Single-frame (two-field image) 3-D PTV for high speed flows

Abstract

A single-frame 3-D PTV algorithm was constructed to measure 3-D high-speed flows with NTSC cameras. The measurement system consists of three NTSC cameras, an optical instrument called AOM, a digital image grabber and a hosting computer. The tracking algorithm of particles' pair is based on a concept of a spatial match probability. The measurement system is used to probe the turbulent properties of the backward-facing step flow. A preliminary test of the measurement system is also made on the measurement of 3-D vectors of 36 targets on a rotating table to verify its validity. The measurement uncertainty of the system is systematically evaluated through the preliminary test. A set of virtual images is constructed by using the vectors selected randomly from the grid vectors that had been obtained by the experiment on the backward-facing step flow with the system. A performance test is made on the vector recovery using the virtual images and it is validated.