The effect of base suction on a plane wake was found to produce significant changes
in wake dynamics. The wake is produced by merging two boundary layers from the
trailing edge of a splitter plate in a two-stream water tunnel. A threshold suction
speed exists which is approximately equal to half of the free-stream velocity. If the
suction speed is below the threshold, the wake flow is unstable. If the suction speed
is above the threshold, the wake becomes stable and no vortex shedding is observed.
In the present experiment, the suction technique can stabilize a wake at a maximum
tested Reynolds number of 2000.
The suction significantly reduces the length of the absolutely unstable region in
the immediate vicinity of the trailing edge of the splitter plate and produces a non-parallel flow pattern, resulting in the breakdown of global instability. The global
growth rate changes from positive (unstable flow) to negative (stable flow) at the
suction speed equalling 0.46 of the free-stream velocity. The threshold suction speed
can be accurately predicted by the global linear theory of Monkewitz et al. (1993)
with a non-parallel flow correction.