Direct numerical simulation of transition delay in hypersonic blunt-cone boundary layer subject to velocity–temperature hybrid control

Hypersonic boundary-layer transition exerts a substantial influence on the aerodynamic performance of hypersonic vehicles. In this study, direct numerical simulations are conducted on a three-dimensional blunt-cone configuration to examine transition delay subject to a velocity–temperature hybrid control method. This method delays transition by approximately 44% on the leeward side and reduces skin friction by 23.8%. Power spectral density analysis further confirms that the dominant spectral peak frequency aligns with the second Mack mode, and spectral proper orthogonal decomposition (SPOD) demonstrates a significant suppression of the wall-normal propagation distance of pressure disturbances. Furthermore, momentum potential theory is employed to elucidate the physical mechanism linking variations in the acoustic component, which contains the second Mack mode, to transition delay. In the uncontrolled case, the acoustic and vortical components exhibit a higher degree of similarity compared to the entropy component. In the controlled case, all three fluid-thermodynamic components are suppressed. SPOD further reveals that the first spectral peak of the vortical and acoustic components nearly vanishes, accompanied by a corresponding attenuation of the associated first mode. This implies that the reduction in the acoustic component is primarily responsible for delaying transition.