Responses of a Two-Dimensional Multi-Stream Supersonic Jet Flow to External Perturbations*

Resolvent and stability analyses are performed for a two-dimensional supersonic jet flow bounded by an aft-deck. The goal is to uncover the underlying physics of the base flow and to gain insights into flow responses of control-induced perturbations. The jet flow consists of a Mach 1.6 main stream and a Mach 1.0 bypass stream separated by a splitter plate (SP). A vortex shedding phenomenon induced by the mixing of the two streams is observed, and the shedding frequency corresponds to the far-field resonant tone observed in experiments. Using resolvent analysis, a range of frequencies with zero spanwise wavenumber is analyzed to examine the flow responses to external perturbations introduced by active control. At the shedding frequency, forcing modes are found near the SP trailing edge (SPTE) and response modes are in the SP shear layer. Therefore, steady sonic micro-jet actuation is placed around the SPTE at various injection angles with the control objective of suppressing the tone and also aft-deck surface loading. Actuation on the top surface of the SP can most effectively weaken shock strength, and actuation on the SPTE surface can significantly reduce surface loading. For optimal control cases, perturbation dynamics will be further examined to reveal the control mechanism.