  The interaction between near-wall turbulence and wall curvature is described
for the incompressible flow in a plane channel with a small
concave-convex-concave bump on the bottom wall, with height comparable to the
wall-normal location of the main turbulent structures. The analysis starts from
a database generated by a direct numerical simulation and hinges upon the
anisotropic generalised Kolmogorov equations, i.e. the exact budget equations
for the second-order structure function tensor. The influence of the bump on
the wall cycle and on the energy production, redistribution and transfers is
described in the physical and scale spaces. Over the upstream side of the bump,
the energy drained from the mean flow to sustain the streamwise fluctuations
decreases, and the streaks of high and low streamwise velocity weaken and are
stretched spanwise. After the bump tip, instead, the production of streamwise
fluctuations grows and the streaks intensify, progressively recovering their
characteristic spanwise scale. The wall-normal fluctuations, and thus the
quasi-streamwise vortices, are sustained by the mean flow over the upstream
side of the bump, while energy flows from the vertical fluctuations to the mean
field over the downstream side. On the concave portion of the upstream side,
the near-wall fluctuations form structures of spanwise velocity which are
consistent with Taylor-G\"ortler vortices at an early stage of development.
Their evolution is described by analysing the scale-space pressure-strain term.
A schematic description of the bump flow is presented, in which various regions
are identified according to the signs of curvature and streamwise pressure
gradient.
