Stabilizing cylinder flow at supercritical Reynolds number using surface velocity perturbations and momentum forcing

The stabilization of the vortex shedding behind a cylinder has been a classical breeding ground for development of flow control rooted in linear stability/sensitivity analysis techniques. We extend prior efforts by probing two new classes of actuation: surface velocity perturbations in the local normal direction, and spatio-temporally varying momentum forcing throughout the flow domain. The former is motivated by advances in materials science, which enable realizable actuation on the body surface, and the latter is an extension of studies that focused on time steady, spatially localized actuation. We use adjoint-based optimization to inform an actuation protocol that drives the unsteady flow at a Reynolds number of 100 to the flow's unstable base state. For the surface actuation protocol, we will assess the effect of the horizon optimization window, which was shown in tangential actuation to affect the reduction in temporal oscillations. For the full-domain actuation, we will compare the mechanisms for mitigating vortex shedding to those shown via sensitivity analysis for small, stationary secondary cylinders, possibly providing further insights into how the wake can be further manipulated towards a desired control outcome.