Current technology of smart actuators and compliant structures finally allows for conformable wings for application to micro air vehicles. High wing flexibility is critical to achieve high maneuverability and control of flow separation.

Nature is often the source of inspiration in these applications, as the extremely high energy effciency of natural fliers and swimmers is achieved with highly deformable surfaces. However, wing adaptation is obtained in part by a reduction of stiffness in the wing primary structures, and this may also have an big impact in the aeroelastic stability characteristics, which makes studying this problem particularly challenging.

We've just been awarded a research grant from EPSRC (together with the University of Southampton) to continue this work to incorporate integral actuation into the membranes for enhanced aerodynamic performance. Additional interest in this area include energy harvesting devices that exploit wind-induced vibrations of flexible structures with embedded electromechanical transducers.

Measured vorticity at AoA=20 for membrane with round (left) and rectangular (right) supports
Measured vorticity at AoA=20 for membrane with round (left) and rectangular (right) supports

Current projects

Aeromechanics of Actuated Membrane Wings (Buoso)

High-fidelity optimization of actuated membrane wings

Investigators: Ruben Sanchez, Rafael Palacios

Membrane wings offer the prospect of extraordinary performance characteristics for small air vehicles -- if we only knew how to actuate them as bats do. To address this, in this project we aim to explore the potential of embedded electromechanical systems on membrane wings to achieve on-demand aerodynamic performance. This will first the development of computational multiphysic models that capture the complex dynamic interactions between electric, elastic and fluid fields on highly-deforming geometries.  Our results show the potential for this technology to allow controllable outdoors flight of very small fixed-wing air vehicles.

Fig. 1 - Flow over flexible membrane wing
 Flow over flexible membrane, alfa = 12 deg, Re = 2500, prestretch = 1
Velocity contours over flexible latex membrane wing. Re = 2500, α = 12° 
Summary of the table's contents

Past projects

Aeromechanics of actuated membrane wings

Investigators: Dr Stefano Buoso (link to PhD thesis)

Membrane wings offer the prospect of extraordinary performance characteristics for small air vehicles -- if we only knew how to actuate them as bats do. To address this, in this project we aim to explore the potential of embedded electromechanical systems on membrane wings to achieve on-demand aerodynamic performance. This will first require the development of computational multiphysic models that capture the complex dynamic interactions between electric, elastic and fluid fields on highly-deforming geometries. Then, reduced-order models are built from which control systems can be derived. Our results have shown the potential for this technology to allow controllable outdoors flight of very small fixed-wing air vehicles.

Aeromechanical Performance of Compliant Aerofoils (2009-2013)

Main investigator: Sara Arbos (link to PhD thesis)

This project examined the dynamic response of membrane as well as composite-flexible aerofoils. Emphasis was on the effect of the geometry of leading and trailing edge supports, which are necessary to attach such very flexible wings on an actual vehicle. A variety of diagnostic methods including photogrammetry, unsteady lift and drag force measurements, wake measurements using hot-wire anemometry and Particle Image Velocimetry was utilised to isolate the cause and effect relationships of the dominant unsteady effects. The conjunction of hot-wire results with photogrammetry imagery of the membrane deformation indicates that the membrane vibration is coupled with the vortex shedding.

For low angles of attack the wake characteristics are highly affected by the leading- and trailing-edge geometry; as incidence increases the wake characteristics become less dependant on the support’s geometry, eventually reaching a point in which they are fully independent of it and closely resembling a fully stalled rigid aerofoil. The results of this study should provide valuable insight for future use of membrane wings in micro air vehicles