Dr Coull's research aims to improve the performance of aircraft engines by reducing fuel consumption, cost and generated emissions. This work includes investigations of fundamental fluid mechanics, but with a strong emphasis on improving design and design methods. This work focuses on the low and high pressure turbines, and is conducted in close collaboration with Rolls-Royce. The low pressure turbine research has focused on the problem of blade design, which is complex due to the unsteady, multi-mode transition processes in the blade surface boundary layers. Bringing together experimental, computational and analytical approaches, this work has improved both understanding of the design space and the underlying physics of the problem. Much of this work has helped to guide turbine design in Rolls-Royce and their partners. A clearance gap must be maintained to prevent contact between the rotating blade tips and the stationary casing. In the high-pressure turbine, hot gas leaking through this clearance gap reduces the turbine efficiency and burns away the tip. Dr Coull has focused on developing tip designs to mitigate these problems, and various successful strategies have been identified. In addition to his core research, Dr Coull has done significant collaboration in the development of MEMS flow sensors.