  Dynamic stall at low Reynolds numbers, $\mathit{Re} \sim \mathcal{O}(10^4)$,
exhibits complex flow physics with co-existing laminar, transitional, and
turbulent flow regions. Current state-of-the-art stall onset criteria use
parameters that rely on flow properties integrated around the leading edge.
These include the leading edge suction parameter or $\mathit{LESP}$ (Ramesh et
al., 2014) and boundary enstrophy flux or $\mathit{BEF}$ (Sudharsan et al.,
2022)), which have been found to be effective for stall onset at moderate to
high $\mathit{Re}$. However, low $\mathit{Re}$ flows feature strong vortex
shedding events occurring across the entire airfoil surface, including regions
away from the leading edge, altering the flow field and influencing the onset
of stall. In the present work, the ability of these stall criteria to
effectively capture and localize these vortex shedding events in space and time
is investigated. High-resolution large-eddy simulations for an SD7003 airfoil
undergoing a constant-rate, pitch-up motion at two $\mathit{Re}$ (10, 000 and
60, 000) and two pitch rates reveal a rich variety of unsteady flow phenomena,
including instabilities, transition, vortex formation, merging, and shedding,
which are described in detail. While stall onset is reflected in both
$\mathit{LESP}$ and $\mathit{BEF}$, local vortex-shedding events are identified
only by the $\mathit{BEF}$. Furthermore, these events can be localized in space
and time by considering the contributions to the $\mathit{BEF}$ from different
airfoil sections, which holds significant promise for effective flow control.
