Simulation of large scales and aeroacoustics of perfectly expanded supersonic jets

Abstract

The present research work will perform studies and development of a numerical methodology for the analysis of turbulent flows due to the interaction of rocket-engine exhaust plume gases with the ambient air, in a perfectly expanded supersonic regime. The major motivation for the work is the creation of results that will allow future studies on the prediction of sound propagation and acoustic radiation for such complex flows. One of the most important design issues with large launch vehicles is, precisely, the acoustic loading due to the very complex interaction of high speed and high temperature exhaust plumes with the ambient air. Such sound emissions could damage the launching structure and, especially, the fairly fragile structure of the launcher upper stages, due to the reflection of the exhaust sound waves towards the upper vehicle. Moreover, the resulting pressure fluctuations could also damage the structure of different parts of the launcher due to vibro-acoustic fatigue. In general, the existing "best practice" guides for launch vehicle design indicate that acoustic loadings should be treated as critical loads both at take-off conditions and in the transonic regime. In this context, the present 12-month post-doctoral work proposal will perform preliminary developments in order to allow a future treatment of the actual rocket-engine exhaust plume acoustic problem. Therefore, the present work will prepare the necessary computational fluid dynamics (CFD) simulation tools, using a large eddy simulation (LES) formulation, such that, in the next period, one could actually start treating the sound propagation problem due to the launch vehicle exhaust plume interaction with the atmospheric air. Clearly, in the long run, the computational work, which will be initiated here, will attempt to establish the basis for experimental characterizations and definition of key technologies such that devices, that could contribute to mitigate the level of aeroacoustic noise generated by such large launch vehicles, could be appropriately developed.