Installation and interference drag decomposition via RANS far-field methods

Computation of the engine installation drag is important to both airframers and engine manufacturers who wish to assess performance of their respective system. This force comprises the interference drag that results from the interaction between the wing and the engine's nacelle. Its evaluation is cumbersome because of the coupled nature of this phenomenon. It is thus proposed to decompose the installation drag in terms of interference and nacelle drags that, using the far-field method, can be further discretized in terms of viscous, wave, induced, spurious and pre-entry forces. By using simulations on the isolated nacelle, the wing-body and the wing-body-pylon-nacelle configurations, it is thus possible to compute and decompose both the interference and installation drags. Simulations are performed with ANSYS Fluent 14.5 on the DLR-F6 equipped with CFM56 nacelles in power-on conditions. A far-field method to compute and decompose the installation and interference drags is thus introduced for the first time. Results have shown that the installation and interference drags in powered conditions account for more than 25% and 5% of the total configuration drag, respectively. It is also shown that the viscous drag and the pre-entry thrust are the two main contributors to the installation drag, each accounting for about 40%.