Jet screech is an intense pure tone which has attracted decades of research interest due to its possible detrimental effect to engineering structures. Its modes and closure mechanisms have been investigated analytically, experimentally and numerically, however, there are still outstanding questions on the generation and propagation of instabilities in the near-field region. Recent studies have identified that the instabilities also travel inside the jet potential during the screech process to form the complete feedback loop. Using dynamic mode decomposition on a 3D pressure near-field from large eddy simulation results, the present study examines the viability of the modal decomposition to provide further insights into the screech modes and its associated characteristics and investigates the effect of temperature mixing in jet screech. The results show that the modal decomposition approach identifies very well the helical structure of the screech mode. Furthermore, a method is proposed to reveal the temporal evolution of the dynamic screech mode. It was found that the bulk behaviour of the pressure field at screech frequency propagates backward towards the nozzle exit.
|Number of pages||11|
|Journal||Journal of Aerospace Engineering|
|Early online date||20 Apr 2021|
|Publication status||Published - 1 Jul 2021|
Bibliographical noteFunding Information:
The authors gratefully acknowledge the support provided for this study by the Singapore Ministry of Education AcRF Tier-2 Grant (Grant No. MOE2014-T2-1-002) and by the School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore. The authors also thank Dr X. F. Wei for providing the experimental data.
© 2021 American Society of Civil Engineers.
- Dynamic Mode Decomposition
- Jet Screech
- Underexpanded jet