HR: 0830h
AN: A31C-0039    [PDF]
TI: PIV Measurements of Atmospheric Turbulence and Pollen Dispersal Above a Corn Canopy
AU: * Zhu, W
EM: wzhu@titan.me.jhu.edu
AF: The Johns Hopkins University, Whiting School of Engineering, Dept. of Mechanical Engineering,, 3400 N. Charles Street, Baltimore, MD 21218 United States
AU: van Hout, R
EM: vanhout@pegasus.me.jhu.edu
AF: The Johns Hopkins University, Whiting School of Engineering, Dept. of Mechanical Engineering,, 3400 N. Charles Street, Baltimore, MD 21218 United States
AU: Luznik, L
EM: lluznik@titan.me.jhu.edu
AF: The Johns Hopkins University, Whiting School of Engineering, Dept. of Mechanical Engineering,, 3400 N. Charles Street, Baltimore, MD 21218 United States
AU: Katz, J
EM: katz@titan.me.jhu.edu
AF: The Johns Hopkins University, Whiting School of Engineering, Dept. of Mechanical Engineering,, 3400 N. Charles Street, Baltimore, MD 21218 United States
AB: Dispersal of pollen grains by wind and gravity (Anemophilous) is one of the oldest means of plant fertilization available in nature. Recently, the growth of genetically modified foods has raised questions on the range of pollen dispersal in order to limit cross-fertilization between organically grown and transgenic crops. The distance that a pollen grain can travel once released from the anther is determined, among others, by the aerodynamic parameters of the pollen and the characteristics of turbulence in the atmosphere in which it is released. Turbulence characteristics of the flow above a pollinating corn field were measured using Particle Image Velocimetry (PIV). The measurements were performed on the eastern shore of the Chesapeake Bay, in Maryland, during July 2003. Two PIV systems were used simultaneously, each with an overall sample area of 18x18 cm. The spacing between samples was about equal to the field of view. The PIV instrumentation, including CCD cameras, power supply and laser sheets forming optics were mounted on a measurement platform, consisting of a hydraulic telescopic arm that could be extended up to 10m. The whole system could be rotated in order to align it with the flow. The flow was seeded with smoke generated about 30m upstream of the sample areas. Measurements were carried out at several elevations, from just below canopy height up to 1m above canopy. The local meteorological conditions around the test site were monitored by other sensors including sonic anemometers, Rotorod pollen counters and temperature sensors. Each processed PIV image provides an instantaneous velocity distribution containing 64x64 vectors with a vector spacing of ~3mm. The pollen grains (~100mm) can be clearly distinguished from the smoke particles (~1mm) based on their size difference. The acquired PIV data enables calculation of the mean flow and turbulence characteristics including Reynolds stresses, spectra, turbulent kinetic energy and dissipation rate. Data analysis is currently in progress and results, focusing on the flow very near to the canopy will be presented. This research is funded by the National Science Foundation (NSF).
UR: http://pegasus.me.jhu.edu/~lefd/BioComp/FieldExperiment/FieldExperiment.htm
DE: 3307 Boundary layer processes
DE: 3322 Land/atmosphere interactions
DE: 3379 Turbulence
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting