The Evolution and Breakdown to Turbulence of a Wave Packet Propagating in a Laminar Boundary Layer
Abstract
The research being carried out on boundary layers excitated by localised point disturbance is intended to provide fresh insight into the complex non-linear processes that occur prior to breakdown. Initially only pulsed disturbances were being considered, but recently more general forms of excitation have also been treated - pure tones, white noise and a superposition of tones and noise. Natural transition is initiated by the background turbulence and acoustic fields present in the flow. Unstable Tollmien-Schlichting waves are generated, and these eventually amplify sufficiently to produce a variety of non-linear interactions. The dominant non-linear features that arise are dependent on the spectrum of the wavetrain, and hence on that of the excitation provided by the environment. Observations for a range of controlled disturbances of different spectral content provide a number of different phenomena, although it is thought that these apparently diverse behaviour patterns are in some sense linked together. The non-linear evolution of a wavetrain van be considered to be defined a number of different phenomena, although it is thought that these apparently diverse behaviour patterns are in some sense linked together. The non-linear evolution of a wavetrain can be considered to be defined in terms of a complex non-linear transfer function linking the input excitation to the velocity observed at some downstream location. It is therefore expected that information collected for different excitations can eventually be interpreted in terms of a single evolution equation. (KT)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1981
- Accession Number
- ADA215874
Entities
People
- M. Gaster