Nonlinear synchronization in open flows
Résumé
The selection criteria governing finite-amplitude synchronized oscillating states are discussed for model systems and real wake flows in a domain of infinite streamwise extent. Two types of nonlinear global modes are possible: hat modes with overall smoothly varying amplitude and elephant modes with a sharp front. The vortex street in wake flows is of elephant type, as observed in direct numerical simulations of a real spatially developing wake. Furthermore, the elephant frequency selection criterion is in excellent agreement with the numerically determined vortex shedding frequency.
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