Nosetip bluntness effects on transition at hypersonic speeds: experimental and numerical analysis under NATO STO AVT-240

Mechanism for frustum transition over blunt cones at hypersonic speeds

“…Given the absence of a significant modal growth up to the measured transition location, the transient growth mechanism was investigated as a potential cause for the onset of transition by Paredes et al. (2018, 2019 d , c ). Their linear optimal growth analysis showed appreciable non-modal growth over the streamwise interval of that precedes the measured transition location at .…”

“…This finding may not provide a definitive link between transient growth and the onset of transition, but is qualitatively consistent with the experimental observations that transition during the reversal regime on large-bluntness configurations was highly sensitive to wall roughness, and additionally, was dominated by disturbances originating near the nose tip. The predictions of optimal transient growth were used to design an azimuthally periodic array of microroughness elements located near the sonic point at the nose tip (Paredes et al 2019d). The measurements showed that variable bluntness models with similar values of roughness Reynolds number, Re kk , affected transition only on the blunter cone, demonstrating that transition onset in the latter case is associated with the combined effects of sufficiently large bluntness and roughness.…”

Ionization and dissociation effects on boundary-layer stability

“…Such a decoupling is necessary in order to understand the effect that each of these phenomena individually have on the instability growth, and to ultimately design solutions effectively controlling the transition dynamics. Some examples of control strategies in low-enthalpy scenarios can be found in the works of Ren, Fu & Hanifi (2016), Fransson et al (2006) and Paredes et al (2018).…”

Effect of a Roughness Element on the Receptivity of a Hypersonic Boundary Layer over a Blunt Cone Due to Pulse Entropy Disturbance with a Single Frequency

“…There are many factors that affect the receptivity of the hypersonic boundary layer such as free stream disturbances, wall temperature, and roughness element. Nose-bluntness [1][2][3] and entropy-layer instability [2][3][4] also affect the flow state in the boundary layer. The factors are simply divided into the free stream disturbances and surface disturbances [5], as shown in Figure 1.…”