Local law-of-the-wall in complex topography: a confirmation from wind tunnel experiments

It is well known that in a neutrally-stratified turbulent flow in a deep co nstant-stress layer above a flat surface, the variation of the mean velocit y with respect to the distance from the surface obeys the logarithmic law ( the so-called "law-of-the-wall"). More recently, the same logarithmic law h as been found also in the presence of nonflat surfaces. It governs the dyna mics of the mean velocity (i.e., all the smaller scales are averaged out) a nd involves renormalized effective parameters. Recent numerical simulations analyzed by the authors of the present Letter show that a more intrinsic l ogarithmic shape actually takes place also at smaller scales. Such a genera lized law-of-the-wall involves effective parameters smoothly depending on t he position along the underlying topography. Here, we present wind tunnel e xperimental evidence confirming and corroborating this new-found property. New results and their physical interpretation are also presented and discus sed. (C) 2001 Elsevier Science B.V. All rights reserved.