ABSTRACT
This chapter discusses all interferograms which have been reconstructed from Mach–Zehnder holograms, which were recorded by using the interferometer. The subsonic turbulent heated air jet generated by a heat gun is one of the interesting phase objects for studying temperature turbulence. Dual hologram shearing interferometry with enhanced sensitivity was proposed for visualizing and measuring the density gradients of compressible flows in a supersonic wind tunnel. The technique is especially useful for a low free-stream density or a strong turbulent flow. Experimental efforts in the last two or three decades have shown that holographic reference beam interferometry is a powerful diagnostic tool for gas-dynamic studies, including wind tunnel testing. This technique has the potential of providing reliable optical information about a flow field, but the biggest difficulty has always been the retrieval of data from the interferograms. The holographic variable shear interferometer, designed on the basis of a conventional single-pass Z-type Schlieren scheme.
