PRODIGE: Virtual certification methodologies are on the horizon
Results from wind tunnel tests and computational fluid dynamics analyses are often not accurate enough, yielding conservative designs with heavier-than-necessary components in aircraft. Clean Sky's PRODIGE (PRediction of aerOdynamics and hinge moment loaDs at hIgh Mach and fliGht REynolds number) project is developing a virtual certification scheme that will verify such tests. Their approach focuses on testing methodologies for assessing the aileron efficiency and hinge moment data predictions on a Falcon 8X business jet. Understanding the reasons for these discrepancies and improving the predictions would allow for safe and leaner actuator sizing, weight reduction and more accurate flight control definition, leading to fuel savings.
‘PRODIGE is making a contribution towards making virtual certification a reality, and in this project we're developing a methodology to ensure that there is an accurate prediction of the aileron efficiency and hinge moments for various deflection angles in transonic conditions. We use this data to improve the current computational fluid dynamics (CFD) models to better size the actuators,’ says Clean Sky project officer Dr. Sonell Shroff.
According to Shroff, with such accurate tools at our disposal, improved aircraft could be designed in a shorter period of time as compared to the current standard. A virtual certification would reduce costs and material usage, making time to market shorter and contributing to European competitiveness.
‘In order to face marketplace competition, the aerospace industry is strongly pushing for the adoption of a virtual aircraft development approach. The goal is to move from virtual testing of sub-assemblies to virtual certification of an aircraft. PRODIGE contributes to this strategy by providing accurate loads and hinge moments data to feed the development of more reliable tools which will speed up and improve the aircraft design, thereby avoiding subsequent and costly iterative adjustment processes,’ says Nicola Paletta, R&T Manager and project coordinator at IBK-Innovation.
In terms of the project's progress, she reports that the model design, including the local balance to measure the aileron hinge moment in the wind tunnel, is complete. Most of the model is already being manufactured, and the CFD-CSM solution – to predict the aerodynamic loads in the wind tunnel by taking into account the model structure flexibility – has been set up and used to predict the actual hinge moment expected in the wind tunnel operational conditions.
‘The next steps are the completion of the wind tunnel model manufacture and instrumentation and then aileron balance calibration in cryogenic conditions, in preparation for the wind tunnel test campaign in the European Transonic Windtunnel (ETW) after summer 2020,’ says Paletta.
The ETW is well suited for achieving Reynolds and Mach numbers comparable to flight test conditions. Testing will be conducted in the ETW with a cryogenic model that is representative of the Falcon 8X business jet for which flight test data are available. One important capability of the ETW is its ability to discriminate between Reynolds number effects and aeroelastic effects by adapting stagnation pressure and temperature in the wind tunnel.
‘The development of more reliable tools for the correct prediction of loads and hinge moments will allow for the design of more efficient aircraft, helping in the fulfilment of the ACARE goals, which are fundamental for all Horizon 2020 projects, and will support the competitiveness of the European aeronautic industry,’ says Paletta.
Paletta observes that studies performed by European and North American manufacturers indicate that, during the 2022-2031 period, deliveries for light, medium and large categories of business jets are projected to be up to 14,000 aircraft. Therefore, capturing a significant percentage of this market could have a tremendous influence on many jobs in multiple sectors of the European workforce.
‘Not only can this seriously impact employment, but it can also create a noteworthy potential for growth within Europe,’ says Paletta.
The benefits are not limited to job growth either. Correctly predicting the handling qualities and hinge moments induced by the deployment of wing control surfaces, such as spoilers and ailerons, will contribute to improving the general aircraft sizing processes, lowering the final weight and even reducing ticket costs.
‘The reduction of the aircraft weight, with the consequent reduction of operation costs, could have an impact on the flight tickets’ prices, with an immediate benefit for consumers,’ explains Paletta.
According to Thomas Delille, aerodynamics specialist engineer at Dassault, the anticipated outcome of the PRODIGE project will not only help define a better process for next generation aircraft to predict loads and hinge moments to aid the proper sizing of the aircraft structure and actuators without weight excess and more accurately defining flight control. He also points to the broader ecological and societal benefits:
‘The potential environmental benefits for Europe and its citizens are to be able, from the design phase, to accurately size the aileron actuators and the aircraft structure and thus optimise the weight of the aircraft which is an important parameter impacting fuel consumption.’
The 30-month project, which is scheduled to end later this year, is being coordinated by IBK Innovation GmbH. The consortium includes TU Darmstadt, which is responsible for the balance design, balance instrumentation, calibration and testing; Deharde, which manufactures the wind tunnel model and associated instrumentation; and DREAM Innovation, which provides design support by performing CFD calculations to support local and global loads and deformations for balance design and analysis of the aeroelastic effects.
Paletta reports that for a high-tech company like IBK Innovation, the Clean Sky way of working ‘allows delivering innovation in close cooperation with the aeronautical industry. This cooperation leads to “more targeted” activities related to research and technology development, with an immediate impact on the end-users. This working framework is beneficial for SMEs since it allows improving skills, increasing the track-record, and strengthening the network, with a significantly positive impact.’
Delille agrees, saying that Clean Sky brings the aviation community together in a unique way.
‘Clean Sky 2 is a great technological laboratory which makes it possible to benefit from European funding, to share costs, the means, the risks and the successes between all partners,’ says Delille. ‘It's a real multinational cooperation, mixing industries, research centres and university laboratories. It gives us an opportunity to work with new partners, and makes it possible to pool testing resources on multi-domain topics including aerodynamics, structures, engines and systems. For the most promising technologies, it's possible within the Clean Sky 2 context to increase TRLs up to level 6 – and that's a great boost for European industries.’