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QUIET AEROFOIL WITH ADAPTIVE POROUS SURFACES (QUADPORS)

Lead Research Organisation: Brunel University London
Department Name: Mechanical and Aerospace Engineering

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 Porous treatment on an aerofoil's trailing edge is a well-known method for reducing turbulent broadband noise. However, the porous trailing edges used in research thus far have been predominantly unstructured, geometrically complex, and non-repeatable from one sample to another. This lack of consistency makes it difficult to generalise their aeroacoustic performance, except when described in bulk terms such as flow resistivity.

In our EPSRC project (QUADPORS), my research team has developed a novel concept called SIMPLE (Selective Interference Mono-Porous Line Trailing Edge). Unlike conventional porous trailing edges, SIMPLE utilizes a single line of perforated holes to enforce an acoustic interference phenomenon, effectively canceling out sound waves and allowing for precise frequency tuning of noise reduction. Notably, this acoustic wave cancellation effect remains stable across different Reynolds numbers, making it highly attractive for wind turbine and aviation applications.

This breakthrough is unprecedented. To the best of our knowledge, this is the first time turbulent trailing edge noise has been significantly reduced through such a minimal intervention at the trailing edge. Additionally, SIMPLE introduces negligible aerodynamic penalties, which makes it particularly appealing to industry stakeholders.

Overcoming Challenges & Recent Progress:
Our next objective is to test the SIMPLE trailing edge under high-pressure loading conditions, specifically in cases where an angle of attack is present. However, this effort was unexpectedly disrupted due to the sudden closure of our laboratory in September 2023 following the RAAC (Reinforced Autoclaved Aerated Concrete) issue at Brunel University. The closure, which affected multiple buildings, was widely reported, including in BBC News (https://www.bbc.co.uk/news/education-66742626). Our lab remained inaccessible until April 2024, when the RAAC issue was resolved, and it was finally reopened.

Despite these challenges, progress on the project continued, thanks to the generosity of our academic partner, the University of Southampton, and our industrial partner, the German Aerospace Centre (DLR)/TU Cottbus, who provided access to their aeroacoustic wind tunnel facilities for experimental work.

During this period, we made another key discovery: applying porous treatments to both the leading edge and trailing edge can effectively reduce both impingement noise and self-noise, while still maintaining frequency tuning capabilities. This breakthrough represents a major advancement and was achieved since our last Researchfish submission in March 2024.

Intellectual Property & Future Plans:
The discovery of the SIMPLE concept and its enhanced performance in trailing edge self-noise reduction has prompted us to pursue intellectual property protection. We are currently working with IP specialists to file a patent application, ensuring that this innovative technology can be safeguarded and further developed for industrial adoption.
Exploitation Route The SIMPLE trailing edge described above can be easily adopted in industrial fan blade, such as wind turbine blades and home appliance (e.g. air condition).
Sectors Education

Energy

Environment

Manufacturing

including Industrial Biotechology
 
Description Industries such as wind energy have historically been skeptical about the use of porous materials in their turbine blades, primarily because these blades serve as lifting surfaces where aerodynamic efficiency is paramount. The general concern has been that introducing porosity could compromise structural integrity, reduce aerodynamic performance, or lead to unpredictable acoustic behavior. However, our pioneering work in this project has begun to shift this perspective. By developing a structured and miniature pore concept, we have demonstrated that carefully designed and engineered porosity can deliver significant noise reduction without compromising aerodynamic efficiency. The frequency fine-tuning capability of this approach allows for precise acoustic frequency control, making it adaptable to different operational conditions. Furthermore, our research has shown that this technology performs exceptionally well at high Reynolds number flows, which is crucial for its application in large-scale wind turbines. The success of this innovation has sparked growing interest within the wind turbine industry. Our collaboration with Vestas Wind Systems will eventually lead to large-scale validation, reinforcing the credibility of this approach. As more wind turbine manufacturers recognise and adopt this technology, it could redefine industry standards, leading to quieter and more efficient wind turbines. Beyond industry adoption, this advancement holds significant societal impact. One of the primary objections to wind farms, particularly in residential and rural communities, is noise pollution. The implementation of low-noise turbine blades could greatly improve public perception of wind energy, making it more socially acceptable and easier to integrate into both urban and rural landscapes. Reduced noise emissions would also minimise the impact on wildlife, particularly bird and bat populations, aligning with broader environmental and conservation goals. Looking ahead, continued research, field testing, and collaborations with industry leaders will be essential to further optimise the structured porous technology and accelerate its adoption. If widely implemented, this breakthrough could contribute to the global transition toward cleaner, more sustainable energy solutions, cementing wind power as a cornerstone of renewable energy infrastructure.
First Year Of Impact 2024
Sector Education,Energy,Environment
Impact Types Societal

Economic
 
Description New Generation of STE for Enhanced Reduction of Blade Noise
Amount £136,117 (GBP)
Organisation Vestas Wind Systems A/S 
Sector Private
Country Denmark
Start 09/2025 
End 03/2029
 
Description SIMPLE (Selective Interference Mono Porous Line trailing Edge)
Amount £45,500 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2024 
End 12/2025
 
Title Generation of deterministic turbulent flow to study aerodynamic noise mechanisms in spatial and temporal domains 
Description The use of bio-inspired serration technology to reduce aerofoil trailing edge noise is a well-known method. However, the underlying mechanisms are still not understood well. This is due to the difficulty in mapping the unsteady nature of turbulent flow in both time and space when passing over the serration surface. To achieve this, it is often required the use of high fidelity experimental and numerical tools, e.g. time-resolved particle image velocimetry or direct numerical simulation. These are very expensive and are not easily accessible. The novelty of this doctoral research is that a pseudo-turbulent flow can be generated in a controlled manner near the trailing edge serration surface, whilst the spatial and temporal developments can be traced and studied by low-fidelity experimental technique such as the hot wire and low frequency response PIV system. The technique allows a detailed study of the mechanism of serration technology in the reduction of trailing edge self-noise. The technique can also be extended to other flow/acoustic studies, such as the laminar instability noise where the passing of synthetic turbulent flow is used as a re-setting mechanism for the aeroacoustics feedback loop structure. It can also be used to study other self-noise scenarios when the aerofoil trailing edge is subjected to different flow control treatments, such as the porous structure, surface texture, or finlet, whose mechanisms are largely not understood very well at present. Similarly, deterministic turbulence in free flow can also be generated by the active turbulence grid method. Applying the same principle of spatio-temporal capturing of the hydrodynamic field and acoustic far-field, the proposed technique can be extended to the turbulence-leading edge interaction noise. This work is now completed with a successful outcome. Dissemination of the research output based on this technique can be found at "Juknevicius, A and Chong T.P., (2021) The formation of the aeroacoustics feedback loop for a laminar aerofoil, AIAA Aviation 2021, AIAA-2021-2261, doi: 10.2514/6.2021-2261", and "Chong T.P. and Juknevicius, A. (2022) Reconstruction of the deterministic turbulent boundary layer for the study of aerofoil self-noise mechanisms, Experiments in Fluids, 63, 139. doi: 10.1007/s00348-022-03486-7". 
Type Of Material Improvements to research infrastructure 
Year Produced 2021 
Provided To Others? Yes  
Impact The expected impact of this research method is that we can now use low fidelity experimental tool, which is easily available, to study complex flow/acoustic problems. I will implement this method in my recently awarded EPSRC grant "QUADPORS EP/V006886/1". 
URL https://link.springer.com/article/10.1007/s00348-022-03486-7
 
Title Statistical Modelling of Aerofoil Self-Noise Subjected to Structured Porous Trailing Edges 
Description Extensive research efforts in the aeroacoustics community have firmly established the benefits of porous trailing edges to achieve low-noise radiation. However, most studies of porous treatment are based on the use of very complex, open-cell structures to manipulate turbulent flow. Although this implementation has been shown to improve the aeroacoustics performance, the exact physical mechanisms that can be drawn from such a geometry are limited due to their complex topology. This contribution differs from the focus on rectilinear, structured permeable trailing edges. Using a Box-Behnken experimental design method, individual porous parameters can be isolated to allow an investigation on the interdependencies of these parameters on target values such as the overall sound power level, the Strouhal number of the maximum noise reduction and many other characteristics of the far field. Twenty-eight porous trailing edges were produced based on the initial experimental design. Each is unique with the combination of streamwise and spanwise separation distance between the pores, pore size and porous coverage. After various angles of attack and Reynolds numbers had been conducted in experiments, we show that many of these trailing edges can indeed achieve low-noise radiation, and acceptable prediction accuracies are obtained for all the response variables except the total sound power reduction, ?OAPWL, and the lower Strouhal limit of the noise reduction. Further efforts are currently investigated to include a wider range of these interdependencies of parameters to improve the empirical model for the prediction of trailing edge noise reduction by structured porous treatment. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
Impact This empirical model allows engineers to manipulate the pore geometries and optimise the trailing edge noise reduction. 
URL https://arc.aiaa.org/doi/abs/10.2514/6.2022-3092
 
Description Research collaboration with German Aerospace Center (DLR) 
Organisation German Aerospace Centre (DLR)
Country Germany 
Sector Public 
PI Contribution The main investigation in this collaborative activity with DLR relates to the applications of combined porous treatments at aerofoil's leading edge and trailing edge to study the simultaneous reduction of turbulence-leading edge interaction noise, and trailing edge self-noise. My research team manufactured the aerofoil model, and designed the experimental plan. We flew to TU Cottbus in Germany in February 2024 and had spent 2 weeks to conduct aeroacoustics experimental testing.
Collaborator Contribution In this collaboration, the DLR let us use their aeroacoustics wind tunnel facility and equipment at TU Cottbus free of charge and without any time restriction. They have also participated in numerous meetings with us to discuss the experimental plan and strategy, and analysis and interpretation of the acquired experimental data. They will also contribute in the preparation of journal articles and conference proceedings. We also anticipate that our research collaboration will continue in the future for other research topics.
Impact The results have been published in: Philip C. Woodhead, Tze Pei Chong, Phillip Joseph, Chaitanya Paruchuri, Sergi Palleja Cabre and Thomas F. Geyer. "Experimental Investigation of the Influence of Leading and Trailing Edge Porous on Aerodynamic Noise," AIAA 2024-3339. 30th AIAA/CEAS Aeroacoustics Conference (2024). June 2024.
Start Year 2024
 
Description Demonstration at University open day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Every year Brunel University will organise many open days in which I regularly involve in the presentations on research and teaching activities to the visitors. The open days in Brunel provide a good opportunity to inform the general public about the innovative research conducted in the area of aircraft noise reduction. I have the opportunity to demonstrate the plasma actuators that could be used for aircraft engine fan noise reduction, which generates interests among the visitors and encourages more students to engage in the STEM education.

Given the close proximity of Brunel University to Heathrow Airport and the noise-sensitive areas that are under the flight paths, my research on the plasma actuators (EP/K002309/1), serration technology (EP/N018737/1) and porous treatments (QUADPORS, EP/V006886/1) that aim to reduce fan noise radiated from the aircraft engine has a high potential to achieve significant social impact. This is because a lot of these visitors are from the local area who are genuinely concerned about the impact of the aviation noise and are interested to know more about the recent trend in the technological development. My EPSRC-funded research is well placed to demonstrate that the academic research community as well as the government are motivated to continuously develop the latest technology to address this important societal issue.
Year(s) Of Engagement Activity 2013,2014,2015,2016,2017,2018,2019,2023
 
Description Guest lecturer to University students at Technische Hochschule Nürnberg Georg Simon Ohm, Germany 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Undergraduate students
Results and Impact I was invited to Technische Hochschule Nürnberg Georg Simon Ohm, Germany, to deliver guest lectures to an audience of 50-60 undergraduate and postgraduate students on the topics of aircraft noise and wind turbine noise. The lectures generated lively discussions and insightful questions from the students.

A few months later, a professor from the university provided feedback, reporting a noticeable increase in student interest in aeroacoustics following the lectures. This positive response highlights the growing awareness and enthusiasm for the field, reinforcing the importance of continued engagement and knowledge-sharing in this area.
Year(s) Of Engagement Activity 2024
 
Description Interview for national news (ITV London) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Media (as a channel to the public)
Results and Impact Interviewed by an ITV journalist for ITV News London (18:00, 27/01/2025, ITV London, 30 mins) to provide expert insight on the environmental impact of the proposed Heathrow third runway.
Year(s) Of Engagement Activity 2025
URL https://learningonscreen.ac.uk/ondemand/index.php/prog/16F3C6EC?bcast=142476313
 
Description Outreach activities at the new "STEM Centre" at Brunel University 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact The new £5 millions "STEM Centre" at Brunel offers an opportunity in which my research students and myself will set up programme to get the general public and school students involved in scientific activities and inform them the innovative research conducted in the areas of aircraft and wind turbine noise reduction. We also set up simple experiments (e.g. plasma actuators for active control, and serration and porous treatment for the bio-inspired flow control) to encourage the school students to take part in the exercises. We always receive positive feedback from the school students as they find it fascinating that the unique bio-features from owl can be mimicked to the fan blade to achieve good aeroacoustic and aerodynamic performances. We also receive feedback from schools about the increased interest in the aeroacoustic field.
Year(s) Of Engagement Activity 2016,2017,2018,2019,2023
 
Description Seminars organised by Brunel Aerospace Research Centre 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact As the Co-Director for the Aerospace Research Centre, I actively establish and develop sustained academic and professional networks nationally and internationally which bring benefit to the University. I twice invited the Director of the German Aerospace Centre (DLR) for the Institute of Electrified Aero Engines, Professor Lars Enghart, to participate in person for the "Brunel Aerospace Research" seminar on 20 June 2022 and 15 November 2025. Other external participants include academics from TU Cottbus (Germany), and Bristol University. Internal invitations were sent to colleagues both within and outside the Aerospace Research Group, as well as academics from other departments. During the meeting, I disseminate major results of my three EPSRC projects (EP/K002309/1, EP/N018737/1 and EP/V006886/1). At the conclusion of this seminar, several avenues for research collaborations have been discussed and currently in development.
Year(s) Of Engagement Activity 2022
URL https://www.brunel.ac.uk/research/Centres/aerospace