Effect of aeroelasticity on the aerodynamics of wheat

The objective of this study was to measure the aerodynamic forces on the grain-bearing spike of five varieties of wheat, chosen for varying wind tolerance. The green spikes were harvested at the dough stage and tested in a wind tunnel in laminar flows of up to 15 m/s at three orientations. There was a four-fold variation in drag between varieties, and some varieties showed a two-fold variation in drag according to orientation. Wind-induced deformation reduced the drag coefficient by up to 50% as airspeed was increased to 10 m/s, and the lift/drag ratio sometimes changed sign over this range. These aeroelastic effects increased aerodynamic stability and streamlining, and substantially reduced the drag force. Hence, it may be possible to increase the wind tolerance of wheat by increasing the flexibility of its spike. (C) 2000 Published by Elsevier Science S.A. All rights reserved.