Development and Application of LED Illumination Color PIV

2006 ◽  
Author(s):  
Shenq-Yuh Jaw ◽  
Robert R. Hwang ◽  
K. L. Shyu
Keyword(s):  
Turbulent Flows ◽  
Channel Flow ◽  
Particle Image ◽  
Time Derivative ◽  
Digital Camera ◽  
Soap Film ◽  
Velocity Fields ◽  
Flow Measurements ◽  
Full Field ◽  
Particle Images

In this study, red, green, and blue light-emitting diodes (LED) are adopted as the light source to illuminate sequentially a two-dimensional soap film channel flow. Triple-exposure particle image is recorded on the same image frame by a 3-ccd color camera. Since the particles illuminated by the R, G, B LED will only be recorded on the R, G, B ccd-chip of the digital camera, three sequential exposure, R, G, B particle images can be obtained from separating the triple-exposure particle image. Two sequential velocity fields can be determined from the correlation analysis of the R-G and G-B sequential particle images. Time derivative of the velocity fields, and hence the evolution of the unsteady flow or the characteristics of turbulent flows can be analyzed from the two velocity fields determined. The color PIV method incorporated with the LED light has proven to be a cheap, safe, and powerful tool for the full-field flow measurements. Results of the flow past circular cylinder in the confined soap film channel flow are presented.

Research Methodology of Cross-Flow Cylinder Pipe Hydrodynamical

2013 ◽  
Vol 8 (4) ◽  
pp. 110-117
Author(s):  
Konstantin Dobroselsky
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Visualization ◽  
Turbulent Flows ◽  
Research Methodology ◽  
Particle Image ◽  
Cross Flow ◽  
Velocity Fields ◽  
Experimental Setup ◽  
Flow Around A Cylinder ◽  
Image Velocimetry

Experimental setup (hydrodynamic pipe) for the study of turbulent flows has been upgraded. Test experiments with a cross-flow around a cylinder have been carried out. Using the method of flow visualization PIV (Particle Image Velocimetry) the velocity fields around the cylinder for precavitational and cavitation regimes (Re = 2,8 · 105 ) have been obtained

scholarly journals Experimental Study by Optical and Statistical Methods of Large-Scale Velocity Fluctuations in the Flow Past a Cylinder

2019 ◽  
Vol 14 (3) ◽  
pp. 5-14
Author(s):  
S. S. Abdurakipov ◽  
K. G. Dobroselsky
Keyword(s):  
Experimental Study ◽  
Turbulent Flows ◽  
Large Scale ◽  
Particle Image ◽  
Velocity Fields ◽  
Velocity Fluctuations ◽  
Flow Past ◽  
Image Velocimetry ◽  
Flow Past A Cylinder ◽  
Proper Orthogonal

Using an optical method for measuring the velocity fields Particle Image Velocimetry (PIV) and a statistical method for analyzing coherent structures in turbulent flows Proper Orthogonal Decomposition (POD), an experimental study of the spatial structure of large-scale velocity fluctuations in the precavitational and cavitational flow past a circular cylinder with a Reynolds number of 280 000 was carried out.

scholarly journals Experimental Validation of Falling Liquid Film Models: Velocity Assumption and Velocity Field Comparison

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1205
Author(s):  
Ruiqi Wang ◽  
Riqiang Duan ◽  
Haijun Jia
Keyword(s):  
Experimental Data ◽  
Particle Image Velocimetry ◽  
Velocity Field ◽  
Experimental Validation ◽  
Particle Image ◽  
Velocity Fields ◽  
Number Range ◽  
Comparison Results ◽  
Image Velocimetry ◽  
Experimental Particle

This publication focuses on the experimental validation of film models by comparing constructed and experimental velocity fields based on model and elementary experimental data. The film experiment covers Kapitza numbers Ka = 278.8 and Ka = 4538.6, a Reynolds number range of 1.6–52, and disturbance frequencies of 0, 2, 5, and 7 Hz. Compared to previous publications, the applied methodology has boundary identification procedures that are more refined and provide additional adaptive particle image velocimetry (PIV) method access to synthetic particle images. The experimental method was validated with a comparison with experimental particle image velocimetry and planar laser induced fluorescence (PIV/PLIF) results, Nusselt’s theoretical prediction, and experimental particle tracking velocimetry (PTV) results of flat steady cases, and a good continuity equation reproduction of transient cases proves the method’s fidelity. The velocity fields are reconstructed based on different film flow model velocity profile assumptions such as experimental film thickness, flow rates, and their derivatives, providing a validation method of film model by comparison between reconstructed velocity experimental data and experimental velocity data. The comparison results show that the first-order weighted residual model (WRM) and regularized model (RM) are very similar, although they may fail to predict the velocity field in rapidly changing zones such as the front of the main hump and the first capillary wave troughs.

Analysis of local velocity gradients in rapid mixer using particle image velocimetry technique

2002 ◽  
Vol 2 (5-6) ◽  
pp. 47-55
Author(s):  
N.-S. Park ◽  
H. Park
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Velocity Fields ◽  
Local Velocity ◽  
Mixing Condition ◽  
Particle Image Velocimetry Technique ◽  
Velocity Gradients ◽  
Image Velocimetry ◽  
Current Design ◽  
G Value

Recognizing the significance of factual velocity fields in a rapid mixer, this study focuses on analyzing local velocity gradients in various mixer geometries with particle image velocimetry (PIV) and comparing the results of the analysis with the conventional G-value, for reviewing the roles of G-value in the current design and operation practices. The results of this study clearly show that many arguments and doubts are possible about the scientific correctness of G-value, and its current use. This is because the G-value attempts to represent the turbulent and complicated factual velocity field in a jar. Also, the results suggest that it is still a good index for representing some aspects of mixing condition, at least, mixing intensity. However, it cannot represent the distribution of velocity gradients in a jar, which is an important factor for mixing. This study as a result suggests developing another index for representing the distribution to be used with the G-value.

scholarly journals NUMERICAL SIMULATION OF AIR – WATER FLOWS IN AN EVAPORATIVE CONDENSER

2009 ◽  
Vol 8 (1) ◽  
pp. 24 ◽  
Author(s):  
I. C. Acunha Jr ◽  
P. S. Schneider
Keyword(s):  
Turbulent Flows ◽  
Simple Algorithm ◽  
Continuous Phase ◽  
Velocity Fields ◽  
Temperature Fields ◽  
Two Phase ◽  
Equipment Manufacturer ◽  
Functional Aspects ◽  
Water Behavior ◽  
Complex Phenomena

Evaporative condensers present a hard problem for numerical modeling because of the complex phenomena of heat and mass transfer outside of the bundle tubes in turbulent flows. The goal of this work is to study the air and water behavior inside an evaporative condenser operating with ammonia as the refrigerant fluid. A commercial CFD software package (FLUENT) is employed to predict the two-phase flow of air and water droplets in this equipment. The air flow is modeled as a continuous phase using the Eulerian approach while the droplets water flow is modeled as a disperse phase with Lagrangian approach. The coupling between pressure and velocity fields is performed by the SIMPLE algorithm. The pressure, velocity and temperature fields are used to perform qualitative analyses to identify functional aspects of the condenser, while the temperature and the relative humidity evolution contributed to verify the agreement between the results obtained with the numerical model and those presented by equipment manufacturer.

Direct numerical simulation of turbulent channel flow up to

2015 ◽  
Vol 774 ◽  
pp. 395-415 ◽  
Author(s):  
Myoungkyu Lee ◽  
Robert D. Moser
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Mean Velocity ◽  
Layer Structures ◽  
High Reynolds

A direct numerical simulation of incompressible channel flow at a friction Reynolds number ($\mathit{Re}_{{\it\tau}}$) of 5186 has been performed, and the flow exhibits a number of the characteristics of high-Reynolds-number wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Kármán constant ${\it\kappa}=0.384\pm 0.004$. There is also a logarithmic dependence of the variance of the spanwise velocity component, though not the streamwise component. A distinct separation of scales exists between the large outer-layer structures and small inner-layer structures. At intermediate distances from the wall, the one-dimensional spectrum of the streamwise velocity fluctuation in both the streamwise and spanwise directions exhibits $k^{-1}$ dependence over a short range in wavenumber $(k)$. Further, consistent with previous experimental observations, when these spectra are multiplied by $k$ (premultiplied spectra), they have a bimodal structure with local peaks located at wavenumbers on either side of the $k^{-1}$ range.

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