Effect of configuration variation on externally blown flap noise

Externally Blown Flap Noise Research

“…2(a)) is dominated by the dipole noise field associated with the fluctuating pressures generated on the flap surfaces by the impinging turbulent exhaust jet (ref. 16). The overall sound pressure level measured in this region has been found to vary as the sixth power of the peak flap impingement velocity, Vi p, and as the first power of the exhaust plume impingement area, A i (refs.…”

“…5(a)) that the entire flow within the high velocity region hits the flaps, then the RMS acoustic pressure, p, can be represented by the following relation (ref. 16). …”

“…The normalized sound pressure level spectral density (SPL -OASPL + 10 log VE/DT -10 log Af) for the 700 microphone is plotted as a function of Strouhal number (f DT/VE) for four of the large scale models in figure 8 (taken from ref. 16). …”

“…Normalized overall sound pressure level (OASPL -10 log Ai(50/R) 2 ) for 2 -flap models (#3, #5, #6, and #10 of table I) having single stream (conical and plug) nozzles and 600 trailing flap position are plotted at the angle corresponding to the radial peak value as a function of the peak impingement velocity, Vi,p, in figure 10 (from ref. 16). …”

“…Flap noise data for four 2-flap EBF configurations having low velocitydecay nozzles are correlated in figure 9 (taken from ref. 16) in terms of exhaust flow parameters defined at the nozzle exit station. The normalized overall sound pressure level (OASPL -10 log AT) for the 700 microphone is plotted as a function of the effective nozzle exhaust velocity for models #3, #5, #6, and #1 of table I.…”