Noise sources from a cylindrical cavity

The expansion of air tra±c operations is nowadays limited by environmental constraints on noise. Advances in jet noise reduction have increased the importance of landing noise from the airframe as a signi¯cant contribution to the e®ective perceived noise level around airports. The most acoustically active airframe components in a civil aircraft are the high lift systems and the landing gear. Nonetheless, other components, such as fuel vents or ailerons, also contribute to the overall noise emissions. This study considers a cylindrical cavity as a low ¯delity fuel vent model. Di®erent diameter to depth ratios and in°ow velocities are simulated by means of an in-house compressible Euler solver. The predictions for a diameter to depth ratio of 0.714 show an unsteady asymmetric vortex structure at the in°ow Mach numbers of 0.235 and 0.3. The alternate impingement of this vortex on the right and on the left of the cavity trailing edge produces pressure waves and the °ow instability is self-sustained. The simulations of a cavity with a length to depth ratio of 2.5 at the same Mach numbers show a similar self-sustained instability where the °ow recirculation is symmetric about the cavity mid-plane. To identify and localize the most acoustically active regions in the inviscid °ow model, the double divergence of the Lighthill stress tensor was computed from the aerodynamic predictions. This work sets the basis to perform a Ffowcs Williams and Hawkings acoustic analogy to predict the fuel vent contribution to landing noise. Nomenclature c Speed of sound ± (f) Dirac delta function e Internal energy F Inviscid °uxes, F = [u; u u+