A COSMOLOGICAL HYDRODYNAMIC CODE BASED ON THE PIECEWISE PARABOLIC METHOD

We present a hydrodynamical code for cosmological simulations which us es the piecewise parabolic method (PPM) to follow the dynamics of the gas component and an N-body particle-mesh algorithm for the evolution of the collisionless component. The gravitational interaction between the two components is regulated by the Poisson equation which is solve d by a standard fast Fourier transform (FFT) procedure. In order to si mulate cosmological flows we have introduced several modifications to the original PPM scheme which we describe in detail. Various tests of the code are presented including adiabatic expansion, single and multi ple pancake formation and three-dimensional cosmological simulations w ith initial conditions based on the cold dark matter scenario.