| The experimentally determined response of the time-averaged turbulence of a Retheta = 4590 boundary layer exposed to a large favorable pressure gradient is presented. The favorable pressure gradient is generated using a linear contraction with a contraction ratio of 9.5 : 1 and is characterized by a peak acceleration parameter, Kmax = 4.4 x 10-6. Three components of velocity are measured using multiple X-wires and the wall shear stress is directly measured using oil film interferometry. The accelerated boundary layer is found to exhibit behavior typical of relaminarization for values of K ≥ 3.0 x 10-6 . The onset of reverse transition is believed to coincide with the modification of the near-wall structure and its eventual propagation into the downstream boundary layer.{09}Measurements of the time-averaged turbulence flow field support this. Finally, a conceptual model of the motions of the coherent structures in the accelerated turbulent boundary layer is shown to be consistent with the measured data. |
