Bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics at energies available at the BNL Relativistic Heavy Ion Collider

The interplay between shear and bulk viscosities on the flow harmonics, vₙ's, at the BNL Relativistic Heavy Ion Collider is investigated using the newly developed relativistic $2+1$ hydrodynamical code v-usphydro that includes bulk and shear viscosity effects both in the hydrodynamic evolution and at freeze-out. While shear viscosity is known to attenuate the flow harmonics, we find that the inclusion of bulk viscosity decreases the shear viscosity-induced suppression of the flow harmonics, bringing them closer to their values in ideal hydrodynamical calculations. Depending on the value of the bulk viscosity to entropy density ratio, ζ/s, in the quark-gluon plasma, the bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics may require a reevaluation of the previous estimates of the shear viscosity to entropy density ratio, η/s, of the quark-gluon plasma previously extracted by comparing hydrodynamic calculations to heavy-ion data.