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The simulation of broadband noise with CAA techniques is discussed. Unsteady broadband sound sources are modeled in the time-domain with a highly efficient computational method. The generated fluctuations reproduce very accurately autocorrelations and integral length-scales such as that provided by a RANS simulation of the time-averaged turbulent flow problem. It is argued that an approach based on synthetically generated sources has to be seen as an algorithmic extension of traditional statistical broadband methods in the frequency domain. Fluctuating quantities are generated by spatially filtering convective white-noise. The discrete realization of convective white-noise is based on random particles that are advanced using an area-weighted mean of the mean-flow from neighboring mesh points. The spatial filtering is realized by interpolating the random values with a particle shape function onto the neighboring mesh points and applying subsequently a sequence of 1D filtering operations. Sample results for different aeroacoustic applications of the method are presented.

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The present paper studies the application of a low-cost CAA approach to a slat noise problem. A new fast and cheap stochastic approach is introduced to model the unsteady turbulent sound sources in the slat-cove. It is based on the spatial filtering of a random white-noise field and incorporates information about the integral length scale and the turbulent kinetic energy from a steady RANS computation. The stochastic method, which stems from the LES inflow boundary condition proposed by Klein et al.6 that reproduces first-and second-order one-point statistics, is extended in this paper for aeroacoustic applications. The extended formulation yields a perfectly solenoidal velocity field that is capable to reproduce exactly the complete second-order two-point correlation tensor of homogeneous isotropic turbulence. Results for the sound generation at the slat are given for the underlying RANS mean-flow field being based on a Menter SST turbulence model with and without Kato-Launder modification, respectively. The results for the modeled turbulent flow-field and the radiated acoustic field exhibit physical meaningful characteristics.