Empirical analysis of supersonic jet control using steady minijet injection

Abstract

Manipulation of a Mach 2.0 jet is experimentally investigated based on two steady minijets separated at 180◦. The mass flow rate ratio Cm, of the minijets (ṁm ) to that of the main jet (ṁj ) and the expansion ratio pe /pa (where pe and pa are the nozzle exit and atmospheric pressures, respectively) to understand the mixing capability at design and off-design conditions are examined in detail. Extensive Pitot pressure measurements are performed along the jet centerline, and the jet stream has been visualized using the shadowgraph technique in the orthogonal planes of the manipulated jet. The mixing capability of the manipulated jet quantified based on supersonic core length L∗c which exhibits a strong dependence on Cm and pe /pa. Empirical scaling analysis of the jet control reveals that the relationship L∗c = f1 (ṁm, ṁj, pe, pa ) may be reduced to L∗c = f2 (ξ), where f1 and f2 are different functions and the scaling factor ξ= √ M R pe /pa (M R is the momentum ratio of the minijet to the main jet) is physically the effective momentum ratio or effective penetration depth. The scaling parameter L∗c = f2 (ξ), provides important insights into the jet control physics. © 2019 by American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.