Digital Holography Particle Image Velocimetry for 3D Flow Measurement

摘要

A digital in-line holography recording system was used in the holography particle image velocimetry for a 3D flow measurement that made up of the new full field fluid mechanics experimental technique-DHPIV. In this experiment, the traditional holography film was replaced by a CCD chip that record the interference stripe directly without the darkroom processing, and the virtual image slices in different position were reconstructed by computation using Fresnel-Kirchhoff integral from the digital image. Also complex field signal filter (analyzing image calculated by its intensity and phase from real and image part in Fast Fourier Transform (FFT)) was applied in image reconstruction to achieve the thin depth of image field that has strong effecting with the vertical velocity component resolution. Using the frame-straddle CCD techniques, the 3D velocity was computed by 3D cross-correlation through space interrogation block matching through the reconstructed image slices with digital complex field signal filter. Then the 3D velocity, vortex, iso-surface details and the time evolution movie in a 3D flow field were displayed by numerical computation and experimental measurement using this DHPIV method.