We perform high-fidelity Large Eddy Simulations (LES) of a round, Mach 1.5, turbulent ideally expanded jet that impinges perpendicularly on a at surface. The LES are repeated for various nozzle-to-wall distances with and without sixteen microjets positioned uniformly around the nozzle lip. These flow configurations conform exactly to experiments performed at the Florida Center for Advanced Aero-Propulsion (FCAAP), where it was shown that microjets can drastically reduce the impingement tones. To better understand how super- sonic impinging jets create loud tones, we apply Global Stability Analysis (GSA) about LES mean fields using a multi-block code. The analysis extracts unstable axisymmetric and helical global modes connected to the complex interplay between vortices, shocks, and acoustic feedback. We also apply GSA about a Reynolds-Averaged Navier-Stokes (RANS) base flow and find that results agree well with those obtained from the corresponding LES base flow. An adjoint solver is used to study how upstream fluctuations affect the direct global modes of the supersonic impinging jet and to help predict the effectiveness of micro- jet control. The wavemaker, or region of sensitivity to base flow modification, is computed and found to be most responsive to changes slightly downstream of the nozzle exit.
|Original language||English (US)|
|Title of host publication||23rd AIAA/CEAS Aeroacoustics Conference, 2017|
|Publisher||American Institute of Aeronautics and Astronautics Inc, AIAA|
|State||Published - 2017|
|Event||23rd AIAA/CEAS Aeroacoustics Conference, 2017 - Denver, United States|
Duration: Jun 5 2017 → Jun 9 2017
|Name||23rd AIAA/CEAS Aeroacoustics Conference, 2017|
|Other||23rd AIAA/CEAS Aeroacoustics Conference, 2017|
|Period||6/5/17 → 6/9/17|
Bibliographical notePublisher Copyright:
© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.