Mean-flow measurements in an axisymmetric compressible turbulent wake.

Abstract

Abstract : The mean flow field of the axisymmetric turbulent wake shed by a very slender body at Mach 3 has been mapped with the aid of the pitot and static pressure probes and the hot-wire anemometer. The experimental geometry was chosen so that no inviscid wake existed, and the measurements were carried out to about 100 diameters downstream of the base. The axial variation of the velocity and temperature defects appears to obey classical decay laws following a relaxation distance of at least 40 diameters from the transition region. By contrast, the radial profiles of these properties relax quickly to a self- preserving form; both the temperature and the velocity radial variations fit single-parameter Gaussian distributions quite well. The proper radial similarity variable is the radius divided by the transverse wake scale; equally good agreement obtains for a Howarth-Dorodnitzyn-transformed radius, although this issue is still unsettled because of the low Mach number used. The turbulent Reynolds and Prandtl numbers computed indirectly from the data agree well with similar results from low-speed turbulent flows.