  We use (3+1) dimensional ideal hydrodynamics to describe the space-time
evolution of strongly interacting matter created in Au+Au and Pb+Pb collisions.
The model is applied for the domain of bombarding energies 1-160 AGeV which
includes future NICA and FAIR experiments. Two equations of state are used: the
first one corresponding to resonance hadron gas and the second one including
the deconfinement phase transition. The initial state is represented by two
Lorentz-boosted nuclei. Dynamical trajectories of matter in the central box of
the system are analyzed. They can be well represented by a fast shock-wave
compression followed by a relatively slow isentropic expansion. The parameters
of collective flows and hadronic spectra are calculated under assumption of the
isochronous freeze-out. It is shown that the deconfinement phase transition
leads to broadening of proton rapidity distributions, increase of elliptic
flows and formation of the directed antiflow in the central rapidity region.
These effects are most pronounced at bombarding energies around 10 AGeV, when
the system spends the longest time in the mixed phase. From the comparison with
three-fluid calculations we conclude that the transparency effects are not so
important in central collisions at NICA-FAIR energies (below 30 AGeV).
