Colletti, Alex , Clemente, Matthew , Caden, Andrew , Anderson, Sean , Cheetham, Matthew , O’Connell, Dennis , Grega, Lisa , Thatcher, Scott L. , Osborn, Jeffrey M. .
Aerodynamic Characteristics of Saccate Pollen.
An experimental investigation was performed to examine the aerodynamic features of saccate pollen through measurement and comparison of drag coefficients. Sacci, or air-filled bladders, are common characters of pollen grains of many anemophilous gymnosperms. Previous studies of structurally different pollen types using electron microscopy and mathematical modeling have quantitatively demonstrated that sacci reduce the settling velocities of several saccate pollen types, thus increasing dispersal distance. This is due to the fact that sacci add significant volume, yet minimal mass, to the grains. Only when sacci add significant mass, due to thick walls and/or dense endoreticulations, did the pollen grain settling velocity increase. The current study further validates and refines the mathematical model by obtaining higher resolution drag coefficients for each pollen geometry, as well as addresses the effects of saccus size and pollen surface ornamentation on drag. To date, drag coefficients for pollen can only be estimated based on existing data for generalized oblate or prolate spheroids. Using empirically validated computational models of pollen grains, which were developed using structural characteristics of actual extant (Pinus, Falcatifolium, Dacrydium) and fossil (Pinus, Pteruchus, Caytonanthus, Gothania) bisaccate and monosaccate pollen, physical scaled-up models were created using a stereolithography-based three dimensional printer. These scale models were dropped in a glycerin-filled tank so that Reynolds numbers could be matched to their full-scale, actual pollen counterparts. The Reynolds number range studied thus far varied between 0.01 and 0.5. Based on detailed measurements of terminal velocities for the various 3D physical scaled-up models, drag coefficients were computed. Comparisons will be made among different pollen geometries, configurations (with or without sacci), and surface ornamentation patterns. The new experimental results will also be compared to drag data for commonly reported generalized geometries (spheres, spheroids) in order to assess the importance of actual shape on aerodynamic properties.
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1 - The College of New Jersey, School of Engineering, P.O. Box 7718, 2000 Pennington Road, Ewing, NJ, 08628-0718, USA
2 - Truman State University, Department of of Mathematics and Computer Science, 100 E. Normal Street, Kirksville, MO, 63501-4221, USA
3 - The College of New Jersey, School of Science, P.O. Box 7718, 2000 Pennington Road, Ewing, NJ, 08628-0718, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM