  The dynamics of a Bose-Einstein condensate are examined numerically in the
presence of a one-dimensional bichromatic optical lattice with external
harmonic confinement. The condensate is excited by a focusing red laser. For
this purpose, the time-dependent Gross Pitaevskii equation is solved using the
Crank Nicolson method in real time. Two realizations of the optical lattice are
considered, one with a rational and the other with an irrational ratio of the
two constituting wave lengths. For a weak bichromatic optical lattice, the
long-time averaged physical observables of the condensate respond only very
weakly (or not at all) to changes in the secondary optical lattice depth.
However, for a much larger strength of the latter optical lattice, the response
is stronger. It is found that qualitatively there is no difference between the
dynamics of the condensate resulting from the use of a rational or irrational
ratio of the optical lattice wavelengths since the external harmonic trap
washes it out. It is further found that in the presence of an external harmonic
trap, the bichromatic optical lattice acts in favor of superflow.
