Two reference beam holographic interferometry for aerodynamic flow studies

SUMMARY Double exposure holographic interferometry with two reference beams makes it possible to obtain, after processing, many different interferometric presentations from a single hologram of an aerodynamic flow field. A double-reference-beam holographic set-up has first been tested in the laboratory, then applied to interferometric gas flow studies in a wind tunnel. This technique is particularly adapted to transient phenomena studies such as aerodynamic flows in shock tubes. Following the good results obtained from the first wind tunnel experiments, a more sophisticated dual-reference-beam holographic bench has been built. This apparatus permits both studies of transparent media (such as aerodynamic flows) and scattering object deformations (such as gas turbine blades). An optical scheme is presented as well as interferograms obtained in the laboratory.