Overview
The AFDAR project was about advanced flow diagnostics in aeronautical research. The progress beyond the State-of-the-Art (with respect to current technologies) is summarised by three breakthroughs:
- Three-dimensional volumetric measurements over wings and air-foils;
- Time-resolved measurements and aerodynamic analyses, of which several orders of magnitude faster than today;
- Turbulence characterisation in aerodynamic wind-tunnels at resolution orders of magnitude higher than those today by Long Range Micro Particle Image Velocimetry.
The objective of AFDAR has been to develop, assess and demonstrate new image-based experimental technologies for the analysis of aerodynamic systems and aerospace propulsion components. The main development focused on new three-dimensional methods, based on Particle Image Velocimetry (PIV) to measure the flow field around aircraft components and on the high-speed version of the planar technique for the analysis in time-resolved regime of transient/unsteady aerodynamic problems.
The project ultimately aimed to support the design of better aircraft and propulsion systems by enabling the designer to use experimental data during the development cycle of unprecedented completeness and quality. The work also covered the simultaneous application of PIV-based techniques and other methods to determine aero-acoustic noise emissions from the airframes and to improve combustion processes to lower NOx, CO2 and soot emissions from engines.
The consortium was led by a Dutch University of Technology and listed various partners, including a Russian research Institute and an Australian University. Industries were also involved in this work, either as a participant or as a contributor under subcontract and provided testing facilities. As final results of the project, a detailed analysis of the new measurement systems was delivered and a number of demonstrations were performed to validate the concepts in industrial environments. Special emphasis was given to the dissemination of results by meetings, publications, workshops and other initiatives.
Funding
Results
1) The tomographic PIV technique was diffused among participants and the main issues related to hardware components, as well as measurement procedures (calibration, 3D reconstruction) were then shared by a large part of the consortium. Original solutions were already obtained on the side of system acceleration, making it possible to use this method with feedback on the experimentalist almost as rapidly as conventional PIV.
2) The use of long-range PIV in conjunction with statistical image analysis has been successful thus far and a large increase in measurement spatial resolution at distances typical of industrial wind tunnels is to be expected.
3) The dynamic range and accuracy of PIV is being significantly improved for time-resolved experiments. This will lead to much faster systems for the analysis of aircraft aerodynamics, yet at an accuracy comparable to State-of-the-Art PIV systems.
4) The first experiments that combine combustion scalar diagnostics and velocimetry have been conducted with a positive perspective that rigorous measurement protocols will be distilled from that experience.
5) The preparatory activities needed for the experiments dealing with applications of relevance to industry have been conducted, all achieving the technical feasibility.
Innovation aspects
Emission reduction was addressed with research conducted on ultra-low NOx emission combustors and on the aero-acoustic analysis of wing profiles. In both cases, the use of particle image velocimetry was unprecedented which should enable a more advanced optimisation of high-lift configurations operating off-design. Impact in the propulsion area was due to three main activities developing advanced experimental analysis of aircraft engine subsystems: combustion diagnostics, three-dimensional aerodynamic analysis of combustor flows and a transonic turbine cascade. In flight physics the research focused on the external aerodynamics of complex wing configurations (three-elements air-foil in high-lift) that are not yet reliably predicted by CFD simulations, especially in relation to the unsteady flow conditions and vortex-dominated phenomena. Proposed experimental approaches contributed to a significant step forward in determining such unsteady effects and possibly providing models to be later implemented in numerical prediction tools. It also impacted the objective of improving cost-efficiency (reduction of development costs, area 7.1.4.1), already demonstrated in the first part of the project where the improvement of experimental tools accelerated the design cycle and gave more rapid and extensive support to the improvement of the numerical cycle.
Technical Implications
More complete measurements of boundary layers, especially in adverse pressure gradient, wakes, tip and trailing vortices, will significantly improve the reliability of computer simulations by reducing the uncertainty, for instance, on turbulence closure models. The same considerations will apply for the development of aero-engines where the experimental approaches propose to combine flow analysis and thermal and chemical species mapping which are deemed fundamental towards the understanding of the combustion process. Lastly, the technologies that have been developed in AFDAR are necessary for the objective: Pioneering the air transport of the future (breakthroughs and emerging technologies, area 7.1.6.1) for aerodynamics (AAT.2010.6.1.1 Lift) and combustion (AAT.2010.6.1.2 Propulsion). Clearly any new technology based on new concepts, such as sustained unsteady flow regime (synthetic jets, active flow control, moving/morphing wings and wing elements) that at present cannot be simulated by computers, will require the support of detailed experimental observations with the techniques that have been proposed in the AFDAR project.
Strategy targets
The main impacts with regards to the work-programme are in relation to:
- 7.1.1 - The greening of air transport/flight physics and propulsion;
- 7.1.4 - Improving cost efficiency