Attenuation of Flow Separation Using Herringbone Riblets at M∞=5

In this Paper, the effect of herringbone riblets as a means of suppressing shockwave-induced flow separation is investigated. A spanwise array of ribleted strips is applied behind the leading edge of a double ramp model placed in a Mach 5 freestream. The high-speed schlieren technique is used to examine the shockwave pattern and the state of the boundary layer developing along the surface of the model. Both pressure-sensitive paints and temperature-sensitive paints are employed to assess the impact of riblets on the interaction between the shockwave and the boundary layer. The results from this experiment show that herringbone riblets are capable of suppressing shock-induced flow separation and hence improving pressure recovery. Furthermore, it is also revealed that these microscale riblets induce large-scale streamwise vortical structures within the boundary layer similar to those observed in incompressible flows. It is believed that these vortices promote momentum transfer within the boundary layer, hen...