Influence of Different Forcing Mechanisms on the Evolution of Kelvin Helmholtz Instability in a Supersonic Shear Layer

We examine the development of Kelvin-Helmholtz (K-H) instability in a Mach 1.3 shear layer downstream of a splitter plate using a sequence of large eddy simulations (LES). Emphasis is placed on how the type of initial perturbation, not just its frequency, affects K-H evolution. Using our baseline case, we first establish reference K-H behavior in the absence of forcing, where naturally occurring perturbations amplify into coherent structures that grow as they convect downstream. Building on this foundation, we introduce systematic variations by imposing controlled perturbations using pressure, temperature, and momentum forcing, each applied at the same frequency and wave number. Despite sharing the same spectral content, these distinct forms of perturbation yield markedly different flow responses, significantly modifying vortex growth rates, coherence, and spatial organization. Changes in these large-scale structures further alter the near-field acoustic signature, highlighting a direct link between early shear layer evolution and noise generation. By isolating the role of perturbation type, this work offers new insight into how early-stage shear layer dynamics can be shaped, potentially guiding the development of targeted control strategies for high-speed flow applications.