Effects of Boattailing on the Turbulence Structure of a Compressible Base Flow

Abstract

The large-scale turbulent structures in the near wake of a boattailed, axisymmetric afterbody immersed in a supersonic  ow are examined using a planar Mie/Rayleigh scattering visualization technique. Seven key regions in the near wake are studied in both sideand end-view orientations. Estimates of the mean structure size, shape, and inclination are made using spatial correlation analysis, and the effects of the turbulent structures’ passage are measured via steadiness and convolution analysis techniques. The results indicate that base drag is decreased by afterbody boattailing because the turbulent structures are generally less active in the separated  ow region, and, as a result, shear-layer growth is suppressed. The latter result occurs because the large-scale turbulent structures are further inclined down toward the mean  ow direction and tend to be organized more in the streamwise than in the spanwise direction near the base.