The merging flow characteristics in dual Rushton turbine stirred tanks were investigated using particle image velocimetry (PIV) experiments and large eddy simulation (LES) methods. The velocity and turbulent kinetic energy (TKE) were carefully measured with a high resolution PIV system. The regions with high TKE levels are affected by the movement of the trailing vortices generated behind the blades of the two turbines. The effects of the blade arrangements between the upper and lower turbines on the flow characteristics were discussed, but they are negligible for the phase-averaged flow fields. However, the phase-resolved data are totally different under various blade arrangements. The LES results of velocity, TKE, and trajectories of the trailing vortex cores were quantitatively compared with the PIV experiments and the laser Doppler velocimetry (LDV) data in the literature. Both the phase-averaged and phase-resolved LES results are in good agreement with the PIV experimental data and are better than the simulation results of the k-epsilon model. The good agreement between LES simulations and PIV experiments shows that the LES method has great potential for predicting complex flow fields in stirred tanks.