  An experimental study in a wind tunnel is presented to explore the wake of a
floating wind turbine subjected to harmonic side-to-side and fore-aft motions
under laminar inflow conditions. The wake recovery is analysed as a function of
the frequency of motion, measured by the Strouhal number, St. Our findings
indicate that both directions of motion accelerate the transition to the
far-wake compared to the fixed turbine. The experimental outcomes confirm the
CFD results of Li et al. (2022) showing that sideways motions lead to faster
wake recovery, especially for St in [0.3, 0.6]. Additionally, we find that
fore-aft motions also lead to better recovery for St in [0.3, 0.9]. Moreover,
we see that the recovery is closely linked to non-linear spatio-temporal
dynamics. Special nonlinear dynamical effects are found in the shear layer
region of the wake (y = R). For both directions of motion and St in [0.25,
0.55], the noisy wake dynamics synchronise to the frequency of the motion. For
fore-aft motions and St in [0.55, 0.9], the wake shows more complex
quasi-periodic phenomena. In fact, the driven frequency and a selfgenerated
meandering mode emerge and interact non-linearly, as proved by occurring mixing
components. Sideways motions result in large spatial structures of meandering.
Fore-aft motions induce pulsing of the wake. Both modes are linked to the
synchronisation effect. The quasi-periodic phenomena of fore-aft motions are
connected to meandering mode. Overall, the spatio-temporal phenomena lead to
faster recovery likely due to an increase of momentum transport towards wake
centre.
