Experimental characterisation of a high Reynolds number turbulent boundary layer subjected to an adverse pressure gradient

The observation of large-scale coherent structures in turbulent boundary layers has sparked great experimental and numerical interest. While most studies have focussed on channel flows and zero pressure gradient (ZPG) boundary layer flows, our understanding of wall turbulence under the influence of a streamwise pressure gradient is still quite limited due to the lack of sufficiently high Reynolds number data and large facilities to reach an equilibrium state where theoretical scaling laws can be relevant [1]. The length of these structures (7-14 \delta [2]) requires a large field of view and a high spatial resolution to measure all relevant spatial scales. [1] L. Castillo and W. K. George. Similarity analysis for turbulent boundary layer with pressure gradient: outer flow. AIAA journal, 39.1:41-47, 2001. [2] N. Hutchins and I. Marusic. Evidence of very long meandering features in the logarithmic region of turbulent boundary layers. J Fluid Mech, 579:1-28, 2007.