Caution: tripping hazards

Abstract

A turbulent boundary layer formed over an external surface is spatially evolving. The flow develops from an initial set of conditions and accordingly the state of the layer at some downstream location owes a debt to its upstream history. Schlatter & Örlü ( J. Fluid Mech. , this issue, vol. 710, 2012, pp. 5–34) demonstrate succinctly this sensitivity to upstream history, finding that relatively minor modifications to the trip parameters can produce non-canonical development up to surprisingly high Reynolds numbers. This interesting study will serve as a cautionary note to experimentalists and numericists while providing a plausible explanation for some of the disparity noted among previously published results.