In-Flight determination of acoustic and hydrodynamic pressure fluctuations

Abstract

In-flight measurements and wind tunnel measurements of pressure fluctuations underneath a turbulent boundary layer were conducted. The characteristics of turbulent structures in the boundary layer is important for determination of the excitation of aircraft panels and therefore for the generation of cabin noise. A transient pressure transducer array was used in a flight test in order to obtain properties of the boundary layer concerning the turbulent excitation of aircraft hull at full scale. The array was designed to distinguish between acoustical and convective waves by means of frequency and wavenumber. Another feature of the array was the ability to extract the direction of flow directly out of the transducer phase data. The consideration of flow direction is important when investigating the convective transport of coherent structures in the turbulent boundary layer. Using the present array, the alignment of the transducers with the flow is not necessary. A similar array was used in wind tunnel tests at equal conditions.