VALIANT - VALidation and Improvement of Airframe Noise prediction Tools
Overview
Background & policy context:
The overall noise radiated by modern aircraft has two sources: the engine and the airframe. The airframe noise has a broadband character and is mainly due to the interaction of the turbulent airflow with high lift devices (slats and flaps) and landing gears. And to a second extent to cavities, spoilers and boundary layers developing along the fuselage.
One of the major ACARE objectives was the reduction of perceived noise level of fixed-wing aircraft by 50% by 2020 compared to 2001. In achieving this, reduction of airframe noise is very important especially for large aircraft, as the development of quieter engines continues.
Objectives:
The focus of the project was on broadband noise generated by the turbulent flow around the airframe, as it is one of the most important components of aircraft generated acoustic nuisances. Its prediction and subsequent reduction was essential for achieving the ACARE2020 objectives of noise level reductions.
However, the complexity and diversity of broadband turbulent noise sources makes that prediction with present numerical tools extremely challenging and far from mature.
The objectives of the VALIANT project were to generate new experimental data and to validate and improve numerical tools for prediction of airframe noise generated from landing gears, slats, flaps and local separation regions.
Methodology:
The VALIANT project was an upstream research-oriented project, with the objective to tackle this challenge by generating new experimental data and validating and improving numerical tools for prediction of airframe noise generated from landing gears, slats, flaps and local separation regions.
Due to the extremely complex physical nature of the phenomenon and the high computational cost of computing full aircraft configurations on the one hand, and a lack of a reliable experimental database on the other hand, VALIANT focused on key generic test cases representing the major broadband airframe noise mechanisms associated with multiple body interactions: flow past two-struts (landing gear), flow past air foil with flap, flow past air foil with slat and turbulent flow past a gap. For all these configurations, the components of the noise prediction chain (for turbulent/source region, near- and far-field propagation domains) and their mutual interactions are evaluated and avenues of improvement developed.
It was expected that by validating and improving the predictive tools, a deeper insight into the mechanisms behind airframe noise would be obtained, which is an essential step towards new efficient airframe noise reduction concepts and their optimisation to achieve the required breakthrough towards quieter aircraft.
The consortium was formed by 12 European and Russian partners: 2 universities and 7 research establishments including the most important technology providers to the airframe industry, and 3 companies (2 SMEs) providing dedicated engineering services and software tools in aero acoustics to transport industries with emphasis on aeronautics.
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