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Extensive studies for the dynamic response of downstream structures to von Kármán wakes generated by upstream structures have been performed thus far. However, a critical gap remains in how a downstream structure responds to thrust-generating wake patterns typically produced by swimming fish in nature. To bridge this crucial gap, numerical simulations are performed on a system consisting of an upstream flexible fin and a downstream rigid cylinder vibrating freely in the cross-stream direction to investigate the interaction of the cylinder with various upstream wake patterns. The various wake patterns are generated by the heaving motions of the fin as the cylinder-diameter-based dimensionless heaving amplitude and frequency are varied. When the von Kármán wake is generated behind the fin, not only the slaloming motion of the cylinder and constructive vortex-to-vortex interaction shed from the fin and the cylinder (hereafter, SC mode) but also the interception motion of the cylinder and mixed constructive and destructive vortex-to-vortex interaction (IM mode) dominate. For a reverse von Kármán wake, both the slaloming motion of the cylinder and destructive vortex-to-vortex interaction (SD mode) and IM mode are prominent. When vortices consisting of the von Kármán wake or reverse von Kármán wake are aligned near the centerline, the SC + SD + IM mode arises. Because the induced velocity created by the destructive vortex-to-vortex interaction plays an important role in the generation of a large pressure difference around the cylinder, the dynamic response of the cylinder to the upstream wake is rank-ordered as SD, IM, and SC modes.
Kim et al. (Mon,) studied this question.