The PIV and CFD technique were adopted to investigate the turbulent flow fields in stirred vessels with novel combined inner-outer agitator. The velocity fields and turbulent kinetic energy stirred by the combined inner outer agitator with different rotating speed ratios were analyzed. Results show that, in the turbulent flow regime, the introduction of outer agitator leads to the slight change of the velocity fields. The combined inner-outer agitator could enhance the turbulent level in stirred vessels, especially in the regions near the vessel wall and bottom, and the region located at mid-height of the two pitched paddles. The lower speed ratio could be beneficial to the rapid mixing of fluids.
