High-performance computing and smoothed particle hydrodynamics. Smoothed Particle Hydrodynamics is a gridless numerical method that can be used to simulate highly complex flows with one or more free surfaces. In the context of engineering applications, very few 3-D simulations have been carried out due to prohibitive computational cost since the number of particles required in 3-D is usually too large to be handled by a single processor. In this work, an improved version of a parallel 3-D SPH code, Spartacus-3D, is presented. Modifications to the code, which include a localisation of all the previously global arrays combined with a switch from global communications to local ones where possible, lead to a more efficient parallel code and allow for a substantial increase in the number of particles in a simulation.