Drag and heat reduction performance of a dual-jet spike configuration in hypersonic flow

High aerodynamic drag and severe aeroheating are the two most important factors impeding the development of hypersonic vehicles. Thus, how to reduce the drag and heat flux effectively in hypersonic flight has attracted worldwide attention. In this paper, a novel strategy combining a spike and a dual-jet has been proposed for the drag reduction and thermal protection. In this configuration, the reaction force generated by the root jet can balance the additional resistance of the rear jet, and the surface heat flux of the vehicle can also be reduced effectively. The flow characteristics and the drag/heat reduction efficiency is explored by numerical simulations. Meanwhile, the influence of the spike length and the total jet pressure on the drag and heat flux are quantitatively analyzed. The results reveal that flow structures of the dual-jet spike configuration are significantly changed, and the drag and heat reduction efficient is greatly improved compared to the cases with a single jet or without any jet. In addition, increasing the spike length ratio (L/D) is beneficial to improve the drag reduction performance, but has a negative effect on the thermal protection. Specifically, by increasing the spike length, from L/D = 1 to L/D = 4, the drag coefficient of the dual-jet spike configuration is decreased by 71.9%, while the total heat flux on the blunt body is increased by 13.7 times. On the other hand, the wall heat flux can be remarkably reduced by increasing the total jet pressure, and it becomes negative when the total pressure ratio of the opposing jet (P_{R, o}) or that of the rear jet (P_{R, r}) is larger than 0.4. However, the variation tendency of the drag coefficient with the increasing of P_{R, o} and P_{R, r} is completely opposite. Due to the drag induced by the opposing jet, the total drag coefficient of the dual-jet spike configuration is increased by 66.7% from P_{R, o} = 0.2 to P_{R, o} = 0.5. On the contrary, thanks to the thrust generated by the rear jet, the total drag coefficient of the dual-jet spike configuration is decreased by 59.3% from P_{R, r} = 0.2 to P_{R, r} = 0.5.