  Bulk viscosity effects on the collective flow harmonics in heavy ion
collisions are investigated, on an event by event basis, using a newly
developed 2+1 Lagrangian hydrodynamic code named v-USPhydro which implements
the Smoothed Particle Hydrodynamics (SPH) algorithm for viscous hydrodynamics.
A new formula for the bulk viscous corrections present in the distribution
function at freeze-out is derived starting from the Boltzmann equation for
multi-hadron species. Bulk viscosity is shown to enhance the collective flow
Fourier coefficients from $v_2(p_T)$ to $v_5(p_T)$ when $% p_{T}\sim 1-3$ GeV
even when the bulk viscosity to entropy density ratio, $% \zeta/s$, is
significantly smaller than $1/(4\pi)$.
