Flapping Wing Aerodynamics

Dragonfly

Insects can hover, move laterally or backward, even fly upside down. Their superior flying capability, together with the recent development in Micro-Electro-Mechanical Systems (MEMS) technology has inspired great interest in designing tiny aerial robots modelled after the insect. Industry, commerce and the military have all identified potential roles for such micro-air vehicles (MAVs), especially where human involvement is considered difficult or dangerous.

Our research project focuses on the unsteady aerodynamics of the flapping wings of insects using both experimental and computational tools developed at NUS.

Picture3 Flapping Wings  Picture4 

3D Flapping Wing Facilities

Two 3-D flapping mechanisms, namely hovering and forward flight, have been built for the projects.

Video 1: Hovering Flapping Mechanis

Video 2: Forward Flight Flapping Mechanism in a Wind Tunnel

Both the mechanisms incorporate compact force sensors for direct measurements of aerodynamic forces. They can generate any predetermined flapping motion such as fruitfly and hawkmoth insects hovering motion.

The purpose of the 2-D experiments is to conduct fundamental study on the unsteady flow of flapping wings in an isolated and simplified condition.

Two 2-D flapping mechanisms have been built, one for hovering and the second one for forward flight experiment.

Picture5 flapping

2-D flapping mecahnism for hovering in a rectangular tank: DPIV and force measurements

Picture6 flapping

2-D Flappping mechanism for forward flight in a re-circulating water tunnel: DPIV measurements

Some 2-D experimental Results

Video 3:Neutral wake pattern generated by a heaving elliptic airfoil in parallel freestream. (Re = 1,000, Stc = 0.5 and Sta = 0.16)

Video 4: Hovering wing. (Re = 1,326, a0 = 30° and A/c = 1.5)

Video 5: Flow structure generated by hovering Hawkmoth wings

The following shows the lift generatd by a hovering Hawkmoth wing over one cycle of flapping:

Picture7 Flapping

Numerical Study (SVD-GFD Scheme)

This computational scheme solves incompressible viscous flow problems with complex geometry and moving boundaries on a hybrid meshfree-Cartesian grid. Spatial discretization is carried out by a combination of standard finite difference and singular value decomposition generalised finite difference (SVD-GFD) approximations. Convecting nodes are treated by an arbitrary Lagrangian-Eulerian formulation of the Navier-Stokes equations.

Picture8 Flapping

The video on your left shows the unsteady flow around a flapping wing model, showing steamtraces and pressure distributions during a flapping cycle - plan view.

   Picture10

The picture on your right reflects the unsteady flow around a flapping wing model, showing stamtraces and pressure distributions during flapping cycle - side view towards body.

To view the webpage in PPT

Contact Person: T.T Lim & K.S. Yeo

Posted on 12th August 2009