Target-Free,Flow-Based Calibration for Stereoscopics PIV

An improvement of the process of stereo-PIV calibration is presented. The central feature of the proposed technique is that the calibration of the stereoscopic system is based upon the measurement of a calibrated flow. This is achieved through a first two-dimensional calibration of the measurement plane using a single target point, followed by a perspective and laser sheet thickness optimization that makes use of the measurement of a known flow, e.g. a uniform flow. This technique results in three-dimensional measurements of enhanced accuracy with a simpler calibration phase, which compensates for the mechanical misalignment and eliminates the errors deriving from the classical target dot identification. The technique is particularly well suited for towing tanks and other large facilities, and is applied to the tip vortex system generated by a submarine bridge fin.