Are there any simulations that can be obtained that use smooth particle hydrodynamics and can be configured to include different initial conditions? I wish to simulate planetary collisions and their impact. I wish to exactly replicate the following link.
I would recommend MPA Garching's Gadget code for cosmological simulations of structure formation. It's primarily gravitational, but I do believe you can include gas effects as well:
GADGET computes gravitational forces with a hierarchical tree algorithm (optionally in combination with a particle-mesh scheme for long-range gravitational forces) and represents fluids by means of smoothed particle hydrodynamics (SPH). The code can be used for studies of isolated systems, or for simulations that include the cosmological expansion of space, both with or without periodic boundary conditions. In all these types of simulations, GADGET follows the evolution of a self-gravitating collisionless N-body system, and allows gas dynamics to be optionally included. Both the force computation and the time stepping of GADGET are fully adaptive, with a dynamic range which is, in principle, unlimited.
I don't know if this is what is commonly used for tasks such as yours, but it might be a place to start looking.