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The main motivation of the current study is to propose a high-pressurehydrogen injection as an hybrid active flow control technique in order tomanipulate the flow-field in front of a blunt nose during hypersonic flight.Hydrogen injection can lead to self-igition under the right environmentconditions in a stagnation zone, and may cause thermal heat addition throughcombustion and provide the counterjet effect together by pushing bow shockupstream. The axisymmetric numerical simulations for the hemispherical bluntnose are performed at a Mach 6 freestream flow with 10000 Pa pressure and 293 Ktemperature. The sonic and supersonic hydrogen and air injections are comparedfor drag reduction at the same stagnation pressure ratio $PR$ and momentumratio ($R_{MA}$). The sonic air and hydrogen injection scenarios show similarperformance in terms of drag reduction and similar SPM flow features, buthydrogen injection has a mass flow rate 3.76 times lower than air. Supersonichydrogen injection at $M_j$ 2.94 behaves differently than supersonic airinjection and can achieve up to 60 % drag reduction at lower PR and LPM modewith lower mass flow rate. Additionally, air injection achieves a dragreduction of 40 % in SPM mode at higher PR with very high mass flow rate.

Drag Control by Hydrogen Injection in Shocked Stagnation Zone of Blunt Nose