Jiang Yu

Under low-density hypersonic flight conditions, conventional aerodynamic control authority is markedly reduced, making transverse jets a promising approach for direct force control. However, the interaction mechanisms of multiple jets under such conditions remain unclear. In this paper, numerical simulations were employed to investigate the flowfield structure, aerodynamic characteristics, and their coupling-induced variations in twin transverse jets under low-density hypersonic crossflow. The results show that the twin-jet flow is not a simple superposition of two isolated single jets, but exhibits distinct near-wall separation, compression, and wake evolution patterns induced by jet–jet interaction. The upstream jet aerodynamically shields the downstream injector, modifies its local crossflow conditions, and consequently enhances downstream jet penetration and wake development. Conversely, the downstream jet affects the upstream flow through the near-wall boundary layer by pushing the primary separation region farther upstream, restricting the free expansion of the upstream jet, and intensifying compression and recirculation in the inter-jet and near-wake regions. Macroscopically, the aerodynamic force analysis reveals that the control force coefficient increases with jet strength, whereas the control force amplification factor decreases continuously. Compared with a single-jet configuration at matched total jet mass flow rate, the twin-jet configuration yields a higher control force and a lower total moment. These findings provide fundamental physical insights into the design and optimization of multi-jet direct force control systems under low-density hypersonic flows.

In our previous study, the transition behavior of a flared cone–swept fin configuration was investigated under an angle of attack (AoA) of 0°. To further explore the role of AoA in complex three-dimensional geometries with strong fin–body interactions, wind tunnel experiments were conducted at Ma = 9.3, Re = 1.36 × 10⁷/m, with AoA ranging from −6° to 6°. Global surface temperature distributions were obtained using temperature-sensitive paint (TSP), while localized heat flux and pressure fluctuations were captured using thin-film thermocouples and high-frequency pressure sensors. The results show that varying AoA shifts the location of high heat flux between the upper and lower surfaces of the flared cone and induces a switch from streamwise to separation vortices. The windward side exhibits stronger disturbance responses than the leeward side. The junction region between the flared cone and the near-horizontal surface is highly sensitive to AoA variations, consistently exhibiting pronounced second-mode instabilities. These findings provide experimental support for understanding transition mechanisms under the combined effects of shock/boundary layer interaction (SBLI), crossflow, and adverse pressure gradients, with implications for transition prediction and thermal protection system design.