An Alternative Approach to Disturbances in Boundary Layers
By modelling the boundary layer on a flat plate as a piece-wise linear velocity profile it is possible to analyze disturbances in the flow in a systematic manner. The approach is that of an initial-value, boundary-value problem but, unlike classical normal modes employed in stability theory, the solutions here can be obtained in closed form and they are non separable. A specific example is treated where the vertical component of the perturbation velocity is prescribed as a localized pulse initially. The amplitude is then depicted as a function of time and the coordinates of the plane of the flat plate at a fixed vertical location. The role of three-dimensionality and the initial transient period of development — heretofore unknown — are both shown to be of significant importance in the dynamics. An argument is given to strongly suggest that the origin of large-scale oscillations known to be prevelant in turbulent shear flows may well be explained using these bases.
KeywordsVorticity Smoke Hunt
Unable to display preview. Download preview PDF.
- Betchov, R., Criminale, W.O., 1967, Stability of Parallel Flows, Academic Press.Google Scholar
- Criminale, W.O., 1987, Understanding the origins of coherent structure, Proceedings, 2nd Inth. Symp. on Transport Phenomena in Turbulent Flows, Tokyo.Google Scholar
- Easthope, P.F., 1984, An alternative approach to layer disturbances, Ph.D. Diss., University of WashingtonGoogle Scholar
- Lee, M.J., Hunt, J.C.R., 1990, The Structures of sheared turbulence near a plane boundary, Turbulent Shear Flows, 7: 1–20, Springer Verlag.Google Scholar