Three-dimensional instability of flat-plate boundary layers: Theory and experiment

Abstract

The three-dimensional instability of the flat-plate boundary layer has been investigated. Experimental results obtained in the Blasius flow excited by a point source were analyzed by means of a spatial Fourier decomposition. The data are compared with theoretical solutions of the Orr-Sommerfeld equation based on a parallel-flow approximation of the Blasius flow. Very good agreement was found for the dispersion characteristics of the wavenumbers and phase velocities as functions of the wave angle, of the frequency parameter and of the Reynolds number. The growth rates showed mainly a qualitative agreement.