Stroboscopic projections (dots) and outermost KAM tori (surfaces) of selected sets for S = 0 shown over one full period of the driving. The low-opacity surfaces in (d) represent isosurfaces of the instantaneous stream function for $ψ=±0.4$ and ±0.6. The phase at the front face of the domain corresponds to $ϕ0=0$ in (a)–(c) and to $ϕ0=3π/2$ in (d). (a) Str = 0.1, Re = 20, (b) Str = 0.25, Re = 50, (c) Str = 0.01, Re = 5, and (d) Str = 0.05, Re = 500. (d) is reproduced with permission from L. Babor and H. C. Kuhlmann, Proc. Appl. Math. Mech. 20, e202000194 (2021). Copyright 2021 Authors, licensed under a Creative Commons Attribution Licence.