A smoothed particle hydrodynamics (SPH) method is developed for the study o
f relativistic heavy-ion collisions. In order to describe the flow of a hig
h-energy but low baryon number density fluid, entropy is taken as the SPH b
ase. The method is formulated in terms of a variational principle, and the
SPH equations for an arbitrary curvilinear coordinate system are obtained.
Several examples show that SPH is a promising tool for the study of hadroni
c flow in relativistic heavy-ion processes.