  We investigate the global frequency selection of two-dimensional vortex
shedding in the flat plate wake. The analysis is based on the mean flow
velocity profiles obtained from experimental measurements carried out for two
values of Reynolds number, 1850 and 3350, which are based on the plate
thickness and the free-stream velocity. Two different trailing edge geometries
of the flat plate are considered in this study: blunt and circular. By
performing local spatio-temporal analyses on the measured mean flow velocity
profiles, we estimate the global shedding frequency of the flow. This is in
excellent agreement with the shedding frequency measured experimentally. To
complement the study, we carry out a low-dimensional modeling based on the
proper orthogonal decomposition (POD) of the flow fields which is novel for
flat plate wakes. We observe that a model based on only two POD modes produces
an accurate estimate of the global shedding frequency. Our results also
highlight the role of the nonlinear interaction strength between the mean flow
with the higher harmonics thereby experimentally supporting the theoretical
criterion outlined in Sipp & Lebedev (JFM 2007).
