DRAG OF TWO-DIMENSIONAL STEPS AND RIDGES IMMERSED IN A TURBULENT BOUNDARY LAYER AT SUBSONIC AND SUPERSONIC SPEEDS.

The Item covers the Mach number ranges 0 less than equivalent to M//1 less than equivalent to 0. 8 and 1. 4 less than equivalent to M//1 less than equivalent to 3. 0. Data are not yet available for the drag of these excrescences at transonic speeds but the data at subsonic and supersonic values indicate intermediate peaks in the drag coefficient. The Item derives from experimental data for excrescences in a turbulent boundary layer on a flat plate at zero incidence and with zero heat transfer. It is applicable to excrescences with heights up to about one tenth of the boundary-layer thickness. Guidance on other aspects of applicability, including the presence of streamwise pressure gradients, is given.