Abstract
Motivated by the problem of the installation effects of modern turbofan engines, we experimentally investigated the interaction between a compressible subsonic jet and a tangential flat plate. Measurements of wall pressure fluctuations were performed in a semi-anechoic environment addressing the effect of several governing parameters, such as the stream-wise and span-wise location, the jet Mach number and the radial distance of the plate surface from the jet axis. The statistical properties of the wall pressure signals were analyzed in terms of both power spectra and cross-correlations, with the latter providing the estimation of the phase speed. The analysis is also carried out in the time-frequency domain through the application of the wavelet transform to further characterize the dynamics of the wall pressure signatures.
Highlights
One of the most important topics of current research into aircraft engines concerns the reduction of noise and pollutant emissions
In order to keep the same level of thrust, the reduction of jet velocity must be compensated by increasing the mass-flow rate passing outside of the engine primary body
The wall pressure statistics were characterized in the frequency domain through the power spectral density (PSD) evaluated with the Welch method [19] and presented as a function of the Strouhal number, defined as follows: fD
Summary
One of the most important topics of current research into aircraft engines concerns the reduction of noise and pollutant emissions. The strategy used by aircraft manufacturers to mitigate CO2 release is to reduce the mass-flow rate passing in the engine’s combustion chamber, exhausting from the primary nozzle. In order to keep the same level of thrust, the reduction of jet velocity must be compensated by increasing the mass-flow rate passing outside of the engine primary body. Given that the noise emissions from the engine jets are essentially proportional to the eighth power of the velocity according to Lighthill [1], the mass-flow increase in the secondary flow must be achieved by increasing the nozzle size rather than the exhausting jet velocity. Design constraints in terms of ground clearance cause a more aggressive close-coupled architecture for the under-wing installation of the engine and a stronger jet-wing/flap interaction
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