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Flow past a sphere: Topological transitions of the vorticity field. (English) Zbl 0745.76055

Summary: On the basis of unsteady three-dimensional structures in a separated flow field and of the visualization techniques for unsteady phenomena, the flow field of a sphere placed in a uniform flow is analyzed numerically. In the initial flow field, an axisymmetric flow structure characterizes this field. A topological transition suddenly takes place, and a periodical structure appears in the wake region. These structures are visualized and confirmed by analyzing the vector fields (velocity and vorticity fields). In these unsteady flow fields, the initial flow field is defined by an axisymmetric structure but the developed field does not have the axisymmetry. A plane-symmetry, however, appears and is preserved.

MSC:

76M20 Finite difference methods applied to problems in fluid mechanics
76D05 Navier-Stokes equations for incompressible viscous fluids
76D25 Wakes and jets
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