A comparison between boundary layer measurements in a laminar separation bubble flow and linear stability theory calculation.

Abstract

Examines wind tunnel results for the boundary layer flowfield associated with a two-dimensional Liebeck LA2573A aerofoil, Reynolds number ranging from 235000 to 500000. A laminar separation bubble evident in the boundary layer contributes to drag in this range. Presents measurements of drag, mean and turbulent boundary layer velocity profiles and calculates integral parameters associated with these profiles. Spectral measurements show the growth of boundary layer velocity fluctuations within a range of frequencies in the laminar separation and transition regions. Peak frequencies measured in the velocity spectra for the instability region agree with most amplified wave number and frequency scaling predicted by linear stability theory for these inflectional profiles. Maximum measured growth rates correlate with profiles predicted using Falkner-Skan profiles at corresponding frequency of maximum amplification. (from authors' abstract)