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Breaking of axisymmetry and onset of unsteadiness in the wake of a sphere. (English) Zbl 0977.76028
From the view point of nonlinear dynamical system theory the paper investigates the instabilities at the first stage of transition to turbulence in the wake flow after a sphere. The linear stability analysis and the full Navier-Stokes simulation based on a spectral method and on an azimuthal expansion are used to determine the primary instability threshold as well as the threshold of a secondary (Hopf-type) instability. The computed azimuthal modes (corresponding to the nonlinear instability modes) are used to explain the occurence of the bifid wake.

76E30 Nonlinear effects in hydrodynamic stability
76D25 Wakes and jets
37N10 Dynamical systems in fluid mechanics, oceanography and meteorology
76F06 Transition to turbulence
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