Interplay of shear and bulk viscosity in generating flow in heavy-ion collisions

We perform viscous hydrodynamic calculations in $2+1$ dimensions to investigate the influence of bulk viscosity on the viscous suppression of elliptic flow in noncentral heavy-ion collisions at Relativistic Heavy Ion Collider energies. Bulk and shear viscous effects on the evolution of radial and elliptic flow are studied with different model assumptions for the transport coefficients. We find that the temperature dependence of the relaxation time for the bulk viscous pressure, especially its critical slowing-down near the quark-hadron phase transition at Tc, partially offsets effects from the strong growth of the bulk viscosity itself near Tc and that even small values of the specific shear viscosity η/s of the fireball matter can be extracted without large uncertainties from poorly controlled bulk viscous effects.