Direct aeroacoustics simulation of automotive engine cooling fan system: effect of upstream geometry on broadband noise

Leakage Noise and Related Flow Pattern in a Low-Speed Axial Fan with Rotating Shroud

“…The filtered spectra have smoother trends and show the interesting aspects more clearly. These are the subharmonic, narrowband humps due to the leakage flow, which are present in all of the cases, e.g., see Piellard et al [4] or Canepa et al [9]. Due to the leakage flow prerotation, their characteristic St values are smaller than the ones of the blade passing frequency (BPF) harmonics (St = 9, 18, 27, etc.).…”

“…where both u and vθ are referred to the radial location r where the leakage flow is ingested by the blade, e.g., see Piellard et al [4]. The apparent growth of the low-frequency part with Ψ is expected as the leakage mass flow increases with Ψ also.…”

“…where both u and v θ are referred to the radial location r where the leakage flow is ingested by the blade, e.g., see Piellard et al [4].…”

“…Their interaction with the rotor blades results in noise in the low-to medium-frequency range, with the appearance of narrowband humps at subharmonic frequencies and a general increase of the broadband noise. The leakage flow noise often constitutes the major contribution to the overall radiation and its main features are known, but very few works related to it are available in the literature, e.g., see Fukano et al [2], Fukano and Jang [3], Piellard et al [4], Magne et al [5], Moreau and Sanjosé [6], Zenger et al [7], Na et al [8], Canepa et al [9][10][11][12], Zhu et al [13] and Sanjosé and Moreau [14]. In order to find effective solutions for noise reduction, a deeper insight in the leakage flow features and in the effect of relevant parameters is necessary.…”

Experimental Validation of a Semi-Analytical Trailing-Edge Noise Model Including Broadband Scattering

“…In the absence of any interaction noise source, it represents the dominant source of noise generated by rotating machines such as fans, turboengines, 45, 6 wind turbines 18 and high-lift devices. 46 The sound emitted by rotating machines can be computed using direct methods computing simultaneously both sound production and propagation 33,23,34 or using hybrid approaches combining a near-field turbulent flow simulation around the rotating blade and an acoustic analogy for the sound propagation in the farfield. 24,26 In order to further reduce the costs, the noise prediction can rely on Amiet's theory originally 37 and applied to low-speed fans.…”