Dependence ◽  
Interrogation Window ◽  
Light Sheet ◽  
Average Particle ◽  
Local Contrast ◽  
Correlation Peak ◽  
Two Phase ◽  
Strong Light ◽  
Particle Images

Particle image velocimetry (PIV) often employs the cross-correlation function to identify average particle displacement in an interrogation window. The quality of correlation peak has a strong dependence on the signal-to-noise ratio (SNR), or contrast of the particle images. In fact, variable-contrast particle images are not uncommon in the PIV community: Strong light sheet intensity variations, wall reflections, multiple scattering in densely-seeded regions and two-phase flow applications are likely sources of local contrast variations. In this paper, we choose an image pair obtained in a micro-scale mixing experiment with severe local contrast gradients. In regions where image contrast is sufficiently poor, the noise peaks cast a shadow on the true correlation peak, producing erroneous velocity vectors. This work aims to demonstrate that two image pre-processing techniques — local contrast normalization and Difference of Gaussian (DoG) filter — improve the correlation results significantly in poor-contrast regions.

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