Extension of the concept of Ffowcs-Williams and Hawkings type wave extrapolation to non-trivial flow effects and exterior surfaces

In appreciation of Ffowcs-Williams and Hawkings’ seminal contribution on describing the sound radiation from moving objects, this article discusses a concept taking into account local non-trivial flow effects propagation. The approach is motivated by fact that numerical simulation propagation complete full scale aircraft means volume-discretizing (CAA = Computational AeroAcoustics) methods prohibitively expensive. fact, homogeneous use such CAA would waste computational resources since for low speed conditions around subject to very mild almost everywhere may be treated more inexpensive methods. part domain, where strong thus requiring quite restricted. These circumstances exploited given consistent coupling proposed based (alternatively weak) volume discretizing solver Acoustic Perturbation Equations (APE) modified Hawkings (FW-H) type acoustic integral. established in frequency domain requires two basic ingredients, namely a) APE, or Möhring-Howe’s aeroacoustic analogy, take non trivial like refraction at shear flows wherever necessary, b) an integral equation areas non-potential mean are negligible. APE realized (i.e. two-ways) form which both components feed back information one another, weak one-way), field output data serves as input equation. If geometry has minor influence arbitrary observer positions, integrals simply evaluated explicitly. other hand, presence important radiation, then implicit some sort solution, case Fast Multipole Boundary Element solver. While conceptually follows spirit FW-H describe sources underlying not Lighthill’s but analogy Möhring-Howe. This consequence way-coupling particle velocity medium needs determined, As feature also provides practically perfect non-reflection boundary even when desireably small does extend far field. validity presented computation demonstrated example cases.