TURBULENCE MEASUREMENTS IN AN AXISYMMETRIC COMPRESSIBLE WAKE

The turbulence characteristics of an axisymmetric wake shed by a very slender body at Mach 3 have been measured with the hot-wire anemometer. The region covered began at transition, located immediately downstream of the model, and ended about 100 virtual (momentum) wake diameters downstream. By using computer-aided corrections to the anemometer frequency response, maps of the temperature and axial velocity fluctuations, their cross correlations, spectral density, and auto-correlation macroscales were obtained as a function of the axial and radial coordinates. Beyond 40 wake diameters from the virtual origin, dynamic equilibration forces these distributions into seemingly self-preserving forms. These forms are identical with their incompressible counterparts except for a coordinate transformation already suggested by the dynamic equilibrium hypothesis and the Reynolds analogy typical of adiabatic flows. The density macroscale is numerically smaller than that of the velocity, although they both approximate the transverse wake scale. Away from the axis, both the fluctuation magnitudes and their spectral densities are apparently distorted by signals associated with the intermittent boundary, which is thought to be weakly periodic with a wavelength on the order of the wake diameter. Copyright © 1968 by the American Institute of Physics.