Affiliations: Office National d'Etudes et de Recherches
Aérospatiales, Centre de Lille, 5, Boulevard Paul
Painlevé, 59045 Lille Cedex, France. E-mail:
[email protected] | Délégation
Générale à l'Armement, Mission
pour la Recherche et l'Innovation scientifique, 8, Boulevard
Victor, 75015 PARIS Cedex, France. E-mail:
[email protected]
Abstract: At ONERA-Lille center a lot of studies have been conducted to
characterize complex flows using an optical method based on differential
interferometry with Wollaston prism and white polarized light source. Several
applications are presented in two-dimensional and axisymmetric flows and in a
gaseous mixture where the two gases interface is submitted to acceleration.
Then, real-time color holographic interferometry (RCHI) has been developed to
obtain the refractive index itself in two dimensional wake flow. The last
improvements concern the extension of this method for analyzing three
dimensional flows. The authors present a specific setup defined in a single
sight direction, the aim being to reproduce the same optical setup along
several sight directions, each shifted by a given angle. This optical technique
uses reflection holograms where the diffraction efficiency of plates is
strongly influenced by the variations in the gelatin thickness produced during
the holograms treatment. Problems are discussed and solutions are proposed to
control the gelatin shrinkage for two different types of used holograms. The
results obtained in a one sight direction make it possible to build in the
future an optical setup allowing several simultaneous line-of-sight optical
measurements.
Keywords: High speed interferometry, Color holography, High speed flow, Panchromatic hologram