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Teaser, summary, work performed and final results

Periodic Reporting for period 1 - U2FAST (Unsteadiness in High-Speed Strong Shock-Boundary Layer Interactions)

Teaser

The project aims to understand and control unsteadiness in hypersonic shock boundary layer interaction (SBLI) near leading edge resulting in leading edge separation of flow. This has direct relevance in performance of aircraft intakes as well as drag. As a result of the...

Summary

The project aims to understand and control unsteadiness in hypersonic shock boundary layer interaction (SBLI) near leading edge resulting in leading edge separation of flow. This has direct relevance in performance of aircraft intakes as well as drag. As a result of the reduced fuel consumption and aircraft noise, the vehicles can be more environmental friendly. The control of unsteadiness using Dielectric Barrier Discharge (DBD) plasma is explored.
The overall objectives are:
1) Make significant advances and novel contributions in the state of the art by providing new physical insight of the unsteady interactions, to rectify their adverse effects by employing plasma based control technique;
2) Gain the experience, knowledge, and credibility to establish the Fellow as a world class engineer and researcher.
The proposed study utilised wind tunnel experiments to obtain a complete spatio-temporal topology and the unsteady flow dynamics of shock induced leading edge separation, to identify the parameters affecting the phenomena and the mechanisms at play, and to implement plasma based flow control mechanism.
The research work which combined experimental and analytical techniques resulted in the identification, for the first time, of bifurcations in the unsteady flow dynamics of SBLI with leading edge separation.
This fellowship has provided Dr Sriram Rengarajan with support and training in all scientific and engineering aspects concerning the development, realization, characterization, analysis and control of SBLI with leading edge separation. This programme was supported by the excellent research environment provided by the host, Prof Kontis, University of Glasgow UK, with state-of-the-art facilities and training. This programme also benefited from the strong links between the host group and leading UK and international research groups.

Work performed

Task 1: Literature survey, design and manufacture of models for SBLI have been conducted. Test models consists of a flat plate on which one of the two compression ramps were mounted at a distance of 40 mm from the leading edge.
Task 2: Ludwieg tube tunnel experiments were conducted with the test models, with time resolved schlieren imaging and surface pressure measurements.
Task 3: Detailed time series analysis of the measurements were performed.
Task 4: Flow field induced by a novel DBD actuator configuration in quiescent air, and the flow control using the DBD actuator in cavity flow (having some analogous features with SBLI) simulated in University of National Wind Tunnel Facility are studied.
- Overview of research results:
1) Analysis and characterization of SBLI with leading edge separation: Overall, statistically steady flow was observed with the 45 degree angle compression corner; the low amplitude pressure fluctuation had Strouhal number of ~0.09 which was an order of magnitude higher than those reported in the literature for turbulent SBLI, and comparisons were done with cavity shear layer mode. With 90 degree angle compression corner (step), large amplitude to and fro motion of shock structure, similar to pulsation over spiked circular cylinders (the analogous axisymmetric case) was observed; though the flow with step is non-periodic unlike the pulsation over spiked circular cylinder. Overall, the analysis and characterization suggested bifurcations in unsteady SBLI as the parameters are varied
2) Flow control by DBD actuator: Time resolved planar particle image velocimetry investigations of the DBD flow control of low speed cavity flow demonstrated suppression of cavity oscillations. The present DBD generated flow speeds are not sufficient to control hypersonic flows. However, the control mechanism of the novel configuration at low speeds gives some valuable suggestions which can be extended to high speeds.
- Publications/presentations in high quality international open access journals, conferences and workshops are being pursued enthusiastically (3 journal papers have been written; 1 conferences were attended; 2 more journal articles are in preparation)
- Collaboration activities: Prof Jagadeesh (Indian Institute of Science, Bangalore, India) joined our research activities related to Ludwieg tube tunnel experiments.
- Industrial collaboration and engagement: We had meetings with Dr Michael West (BAE Systems) and Dr. David Evans (Fluid Gravity Engineering Ltd.) for a collaborative project on Future UK Small Payload Launcher (FSPL, June-December 2016; August-October 2017), and discussed with them regularly on the outcomes of the present project which are relevant to FSPL; Dr Sriram Rengarajan and Prof Konstantinos Kontis contributed to the construction of new facility since May 2017 for a space mission proposed by ESTEC/ESA. Dr Sriram Rengarajan and Prof Konstantinos Kontis initiated a project on automotive flow control using DBD in collaboration with Jaguar Land Rover (August 2017), which was inspired from the outcomes of the present project.
- Training: Dr Sriram Rengarajan has been actively engaging in the supervision of UoG and Ph.D. students; He has been in charge of the set-up of number of facilities and associated diagnostics and heavily involved in the running of the research group; He also engaged in teaching activities in the Aerospace program at UoG, as a tutor in two courses from January-April 2016; UoG provided him with early career development program (2016-2017): Ph.D. supervision and research collaboration engagement as well as laser safety training.

Final results

The unsteadiness in shock induced leading edge separation has been rigorously characterized for the first time with the identification of important bifurcations, which is the foremost scientific breakthrough of the project. The technological nature of research project has attracted the interest of industrial partners and academic collaborators. Three journal articles and a conference proceeding have been prepared during this research program. Currently, he is planning on submitting two more journal manuscripts. One of the objectives of this investigation was to identify further groups in society, which may benefit from the findings of this study. The automotive and energy sector industries (Jaguar Land Rover, ATKINS) and consultancies (Fluid Gravity Engineering Ltd) have been approached for employing the developed technologies.
Impact of the rigorous characterization of unsteady SBLI near leading edge and exploration of plasma based flow control is in 1) Control of engine intake flow field 2) Control of external shock structures 3) Manipulation of pressure and heat loads in flow fields over vehicle involving SBLI. The fellowship can thus have impact on faster, greener and more efficient civilian air transport as well as space missions.
The work on plasma flow control, although intended towards the control of SBLI, has also attracted the attention of automotive and energy industries. Inspired by the multidisciplinary nature of the research on plasma flow control, a new project has kick-started with Jaguar Land Rover, starting from August 2017, to investigate the reduction of automotive vehicle drag and greenhouse gas emission by means of unsteady plasma actuation. Dr. Sriram Rengarajan actively contributed to the project during his stay at University of Glasgow, and continues to collaborate in technical discussions. The outcomes can thus help in developing greener aerospace as well as automotive vehicles.

Website & more info

More info: https://www.gla.ac.uk/schools/engineering/research/divisions/aerospace/.