Periodic axial motion of the inner cylinder in Taylor–Couette
flow is used to delay
transition to Taylor vortices. The outer cylinder is fixed. The marginal
stability
diagram of Taylor–Couette flow with simultaneous periodic axial motion
of the
inner cylinder is determined using flow visualization. For the range of
parameters
studied, the degree of enhanced stability is found to be greater than that
predicted
by Hu & Kelly (1995), and differences in the scaling with
axial Reynolds number are
found. The discrepancies are attributed to essential differences
between the base flow
in the open system considered by Hu & Kelly, where mass is conserved
over one
period of oscillation, and the base flow in the
enclosed experimental apparatus, where
mass is conserved at all sections at all times.