  The wake behind a cube with a face normal to the flow was investigated
experimentally in a water tunnel using laser induced fluorescence visualisation
(LIF) and particle image velocimetry (PIV) techniques. Measurements were
carried out for moderate Reynolds numbers between 100 and 400 and in this range
a sequence of two flow bifurcations was confirmed. Values for both onsets were
determined in the framework of Landau`s instability model. The measured
longitudinal vorticity was separated into three components corresponding to
each of the identified regimes. It was shown that the vorticity associated with
a basic flow regime originates from corners of the bluff body, in contrast to
the two other contributions which are related to instability effects. The
present experimental results are compared with numerical simulation carried out
earlier by Saha (Phys. Fluids, vol. 16, 2004, pp. 1630-1646).
