Optical Diagnostic Development

	*Development and Applications of PIV*
	Particle image velocimetry(PIV) has been implemented and extensively used to measure a wide range of thermal and flow phenomena, including non-periodic turbulent flows shedding from broken surface waves in a surf zone (large-scale), high Reynolds numbered U-channel flows (laboratory scale), and heated capillary pore flows (meso- to micro-scale). For reference, click here [146 KB in PDF] For the most recent progress, click here.

	A cinematographic digital PIV system has been devised to appropriately record non-periodic turbulent flows. This new system allows a temporal post processing, in addition to the conventional spatial post processing, to further improve the vector validation.

	For reference and recent progress, click here [964KB in PDF] Figures (from #1 to #11 except #5) [1.1MB in DOC] Figure 5 [1.4 MB in DOC] *Accepted for publication in Experiments in Fluids (2000)*

	Optical diagnostic improvement has been proposed for a possible cure for PIV image bias occurring when a rotating mirror is used to solve the directional ambiguities, for the case of auto-correlation.
	For references, click here

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	*Tomographic Image Reconstruction* *Using Genetic Algorithm*
	New tomographic image reconstruction algorithm has been developed to use the principle of "the fittest survival" based on a genetic algorithm (GA), a robust multi-parallel optimization (solution search) algorithm. This GA-based tomography is innovative in that multiple parameters, such as bubble positions, shapes and sizes for two-phase flow cases, for example, can be simultaneously optimized while the most conventional algebraic reconstruction technique (ART) can optimize a single parameter at once.

	For references, click here

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	*Speckle Photography for Nonintrusive Temperature Measurement*
	Laser speckle photography can nonintrusively measure the full-field temperature distributions for optically thin media and its principle is to detect micro-scale dislocations of optical speckle patterns occurring by the ray refraction in the presence of a phase object field. A speckle photography system, using a 50 mW helium-neon laser, has been developed and also compared with Mach-Zhender interferometry diagnostics.
	For references, click here

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