Boundary layer transition plays an important role in aerodynamic heating of blunt capsule shapes. While linear growth of modal instabilities can be excluded for spherical windward geometries up to very large Reynolds numbers, transition may occur from disturbances created by surface roughness and fluctuations of the freestream. Research on boundary layers of capsule shapes with roughness is relevant, as re-entry vehicles by their design cannot avoid certain manifestations of roughness. The present paper reports on a number of related experiments on Apollo-type capsule models in a range of hypersonic wind tunnels. The ACE Tunnel of Texas A&M University, USA, provided Mach 6 experiments with distributed roughness at relatively low Reynolds numbers, 2.5- 10~5展开▼
