Research Advancement and Application on Vector Aeroacoustics

In acoustic analogy theory, the perturbation of density or acoustic pressure is used as variable of the wave operator to describe the noise generated from fluid and its interaction with solid surfaces, but it is unable to directly describe the acoustic energy propagation with the acoustic scalars. In fluid mechanics, scalars are used to characterize the instantaneous and local states of fluid, while vectors are used to describe the transfers of mass and energy. Inspired by this idea, the vector aeroacoustics was developed and this paper presented the overview of recent advancement on this research. Some advancements were as summarized as follows. (1) The vector wave equation of aeroacoustics and the corresponding solutions have been proposed, in which the acoustic velocity was regarded as the variable of the wave operator. (2) The acoustic intensity vector field around rotating sources was visualized, revealing the following three radiation modes of acoustic energy:spiral mode, R-A mode and acoustically black-hole mode. (3) Analytical acoustic power spectrum formulations for the rotating point sources have been developed to identify the spatial and frequency features of the source on rotating blades. (4) Vector aeroacoustics method and the equivalent source method were combined to show the acoustic intensity vectors around the sources and scattering surfaces, visualizing the primary absorption position as well as calculating the acoustic power absorbed by impedance surfaces.