Investigation into the capabilities and characteristics of tomographic particle image velocimetry measurement techniques
1 online resource (49 pages) : PDF
University of North Carolina at Charlotte
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.
3D LEAST SQUARES MATCHINGPIVRELAXATIONSMART VOXEL RECONSTRUCTIONTOMOGRAPHIC PARTICLE IMAGE VELOCIMETRYTOMOPIV
Goudarzi, NavidHellman, Samuel
Thesis (M.S.)--University of North Carolina at Charlotte, 2018.
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