Double-pulse, diffuse-illumination interferometry has been used to stu
dy the organized structures in the wake of a circular cylinder (M=0.6,
Re-d=300,000). The interferograms show striking similarities to the f
low visualization pictures of the incompressible wakes of circular cyl
inders as obtained by other investigators. In particular, the interfer
ograms taken with very short pulse intervals show concentrations of fi
ne scale turbulence in the von Karman vortices and the existence of st
reamwise vortices between these counter-rotating large-scale vortices.
The fact that most of the features observed in low speed wakes using
a variety of techniques can be observed in the interferograms illustra
ted the potential of interferometry for the study of turbulent structu
res in compressible flows.