Acoustic response of turbulent cavity flow using resolvent analysis.

The decomposition of hydrodynamic and acoustic components of cavity flows can aid the understanding of the flow-acoustic interaction, which produces a variety of adverse effects in applications. We apply the approach of combining the resolvent analysis and Doak's momentum potential theory to examine the input-output flow-acoustic characteristics of compressible flow over an open cavity at Re=10,000. The methodology can decompose hydrodynamic and acoustic components from an input-output framework. We further localize the forcing at the leading-edge and front wall of the cavity and filter with a single component of velocity, density, and temperature forcing. For the subsonic flow at M=0.6, The strong acoustic component appears at the trailing edge of the cavity at a lower frequency. while as the frequency increases, the intense acoustic structure moves close to upstream and overlap with the hydrodynamic component. This tendency is also observed in the supersonic flow condition M=1.4. Compared to different types of forcing, the streamwise velocity forcing achieves the largest energy amplification. However, it substantially reduces by moving the forcing location from the leading-edge to the front wall of the cavity. This work provides an alternative approach to examine input-output flow-acoustic characteristics where resonance is dominant and provides guidance for the development of flow control strategies.