Acoustic receptivity of the boundary layer over parabolic bodies at angles of attack


Haddad O., Erturk E. , Corke T.

JOURNAL OF FLUID MECHANICS, vol.536, pp.377-400, 2005 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 536
  • Publication Date: 2005
  • Doi Number: 10.1017/s0022112005005100
  • Title of Journal : JOURNAL OF FLUID MECHANICS
  • Page Numbers: pp.377-400

Abstract

The effect of angle of attack on the acoustic receptivity of the boundary layer over two-dimensional parabolic bodies is investigated using a spatial solution of the Navier Stokes equations. The free stream is decomposed into a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke (1998) and Erturk & Corke (2001) in which the solution for the basic flow and linearized perturbation flow are solved separately. Different angles of incidence of the body are investigated for three leading-edge radii Reynolds numbers. For each, the angle of attack ranges from 0 degrees to past the angle where the mean flow separates. The results then document the effect of the angle of incidence on the leading-edge receptivity coefficient (K-LE), and in the case of the mean flow separation, on the amplitude of Tollmien-Schlichting (T-S) waves at the linear stability Branch II location (K-II). For angles of attack before separation, we found that the leading-edge receptivity coefficient, KLE, increased with angle of incidence which correlated with an increase in the pressure gradient at the physical leading edge. When a separation zone formed at larger angles of incidence, it became a second site of receptivity with a receptivity coefficient that exceeded that of the leading edge. This resulted in dramatic growth of the T-S waves with Branch II amplitudes more than 100 times larger than those at angles just before separation, and 1000 times more than those at 00 angle of attack.