  The effect of freestream turbulence on the spreading of the near wake of a
circular cylinder is investigated through particle image velocimetry (PIV)
data. Different ``flavours'' of freestream turbulence, in which the turbulence
intensity and integral length scale are independently varied, are subjected to
the cylinder. The time-averaged spreading of the near wake is decoupled into
the growth through entrainment and the envelope of the spatial extent of the
instantaneous wake due to wake ``meandering'', induced by the presence of
large-scale coherent structures, i.e. the von Karman vortex street. Unlike for
the far field of a turbulent wake, examined by Kankanwadi and Buxton (2020), it
is shown that freestream turbulence enhances the entrainment rate into the wake
in comparison to a non-turbulent background. Both the turbulence intensity and
the integral length scale of the background turbulence are important in this
regard, contrasting to the far wake where only the turbulence intensity is
important. Additionally, wake meandering is enhanced by the presence of
background turbulence, and here the integral length scale is the dominant
parameter. Combining these findings yields the oft-reported result that
background turbulence enhances the time-averaged near-wake growth rate. The
influence of wake meandering is isolated by conducting similar experiments in
which a splitter plate is mounted to the rear face of the cylinder, thereby
eliminating the von Karman vortex street. These results show that when
large-scale vortices aren't present within the turbulent wake then freestream
turbulence actually suppresses the entrainment rate, relative to a
non-turbulent background, in results that mirror Kankanwadi and Buxton (2020).
We therefore postulate that freestream turbulence has the effect to enhance
large-scale entrainment via engulfment, but suppress entrainment via
small-scale nibbling.
