  In the current work we numerically study the effect of traveling-wave surface
morphing actuation on the suction surface of NACA0012 at Re = 1,000. Although
this actuation strategy has been studied at higher Reynolds numbers for an
airfoil and a rectangular flat plate, its effects at low Reynolds numbers have
not yet been investigated. The kinematics of actuation are defined by
wavenumber and wavespeed, both of which are varied over a wide range of values
to include parameters that considerably change the lift dynamics as well as
those that do not. We first study the effect of actuation at an angle of attack
of $\alpha$=5{\deg}, where the unactuated flow is steady. The lift dynamics are
found to align with the surface morphing kinematics, and there is a
low-pressure minimum shown to be introduced into the flow-field by morphing
that advects at a speed agnostic to the morphing parameters. Lift benefits are
found to be maximal when the morphing kinematics align with this intrinsic flow
speed. We then investigate the role of morphing in the presence of an unsteady,
separated baseline flow (with intrinsic vortex-shedding processes) at
$\alpha$=15{\deg}. At this higher angle of attack, we identify three distinct
behavioral regimes based on the relationship between morphing and the
underlying shedding frequency. Of these regimes, the most beneficial to mean
lift is the lock-on regime, where the vortex-shedding dynamics align with the
morphing kinematics. We also identify other regimes where morphing can become
out of phase with the vortex-shedding dynamics, termed here the interactive
regime, and where morphing leaves the unactuated dynamics unaltered, termed
here the superposition regime. At the higher angle of attack, parameters
leading to lift benefits/detriments are explained in terms of the effect of
morphing on the leading and trailing-edge vortex.
