OBSERVATIONS OF SPHERE WAKES OVER A WIDE RANGE OF VELOCITIES AND AMBIENT PRESSURES
Final rept. Jan 1965-Mar 1968
ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AFB TN
Pagination or Media Count:
The behavior of the near and far wake of spheres for a wide range of velocities, 4000 approx. V approx. 23,000 ftsec, and ambient pressures, 10 approx. p approx. 730 mm Hg, has been studied with schlieren techniques in an aeroballistic free-flight range. In the present report, attention is drawn to some of the problems of interpreting photographs of this type. It is shown that the mode of operation of the schlieren system, e.g., vertical or horizontal knife edge, can exercise a profound effect on the aspects of the flow that are visualized. The breakthrough phenomenon, which has been considered to exist only at near reentry velocities, is shown to exist at lower supersonic speeds. Schlieren photographs of the far wake of hypersonic spheres in the Reynolds number range of 30,000 approx. Re approx. 80,000 bear a marked resemblance to photographs of the wake of a subsonic bluff body. For both hypersonic and subsonic cases, this photographic evidence indicates the existence of a large- scale vortex structure in the wake.
- Fluid Mechanics