A METHOD OF SMOOTHED PARTICLE HYDRODYNAMICS USING SPHEROIDAL KERNELS

We present a new method of three-dimensional smoothed particle hydrody namics (SPH) designed to model systems dominated by deformation along a preferential axis. These systems cause severe problems for SPH codes using spherical kernels, which are best suited for modeling systems w hich retain rough spherical symmetry. Our method allows the smoothing length in the direction of the deformation to evolve independently of the smoothing length in the perpendicular plane, resulting in a kernel with a spheroidal shape. As a result the spatial resolution in the di rection of deformation is significantly improved. As a test case we pr esent the one-dimensional homologous collapse of a zero-temperature, u niform-density cloud, which serves to demonstrate the advantages of sp heroidal kernels. We also present new results on the problem of the ti dal disruption of a star by a massive black hole.