Drag Prediction of Engine -Airframe Interference Effects Using Unstructured Navier -Stokes Calculations

Navier-Stokes calculations on hybrid grids using the TAU software of the MEGAFLOW project are performed to compute engine installation drag for the DLR, German Aerospace Research Center, F6 transport aircraft configuration at cruise flight conditions with conventional and with very-high-bypass-ratio nacelles at three and two different locations, respectively. The results are verified by a comparison with experimental data from different wind-tunnel campaigns carried out with Office National d'Etudes et de Recherches Aerospatiales. Numerical discretization errors are reduced by several steps of grid adaptation, resulting in grid densities up to 8.4 x 10 6 nodes. It is demonstrated that the installation drag of the different configurations, which vary only a few drag counts (10 -4 ), can be computed consistently, although the total drag forces are predicted lower than results of experiments. Successive grid refinement leads to a decrease of the differences between calculated and measured installation drag

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