In this work, a qualitative and quantitative characterization of the three-dimensional flow in a lid-driven cylindrical cavity with different optical techniques is presented. Mach–Zehnder interferometry and photographic techniques have been used for a qualitative description of some flow features. However, the real challenge is to obtain quantitative measurements, as the cavity dimensions and geometry prevent the application of 3D digital techniques for measuring the flow velocity in the whole cavity with enough spatial resolution. Digital in-line holography was applied to the measure of the vortex-breakdown bubble that appears near the cavity bottom at Re = 2000. A 22 × 22 × 80 mm3 volume was recorded, its longest dimension parallel to the camera optical axis. This large volume in a liquid fluid combined with a high particle density forces us to develop new analysis strategies. Holograms have been analyzed using a new method, called Adaptive Cross Correlation with Tracking From Beginning, which includes the use of the reconstructed complex amplitude for particle localization. Particle tracking is based on the three-dimensional cross correlation of three-dimensional interrogation windows. The particle set defined in the first hologram is always used to find the particle position in subsequent holograms. This method provides an accurate 3D velocity map and the vortex-breakdown bubble spatial structure. Experimental and numerical data show a very good agreement. A new criterion for determining the accuracy in the particle position along the optical axis is introduced, achieving a spatial resolution of 0.1 mm. This tracking method can be applied not only to laminar flows but also to turbulent flows.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.