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 aerofoil trailing edge is a well known method to achieve turbulent broadband noise reduction. However, almost exclusively all the porous trailing edges used thus far by the research community are unstructured, complex in geometry and non-repeatable from one sample to another. In other words, it is difficult to generalise the aeroacoustics performance of porous trailing edge unless when they are described in bulk terms (e.g. flow resistivity). In this EPSRC project (QUADPORS), my research team has developed what we call a SIMPLE --> Selective Interference Mono Porous Line trailing Edge, concept. Using only a single line of perforated holes, we can enforce an acoustic interference phenomenon to cancel out the sound waves, which gives us the capability to fine tune the noise reduction frequency. The acoustic wave cancellation capability does not fade with the Reynolds number, making this method attractive to wind turbine and aviation industries. This is unprecedented and to our best knowledge, the first time turbulent trailing edge noise can be reduced by such minimal intervention on the trailing edge. Moreover, there is very little aerodynamics penalties, which will be very attractive to industries.

The project is still ongoing, where the next phase is to test the SIMPLE trailing edge at large pressure loading condition. The results will be reported in next year's Researchfish submission.
Exploitation Route The SIMPLE trailing edge described above can be easily adopted in industrial fan blade, such as wind turbine blades, aircraft propellers and home appliance (e.g. air condition).
Sectors Aerospace, Defence and Marine,Education,Energy,Environment,Manufacturing, including Industrial Biotechology,Transport
 
Title Design of a low-noise anechoic wind tunnel 
Description In order to validate the effectiveness of the plasma actuator in the reduction of aerofoil self-noise, as per the EPSRC project (EP/K002309/1), it is necessary to perform the experiment in a very low-noise aeroacoustics wind tunnel that cannot be bought "off the shelf". On a tight schedule and budget, I have designed, project managed and characterised a very unique anechoic wind tunnel facility at Brunel University that has become one of the only two available in the UK's universities - the other one is situated at the Institute of Sound and Vibration Research (ISVR), University of Southampton. Brunel's anechoic wind tunnel has been shown to produce very low background noise and low turbulence free jet and it is extremely versatile. It can support projects other than this particular EPSRC project (EP/K002309/1). For example, this wind tunnel continues to support my other EPSRC projects such as the EP/N018737/1 (completed) and EP/V006886/1 (ongoing). 
Type Of Material Improvements to research infrastructure 
Year Produced 2015 
Provided To Others? Yes  
Impact The anechoic wind tunnel developed here consists of an open jet wind tunnel situated inside an anechoic chamber. Some of the aeroacoustic research groups in the UK, as well as from overseas, are recently developing their aeroacoustic wind tunnel facilities largely based on this model. 
 
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 Use of plasma actuators to generate various base-flow conditions 
Description A plasma actuator can be configured such that the travelling waves it generated can either enhance or deteriorate the flow. For all of the experiments carried out in the EP/K002309/1 project, the plasma actuators were optimised to the configurations such that they can suppress the wake vortex shedding and reduce the turbulence level of the boundary layer in order to produce a less-turbulent and steady flow. Measuring the flow separation noise is one of the main objectives for the current EP/N018737/1 project. To develop a "triggering" method for the boundary layer without subjecting it to large pressure loadings, we are developing a novel method to use the plasma actuator to produce an adverse flow (large scale boundary layer separation) in an otherwise laminar flow condition. This will enable us to study the leading edge and boundary layer separation noise without the need of extensive modification of the current wind tunnel facility. 
Type Of Material Improvements to research infrastructure 
Year Produced 2017 
Provided To Others? Yes  
Impact As stated in the "Collaborations and Partnerships" section, the limitation on performing aeroacoustic measurements on high angle of attack, and large pressure loadings for aerofoil by an open jet wind tunnel can be overcome by using the plasma actuator to generate a large scale boundary layer separation artificially. This advanced experimental technique would enable us to study and measure the flow separation noise - something that has hitherto not been investigated adequately in the research community due to limitation in the capability of the wind tunnel facility. 
 
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 Aerofoil Trailing Edge Self-Noise Prediction and Reduction for the Next-Generation Wind Turbines at VESTAS 
Organisation Vestas Wind Systems A/S
Country Denmark 
Sector Private 
PI Contribution This collaboration concerns a 3-year PhD research programme funded by Vestas Wind Systems (50%), and the other 50% is funded by the EPSRC DTP (Doctoral Training Partnership). This industrial collaboration runs almost in parallel with my EPSRC grant on the "Quiet Aerofoils of the Next Generation EP/N018737/1", and has two major aims. First is to encourage new serration technologies that are developed in the EPSRC project to be easily transferred to Vestas in order to improve the Technological Readiness Level (TRL). The second aim is to develop next generation hybrid technology to wind turbine blade. To achieve the above aims, the following objectives have been established for our research team at Brunel: (1) improvement of the understandings of the noise reduction mechanism by a serrated trailing edge under different loading conditions, (2) understanding of the sensitivities of the serrated trailing edge with flap angles in noise and aerodynamic performances, (3) appreciation of the effect of small changes in geometries parameters and aerofoil geometry, (4) development of the novel and innovative serration designs, (5) and most importantly, to combine the serration technology with another passive control device to form a hybrid device in order to harness extra benefits for noise reduction. Vestas is also one of our industrial collaborators for another EPSRC project EP/V006886/1 - Quiet Aerofoil with Adaptive Porous Surface (QUADPORS), which is still ongoing. In this project, we are developing the adaptive porous trailing edge for self-noise reduction. In this project, we have developed a new concept - "Selective Interference Mono-Porous Line trailing Edge - SIMPLE" which has frequency tuning capability, credential at high Reynolds number and minimal aerodynamic penalties. This concept has attracted attention from Vestas, who has expressed interest to fund further development of this concept after the QUADPORS project.
Collaborator Contribution Vestas supports the research programme by participating in bi-weekly review meeting, providing comments/feedbacks from the industrial perspective and facilitating on-field aeroacoustics tests of a real-size wind turbine in one of their test facility.
Impact The PhD student who worked in this project commenced at October 2017, and completed all the experiments in December 2020. The major contribution of this work is the development of a novel hybrid device that contains serration and surface treatment technology (Finlet) for a much improved aeroacoustics performance for aerofoil. This particular research output has been first disseminated in the "Schroeder, E., Chong, T. P., Kamruzzaman, M., Hurault, J., & Joseph, P. (2019). Aerofoil trailing edge self-noise reduction by Surface Mounted Attenuation Devices. In Proceedings of the International Congress on Acoustics Vol. 2019-September (pp. 5327-5334). doi:10.18154/RWTH-CONV-240018." Following this, we have uncovered a novel way to maximise the serration and Finlet to achieve an even greater level of noise reduction. Full results have been documented in the "Jung-Hoon Kim, Max M. Scholz, Tze Pei Chong, Phillip Joseph and Tomas Vronsky. (2022). Executing the Source-Radiation Targeting on Aerofoil Trailing Edge Noise by the Finlet-Serration. In Proceedings of the 28th AIAA/CEAS Aeroacoustics Conference, Southampton, UK. doi: 10.2514/6.2022-3104". It is expected that Vestas will absorb this technology to further improve its readiness level and eventually adapt it to their wind turbine to achieve noise reduction.
Start Year 2017
 
Description Research collaboration with Shandong University of Science and Technology, China 
Organisation Shandong University of Science and Technology
Country China 
Sector Academic/University 
PI Contribution a
Collaborator Contribution a
Impact a
Start Year 2019
 
Description Transfer of leading edge serration technology from the isolated aerofoil to ducted low-pressure industrial fan 
Organisation University of Applied Sciences Düsseldorf (HSD)
Country Germany 
Sector Academic/University 
PI Contribution Following the award of the EPSRC grant "Quiet Aerofoil of the Next Generation EP/N018737/1", it becomes apparent to me that it is necessary to be able to transfer the low-noise technology developed in the laboratory to the real-world industrial fan blades. The collaboration with Professor Frank Kameier and Dr Till Biedermann from University of Applied Sciences Duesseldorf, Germany, represents a good opportunity not only to improve the technological readiness level of our low-noise aerofoil technologies which are developed in-house, underpinned by advanced manufacturing techniques that have a real prospect to be adopted by industries, but also allows us to step into a niche area that has a large yield potential. My research team at Brunel is responsible for the acquisition and interpretation of the noise and flow data for an isolated, serrated-aerofoil. The understanding of the physical mechanism of noise sources and their suppression mechanisms by serration is then transferred to my partner in Germany so that the serrated-aerofoil can be further developed and implemented in the ducted low-pressure industrial fan. In 2019, I have been named as the visiting researcher for Dr Till Biedermann's successful grant application on the prestigious German Research Foundation, DFG, on the project to implement leading edge serration technology to industrial fan blades.
Collaborator Contribution Professor Frank Kameier and Dr Till Biedermann are both famous experts in the aerodynamic and aeroacoustics optimisation of industrial fan blades. Their expertise in this area greatly facilitates the transfer of superior aeroacoustics and aerodynamic performance parameters from an isolated aerofoil to ducted low-pressure industrial fan. They also let us to test our models in their ISO-standard aeroacoustics ducted fan rig for free.
Impact Dr Biedermann has successfully defended his PhD thesis, which is downloadable in https://depositonce.tu-berlin.de/handle/11303/10084 . The thesis is built upon the transfer of some of the 2D aerofoil results obtained in my EPSRC grant "Quiet Aerofoil of the Next Generation EP/N018737/1" to 3D propellers, which is conducted in the University of Applied Sciences Duesseldorf, Germany. This reflects the deep and fruitful collaboration between us. We have already published our results together in conference proceedings and journal article (see the Publication record in the personal portfolio). The collaboration for this work was interrupted between 2020 and 2022 due to the Covid. Considering that some of the restrictions (e.g. international travel, working in lab) begin to ease, the collaboration with University of Duesserdolf has slowly been re-commenced. Recently, we have been working together on the application of porous treatment to turbomachinery blades. The results will be published in the upcoming ASME Turbo Expo 2023, and the title of the paper is "Aeroacoustic Assessment of Porous Blade Treatment Applied to Centrifugal Fans". Professor Frank Kameier has been named as the research visitor to my upcoming EPSRC proposal on leading edge blowing for quiet aerofoil, where the submission date is expected to be before the end of March 2023.
Start Year 2016
 
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 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 Update on Aerospace Research activities at Brunel 
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 lead for the Aerospace Research Group, I actively establish and develop sustained academic and professional networks nationally and internationally which bring benefit to the University. I 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. Other external participants include academics from TU Cottbus (Germany), and Southern University of Science and Technology (China). 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