  We perform numerical simulations of planar jets of elastoviscoplastic (EVP)
fluid (\citet{saramito2007new} model) at low Reynolds number. Three different
configurations are considered: $(i)$ EVP jet in EVP ambient fluid, $(ii)$ EVP
jet in Newtonian ambient fluid (miscible), and $(iii)$ EVP jet in Newtonian
ambient fluid (immiscible). We investigate the effect of the Bingham number,
\textit{i.e.} of the dimensionless yield stress of the EVP fluid, on the jet
dynamics, and find a good agreement with the scaling for laminar, Newtonian
jets for the centerline velocity $u_c/u_0\propto (x/h)^{-1/3}$ and for the jet
thickness $\delta_{mom}/h\propto (x/h)^{2/3}$ at small Bingham number. This is
lost once substantial regions of the fluid become unyielded, where we find that
the spreading rate of the jet and the decay rate of the centerline velocity
increase with the Bingham number, due to the regions of unyielded fluid
inducing a blockage effect on the jet. The most striking difference among the
three configurations we considered is the extent and position of the regions of
unyielded fluid: large portions of ambient and jet fluids (in particular, away
from the inlet) are unyielded for the EVP jet in EVP ambient fluid, whereas for
the other two configurations, the regions of unyielded fluid are limited to the
jet, as expected. We derive a power law scaling for the centerline yield
variable and confirm it with the results from our numerical simulations. The
yield variable determines the transition from the viscoelastic Oldroyd-B fluid
(yielded) to the viscoelastic Kelvin-Voigt material (unyielded).
