The annular centrifugal contactor has been developed as the central piece of equipment for advanced liquid-liquid extraction processes for use in recycling spent nuclear fuel. While a sufficient base of experience exists to support successful operation of current contactor technology, a more complete understanding of the fluid flow within the contactor would enable further advancements in design and operation of future units. In particular, an important characteristic of the flow that is not well understood and which significantly complicates computational modeling of the contactor is the complex free surface flow in the annular mixing zone. This study presents the results of time-dependent, multiphase computational fluid dynamics (CFD) modeling using the volume-of-fluid (VOF) interface tracking method to characterize the mixing zone in a model centrifugal contactor. Laser doppler velocimetry (LDV) measurements of the actual flow velocities within the contactor were also performed. The experimental results were compared with simulations using various turbulence modeling schemes. The CFD model predictions using a coarse grid large eddy simulation (LES) method are in good agreement with the experimental measurements and observations. (C) 2007 American Institute of Chemical Engineers.