  We obtain, by extensive direct numerical simulations, time-dependent and
equal-time structure functions for the vorticity, in both quasi-Lagrangian and
Eulerian frames, for the direct-cascade regime in two-dimensional fluid
turbulence with air-drag-induced friction. We show that differ- ent ways of
extracting time scales from these time-dependent structure functions lead to
different dynamic-multiscaling exponents, which are related to equal-time
multiscaling exponents by different classes of bridge relations; for a
representative value of the friction we verify that, given our error bars,
these bridge relations hold.
