Dr Cleaver is a lecturer in Aerospace Engineering in the Department of Mechanical Engineering.
David's research is within the field of unsteady aerodynamics. This is an exciting and novel research area which attempts to move beyond classic 'steady-state' aerodynamics so as to improve the efficiency of all forms of fluid dynamic device, from aircraft to gas turbines. In essence, all aero/ fluid dynamic problems are actually unsteady (variation with time) aerodynamic problems, but are usually assumed to be steady (constant with time).
This gap in understanding not only leads to inaccuracy but also lost opportunities. It is these lost opportunities that the unsteady aerodynamics community are trying to exploit through devices such as: plasma actuators, synthetic jet actuators, fluid-structure interactions, and so on.
Previously this research has focused on low Reynolds number oscillating rigid or plunging airfoils applicable to Micro Air Vehicles (MAVs). MAVs are small (<15cm) remote craft suited to search and rescue / reconnaissance applications, however currently there are no practical examples due to the challenges of low Reynolds number (small scale) aerodynamics.
This work took the example of natural flyers (birds / insects), but instead of using large-amplitude low frequency plunging motions it applied small-amplitude high-frequency motion which is more suited to electrical actuators.The results showed up to a 300 per cent increase in lift and thrust. In addition, the results elucidated several fundamental fluid dynamic phenomena such as new modes of vortex behaviour and wake bifurcations.
Currently the focus of David's work is on the application of unsteady aerodynamics to wind turbines. One of the major challenges facing wind turbine development is the large unsteady aerodynamic forces experienced by the blades in both their extreme-load and fatigue-load cases. mActive flow control presents a viable method of limiting these at the first point of contact, the fluid-structure interface, allowing operation at higher wind speeds with larger blades. In addition, appropriate actuation could also increase yields at low wind speeds expanding the performance envelope in all directions.