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Extending the buffet envelope: step change in data quantity and quality of analysis

Lead Research Organisation: University of Southampton
Department Name: Faculty of Engineering & the Environment

Abstract

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
 
Description This project tackled the problem of airfoil and wing buffet - an unsteady phenomenon that limits the flight envelope of commercial aircraft. Better prediction of the flight envelope would enable more efficient wind design and pave the way for the application of flow control methods to extend the envelope, again with implications for fuel saving. The methodology of the project was wall-resolved large eddy simulation, a technique for solving the energy containing scales of turbulence. During the project an improved methodology was developed based on spectral estimation of errors, enabling more effective grid generation to resolve key features in the flow.

Simulations have been run, solving all relevant scales of motion of transonic buffet, considering two different angles of attack. Associated with this project we were successful in being awarded a PRACE project for additional supercomputer resources (at European Tier-0 level not available in UK). A report on this work for a non-technical audience can be found at https://www.gauss-centre.eu/results/computational-and-scientific-engineering/article/shock-related-buffeting-in-aeroplanes/

An improved understanding of the influence of the transitional state of the boundary layer on buffet has now been achieved, with results reported in a series of journal publications that have explored the different modes of unsteady behaviour and the influence of computational parameters. In 2021 a comprehensive parameter study was completed, showing the influence of angles of attach, Mach number and sweep on key flow features as well as a flow reconstruction based on spectral proper orthogonal decomposition (SPOD) that has been published. A particularly important finding has been that a phenomenon previous identified as laminar-buffet has been shown to be associated with a wake mode that can coexist with a lower-frequency true buffet mode. The latter has been shown to have the same physical mechanism as turbulent buffet, which clarifies the role of the boundary layer (laminar or turbulent) and paves the way for applications to laminar-flow (low drag) wings in the future.

A full study has been made of transitional versus tripped cases, with accompanying Reynolds-Averaged Navier-Stokes (RANS) calculation provided by our partners at the University of Liverpool. An important result has been that global stability analysis, resolvent model analysis and spectral proper orthogonal decomposition based on large-eddy simulation, all provide similar mode shapes for the buffet mode on aerofoils. In particular, this validates cheaper prediction methods based on global stability and precursor predictions based on resolvent analysis.

The research has continued beyond the end date of the original project. Recent work has proposed a connection between transonic buffet and unsteady stall without shock waves, which had important conceptual implications for modelling. Geometry effects (via a collaboration with JAXA) are being explored by a collaboration with JAXA.
Exploitation Route The insight gained is useful in the context of next-generation wings exploiting laminar flow technology. The improved simulation techniques can be used in large-eddy simulation of high-speed flows. The data from the simulation is useful for assessing the performance of engineering models.
Sectors Aerospace

Defence and Marine
URL https://www.gauss-centre.eu/results/computational-and-scientific-engineering/article/shock-related-buffeting-in-aeroplanes/
 
Description Videos arising from the simulations have been widely viewed, including a non-technical audience https://www.youtube.com/channel/UCOto08s_01VXuiV4vWEctNQ
First Year Of Impact 2019
Sector Aerospace, Defence and Marine
Impact Types Economic
 
Title OpenSBLI 
Description Open source code released in 2021 
Type Of Material Improvements to research infrastructure 
Year Produced 2021 
Provided To Others? Yes  
Impact Benchmark code for ARCHER2 procurement 
URL https://github.com/opensbli
 
Title Data supporting the article, "Transonic buffet characteristics under conditions of free and forced transition" published in the AIAA Journal, 2022 
Description This dataset supports the publication by Moise, P., Zauner, M., Sandham, N. D., Timme, S. & Wei, H "Transonic Buffet Characteristics Under Conditions of Free and Forced Transition", AIAA Journal, https://doi.org/10.2514/1.J062362. The data contains DataSets.zip, containing ".csv" (comma separated values, CSV) files in ASCII format. These CSV files correspond to several plots presented in the article, "Transonic Buffet Characteristics Under Conditions of Free and Forced Transition" published in the AIAA Journal, 2022. Plots with aerofoil geometry are not provided due to copyright reasons. All CSV files are named in a "fig[No][subfigure][description].csv" format (e.g. fig30d_X.csv refers to figure 30d in the article with X being the variable stored). The figures for which data is provided are: 3,6,7,8,11,12,13,18,A1,B1. A sample MATLAB script, sample Code.m is provided for plotting the data in the .csv files. Padeep Moise is an Assistant Professor, Department of Aerospace Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India (email pmoise@iitk.ac.in) 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
URL http://eprints.soton.ac.uk/id/eprint/471665
 
Description Collaboration with JAXA on test cases 
Organisation Japanese Aerospace Exploration Agency
Country Japan 
Sector Public 
PI Contribution We are conducting a code validation exercise for the Southampton and Jaxa codes for buffet test cases. Southampton are providing results using the in-house SBLI code.
Collaborator Contribution Jaxa are running their codes for these test cases.
Impact Lusher et al (Computer Physics Communications, 2025) is a joint paper arising from the collaboration.
Start Year 2022
 
Title Airfoil generation tool for OpenBuffet parametric airfoils 
Description This tool generates airfoil geometries for parametric studies of transonic buffet. Two files are generated, one for the design condition and one for an angle of attack of zero degrees. The GUI provides a design space, allowing different geometries to be compared. Details can be found in "Open-Source Parametric Airfoils to Study Geometric Effects on Buffet" presented at the AIAA Aviation Forum 2024, Las Vegas on 29 July -2 August 2024. 
Type Of Technology Software 
Year Produced 2024 
Open Source License? Yes  
Impact Enables non-proprietary airfoils to be use for buffet studies. 
URL https://zenodo.org/doi/10.5281/zenodo.12204411
 
Description Workshops 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The project final workshop was organised by Timme and Sandham at the University of Liverpool in September 2022. A second follow-up hybrid workshop was help in 2024 at JAXA in Tokyo with around 80 attendees (20 in person, inlcuding Boeing, NASA, JAXA, DLR, ONERA ) and 18 presentations.
Year(s) Of Engagement Activity 2022,2024