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.

Completed August 2018

The Objective of the Research

The objective of this research project was 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 developed 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.

This project is 50% government funded through Innovate UK and the Aerospace Technology Institute.

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 has delivered improved tools that design and manufacturing organisations could 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. This project has delivered a design tool that can be used to quantify the drag reductions (and therefore fuel and emissions savings) 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:

  1. A comprehensive review of current methods and data for the effects of surface deviations, excresences and leakage. This work package reviewed and documented the past research and existing methods and data and so identified the areas where new data was acquired for the development and validation of improved modelling.
  2. Wind tunnel testing. The ASTEROID project performe wind tunnel tests to obtain new data for method development and validation. Low speed tests were completed at Cranfield University and at City University. Transonic testing was carried out at the University of Cambridge.
  3. 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) were modified to simulate the effects of typical excrescences.
  4. Maintenance and repair. As part of the project IHS ESDU developed an enhanced user interface for ESDU excrescence drag methods that enables 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.
  5. 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 was developed and validated as another method for the determination of the aerodynamic effects.

The Primary Participants

  • 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.


The ASTEROID project is 50% funded by the UK Government through Innovate UK.

Project ASTEROID Timeline

The project was formally completed on 31st August 2018. The primary participants continue to build on the achievements of the research for the further development of excrescence drag methods.

Further Information

For further information concerning ASTEROID contact:

Adam Quilter

25 Ropemaker Street, London, EC2Y 9LY
United Kingdom
Phone: +44 (0)20 3159 3259