  A flat plate turbulent boundary layer (TBL) is experimentally subjected to a
family of 22 favorable-adverse pressure gradients (FAPGs) by using a ceiling
panel of variable convex curvature. We define a FAPG as a sequence of
streamwise pressure gradients in the order of favorable followed by adverse,
similar to the pressure gradient sequence over the suction side of an airfoil.
The adverse pressure gradient region of this configuration is studied using
particle image velocimetry (PIV) in the streamwise--wall-normal plane. The
streamwise mean and Reynolds stresses are presented and discussed in this work.
Although favorable and adverse pressure gradients are known to evoke opposing
responses from a TBL, the current adverse pressure gradient (APG) that followed
a favorable pressure gradient (FPG) was not found to 'reverse' the effect of
the FPG. Instead, a complex response that is neither characteristic of a ZPG
nor an APG TBL was observed. The Reynolds stresses showed a bimodal structure,
with the outer-scaled stresses strengthening along the streamwise direction in
$y < ~ 0.2 \delta$ and weakening in $y > ~ 0.2\delta$, where $y$ is the
wall-normal coordinate, and $\delta$, the local boundary layer thickness. These
were signatures of a new internal layer, previously observed in bump/hill
flows, formed due to the pressure gradient sign change from favorable to
adverse. The non-typical structure of and trends in the statistics were more
significant in the stronger pressure gradient cases, where the stronger
upstream FPG seemed to have exerted a stronger influence on the downstream APG.
The current dataset with 22 cases provided a well-resolved picture of the
breakdown of equilibrium of the ZPG TBL under an FAPG configuration. The
statistics for all the cases are included under the ancillary file section.
