ASTEROID - A research project concerning the aerodynamic effects of small changes of aircraft shape; developing methods for use by the aircraft design industry for the optimisation of aerodynamic cleanliness in manufacture, maintenance and repair.
The Objective of the Research
The objective of this research project is to develop improved computational methods to determine the aerodynamic effects of small local changes in external shape and airflow - (i.e. excrescences, surface deviations and airflow leakage).
The project is developing methods to quantify the effects on aeroplane performance of: steps and gaps between adjacent panels, small protuberances, holes and indentations, external repair patches; and also of airflow leakage arising from ineffective sealing between components.
Context of the Research
All structures, including airframes, are manufactured and assembled to specified tolerances. In general, the smaller (tighter) the tolerances, the higher will be the cost of manufacture. It is not possible to build an aircraft (including all joints, fairings, cowlings and doors) to exactly the shape set out in the design – i.e. the optimised shape for highest performance and minimum fuel burn. This project will deliver improved tools for design and manufacturing organisations to use to quantify the performance penalties arising from deviations from the design and so enable the trade-off between manufacturing tolerances and aircraft performance to be quantified.
Once in-service the external 'cleanliness' of an aircraft will reduce due to the general ageing of paint and seals and the deterioration in the alignment of cowlings, doors and other moveable components. In addition, if an aircraft suffers damage in service, choices have to be made about the nature of the repair – whether it will restore the original shape (usually the most expensive option) or whether it is acceptable to change the external profile by adding an external plate to cover the damaged area. The project will deliver a design tool that can be used to quantify the reduced fuel burn that may be achieved by optimising repairs and the fit of components in service.
The Research and Development Programme
This research and development programme includes the following work packages:
- A comprehensive review of current methods and data for the effects of surface deviations, excresences and leakage. This work package has reviewed and documented the past research and existing methods and data and so has identified the areas where new data needs to be acquired for the development and validation of improved modelling.
- Wind tunnel testing. The ASTEROID project is performing wind tunnel tests to obtain new data for method development and validation. Low speed tests have been completed at Cranfield University and at City University. Transonic testing is being carried out at the University of Cambridge.
- Integral Boundary Layer (IBL) model development. Using flow measurements from the wind tunnel tests and other data identified by the review, Computational Fluid Dynamics-coupled IBL methods such as VGK (Viscous Garabedian and Korn) and VFP (Viscous Full Potential) will be modified to simulate the effects of typical excrescences.
- Database population and interactive tool. Using the validated IBL modelling, a trend analysis will be performed to obtain aerodynamic data for a wide range of shapes covering a range of Reynolds numbers, Mach numbers and pressure gradients.
- Maintenance and repair. IHS ESDU is developing an enhanced user interface, which will include the facility to creation of input geometries via graphics, that will enable designers to calculate rapidly and repeatedly the drag effects of excrescences. This will enable designers to optimise the specification of manufacture, repair and maintenance instructions.
- RANS-based Surface Discontinuity modelling. A tailored Fluent User Defined Function (UDF) that can locally manipulate the flow in order to simulate surface discontinuities using Reynolds Averaged Navier Stokes methods will be developed and validated as another method for the determination of the aerodynamic effects.
- IHS ESDU - ESDU (formerly the Engineering Sciences Data Unit) has a long history of developing aerospace design data and methods in the form of "Data Items" and accompanying software. IHS ESDU methods are used by numerous design organisations in the aerospace industry worldwide. The IHS ESDU methods are rigorously validated by committees of technical experts. The Transonic Aerodynamics Committee will provide technical scrutiny of this project.
- University of Leeds - Specialists at the University of Leeds have long experience in the field of aerodynamic design and research.
- BHR Group - Originally set up as the British Hydromechanics Research Association in 1947, BHR Group is now an independent engineering research and consultancy company based on its core expertise in fluids engineering.
- British Airways - British Airways is providing the consortium with expert advice on the repair and maintenance of turbofan-powered aeroplanes that operate at high altitudes and high subsonic Mach numbers.
- Eastern Airways - As an operator of turbo-propeller-powered aeroplanes, Eastern Airways is providing the consortium with expert advice on the repair and maintenance of aeroplanes that operate in the lower speed/altitude regime over relatively short distances.
- University of Cambridge, Cranfield University and City University. The wind tunnel testing is being carried out using the test facilities and workshops of these universities. The universities provide the project with expertise concerning test instrumentation and the analysis of the recorded data.
The ASTEROID project is 50% funded by the UK Government through Innovate UK.
Project ASTEROID Timeline
- 1st March 2016 – Project formally launched.
- 30th September 2016 – Review of current methods and data completed; weaknesses identified.
- 3rd October 2016 – High speed (Mach 1.4) wind tunnel testing began – first series.
- 1st March 2017 – 1st series of high speed testing completed.
- 10th July 2017 – Low speed wind tunnel testing began. Two series in two different tunnels.
- 1st December 2017 – Low speed wind tunnel testing completed.
- November 2017 – University of Leeds presented a Paper at the DiPaRT 2017 Conference, Bristol, UK.
For further information concerning ASTEROID contact:
Cliff Whittaker, Project Manager – ASTEROID
Phone: +44 (0)20 3159 3259