Measurement of 3D laminar flow inside a micro tube using micro digital holographic particle tracking velocimetry

Abstract

A micro digital holographic particle tracking velocimetry ( HPTV) system consisting of a high-speed camera and single laser with acoustic optical modulator chopper was established. This system can capture 4000 hologram fringe images directly for 1 s. The temporal evolution of water flow in a micro tube of 100 mu m inner diameter is obtained successfully using this micro digital HPTV system. By using an object lens with a large numerical aperture ( NA), we could get holographic images of tracer particles in a volume of thin depth. The angular spectrum method is advantageous in holographic reconstruction, with the ability to remove noises and unwanted holographic terms. The information on the 3D particle location of tracer particles was reconstructed numerically. This micro digital HPTV system was applied to water flow in a micro tube for measuring instantaneous 3D velocity field data consecutively with a different particle number density and flow rate. The mean velocity field distribution was obtained by statistical averaging instantaneous velocity fields.