Overview
The DREAm-TILT project was focused on the assessment of drag reduction achieved through the aerodynamic optimisation of some critical components of the ERICA tiltrotor fuselage. This was accomplished both from an experimental and a numerical point of view.
A CFD-based optimisation activity had 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) had been identified, that contribute to reduce aircraft drag and enhance aerodynamic efficiency.
In DREAm-TILT, the benefits obtained from the aerodynamic optimisation in terms of drag reduction were thoroughly assessed through a dedicated wind tunnel campaign: specifically, the final optimised fuselage were tested and the drag reduction with respect to the original configuration was determined. All the optimised components were 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 visualisation was ran and infrared thermography carried out to enhance knowledge on the transition and separation regions for the different drag reduction configurations.
Moreover, a CFD activity was 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 were performed for both basic and optimised configurations. In a second stage, the numerical results on both the baseline and optimised ERICA geometries were compared with the acquired wind tunnel data. Finally, the numerical models already tested and validated were used for the assessment of the aerodynamic performance of the optimised ERICA fuselage at full scale conditions (Mach = 0.58), including the rotor effects.
Funding
Results
Executive Summary:
The DREAm-TILT project was focused on the assessment of drag reduction achieved through the aerodynamic optimization of some critical components of the ERICA tiltrotor fuselage. This was accomplished both from an experimental and a numerical point of view.
Specifically, a CFD-based optimisation activity was previously carried out in GRC2 by University of Padova and HIT09 S.r.l. in order to reduce the drag levels of some specific components of the reference tiltrotor configuration, and proper shapes of some fuselage components (i.e. wing/fuselage junction, wing/nacelle junction, nose, landing gear sponson and empennage) were identified, that contribute to reduce aircraft drag and enhance aerodynamic efficiency. In particular, an in-house multi-objective evolutionary algorithm was used coupled with both commercial and open-source CFD solvers. Thanks to the capability of the optimisation tool used to handle multi-objective problems with multiple criteria constraints, all the constraints related to architectural/structural issues, pilot visibility, aircraft stability and controllability were properly taken into account as well during optimization. The numerically obtained results from optimisation were very encouraging: actually, the overall predicted gain in drag reduction was around 8% with respect to the baseline (without taking into account rotor blade stubs effects), which is expected to lead to a significant reduction in fuel consumption as well.
In DREAm-TILT, the benefits obtained from the aerodynamic optimisation in terms of drag reduction were first thoroughly assessed through a dedicated wind tunnel campaign: specifically, the final optimised fuselage was tested and the drag reduction with respect to the original configuration determined achieving a drag reduction of 4.5% (including rotor blade stubs effects). All the optimised components were 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 visualisation runs and infrared thermography were finally carried out to enhance knowledge on the transition and separation regions for the different drag reduction configurations.
In parallel, a CFD activity was carried out on both the model scaled aircraft tested in the wind tunnel 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 were performed for both basic and optimised configurations of the scaled model. In a second stage, the numerical results on both the baseline and optimised ERICA geometries were compared and fully validated against the acquired wind tunnel data. Finally, the numerical models already tested and validated were used for the assessment of the aerodynamic performance of the optimized ERICA fuselage at full scale conditions (Mach = 0.58), including the rotor effects.
Overall, drag reduction obtained by CFD on the scaled model at optimisation attitude was around 4%, while it was equal to 4.5% at full scale conditions. Numerical results were in good agreement with wind tunnel data and the initial drag reduction target required by GRC (-3.5%) was definitely achieved and overcome.