  Hydrodynamics with cylindrical symmetry in transverse direction and
longitudinal scaling flow is employed to calculate the transverse momentum
spectra of various hadrons and clusters (e.g. pi, K, N, Phi, Lambda, d, He) in
central heavy-ion collisions at CERN-SPS and BNL-RHIC energies up to pT=4 GeV.
We discuss the sensitivity of these spectra with respect to the initial
transverse density profile as well as to the choice of ``freeze-out''
hypersurface. For SPS energy and pT<2 GeV, overall good agreement of the pT
distributions with data is found when freeze-out occurs along the T=130 MeV
isotherm. Even high-pT neutral pion data can be described for a particular
choice of the initial transverse density profile. It is shown that the average
transverse velocity <vT> of heavy hadrons and hadronic clusters is a good
measure for the collective flow velocity. The latter is found to be rather
similar for SPS and RHIC energies, due to the ``stall'' of the flow within the
long-lived mixed phase at RHIC. In case of thermalization and hydrodynamical
expansion, the mean transverse momentum <pT> increases linearly with the hadron
mass. In contrast, the string model FRITIOF7.02, which does not account for
rescattering of secondary hadrons, predicts a strong dependence of <pT> on the
quark composition of the hadron. Due to the different sensitivity to hard
processes, hadrons with charm (anti-)quarks acquire significantly more
transverse momentum than hadrons without c (or even without s) quarks.
