Capability enhancement for stereoscopic particle image velocimetry system

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Stereoscopic particle image velocimetry (SPIV) is a laboratory instrument for measuring flow velocity in wind tunnels, towing tanks, and water channels.  SPIV uses a pair of powerful pulsed lasers to produce a laser light sheet, which illuminates seeding particles introduced into the flow.  A pair of digital cameras, aligned obliquely to the flow in a stereoscopic configuration, is synchronized with the lasers to photograph the flow containing the seeding particles.  Using computer software, a sequence of digital images of the flow is transformed into a time series of velocity vector fields.  In each field, the complete velocity vector is obtained at hundreds of points, giving an instantaneous picture of the fluid motion.  The velocity fields are analyzed to study how the flow behaves in space and time.  The method can be applied to very complex flows, including those that are unsteady, rotating, reversing, or turbulent.     The applicant uses SPIV for research in bluff-body aerodynamics and fluid-structure interactions. This research is important in the engineering design of buildings, chimneys, and offshore structures.  The study of these flows is motivated by industrial concerns related to flow-induced vibrations, turbulent buffeting, aerodynamic drag, dispersal of pollutants from stacks, and the safety of hydraulic structures.     The proposed equipment will significantly enhance the measurement and analysis capabilities of the applicant's existing SPIV system. The original system, which was acquired in 2000, was one of the first commercially available SPIV systems and the first of its kind in Canada.  With rapid development and maturation of this technology, a three-fold capability enhancement is now proposed for the existing SPIV infrastructure: (i) new higher-resolution digital cameras, to increase the spatial resolution of the velocity fields and resolve smaller flow structures; (ii) new high-speed camera interface and computer, to increase the data acquisition rate and duration of the experiments; and (iii) new analysis software, with the Proper Orthogonal Decomposition technique, to improve the analysis of turbulent vortex structures in space and time.