Boundary-layer receptivity due to distributed surface imperfections of a deterministic or random nature
Acoustic receptivity of a Blasius boundary layer in the presence of distributed, two-dimensional surface irregularities is investigated analytically. It is shown that, out of the entire spatial spectrum of the surface irregularities, only a narrow band of Fourier components can lead to an efficient conversion of the acoustic input at any given frequency to an unstable eigenmode of the boundary layer flow. The location and the width of this most receptive band of wave numbers is fixed with respect to the instability wave number at the lower-branch station for the frequency under consideration. Random irregularities which are spatially homogeneous in nature, and also possess a continuous spectrum in the streamwise direction, lead to instability amplitudes that are intermediate to those caused by the periodic and isolated irregularities. The duality between the localized and distributed receptivity analyses is also discussed.
scientific article; zbMATH DE number 167452
scientific article