Graduate School in Nonlinear Science

Sponsored by The Danish Research Agency

 
MIDIT                              OFD                          CATS
Modelling, Nonlinear Dynamics      Optics and Fluid Dynamics    Chaos and Turbulence Studies
and Irreversible Thermodynamics    Risø National Laboratory     Niels Bohr Institute and 
Technical University of Denmark    Building 128                 Department of Chemistry
Building 321                       P.O. Box 49                  University of Copenhagen 
DK-2800 Lyngby                     DK-4000 Roskilde             DK-2100 Copenhagen Ø
Denmark                            Denmark                      Denmark


LEAVES, FEATHERS, AND FLOWER STEMS:
TWISTING IN THE WIND WITHOUT BENDING VERY MUCH

by Steven Vogel
Duke University
Durham, North Carolina, USA


Thursday, November 1, 2001, 14.00 h
at Fluid Mechanics, Room 017, Building 403, DTU


Abstract: Low torsional stiffness is usually something to be avoided or offset in our structures, and insufficient levels have troubled some airplanes and buildings. Nature, though, goes in for less rigid structures than we humans build; and in her world solid and fluid mechanics don't stay obligingly distinct. She seems to build quite a variety of beams and columns deliberately designed to have low torsional stiffness relative to their flexural stiffness. For instance, low torsional stiffness permits insect wings and bird feathers to twist as needed to maintain appropriate angles of attack and permits leaves to minimize their drag in high winds by reconfiguring and clustering.