Vortex Packets in Turbulent Boundary Layers with Application to High Reynolds Number Effects, Isolated and Patterned Roughness, Near Wall Modeling and Strategies for Drag Reduction

摘要

The scientific goals of this work are to develop a complete physical model of turbulence in wall boundary layers and to develop means of describing and modeling surface roughness effect. We make use of recent developments in our understanding of the mechanistic structure of near wall turbulence for smooth walls at low Reynolds numbers to understand how large Reynolds number and wall roughness affect turbulence. We build upon experimental and computational evidence from smooth walls to extend the mechanistic picture of turbulence based on a paradigm of hierarchy of hairpin packets to high Reynolds number, when roughness effect increases in importance. Both experimental measurements of velocity field in smooth and rough walls and direct numerical simulations of evolution and interaction of hairpin vortices are used.