Investigation into the capabilities and characteristics of tomographic particle image velocimetry measurement techniques

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Bisel, T. (2018). Investigation into the capabilities and characteristics of tomographic particle image velocimetry measurement techniques. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

Literature describing measurement results obtained using tomographic particle image velocimetry (TomoPIV) systems has become increasingly common, but details on the processes used to obtain those results and reasons for selecting specified analysis settings are not often explained. In this thesis, an overview is given of techniques and methodologies found to be useful when conducting TomoPIV measurements using an asymmetric four-camera system, including image pre-processing techniques and methods of improving analysis settings. Effective image pre-processing techniques include background subtraction for removing static background noise and improving signal-to-noise ratios and a customized filter that easily and reliably increases voxel reconstruction speed and reduces memory requirements. The custom filter acts to concentrate light intensity around particle locations while muting background pixel intensities. The effects on final measurement results are observed for voxel reconstruction and 3D least squares matching (LSM) settings, including relaxation number, reconstruction iterations, and interrogation volume size. The effects of surface reflections of laser light on TomoPIV results are also investigated by comparing measurement results of a cubic bluff body painted first with a flat white aerosol paint, and second with an airbrushed Rhodamine 6G fluorescent paint. Fluoresced light is blocked by bandpass filters, resulting in minimal reflections from the Rhodamine 6G paint and no observed impact on measurement results. White paint results in intense surface reflections and increased image noise, preventing reliable recognition of distant particles. Comparison of averaged 3D vector map results for both coatings reveals that allowable measurement depth decreases as surface reflection intensity increases.

Details
Author

Bisel, Tucker

Title

Investigation into the capabilities and characteristics of tomographic particle image velocimetry measurement techniques

Physical Description

1 online resource (49 pages) : PDF

Date

2018

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

Literature describing measurement results obtained using tomographic particle image velocimetry (TomoPIV) systems has become increasingly common, but details on the processes used to obtain those results and reasons for selecting specified analysis settings are not often explained. In this thesis, an overview is given of techniques and methodologies found to be useful when conducting TomoPIV measurements using an asymmetric four-camera system, including image pre-processing techniques and methods of improving analysis settings. Effective image pre-processing techniques include background subtraction for removing static background noise and improving signal-to-noise ratios and a customized filter that easily and reliably increases voxel reconstruction speed and reduces memory requirements. The custom filter acts to concentrate light intensity around particle locations while muting background pixel intensities. The effects on final measurement results are observed for voxel reconstruction and 3D least squares matching (LSM) settings, including relaxation number, reconstruction iterations, and interrogation volume size. The effects of surface reflections of laser light on TomoPIV results are also investigated by comparing measurement results of a cubic bluff body painted first with a flat white aerosol paint, and second with an airbrushed Rhodamine 6G fluorescent paint. Fluoresced light is blocked by bandpass filters, resulting in minimal reflections from the Rhodamine 6G paint and no observed impact on measurement results. White paint results in intense surface reflections and increased image noise, preventing reliable recognition of distant particles. Comparison of averaged 3D vector map results for both coatings reveals that allowable measurement depth decreases as surface reflection intensity increases.

Genre

masters theses

Subjects--Topics

Mechanical engineering

Degree

M.S.

Keywords

3D Least Squares Matching
PIV
Relaxation
Smart Voxel Reconstruction
Tomographic Particle Image Velocimetry
Tomopiv

Subject Area

Mechanical Engineering

Advisor(s)

Tkacik, Peter

Committee Members

Goudarzi, Navid
Hellman, Samuel

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2018.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Bisel_uncc_0694N_11766

Permalink

http://hdl.handle.net/20.500.13093/etd:1468