Coherent Structures, Chaos and the Role of Modern Dynamics in Turbulent Shear Flows.

摘要

The main objective of this research is to investigate the relationships between modern concepts of nonlinear dynamical systems, chaos theory and fully turbulent boundary layers. The approach that we are taking is to search for a connection between strange attractors and the large-scale coherent structures which appear to play a dominant role in the dynamics of turbulent shear flows. We are attacking the high Reynolds number turbulent boundary layer from two fronts: 1) From the lower Reynolds number transitional boundary layers, which have the proper flow geometry but a lower Reynolds number and therefore lower dimensional dynamics; and 2) from the high Reynolds number free shear layer flows, which have a simpler flow geometry than the fully turbulent boundary layer, but for which the coherent structures and their dynamics appear to be much simpler. Toward this end, a Proper Orthogonal Decomposition Technique was developed and applied to a forced plane mixing layer. Theoretical studies were also undertaken to understand the turbulent dissipation rates and the random occurrence of coherent events. (edc)