Environmental Engineering Reference
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Figure 6-16. Regimes of wake development and associated radial profiles of the veloc-
ity deficit.
Initial Potential Core Regime
In this regime, it is assumed that the shear layer, having a profile given by a standard
radially-symmetric shear layer model, develops according to the normal shear law where
the growth rate of a layer thickness is proportional to the speed difference across it. This
will define a profile shape for any downwind station in the regime. The basic conservation
of drag is then maintained by selecting the effective radius in Equation (6-8),
R
W
,
to con-
serve the momentum deficit in the wake. Axisymmetric shear layers like this are shown
in Abramovitch [1963] and referenced in Lissaman [1976].
Fully-Developed Wake Regime
A suitable model for the flow profile in the far wake, well-supported by experimental
results, is also provided by Abramovitch [1963]. This profile is expressed as a function of
radial distance,
r
, normalized by a radial scale factor. To establish a growth law for the
width of the wake in this regime, we assume that the effective wake radius develops
temporally and spatially according to the following laws:
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