The unsteady turbulent flow in a mixing vessel stirred by a Rushton impeller is predicted using the Large Eddy Simulation technique. The interaction between the moving impeller and the static baffles is accounted for explicitly through a sliding-deforming mesh methodology, thus, eliminating approximations used to account for the effect of the moving impeller. Large-scale structures associated with the trailing vortices are assessed via the vorticity and the turbulent kinetic energy distributions. The phase-resolved predictions are compared with measurement data obtained by laser-Doppler anemometry and favourable agreement is reported both for mean as well as turbulence quantities.