RECEPT

RECEPTivity and amplitude-based transition prediction

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 Obiettivo del progetto (Objective)

'The RECEPT project will deliver upstream aerodynamics research that will contribute (i) to the drive to strengthen the competitiveness of European manufacturing industry, (ii) to the need to improve the environmental impact of aircraft with regards to emissions.

Within the RECEPT project, knowledge about transition phenomena and theoretical/numerical tools obtained during the last 50 years since the eN method was proposed, are used to develop the next generation transition prediction methods. The new method will be an amplitude-based prediction method incorporating true effects of the disturbance environment of the incoming flow, the so called receptivity process, as well as knowledge about actual amplitudes at which disturbances breakdown to turbulence. This will largely remove the need for empirical correlations and render possible accurate prediction of the onset of transition both under wind tunnel and free-flight conditions.

Proposed research activities within RECEPT project will also contribute to design of more advanced transition control devices. Consequently, it will contribute to achieving the objectives for technology readiness to reduce fuel consumption and hence emissions. It directly addresses the topic of AAT.2010.1.1.1, AAT.2010.4.1.1 and AAT.2010.4.2.1.

The RECEPT consortium consists of 12 organisations from 4 different member states (Sweden, Italy, France Germany) and one of International Cooperation Partner Countries, Russia. It contains 3 aircraft manufacturers (Airbus, SAAB, Piaggio), 5 research organisations (CIRA, DLR, FOI, ITAM, ONERA) and 4 universities (Kungliga Teknika Högskolan, Università di Genova, Università di Salerno, Universität Stuttgart). Participation of industry will directly transfer the new knowledge and greatly improved method to the more applied work to be performed within the Joint Technology Initiative – Clean Sky.'

Introduzione (Teaser)

Understanding the origins of turbulent flow remains an important challenge in fluid mechanics. An EU-funded project is developing accurate computational tools that should increase capabilities for designing aircraft with natural laminar wings.

Descrizione progetto (Article)

Growth of unstable disturbances, like those developing on an aircraft wing, largely accounts for the transition to turbulence in boundary layers. The most frequently used transition-prediction method in aeronautics is the so-called eN method. The idea of this approach is that transition occurs when the amplitude of the perturbations has been amplified by a factor equal to eN. This is independent of the actual magnitude of the initial disturbances.

Using transition-prediction methods developed over the last 50 years, the initial linear amplification and the non-linear stage of growth of these perturbations can now be accurately estimated. However, accurate initial conditions for the amplified waves need to be provided to correctly predict the onset of transition.

The EU-funded project http://www.mech.kth.se/drupal7/recept/ (RECEPT) (Receptivity and amplitude-based transition prediction) is developing next-generation transition-prediction methods by adopting an amplitude-based method. Project work is eliminating the need for empirical relations, rendering possible accurate prediction of the onset of transition. This has direct impact on flight performance both under wind tunnel and, more importantly, free-flight conditions.

Project work has involved experiments to investigate the receptivity of 3D boundary layer flows to external vortical perturbations. These were performed in a quiet wind tunnel with controlled external perturbations and surface roughness quality. Numerical approaches served to replicate the physics approached experimentally. Methods and numerical tools with different complexity and approximation levels helped to address the problem. Direct numerical simulations of cross-flow transition on a swept wing provided specific detailed information.

Incorporating substantially more physics into the transition-prediction methods will generate a leap in performance and reliability. Project activities will thus result in more accurate and reliable tools for transition prediction.

Project activities are paving the way to design of more advanced laminar flow control devices. As a result, RECEPT will contribute to achieving objectives related to technology readiness, lowering fuel consumption and, hence, reduced harmful emissions.