DEVELOPMENT AND APPLICATION OF HOLOGRAPHIC PARTICLE IMAGE VELOCIMETRYTECHNIQUES FOR MICROGRAVITY APPLICATIONS

Holographic particle image velocimetry instruments at both velocity ex tremes have been developed and applied. Except for the type of laser r equired, the fundamental recording and data processing methods are sim ilar for both cases. This paper summarizes recording and reconstructio n schemes, software for data reduction, and methods for data presentat ion. An example application focuses on the extreme low-velocity case i n which a three-size matrix of tracer particles was added to a solutio n in a crystal-growth-in-space experiment to quantify and analyse micr oconvection in a microgravity environment. Over 1000 holograms of 1000 particles were produced in a Spacelab mission, leading to the need to process millions of images. Particle velocities ranged from 0.1 to 1 mm h(-1). Reconstructed particle images were located with a computer t raversed microscope imaged on a CCD array, and tracked with software d esigned to establish a reference frame in each hologram and precisely locate the particle centres. The measurements allow determination of t he convective field, the residual gravitational field and gravity-jitt er.