  One of the most remarkable features of the Quark Gluon Plasma is its nearly
perfect fluidity behavior indicated by the small shear viscosity to entropy
density ratio obtained from fitting relativistic viscous hydrodynamics flow
harmonics to experimental data. In recent years, bulk viscosity has also been
considered in the context of event-by-event relativistic hydrodynamics and it
has been found to have a non-trivial interplay with shear viscosity. In this
paper some of the issues are discussed that require further work when
extracting the shear viscosity to entropy density ratio in the presence of a
non-zero bulk viscosity.
