A recently derived scaling law for predicting flyover jet noise from static experiments is presented and extended to the prediction of the noise from coannular jets in flight. The main differences from existing theories are the avoidance of a special turbulence model, the inclusion of the density terms of the source function and the consideration of a stretching of both the axial source and coherence length scales in flight. The flyover case at a specific jet and flight velocity proves to be related to that of a static jet. The corresponding static velocity depends on the emission angle and is lower in the rear arc and higher in the forward arc. The resulting equations are derived for low flight Mach numbers and for emission angles not too close to the jet axis. The influence of the boundary layer about the outside of the nozzle is neglected. The impressive agreement of the prediction with experimental results suggests that this might be valid for jet engines mounted in nacelles. (Krautzig)
Prediction of flyover noise from single and coannular jets
Vorhersgae von Ueberfluglaerm bei Einzel- und ringfoermig orientierten Strahlen
AIAA-Papers ; 1-8
1980
8 Seiten, 9 Bilder, 24 Quellen
Conference paper
English