Heiko Hinrichs

Light-in-flight holography for visualization and velocimetry in three-dimensional flows

Flow visualization and particle image velocimetry of deep volumes are achieved by holographic recordings. Light-in-flight holography is applied to avoid noise from out-of-focus regions during interrogation of the reconstructed image by use of a ruby laser source of small coherence. The scheme permits reconstruction of thin layers in depth without disturbance by the rest of the field. The location of the layers is selected by the position of a reconstructing slit aperture on the hologram. Applications to tracer particles in water and visualization by smoke of an air flow are given.

DIGITAL SPECKLE-PATTERN INTERFEROMETRY AS A FULL-FIELD FLUID-VELOCIMETRY TECHNIQUE

We present a novel fluid-velocimetry technique based on speckle interferometry. The light scattered from an illuminated plane is recorded with a CCD camera at the same time as a speckled reference beam. Substraction of two nonsimultaneous frames provides information about the velocity field for an out-of-plane component. An application to a Rayleigh-Bénard convective flow is given.

3-D velocity registration from optically processed stereoscopic particle image velocimetry records

Particle image velocimetry (PIV) is extended to 30 velocity measurements by stereoscopic imaging. Optical processing yields all velocity components in a single output.

Particle image velocimetry of 3-D flow configurations by holographic recording of a batch of light sheets

Holograms of a particle field illuminated by a set of light sheets are made simultaneously on one recording material differing each in reference beam direction and coherence properties. Each sheet can thus be evaluated separately by ordinary PlY techniques. 2.

Holographic Particle Image Velocimetry(HPIV) — An Extension of PIV to a 3-D Measuring Method

Particle Image Velocimetry is now a well-established, powerful tool for 2-D flow diagnostics. In its most common applications, a thin sheet of laser light illuminates a portion of the flow. A double exposure photograph is taken to record small light scattering particles seeding the flow. The 2-D flow field data obtained by this technique constitute great progress in comparison with single point measurements by conventional anemometry. Opposite to other whole-field techniques like smoke wire visualisation, for example, PIV is a quantitative measuring method. The opportunity to provide velocity data at one instant of time from a large field of view supports studies in the rapidly growing field of non stationary flows. This support would greatly gain, could PIV be extended in two respects: 1. Simultaneous recording over a certain region in depth 2. Registration of out-of-plane-components of the velocity vectors.