We present the results of three-dimensional numerical simulations that include the effects of hydrodynamical forces and gas drag upon an evolving dusty gas disk. We briefly describe a new parallel, two phase numerical code based upon the smoothed particle hydrodynamics (SPH) technique in which the gas and dust phases are represented by two distinct types of particles. We use the code to follow the dynamical evolution of a population of grains in a gaseous protoplanetary disk in order to understand the distribution of grains of different sizes within the disk. Our ``grains'' range from metre to submillimetre in size.
Astronomical Society of the Pacific conference series: Proceedings of 'Extrasolar planets: today and tomorrow', the 19th IAP Colloquium Institut d'Astrophysique de Paris, Paris, France, 2004 / Jean-Philippe Beaulieu, Alain Lecavelier des Etangs and Caroline Terquem (eds.),
Vol. 321, p. 319