The ultimate aim of the program is to provide a design optimization tool for open rotor design. Although open rotors will yield substantial reductions in specific fuel consumption their design presents substantial coupled aerodynamic & aeroacoustic challenges. With regards to aerodynamics, to minimize engine size and hence weight for the tractor configuration the compressor inlet air must be passed down some form of complex geometry, sharply turned inlet duct. The duct entry flow will transmit the unsteady wake component from the upstream rotors. This sharply turned, local adverse pressure gradient, flow is likely to readily become separated and with bifurcated inlets exhibit an unsteady limit cycle behaviour. The interaction of the unsteady upstream flow with the compressor face presents a key CFD (Computational Fluid Dynamics) challenge. Hence, the project involves significant unsteady flow modelling. A key objective is to devise a design optimisation system for engine inlets. However, prior to this a greater flow physics understanding is required to help shape the design optimisation system. Also, it is necessary to develop the necessary CFD tools for Rolls-Royce in house use.