Recent advancements toward the understanding of turbulent boundary layers

Over the past decade almost every aspect of our traditional beliefs about wall-bounded flows has been challenged. Many beliefs have been abandoned and others modified as new theories and new measurements have abounded. No longer are direct measurements summarily dismissed because they contradict a long-standing theory, and even those experimentalists who still believe in the log law only apply it outside y⁺ of several hundred. In this meeting I have been invited to look back at some of the early contributions in this revolution, particularly George and Castillo.^1,2 I shall review briefly a few of the more controversial ideas, and highlight some of the reasons that led us in a different direction. In addition to pointing out some successes, I will discuss some failures and open questions. I will even offer a few new ideas, and of course renew some old challenges.