A finite element model of the Navier-Stokes equations is used 
for numerical simulation of flow past two normal flat plates 
arranged side by side at Reynolds number 80 and 160. The results 
from this simulation indicate that when the gap between the plates 
is twice the width of a single plate, the individual wakes of 
the plates behave independently, with the antiphase vortex shedding 
being dominant. At smaller gap sizes, the in-phase vortex shedding, 
with strong wake interaction, is favored. The gap flow in those 
cases becomes biased, with one of the wakes engulfing the other. 
The direction of the biased flow was found to be switching at 
irregular intervals, with the time histories of the indicative 
flow parameters and their power spectra resembling those of a 
chaotic system.