Scaling properties of the Ffowcs-Williams and Hawkings equation for complex acoustic source close to a free surface
نویسندگان
چکیده
We perform a scaling analysis of the terms composing Ffowcs-Williams and Hawkings (FWH) equation, which rules propagation noise generated by rigid body in motion. Our extends seminal work Lighthill ( Proc. R. Soc. Lond. A, vol. 211, 1952, pp. 564–587) dimensional classical sources (monopole, dipole quadrupole) considering all FWH integral terms. Scaling properties are analysed light perfect/imperfect similarity when laboratory-scale data used for full-scale predictions. As test case we consider hydrodynamic example, namely ship propeller. The data, obtained numerically previous study, were post-processed according to presented herein. properly scale speed sound obtain perfect quantify error with respect imperfect scaling. Imperfect introduces errors acoustic response related both linear nonlinear terms, latter great importance wake is characterized robust organized vorticity. Successively, analyse effect free surface, often present applications. apply method images equation. surface may generate frequency-dependent constructive/destructive interference. an archetypal field (monopole) provides explanation these interference effects. Finally, find that absence introduce model-scale pressure. small microphones placed near becomes relevant far because
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ژورنال
عنوان ژورنال: Journal of Fluid Mechanics
سال: 2021
ISSN: ['0022-1120', '1469-7645']
DOI: https://doi.org/10.1017/jfm.2021.723