The flight of the dandelion fruit

The fluid mechanical principles that allow a passenger jet to lift off the ground are not applicable to the flight of small plant fruit (the seed-bearing structure in flowering plants). The reason for this is scaling: human flight requires very large Reynolds numbers, while plant fruit have comparatively small Reynolds numbers. At this small scale, there are a variety of modes of flight available to fruit: from parachuting to gilding and autorotation. This presentation focuses on the aerodynamics of small plumed fruit that utilise the parachuting mode of flight.If a parachute-type fruit is picked up by the breeze, it can be carried over formidable distances. Incredibly, these parachutes are mostly empty space; making this an extremely efficient mode of transport. Moreover, the fruit can become more or less streamlined depending on the environmental conditions; in this way, they behave as a smart technology. In this presentation, some of the research that we are conducting to reveal the fruit's underlying flight mechanism, including dedicated wind tunnel tests, microfabrication, and direct numerical simulation will be discussed.