Hydrodynamic simulation of elliptic flow

We use a hydrodynamic model to study the space-time evolution transverse to the beam direction in ultrarelativistic heavy-ion collisions with nonzero impact parameters. We focus on the influence of early pressure on the devel opment of radial and elliptic flow. We show that at high energies elliptic flow is generated only during the initial stages of the expansion while rad ial flow continues to grow until freeze-out. Quantitative comparisons with SPS data from semiperipheral Pb+Pb collisions suggest the applicability of hydrodynamical concepts already approximate to 1 fm/c after impact.