Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session A25: Biofluids: Plant Biomechanics |
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Chair: Kaare Jensen, Technical University of Denmark Room: 304 |
Sunday, November 22, 2015 8:00AM - 8:13AM |
A25.00001: Scaling of phloem structure and optimality of sugar transport in conifer needles Kaare H. Jensen, Henrik Ronellenfitsch, Johannes Liesche, N. Michele Holbrook, Alexander Schulz, Eleni Katifori The phloem vascular system facilitates transport of energy-rich sugar and signalling molecules in plants, thus permitting long-range communication within the organism and growth of non-photosynthesizing organs such as roots and fruits. The flow is driven by osmotic pressure, generated by differences in sugar concentration between distal parts of the plant. The phloem is an intricate distribution system, and many questions about its regulation and structural diversity remain unanswered. Here, we investigate the phloem structure in the simplest possible geometry: a linear leaf, found, for example, in the needles of conifer trees. We measure the phloem structure in four tree species representing a diverse set of habitats and needle sizes, from 1 cm (\emph{Picea omorika}) to 35 cm (\emph{Pinus palustris}). We show that the phloem shares common traits across these four species and find that the size of its conductive elements obeys a power law. We present a minimal model that accounts for these common traits and takes into account the transport strategy and natural constraints. This minimal model predicts a power law phloem distribution consistent with transport energy minimization, suggesting that energetics are more important than translocation speed at the leaf level. [Preview Abstract] |
Sunday, November 22, 2015 8:13AM - 8:26AM |
A25.00002: Biophysical analysis of water filtration phenomenon in the roots of halophytes Kiwoong Kim, Sang Joon Lee The water management systems of plants, such as water collection and water filtration have been optimized through a long history. In this point of view, new bio-inspired technologies can be developed by mimicking the nature's strategies for the survival of the fittest. In this study, the biophysical characteristics of water filtration process in the roots of halophytes are experimentally investigated in the plant hydrodynamic point of view. To understand the functional features of the halophytes 3D morphological structure of their roots are analyzed using advanced bioimaging techniques. The surface properties of the roots of halophytes are also examined Based on the quantitatively analyzed information, water filtration phenomenon in the roots is examined. Sodium treated mangroves are soaked in sodium acting fluorescent dye solution to trace sodium ions in the roots. In addition, \textit{in vitro }experiment is carried out by using the roots. As a result, the outermost layer of the roots filters out continuously most of sodium ions. This study on developing halophytes would be helpful for understanding the water filtration mechanism of the roots of halophytes and developing a new bio inspired desalination system. [Preview Abstract] |
Sunday, November 22, 2015 8:26AM - 8:39AM |
A25.00003: Fluid dynamics of two-dimensional pollination in Ruppia (widgeon grass) Naga Musunuri, Daniel Bunker, Susan Pell, Ian Fischer, Pushpendra Singh The aim of this work is to understand the physics underlying the mechanisms of two-dimensional aquatic pollen dispersal, known as hydrophily, that have evolved in several genera of aquatic plants, including Halodule, Halophila, Lepilaena, and Ruppia. We selected Ruppia, which grows in the wetlands of the New Jersey/New York metropolitan area, for this study. We observed two mechanisms by which the pollen released from male inflorescences of Ruppia maritime is adsorbed on a water surface: 1) inflorescences rise above the water surface and after they mature their pollen mass falls onto the surface as clumps and disperses as it comes in contact with the surface; 2) inflorescences remain below the surface and produce air bubbles which carry pollen mass to the surface where it disperses. In both cases dispersed pollen masses combined with others to form pollen rafts. The formation of porous pollen rafts increases the probability of pollination since the attractive capillary force on a pollen raft towards a stigma is much larger than on a single pollen grain. [Preview Abstract] |
Sunday, November 22, 2015 8:39AM - 8:52AM |
A25.00004: ABSTRACT WITHDRAWN |
Sunday, November 22, 2015 8:52AM - 9:05AM |
A25.00005: Scientific designs of pine seeds and pine cones for species conservation Kahye Song, Eunseop Yeom, Hyejeong Kim, Sang Joon Lee Reproduction and propagation of species are the most important missions of every living organism. For effective species propagation, pine cones fold their scales under wet condition to prevent seeds from short-distance dispersal. They open and release their embedded seeds on dry and windy days. In this study, the micro-/macro-scale structural characteristics of pine cones and pine seeds are studied using various imaging modalities. Since the scales of pine cones consist of dead cells, the folding motion is deeply related to structural changes. The scales of pine cones consist of three layers. Among them, bract scales are only involved in collecting water. This makes pine cones reduce the amount of water and minimize the time spent on structural changes. These systems also involve in drying and recovery of pine cones. In addition, pine cones and pine seeds have advantageous structures for long-distance dispersal and response to natural disaster. Owing to these structural features, pine seeds can be released safely and efficiently, and these types of structural advantages could be mimicked for practical applications. [Preview Abstract] |
Sunday, November 22, 2015 9:05AM - 9:18AM |
A25.00006: Switchable and Tunable Aerodynamic Drag on Cylinders Mark Guttag, Francisco Lopez Jimenez, Pedro Reis We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (\textit{Carnegiea gigantea}) which possesses an array of axial grooves, which are thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions. [Preview Abstract] |
Sunday, November 22, 2015 9:18AM - 9:31AM |
A25.00007: The effect of porosity and flexibility on the hydrodynamics behind a mangrove-like root model Amirkhosro Kazemi, Samantha Parry, Keith Van de Riet, Oscar Curet Mangroves play a prominent role in coastal areas in subtropics regions. Mangrove forests are of special interest to protect shorelines against storm surges, hurricane winds, sea-level rise and tsunamis. In addition, mangroves play a critical role in filtering water and providing habitat to different organisms. In this work we study the complex interaction of water flow and mangrove roots which were modeled with a circular array of cylinders with different spacing between them as well as different configurations. In addition, we modeled the flexibility of the roots by attaching rigid cylinders to torsional connectors. The models were tested in a water tunnel for a range of Reynolds number from 2200 to 12000. In a series of experiments we measured the drag force, instant and mean velocity behind the models. We also performed 2D flow visualization for the models in a flowing soap film setup. The results show that the minimum velocity of the wake is highly dependent on the porosity and flexibility of the roots. We observed that there is a small-scale turbulent region. This turbulence is recombined downstream in a larger vortex structure eventually forming a von Karman vortex street wake. We compare the results from rigid cylinder and the flexible counterpart. [Preview Abstract] |
Sunday, November 22, 2015 9:31AM - 9:44AM |
A25.00008: Optimal root arrangement of cereal crops Yeonsu Jung, Keunhwan Park, Ho-Young Kim The plant root absorbs water from the soil and supplies it to the rest part of the plant. It consists of a number of root fibers, through whose surfaces water uptake occurs. There is an intriguing observation that for most of cereal crops such as maize and wheat, the volume density of root in the soil declines exponentially as a function of depth. To understand this empirical finding, we construct a theoretical model of root water uptake, where mass transfer into root surface is modeled just as heat flux around a fin. Agreement between the theoretically predicted optimal root distribution in vertical direction and biological data supports the hypothesis that the plant root has evolved to achieve the optimal water uptake in competition with neighbors. This study has practical implication in the agricultural industry as well as optimal design of water transport networks in both micro- and macroscales. [Preview Abstract] |
Sunday, November 22, 2015 9:44AM - 9:57AM |
A25.00009: Moisture-driven actuators inspired by motility of plants Beomjune Shin, Minhee Lee, Ho-Young Kim We report design and fabrication of moisture-driven actuators mimicking pine cones, wild wheats and seeds of Erodium cicutarium, which can bend and even helically coil with variation of environmental humidity. The actuators adopt a bilayer configuration, one of whose layers is hygroscopically active while the other is inactive. In order to enhance the degree and speed of deformation which critically depends on moisture-responsivity of the active layer, nanofibers of hydrogel are directionally deposited on the inactive layer via electrospinning. As a result, several designs of soft robots are demonstrated which are capable of locomotion by harvesting environmental humidity energy. The dynamics of the robots are analyzed by coupling moisture diffusion kinetics and elastic theory of multi-layer bending. The theoretical predictions are compared with the experimental results, to lead to the optimal design to maximize the locomotion speed measured by travel distance normalized by body length per unit time. [Preview Abstract] |
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