  Regions with reduced and increased values of total enthalpy are observed in a
time-averaged flow behind a bluff body. This energy redistribution takes place
both in the vortex formation region and in the developed vortex wake. The
present paper focuses on studying the effect of the structure of a vortex
street on the intensity of energy redistribution. Two approaches are used. The
first one is direct numerical simulation of the flow behind a transversely
oscillating cylinder, which is known for a variety of vortex patterns in the
wake. The simulations are based on a finite element solution of the
Navier-Stokes equations for a compressible perfect viscous gas. The second
approach is based on simplified point vortex models for infinite periodic
vortex streets, which contain a finite number of vortex chains in equilibrium.
It turns out that these simple models make it possible to obtain satisfactory
qualitative results, particularly if a more precise approximation of velocity
fields in the vortex cores (Rankine vortices) is implemented. It is shown that
the effect of energy redistribution significantly depends on the vortex
structure, namely the mutual arrangement of the vortices and their intensities.
The estimates of the energy separation efficiency in the time-averaged flow are
obtained for the general case of an arbitrary number of chains. A more detailed
analysis is performed for vortex streets with 2, 3, and 4 vortex chains.
