  We performed a numerical study of the efficiency of mixing by alternating
horizontal and vertical shear ``wedge'' flows on the two-dimensional torus. Our
results suggest that except in cases where each individual flow is applied for
only a short time, these flows produce exponentially fast mixing. The observed
mixing rates are higher when the individual flow times are shorter (but not too
short), and randomizing either the flow times or phase shifts of the flows does
not appear to enhance mixing (again when the flow times are not too short). In
fact, the latter surprisingly seems to inhibit it slightly.
