Impact of Deck and Jet Blast Deflector on the Flow and Acoustic Properties of Imperfectly Expanded Supersonic Jets

Abstract

The impact of a representative Aircraft Carrier Deck and Jet blast deflector (JBD) has been investigated by using a recently developed NAVY finite element based flow solver JENRE (the Jet Engine Noise Reduction) at an underexpanded jet condition. The agreement of the flow and near-field acoustic properties of the baseline configuration (without the Carrier deck and JBD) agree well with the experiment data. It is found that the deck surface, which is 1.6D (nozzle exit diameter) below the jet centerline, and a JBD surface, which is roughly 6.0D downstream of the end of the potential core, have little impact on the shock-cell structure and jet potential core. However, the deck impacts the near-field pressure fluctuations by either reflecting the pressure waves or damping the turbulence when the jet flow collides with the surface. The increase caused by the reflection shows more in the spanwise direction than in the vertical direction, and more increase is observed in the high-frequency range downstream of the potential core. The JBD surface redirects the jet plume, causing Mach waves to propagate towards the upward direction of the JBD surface. Pressure waves are also generated near the trailing edges of the JBD surface. The acoustic pressure level is increased upstream of the JBD location, and this increase is largely in the low-frequency range, indicating that the trailing edge effect should be the main cause of this increase.