The plasma synthetic jet actuator (PSJA) is a type of active flow control device. It is able to generate powerful jet at high repetition rate. The PSJA has promising control capability in high-speed flow applications, especially in alleviating the adverse effects of shock wave boundary layer interaction. Despite the significant improvements made so far, the PSJA still suffers problem such as the requirement of multiple high-voltage power units if a PSJA array is under use. Very recently, the novel voltage relay circuit (VRC) is proposed through the principal investigator (PI)'s collaborative project under the joint funding from the Royal Society and Natural Science Foundation of China. The new VRC concept allows multiple PSJAs to be driven through one single high-voltage power unit, which is a technological breakthrough leading to the practical application of PSJA.

The VRC-driven PSJA array is thus proposed as the flow control method to manipulate the transonic shock boundary layer interaction (TSWBLI), which underpins further improvement of the performances of aircraft and its propulsion system. In the UK, the Aerospace Technology Institute (ATI) explicitly includes 'pushing the shock buffeting boundary' as a strategically important target in the development plan for UK aerospace industries for the coming decade. The research outcome will thus contribute to the ATI target and help consolidate the leading position of UK aerospace industry.

The preliminary experiment carried by the PI and his collaborator reveals that the VRC-driven PSJA array is effective in shock modulation. Moreover, the transonic wind tunnel at City, University of London is being strengthened to experiment aerodynamic problems in the transonic regime through the support of National Wind Tunnel Facility. Therefore, funding is applied to implement the VRC-driven PSJA array into the control of TSWBLI. The research outcome is going to exert direct impact to the UK aerospace sector. Although the VRC-driven PSJA is used in the transonic flow in the present project, it is also readily useful in supersonic applications where shock wave boundary layer interaction dominates.

Potential Impact:
The aerospace industry is the powerhouse to UK economy. The present project focuses on mitigation of the adverse effects caused by transonic shock wave boundary layer interaction (TSWBLI) by means of plasma synthetic jet actuators (PSJAs). The control outcome will lead to aircraft wave drag reduction and eventually fuel saving. This project will further contribute to "delaying buffeting onset boundary", one of the targets proposed by the Aerospace Technology Institute, aiming at strengthening UK's leading position in the global aerospace industry. Apart from its importance to the aircraft, TSWBLI is also critical to the gas turbine, especially when high blade loading is adopted in the state-of-art compressor and turbine design. Therefore, the project will also impact the propulsion industry. Alleviation of TSWBLI on the aircraft and its propulsion system will improve their performances, such as a higher cruise speed and a better fuel efficiency. All these improvements will not only make the UK aerospace sector stronger and more competitive but also benefit the public, as people will arrive their destination quicker and live in an environment with less pollution.

The present project also has significant academic impacts. The PSJA array under use will be driven by the novel voltage relay circuit (VRC). The VRC breaks through the long-lasting driving unit issue in PSJA technology and allows driving PSJA array by one single power supply. The VRC technique matured through this project will impact the on-going research on PSJA technology. The VRC-driven PSJA array is experimented to control the TSWBLI in this project, it will also be used by researchers for other high-speed flow control applications, such as supersonic shock wave boundary layer interaction.

The proposed research is in the initial phase of the research roadmap (refer to Pathways to Impact), and it will establish a solid foundation for the later stage research. A consortium of several universities and industries will be formed throughout the roadmap. This consortium will be able to make a significant impact in the areas of PSJA and transonic aerodynamics with an emphasis of TSWBLI.

This project will use the transonic wind tunnel at City, part of the National Wind Tunnel Facility (NWTF). In return, the project outcome will showcase UK's excellence in aerodynamic research, which is the objective of NWTF project.

This project will impact the link between BAE Systems and City, University of London. BAE has established the BAE Systems Chair Professorship in the principal investigator (PI)'s department in 2015, and it is very supportive of this research. This project will strengthen the partnership between City and BAE on research, and accelerate the project impact.

The research will also impact UK-China collaboration in scientific research. This project takes full advantage of the PI's Royal Society-Natural Science Foundation of China project and receives support from the PI's project partner in Xi'an Jiaotong University. The success of this project will allow further in-depth collaboration between the PI and his partner in China. More importantly, it will support the governmental initiative in encouraging international research collaboration.

Finally, but not least, the present project under the support of EPSRC will build a world-leading research group in high-speed flow control with strong industrial support and international link.