Hypersonic Acoustic Loading (HAL)
Abstract
A major problem for high speed airframes is acoustic fatigue, which is due to random pressure loading. A dominant source of acoustic fatigue is the pressure fluctuations beneath turbulent boundary layers (TBLs). In a previous project sponsored by the Air Force Office of Scientific Research (grant FA9550 14 1 0224), the PI investigated hypersonic TBLs and acoustic loading using high order implicit Large Eddy Simulations (iLES) and Direct Numerical Simulations (DNS). The above project showed that high order iLES predict with high accuracy TBLs and acoustic loading that closely matches with DNS but only at a fraction of the computational cost. Furthermore, transitional hypersonic boundary layers were also studied for atmospheric multimode energy spectrum, as initial condition. This is an important development considering that all the past studies for hypersonic transition were performed for single mode perturbations. The spectral analysis of the pressure fluctuations showed consistent results with the available theoretical, experimental and numerical data for fully turbulent boundary layers. However, in the transition region the spectrum roll off diverged from the scaling predictions derived for incompressible and fully turbulent compressible flows. It was shown that different scaling laws govern the spectrum in the transition region. The Mach number has a direct impact on the spectrum, especially in the high frequency region. Increasing the inlet turbulence intensity leads to higher amplitude pressure fluctuations in the mid to high frequency region; faster transition to turbulence; and higher acoustic loading on the panel. The project led to a large set of data that can be further analyzed to deepen our understanding of acoustic loading effects; develop improved pressure fluctuations models; and investigate acoustic models in conjunction with structural analysis. These technical areas motivate the present proposal.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501917018
Entities
People
- Dimitris Drikakis
Organizations
- Air Force Office of Scientific Research
- United States Air Force