Investigation of a turbulent boundary layer flow at high Reynolds number using particle-imaging and implications for RANS modeling

The prediction of pressure induced separation of a turbulent boundary layer (TBL) subjected to an adverse pressure gradient (APG) in the subsonic regime using RANS-based CFD is still associated with significant uncertainties. Recently there was new work on TBL at APG both experimentally, e.g., within the EU project EuHIT (see https://www.euhit.org/), and numerically, e.g. in Gungor et al. (2016) and Kitsios et al. (2016). In this work we present a new experiment described in Knopp & Reuther (2015) and Reuther (2015) whose design includes lessons learned from a precursor experiment, see Knopp et al. (2015). We focus on the inner 15% of the boundary layer. Then we attempt to draw conclusions for RANS turbulence modeling with focus on the length scale equation.