Modeling of Coherent Structure in Boundary Layer Turbulence.
Abstract
The large-scale coherent motion associated with turbulent bursting in a boundary layer is studied with the aid of an inviscid model. The space-time evolution of a disturbance of large horizontal dimensions compared to the wall layer thickness is analyzed under the assumption that the mean flow is parallel. The initial velocity field is assumed to be set up by the action of the turbulent stresses produced by a patch of secondary instability. For short and moderate times, the effects of viscosity and pressure are small, and the evolution of the disturbance is conveniently studied with the aid of Lagrangian techniques. The model is able to reproduce qualitatively many of the observed features of the bursting motion such as the formation of longitudinal streaks, the rapid acceleration after initiation of bursting, and the strong y-coherence of the u-fluctuations. In particular, the model demonstrates how action by the mean shear makes the disturbance eventually evolve into a thin internal shear layer, thus making possible the appearance of a new region of inflexional instability and hence burst regeneration-downstream of the original burst. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1978
- Accession Number
- ADA054851
Entities
People
- M. T. Landahl
Organizations
- Massachusetts Institute of Technology