RESEARCH ON DRAG REDUCTION IN HYPERSONIC TURBULENT BOUNDARY LAYER OVER BLUNT CONE SUBJECT TO WALL BLOWING

Hypersonic vehicles hold immense strategic significance, occupying a pivotal position in modern aerospace development and representing a crucial frontier in contemporary technological competition. Under hypersonic flight conditions, the turbulent skin friction drag is typically three to five times greater than its laminar counterpart, thereby posing a severe constraint on the range and aerodynamic performance of hypersonic vehicles. Therefore, effective flow control methods are urgently required to achieve drag reduction in hypersonic turbulent boundary layers (TBLs), and it is equally essential to reveal the underlying physical mechanisms. In this study, direct numerical simulation (DNS) is employed to investigate the drag reduction performance of wall blowing on a hypersonic blunt cone, with particular attention paid to the drag reduction mechanism within the control region. The results demonstrate that, under the present control method, wall blowing effectively reduces the skin friction on the leeward side of the blunt cone by approximately 31.25% within the control region. This reduction is mainly attributed to the decrease in the mean viscous shear stress. To further uncover the underlying physics, the R–D (Renard–Deck) skin friction decomposition is utilized. It further reveals that wall blowing reduces the streamwise growth term (C_f,G1) by enhancing the wall-normal velocity ( \tildeu_yn ), ultimately leading to a reduction in the total skin friction. Analysis of large-scale coherent structures and spectral characteristics within the inner boundary layer reveals that wall blowing reduces the streamwise scale of hairpin vortices, which are representative large-scale coherent structures. Wavelet-based time–frequency analysis of density fluctuations reveals that wall blowing reduces the contribution from large-scale structures and suppresses their intermittent nature. Consequently, the frequency of large-scale structures in the inner boundary layer increases relatively, ultimately enhancing the turbulence intensity in this region. This finding may provide a feasible direction for suppressing turbulent fluctuations and further improving drag reduction efficiency under wall blowing control.