  We study the bulk viscosity of strange quark matter(SQM) in density dependent
quark mass model(DDQM) under the background of self-consistent thermodynamics.
The correct formulae, with which the viscosity can be evaluated, are derived.
We also find that the viscosity in DDQM can be higher by 2 to 3 orders of
magnitude than MIT bag model. We calculate the damping time scales due to
viscosity coupled to r-modes. The numerical results show the time scale can't
be shorter than $10^{-1}$s.

Astrophysics;High Energy Physics - Phenomenology