Introduction: scaling and structure in high Reynolds number wall-bounded flows

According to Lighthill (1995), Prandtl’s (1904) boundary layer has had the same effect on fluid dynamics as Einstein’s 1905 discoveries had on other of physics, which, by the way, were celebrated in 2005 as the World Year of . That the boundary layer becomes turbulent was formally known to (1908), though, of course, the origin of turbulence in a pipe was studied by Reynolds (1883). The problem of the turbulent boundary layer has been a paradigm in the field of turbulence. Its practical importance in flows air and water vehicles as well as in geophysical fluid dynamics has been for nearly a century now. Advances in our understanding of the -layer scaling and structure can be expected to shed further light on the and multiscale flow dynamics, and also offer basic input to flow control for practically relevant problems such as reducing large vehicle drag (and hence, by implication, emission levels).