As the traditional propellers are suffered from huge centrifugal force, cavitation and low agility, flapping wings/foils can be an alternate option to generate thrust. The flow fields of flapping wing/foils and traditional propellers are complex, and the traditional aerodynamic theories are not sufficient to explain the unsteady forces generation of flapping wings/foils.

In flapping wing flight, the performance is affected by a number of parameters, which include flapping mode (frequency, speed, amplitude and rotation), wing shape and wing structure, etc. To achieve high performance of flapping wing in forward flight, thorough studies on the flow phenomena are required.

Experiment setup

This experiment mainly uses the water channel owned by our laboratory to conduct the experiment. In the meantime, we do flow visualization with PIV system, and observe the correlation between the VIV phenomenon in the flow field and different experimental models.

The PIV system consists of three parts.

First is the particles with density that is similar to water distributed into the water channel. As the water moves, the whole flow field is filled with particles eventually.

The second part is setting up a 2 W green laser, and form a sheet laser which is made by irradiating the slit between two black lines to do the experiment.

The third part is using a high-speed camera to capture the reflective particles and conduct follow-up analysis.

1. Particles

▲ Stirring particles

2. Laser

3. High speed camera- FASTCAM Mini UX50

4. Force/moment transducer

▲ Force/moment transducer

Experiment results

In order to obtain the flow field around the flapping wing, we put the particles into the flow field and move with it, then use the laser to catch the particles, set double shutter camera to shoot synchronized, and finally process by the software to get the flow field.

Future works (application)

Through transducers and PIV technology, we can observe the flow field of the flapping wing, analyze the lift, thrust, and drag force, and then understand the flying mechanism of the flapping wing. It provides good data for the future flapping wing MAV which will be developed in the future.