DREAM-TILT

Assessment of tiltrotor fuselage drag reduction by wind tunnel tests and CFD

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 Obiettivo del progetto (Objective)

'The DREAm-TILT project is focused on the assessment of drag reduction achieved through the aerodynamic optimization of some critical components of the ERICA tiltrotor fuselage. This will be accomplished both from an experimental and a numerical point of view. A CFD-based optimization activity has been carried out in GRC2, and proper shapes of some fuselage components (i.e. wing/fuselage junction, wing/nacelle junction, nose, landing gear sponson and empennage) have been identified, that contribute to reduce aircraft drag and enhance aerodynamic efficiency. In DREAm-TILT, the benefits obtained from the aerodynamic optimization in terms of drag reduction will be thoroughly assessed through a dedicated wind tunnel campaign: specifically, the final optimized fuselage will be tested and the drag reduction with respect to the original configuration will be determined. All the optimized components will be tested sequentially with the aim of getting an accurate drag breakdown and identifying the contribution of each component to the overall aerodynamic performance of the fuselage. Additional classical flow visualization runs and infrared thermography will be finally carried out to enhance knowledge on the transition and separation regions for the different drag reduction configurations. Moreover, a CFD activity will be carried out on both the model scaled and the full scale aircraft in order to evaluate rotor effects and the full scale (Mach dependent) characteristics. In a first phase, a series of blind test simulations at wind tunnel conditions will be performed for both basic and optimized configurations. In a second stage, the numerical results on both the baseline and optimized ERICA geometries will be compared with the acquired wind tunnel data. Finally, the numerical models already tested and validated will be used for the assessment of the aerodynamic performance of the optimized ERICA fuselage at full scale conditions (Mach = 0.58), including the rotor effects.'

Introduzione (Teaser)

Efficient and eco-friendly tiltrotors is one of the ways forward for decongesting air traffic. An EU-funded project is developing numerical and experimental methods to assess drag reduction on its main body.

Descrizione progetto (Article)

The EU Joint Technology Initiative (JTI) Clean Sky is the most ambitious aeronautical research programme ever launched in Europe. Its focus is on reducing noise and emissions associated with air transport with a dedicated section devoted to rotorcraft. The EU-funded project 'Assessment of tiltrotor fuselage drag reduction by wind tunnel tests and CFD' (DREAM-TILT) supports this effort by performing tests and running simulations aimed at assessing the aerodynamic efficiency of tiltrotor fuselage components.

Considering all the operational modes for a tiltrotor, the major drag sources concern the front fuselage, the wing/fuselage fairings, the landing gear sponsons and the rear empennages. The Green Rotorcraft Consortium 2 (GRC2) has already identified properly optimized shapes of these components that contribute to decreasing aircraft drag and enhancing aerodynamic efficiency. To this purpose, Computational Fluid Dynamics (CFD) coupled with innovative design methodologies based on multi-objective evolutionary algorithms were used. Through wind tunnel tests, DREAM-TILT is assessing the optimised fuselage components of future European civil tiltrotors based on ERICA architecture. Furthermore, it is determining drag reduction with respect to the baseline configuration.

All optimised components were tested sequentially to get an accurate drag breakdown and identify the contribution of each component to the overall fuselage aerodynamic performance. In addition, the project carried out additional flow visualisation runs to enhance knowledge on the transition and separation regions for the different drag reduction configurations.

In the first project period, scientists conducted a wind tunnel test campaign on a power-off model of the isolated ERICA tiltrotor fuselage for both the baseline and optimised configurations. The finally measured overall fuselage drag reduction at design incidence was equal to -4.5%. Suitable CFD models for both configurations were assessed as well. In a second stage, scientists performed a series of calculations at full scale conditions using the numerical models validated against wind tunnel data to assess the impact of shape optimization at real operating flight conditions and including also rotor effects.

Project findings are paving the way to design of a more environmentally friendly tiltrotor. Decreasing fuselage drag should have major positive implications in terms of efficiency and fuel consumption.