Abstract

The unsteady near wake flow of circular cylinder has been analyzed by digital three-wavelength holographic interferometry at Mach 0.45. A specific optical setup using three different lasers as luminous light source of the interferometer has been implemented to generate three interference micro fringes in the observed field. A 3CCD sensor records reference (without flow) and measurement (with flow) images and the phase and amplitude maps are computed by direct and inverse Fast Fourier Transforms in delayed time. The frames recording is triggered from the phase of unsteady pressure signal of transducer implemented in the cylinder. Color fringes obtained with this process are those found by real-time color holographic interferometry using holographic plates. The interest by color using is shown as the variation in the background color due to the external disturbances can be quantified on every interferograms. The time evolution of gas density fields and the mean flow are yielded from the refractive index fields.

© 2011 Optical Society of America