Five technical work packages (WP) addressed the project objectives.
WP1 addressed the multi-point, multi-objective design and optimisation of compact nacelles. A family of axisymmetric nacelles for long and medium range operation was generated in order to develop the design tools and identify the main aerodynamic sensitivities. The automated process, using linked tools including in-the-loop computational fluid dynamics (CFD), was controlled by genetic or particle swarm algorithms operating on multiple objectives to identify design optima. The optimisation method was extended to 3D non-axisymmetric configurations (Fig 1), paying attention to off-design conditions. This enabled the down-selection of four designs (long and medium range, conventional and compact configurations) for wind tunnel (WT) test. WP1 enabled ANACO objectives 1, 2 and 3 to be achieved.
WP2 advanced experimental techniques for validation of predicted drag. ANACO used the ARA Transonic Wind Tunnel (TWT) and Z30 isolated nacelle test rig (Fig 2), enabling external drag measurement of sting-mounted models using a rotating wake rake. CFD analyses facilitated optimised model integration with a new, profiled sting (Fig 3) and examined off design characteristics (Fig 4) and rig loading. CFD-based experimental uncertainty analyses aided improvement of the drag rake design and drag correction methods and identified a requirement for improved ingested mass flow calibration. Novel test techniques were also developed including boundary layer particle image velocimetry (PIV) enabling computation of surface shear stress. A new small scale rig (Fig 5) was used for initial shear stress measurement trials including PIV. WP2 also showed, using a numerical study, that generation of a pressure field of the required fidelity using a swept prismatic wing was not feasible. WP2 enabled ANACO objective 4 to be achieved.
WP3 focused on the detailed design and manufacture of the four down-selected nacelle model geometries. Each model was instrumented for the measurement of surface pressure with one model also having unsteady pressure and surface shear stress sensors (Fig 6). Aided by CFD analysis, a bespoke air meter for Z30 rig mass flow calibration was designed and manufactured in support of the main test campaign.
WP4 addressed the preparation and WT test of the Z30 rig and nacelle models. The rig was refurbished and modified following the recommendations of WP2. An initial shakedown WT test was conducted to de-risk the test systems and methods, also supporting the revision of data correction algorithms. The main test entry included rig calibrations (Fig 7) and aerodynamic characterisation of the 4 nacelle geometries (Fig 8) at cruise and off-design conditions, applying novel measurement techniques to one model (Figs 9, 10). WP3 and WP4 enabled objective 5 to be achieved.
WP5 focused on the validation of compact nacelle design methods based on the transonic WT configuration and experimental data, the assessment of the aircraft installed configurations and the generation of design rules for compact nacelles. CFD was used to simulate aircraft installed nacelle configurations for both long and medium range applications (Fig 11). CFD guided the experiment design and CFD simulations provided numerical results for direct comparison with the measurements (Figs 12-14). CFD was used to predict compact nacelle drag benefit when installed on the WT test rig (Fig 3) and on a representative aircraft wing (Fig 15). Advanced methods were developed to map the design space and enable the optimisation of aircraft installed nacelles. WP1 and WP5 together provided guidance on the design methods and design rules for compact nacelles. Objectives 6, 7 and 8 were achieved.
ANACO has provided opportunities for exploitation and dissemination. Experience gained from the experiments, for example in the industrial application of PIV, has been applied to subsequent WT test campaigns. Future Z30 tests will benefit from improved measurement quality and model-rig integration. The new nacelle design process has been used in the subsequent JU ODIN project. Results demonstrating the success of this process and the state-of-the-art numerical design tools developed during ANACO have been disseminated via academic conferences and journal papers.
