Periodic Vortex Streets and Complex Monodromy

Vortex Streets on a Sphere

Strouhal-Reynolds number relationship for vortex streets.

A rationale for the empirically observed Strouhal-Reynolds number relation for vortex shedding in the wake of a cylinder is provided. This rationale derives from a mechanism of vortex formation observed in numerical simulations of two-dimensional vortex shedding coupled with an order of magnitude estimate of the terms in the vorticity transport equation based on this mechanism.

Studies of Two-Dimensional Vortex Streets

Periodic vortex streets, often considered as a model for the organized structures observed in the wake of two-dimensional (2D) bluff bodies, are revisited. After the generation of the shear layers the formation of the vortices is mainly an inviscid process. An intrinsic scaling for the formation of vortex streets is found based on the invariants of motion for 2D inviscid flows; namely the kinet...

Hawkmoth flight stability in turbulent vortex streets.

Shedding of vortices is a common phenomenon in the atmosphere over a wide range of spatial and temporal scales. However, it is unclear how these vortices of varying scales affect the flight performance of flying animals. In order to examine these interactions, we trained seven hawkmoths (Manduca sexta) (wingspan ~9 cm) to fly and feed in a wind tunnel under steady flow (controls) and in the von...

Von Kármán vortex streets on the sphere

We consider streamline patterns associated with single and double von Kármán point vortex streets on the surface of a nonrotating sphere, with and without pole vortices. The full family of streamline patterns are identified and the topological bifurcations from one pattern to another are depicted as a function of latitude and pole strength. The process involves first finding appropriate vortex ...