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The Stokes-flow parachute of the dandelion fruit

Presented by: 
Cathal Cummins University of Edinburgh
Monday 18th September 2017 - 14:10 to 14:30
INI Seminar Room 1
Cathal Cummins1, 2, 3 ,a)
Ignazio Maria Viola1, b)
Maddy Seale2,3,4
Daniele Certini1
Alice Macente2
Enrico Mastropaolo4
Naomi Nakayama2, 3, 5, c)

Institute for Energy Systems
School of Engineering
University of Edinburgh, EH9 3DW

Institute of Molecular Plant Sciences
School of Biological Sciences
University of Edinburgh, EH9 3BF

SynthSys Centre for Systems and Synthetic Biology
School of Biological Sciences
University of Edinburgh, EH9 3BF

Institute for Integrated Micro and Nano Systems
Scottish Microelectronics Centre
School of Engineering
University of Edinburgh, EH9 3FF

Centre for Science at Extreme Conditions
School of Biological Sciences
University of Edinburgh, EH9 3BF

a) Electronic mail: Cathal.Cummins[at][dot]uk
b) Electronic mail: I.M.Viola[at][dot]uk
c)Electronic mail: Naomi.Nakayama[at][dot]uk

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 gliding and autorotation. In this talk, I will focus on the aerodynamics of small plumed fruit (dandelions) 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, yet they are effectively impervious to the airflow as they descend. In addition, the fruit can become more or less streamlined depending on the environmental conditions. In this talk, I will present results from our numerical and physical modelling that demonstrate how these parachutes achieve such impermeability despite their high porosity. We explore the form and function of the filamentous building blocks of this parachute, which confer the fruit's incredible flight capacity. 
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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons