  Kinematic aspects of flow separation in external aerodynamics are
investigated in the Lagrangian frame. Specifically, the initial motion of
upwelling fluid material from the wall is related to the long-term attracting
manifolds in the flow field. While the short-time kinematics are governed by
the formation of a material spike upstream of the zero-skin-friction point and
ejection of particles in direction of the asymptotic separation line, the
trajectories of the fluid tracers are guided by attracting ridges in the
finite-time Lyapunov exponents once they leave the vicinity of the wall. The
wall signature of this initial fluid upwelling event, the so-called
\textit{spiking point} [Serra, M., Vetel, J., Haller, G., "Exact theory of
material spike formation in flow separation", \textit{J. Fluid Mech.}, Vol.
845, 2018], is computed from the curvature of advected material lines and, for
the first time, from high-order numerical derivatives of the wall-normal
velocity obtained from direct numerical simulations of a circular cylinder and
a cambered NACA 65(1)-412 airfoil. As the spline-based boundary parametrization
of the airfoil profile induces oscillations, the principle spiking point can be
recovered robustly through appropriate filtering. The short-term kinematics
correlate strongly with the scaling lengths in the boundary layer.
