Nonlinear analysis of transitional and turbulent boundary layer noise

Abstract

The boundary layer over an axisymmetric surface is characterized by three types of flow; laminar, transitional, and turbulent. The latter stages of the laminar boundary layer are characterized by infinitesimal linear wavelike disturbances, the so-called Tollmien-Schlichting (TS) waves that amplify spatially in the downstream direction. The nonlinear nature of transition produces spectra containing not only the TS frequencies, but sum and difference frequencies as well. Moreover, by applying nonlinear techniques (chaos theory) to evaluate the fluid dynamics within the boundary layer, there is some experimental evidence of the persistence of an underlying structure from transitional to full boundary layer turbulence, that may be associated with the TS mode. The analysis of both theoretical and experimental work in a boundary layer flow leading to these results is the subject of this paper.