Application of a Beamforming Technique to the Measurement of Airfoil Leading Edge Noise

Figure 11

Three-dimensional third-octave band sound maps, PPS 14/4 turbulence grid, 𝑈₀=35 m/s (Re = 548,000), CLEAN-SC beamforming algorithm, center frequency 2 kHz. (Note that all sound maps are scaled to the same maximum level measured for the reference airfoil.).

(a) Nonporous reference airfoil, 𝑟=∞

(b) Porous airfoil made of Needlona felt, 𝑟=130,200 Pa s/m²

(c) Porous airfoil made of Recemat, 𝑟=8,200 Pa s/m²

(d) Porous airfoil made of M-Pore Al 45 ppi, 𝑟 = 1,000 Pa s/m²