  Description of relativistic heavy-ion collisions at the energies of RHIC Beam
Energy Scan program with fluid dynamic approach poses several challenges, one
of which being a complex geometry and a longer duration of the pre-hydrodynamic
stage. Therefore, existing fluid dynamic models for heavy-ion collisions at the
RHIC Beam Energy Scan energies rely on rather complex initial states, such as
UrQMD cascade or multi-fluid dynamics. In this study, we show that functionally
simpler, non-dynamical initial states can be employed for the fluid dynamical
simulations of Au-Au collisions at $\mbox{$\sqrt{s_{_{\rm NN}}}$}=27$ and
62.4~GeV. We adapt the initial states based on Monte Carlo Glauber model
(GLISSANDO 2) and $\sqrt{T_A T_B}$ ansatz based on reduced thickness (T$_{\rm
R}$ENTo $p=0$), extended into the longitudinal direction and finite baryon
density. We find that both initial states, when coupled to a 3D event-by-event
viscous fluid dynamic + cascade model, result in an overall fair reproduction
of basic experimental data: pseudorapidity distributions, transverse momentum
spectra and elliptic flow, at both collision energies. This is a rather
surprising, given that the $\sqrt{T_A T_B}$ ansatz is functionally similar to
the EKRT and IP-Glasma models, which are successful at much larger energies and
rely on a partonic picture of the initial state.
