Effect of the Cone Nose Bluntness and the Ultrasonically Absorptive Coating on Transition in a Hypersonic Boundary Layer

The effect of an ultrasonically-absorptive coating on laminar- turbulent transition on cones with different nose bluntnesses is experimentally investigated. The experiments were performed with a cone with the semi- vertex angle of 7 set at zero incidence in the Mach 8 flow for three Reynolds numbers. A material with a chaotic micropore structure was used as the ultrasonically- absorptive coating. One side of the model, along its generator, was coated with the porous material, while the second represented a rigid surface. The laminar-turbulent transition location was determined from the results of heat flux distribution measurements. The heat flux fluctuations were also measured on the model surface. It was found that the laminar region length increased with an increase in the bluntness radius. The ultrasonically- absorptive coating with a chaotic microstructure effectively stabilizes the boundary layer for all bluntness radii considered, increasing the laminar region length by 30 to 85%.