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Three-Dimensional Stereoscopic Tracking Velocimetry and Experimental/Numerical Comparison of Directional SolidificationMeasurement of three-dimensional (3-D) three-component velocity fields is of great importance in both ground and space experiments for understanding materials processing and fluid physics. The experiments in these fields most likely inhibit the application of conventional planar probes for observing 3-D phenomena. Here, we present the investigation results of stereoscopic tracking velocimetry (STV) for measuring 3-D velocity fields, which include diagnostic technology development, experimental velocity measurement, and comparison with analytical and numerical computation. STV is advantageous in system simplicity for building compact hardware and in software efficiency for continual near-real-time monitoring. It has great freedom in illuminating and observing volumetric fields from arbitrary directions. STV is based on stereoscopic observation of particles-Seeded in a flow by CCD sensors. In the approach, part of the individual particle images that provide data points is likely to be lost or cause errors when their images overlap and crisscross each other especially under a high particle density. In order to maximize the valid recovery of data points, neural networks are implemented for these two important processes. For the step of particle overlap decomposition, the back propagation neural network is utilized because of its ability in pattern recognition with pertinent particle image feature parameters. For the step of particle tracking, the Hopfield neural network is employed to find appropriate particle tracks based on global optimization. Our investigation indicates that the neural networks are very efficient and useful for stereoscopically tracking particles. As an initial assessment of the diagnostic technology performance, laminar water jets with and without pulsation are measured. The jet tip velocity profiles are in good agreement with analytical predictions. Finally, for testing in material processing applications, a simple directional solidification apparatus is built for experimenting with a metal analog of succinonitrile. Its 3-D velocity field at the liquid phase is then measured to be compared with those from numerical computation. Our theoretical, numerical, and experimental investigations have proven STV to be a viable candidate for reliably measuring 3-D flow velocities. With current activities are focused on further improving the processing efficiency, overall accuracy, and automation, the eventual efforts of broad experimental applications and concurrent numerical modeling validation will be vital to many areas in fluid flow and materials processing.
Document ID
20010019997
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Lee, David
(Illinois Univ. Chicago, IL United States)
Ge, Yi
(Illinois Univ. Chicago, IL United States)
Cha, Soyoung Stephen
(Illinois Univ. Chicago, IL United States)
Ramachandran, Narayanan
(Universities Space Research Association United States)
Rose, M. Franklin
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: Pan Pacific Workshop on Microgravity Sciences
Location: Pasadena, CA
Country: United States
Start Date: May 1, 2001
Funding Number(s)
CONTRACT_GRANT: NCC8-66
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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