Fig. 2: Power spectrum response of the turbulent D-shaped body wake under symmetric periodic forcing.

a Experimental response of the global vortex shedding mode amplitude characterized via its power spectral density (PSD) as function of the excitation frequency ω_f normalized by the natural frequency ω₀. The axis Ω denotes the frequency content of the response. b Interpretation of the dominant frequency components of the response across all frequencies of the forcing. Colored overlays highlight the response frequency components at the measured mean vortex shedding rate (white), the forcing frequency and its harmonics mω_f, for integer m, (green), and those obtained by adding and subtracting the previous overlays as functions of the forcing frequency (yellow and blue). c The power spectrum response computed from simulations of a hierarchy of modified Stuart−Landau models, where A is the global mode amplitude, t is dimensionless time, σ and l are the Stuart−Landau coefficients, ε is the forcing amplitude, and \({\hat{F}}_{nm}\) are complex constants that model the interactions between the forcing and the wake. White measurement noise is added to all models.