Session 1INV - Invited Prize Lectures.
INVITED session, Sunday, November 23
304-6-8, Moscone Center
The response of pretransitional laminar boundary layers to free-stream turbulence is an interesting and complex phenomena that has received considerable attention since Klebanoff's early (1971) investigations. The boundary layer acts as a kind of filter that selects out and amplifies the low-frequency components of the motion, resulting in elongated flow structures now known as Klebanoff modes. This talk presents a general asymptotic description of these modes, which are governed by the boundary-region equations of Kemp (1951) rather than by the usual Prandtl boundary-layer equations. While the Klebanoff modes can achieve very large amplitudes, they may not always play a direct role in the formation of turbulent spots. Some preliminary ideas about possible spot formation mechanisms are also presented.
Kemp, N. (1951) The laminar three-dimensional boundary layer and a study of the flow past a side edge. M.Ae.S. Thesis. Cornell University. Klebanoff, P. S. (1971) Effect of free-stream turbulence on a laminar boundary layer. Bulletin Am. Phys. Soc. 16.