INSPiRE project helps European aviation keep the noise down

In order to design aircraft of the future that are quieter it isn’t enough to only reduce the noise of the engines themselves. It's also essential to understand and reduce the noise that is generated due to the interaction of the engine and the surrounding aircraft structures, principally the wing and flaps. Clean Sky's INSPiRE project is boosting European aviation competitiveness by bringing new understanding to this very specific challenge, and equipped with this new knowledge, Europe's aircraft industry will be able to more effectively address the ACARE noise-reduction targets.

The diameters of aero-engines have become noticeably bigger – part of the effort towards more efficiency and leaner fuel-burn. But an unwanted consequence of this trend towards increasing fan diameters is leading to a strong increase in the interaction of noise caused by the jet's proximity to the wing and flap. Countermeasures have been limited due to a lack of understanding of the interaction mechanism, which could be delivered by high-fidelity turbulence-resolving simulations. However, the industrial exploitation of such simulation technologies is constrained by their high computational expense and the absence of sufficiently robust simulation processes for such complex configurations. The INSPiRE (Industrialisation of Jet Noise Prediction Methods) project addresses these challenges using turbulence-resolving approaches known as Detached-Eddy Simulations. 

Such simulations will be developed, implemented and validated for complex installed jet flows (including configurations with noise-reducing design features) within the INSPiRE project. Together with comprehensive best practice guidelines, the developments will make a significant contribution to improving confidence in simulation methods and to achieving industrial exploitation of turbulence-resolving approaches.
 

The project started in July 2016 and is scheduled to run until June 2019. Dr. Ing. Charles Mockett, Senior Research Consultant at CFD Software E+F GmbH, the Berlin-based company coordinating the INSPiRE project, says that "The high speed jets produced by aircraft engines are highly turbulent and generate significant levels of aircraft noise. Predicting and understanding such noise sources using computer simulations is key to designing lower noise aircraft, but such advanced simulations have so far mainly been possible only for simple configurations in academia. The INSPiRE project aims to deliver reliable and efficient jet noise simulation methods that can be applied for realistic problems directly by engineers in industry". 

"Significant reductions in aircraft noise are a stated goal for the European aviation industry. Although the larger-diameter modern aero engines are inherently quieter than their narrow predecessors, the fact that these need to be installed ever closer to the wing is giving rise to a strong new noise source from jet-wing interaction" says Dr. Mockett. "Being able to reduce this noise source will have a direct impact on quality of life for citizens residing near airports throughout Europe. Furthermore, the ability to design low-noise aircraft in a cost-effective manner (e.g. less expensive prototype tests) will improve the competitiveness of the European aviation industries".

The key objectives of the INSPiRE project, the consortium states, are:

  • To enable the simulation of higher frequencies at minimal additional computational overhead through the extension of an innovative meshing strategy
  • To improve the flexibility and reliability of far-field noise integration by pioneering the automatic detection of optimal FWH data surface placement
  • To define and validate procedures to automatically demarcate the initial transient and statistically-steady states of the solution and to define statistical error bars on flow and far- field noise quantities using innovative in-house algorithms
  • To achieve at least a 20% reduction of computational effort for jet noise simulations via accelerated initialisation techniques
  • To validate the enhanced DES/FWH process chain against a database of existing measurements including complex jet-flap configurations and low noise 3D nozzle design
  • To establish, document and verify best practice guidelines corresponding to the newly-developed methodologies, and
  • To ensure direct exploitation of the developed technologies by conducting validation simulations and implementing applicable improved methods in an industrial CFD solver

 

In terms of demonstrations and measurable results, Dr. Mockett reports that the industrialised simulation methods have first of all been tested for a simple round jet case, and that a demonstration of the robustness and performance of the methods for a realistic installed jet mounted on a full aircraft model is currently being carried out. 

"The project set a measurable objective to increase the efficiency of jet noise simulations by 20%. This has been significantly exceeded, with performance measurements from the simple jet case indicating over a factor 7 overall speedup compared to the simulation process used before INSPiRE" says Dr. Mockett. "This was achieved by optimising the settings used to advance the simulation of the unsteady flow in time and no loss of accuracy was incurred. Further improvements are less easy to quantify: The overall time spent by the engineer setting up and running the simulations has been strongly reduced through automation, which also reduces the potential for error".

"By the end of the project," says Mockett," I expect the improved simulation methods to be demonstrated for a complex and realistic configuration. This will pave the way for the simulation process to be integrated into the in-house design processes of an aero engine OEM, which will represent a significant step forward in the field".

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