PhD supervision
Interested in supervising students studying:
- Active flow control for wind turbines
- Unsteady aerodynamics
- Drag reduction techniques.
Dr David Cleaver
MEng, PhD
Profile
Dr Cleaver is a lecturer in Aerospace Engineering in the Department of Mechanical Engineering.
David started studying for a MEng in Aerospace Engineering in 2003, before going onto start a PhD in the field of experimental unsteady aerodynamics in 2007.
On graduation he went on to continue in the same field as a post-doctoral researcher, and then was awarded a lectureship of computational engineering at the University of Bath in 2012.
Research
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.
Active 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.
Teaching units
- Advanced Helicopter Dynamics
Publications
Book Sections
Cleaver, D. J., 2012. Effect of airfoil shape on flow control by small-amplitude oscillations. In: 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. Reston, Va.: American Institute of Aeronautics and Astronautics.
Articles
Cleaver, D., Calderon, D. E., Wang, Z. and Gursul, I., 2013. Periodically plunging foil near a free surface. Experiments in Fluids, 54, 1491.
Cleaver, D., Wang, Z. and Gursul, I., 2013. Investigation of mechanisms of high lift for a flat-plate airfoil undergoing small-amplitude plunging oscillations. AIAA Journal, 51 (4), pp. 968-980.
Cleaver, D. J., 2012. Bifurcating flows of plunging airfoils at high Strouhal numbers. Journal of Fluid Mechanics, 708, pp. 349-376.
Cleaver, D. J., Wang, Z., Gursul, I. and Visbal, M. R., 2011. Lift enhancement by means of small-amplitude airfoil oscillations at low Reynolds numbers. AIAA Journal, 49 (9), pp. 2018-2033.
Conference or Workshop Items
Cleaver, D., Wang, Z. and Gursul, I., 2013. Oscillating Flexible Wings at Low Reynolds Numbers. In: 51st AIAA Aerospace Sciences Meeting, 2013-01-07 - 2013-01-10, Grapevine, Texas.
Cleaver, D. J., 2012. Rigid and Flexible Foils Oscillating Near a Free Surface. In: 50th AIAA Aerospace Sciences Meeting, 2012-01-06 - 2012-01-09, Nashville, Tennessee.
Cleaver, D. J., Wang, Z. and Gursul, I., 2010. Vortex mode bifurcation and lift force of a plunging airfoil at low reynolds numbers. In: 48th AIAA Aerospace Sciences Meeting, 2010-01-07 - 2010-01-10, Orlando, Florida.
Cleaver, D., Wang, Z. and Gursul, I., 2009. Lift enhancement on oscillating airfoils. In: 39th AIAA Fluid Dynamics Conference, 2009-06-22 - 2009-06-25, San Antonio, Texas.
Cleaver, D., Wang, Z. and Gursul, I., 2009. Delay of stall by small amplitude airfoil oscillation at low reynolds numbers. In: 47th AIAA Aerospace Sciences Meeting, 2009-01-05 - 2009-01-08, Orlando, Florida.
Thesis
Cleaver, D., 2011. Low Reynolds number flow control through small-amplitude high-frequency motion. Thesis (Doctor of Philosophy (PhD)). University of Bath.
