Low-speed wind-tunnel measurements of pressure fluctuations on the wing of a twin-jet aircraft (Bristol 188)

Abstract

Root-mean-square intensities and spectra of local pressure fluctuations were measured by transducers at two positions on the inner part of the wing and four on the outer part, while low-frequency pressure fluctuations on the upper surface were obtained at a further fifteen positions on the outboard part of the wing by a 'creeper' and transducer. The low-frequency component of pressure and load fluctuations increases in intensity with increasing incidence; on the inboard wing this increase is fairly abrupt and is associated with a change in the form of the mean flow field about the wing; on the outer wing the intensity increases more gradually with incidence. Buffet boundaries have been assessed tentatively from the incidence associated with rapid rise of load fluctuation on the inner wing; more severe limitations could however be imposed by conditions on the outer wing, where likely buffeting excitation is more difficult to assess. Leading-edge strakes may modify the buffet boundaries, giving a gain of about 0.2 in usable CL trimmed. There is some evidence that leading-edge droop would considerably reduce load fluctuations.