The Production of Intense Shear Layers by Vortex Stretching and Convection

摘要

To the writer's knowledge an account of the formation of the shear layers, which play an important part in the transition process, has not been given, although it is often suggested that the background vorticity has to be both stretched and convected. In this paper a theoretical model is studied, and this shows how the flow field associated with the boundary layer, which is known to have a streamwise vortex component upstream of transition, can convect the vortex lines into regions where they can be stretched very effectively, so producing strong concentrations of vorticity. Correlation with previous experimental results of Klebanoff and Kovasznay is encouraging and it is suggested, therefore, that this work gives one more link in the understanding of transition processes. This Report was prepared for the AGARD Specialists' Meeting on 'Recent Developments in Boundary Layer Research' sponsored by the Fluid Dynamics Panel of AGARD, held in Naples, Italy, 10-14, May, 1965. (Author)