Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session G32: Biological Fluid Dynamics: Plant Biomechanics |
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Chair: Kaare Hartvig Jensen, DTU Room: 614 |
Sunday, November 24, 2019 3:48PM - 4:01PM |
G32.00001: Leaf-to-leaf~spore dispersal of rust induced by rainsplash Hyunggon Park, Seungho Kim, Hope Gruszewski, David Schmale III, Sunghwan Jung, Jonathan Boreyko Rainsplash is an important dispersal mechanism for plant pathogens, but the underlying fluid dynamics are poorly understood. We studied how spore-laden satellite droplets, ejected from rainsplash on a diseased leaf, can subsequently stick to healthy leaves. This natural process was mimicked by rebounding microscopic droplets from an angled superhydrophobic substrate onto an adjacent wheat leaf that was horizontally oriented. The droplets either skipped along the wheat leaf or became stuck, depending upon the droplet's inertia, the orientation of the anisotropic leaf structure with respect to the droplet's path of motion, and whether the leaf was untreated or sprayed with a fungicide. A model successfully demarcated skipping versus sticking behavior by comparing the droplet's inertia against the surface energy required for dewetting to occur upon impact. [Preview Abstract] |
Sunday, November 24, 2019 4:01PM - 4:14PM |
G32.00002: A Finite Element Analysis of the Optimality of Sphagnum Moss Vortex Rings Guido Dominguez, Dwight Whitaker {\em Sphagnum} moss disperses its spores using a vortex ring generated by a pressurized capsule that ruptures on a warm sunny day. This mechanism of spore dispersal enables {\em Sphagnum} to carry its spores beyond the turbulent boundary layer where it grows so that they can be carried indefinitely by wind currents, which would not be possible if the tiny spores were launched ballistically. Here we present a finite element analysis of the explosive spore discharge from {\em Sphagnum} capsules using ANSYS Fluent. We model the spore capsule as a pressurized cylinder with a disk shaped cap that is pushed by the outflowing gas, which is taken to be axisymmetric. The cap impedes the flow of the fluid during as the vortex ring is created and makes this case qualitatively different than the slug flow from a piston-driven system without a cap. By matching the trajectories of vortex rings in our models to high speed videos of capsule explosions we can determine the initial pressure of the capsule. Moreover by analyzing the flow of vorticity out of the capsule we can determine how the cap affects the optimality of vortex ring impulse and compare {\em Sphagnum} vortex rings to the optimal vortex rings produced by animals. [Preview Abstract] |
Sunday, November 24, 2019 4:14PM - 4:27PM |
G32.00003: Wind-Induced Damage Propagation in a Branched Tree Forest. Oluwafemi Ojo, Kourosh Shoele During storms and hurricanes, many destructions occur in forests as a result of wind interaction with tree canopies. The extent of the damage depends on wind gusts and interaction between trees on one hand, and their collective effect on the flow on the other hand, which makes the prediction of the damage pattern of trees challenging. A key survival character of trees subjected to wind-induced stresses is their ability to reconfigure their shapes to reduce the drag forces on them. The survival of trees in these conditions depends on the tree flexibility, cross-sectional changes in the branching nodes, slenderness, and canopy effect. In this study, we investigate the flow interaction with a forest of fractal branched trees to predict the propagation of damage that occurs and investigate the resulting flow field in different storm conditions. Also, a tree breakage model is incorporated into our simulations to study the progressive damage propagation in each tree and in the forest. [Preview Abstract] |
Sunday, November 24, 2019 4:27PM - 4:40PM |
G32.00004: Hydraulic regulation of air spreading in vascular plants using wetted cellulose membranes JooYoung Park, Taesik Go, Jeongeun Ryu, Sang Joon Lee Plants transport water through xylem vessels using strong negative pressure. Thus, the transport system becomes vulnerable to cavitation. For stable water transport, xylem structures have been evolved. Xylem vessels are interconnected by pit membranes consisting of cellulose fibers that function as hydraulic valves to regulate two-phase flows. In this study, the hydraulic roles of pit membranes to prevent spreading of air throughout xylem vessels were investigated using a model system consisting of channels embedding cellulose membranes. We hypothesized that pit membranes normally remain to be wetted in xylem vessels. We noticed in particular the hydraulic role of water film on air bubble spreading that has been overlooked previously. We elucidated the correlation of dynamic characteristics of air flow and pressure variations with the membrane thickness. As a result, the air spreading exhibits two types of dynamics: continuous and discrete spreading. In addition, the thickness of pit membranes affects the behaviors of water film captured by cellulose fibers. Thus, it is a crucial criterion for the reversible gating of further spreading of cavitation throughout xylem networks of under drought condition. [Preview Abstract] |
Sunday, November 24, 2019 4:40PM - 4:53PM |
G32.00005: Superhydrophilic-superhydrophobic water harvester inspired by the wetting property of cactus stem Nami Ha, Hyejeong Kim, Sang Joon Lee Cacti can survive in extremely dry environment thanks to their unique water collecting ability. In addition to the spine which is one of the water collection systems, cactus stem actually plays an important role for harvesting and storing the absorbed water. In this study, the wetting property of cactus stem inspired us to develop a novel water harvester with a superhydrophobic-superhydrophilic double structure. Since the cactus stem is comprised of superhydrophobic cuticular surface and superhydrophilic mucilage cells, it can effectively absorb water and reduce evaporation of the absorbed water. In addition, mucilage cells can release the absorbed water to photosynthetic cells under drought stress. Moreover, a mature stem has microcracks on its surface, which enable for water to be rapidly absorbed into the mucilage cells. Inspired by these characteristics of cactus stem, the biomimetic water harvester has two distinct functions; effective water-absorption with directional water transport and on-demand water-releasing function. The developed water harvester would be utilized for developing an effective 3D plant-inspired water collector. [Preview Abstract] |
Sunday, November 24, 2019 4:53PM - 5:06PM |
G32.00006: Controlling intercellular flow through mechanosensitive plasmodesmata nanopores Kaare H. Jensen, Jan Knoblauch, Karl Oparka, Keunhwan Park In plants, plasmodesmata (PD) are nanopores that serve as channels for molecular cell-to-cell transport. Precise control of PD permeability is essential to regulate nutrient transport; moreover, it is involved in growth, tissue patterning, and defense against pathogens. Callose deposition modulates PD transport but little is known of the rapid events that lead to PD closure in response to tissue damage or osmotic shock. We propose a new mechanism of PD closure as a result of mechanosensing. Pressure forces cause the cell wall, or the dumbbell-shaped ER-desmotubule-complex, to be displaced from the equilibrium position, thus closing the PD aperture. Cell wall elasticity and the filamentous protein tethers that link the plasma membrane to the ER complex play a key role in determining the selectivity of the PD pore. This model of PD control compares favorably with experimental data on the pressure-generated closure of PD. [Preview Abstract] |
Sunday, November 24, 2019 5:06PM - 5:19PM |
G32.00007: Taylor Dispersion in Osmotically Driven Laminar Flows Mazen Nakad, Jean-Christophe Domec, Thomas P. Witelski, Gabriel Katul Sucrose is among the main products of photosynthesis that are deemed necessary for plant growth and survival. It is produced in the mesophyll cells and translocated under positive pressure to different parts of the plant through a hydraulic network (phloem). Progress in understanding this transport mechanism remains fraught with experimental difficulties thereby prompting interest in theoretical approaches and laboratory studies. The Munch's pressure flow model is considered one of the most commonly accepted hypotheses for describing the physics of sucrose transport in such systems. It is based on osmosis to build an energy potential difference between the source (leaf) and the sink (root). The flow responding to this energy potential is assumed laminar and described by the Hagen-Poiseulle equation. The work here will revisit such osmotically driven flow in tubes by including the effects of Taylor dispersion (TD) on mass transport. It is demonstrated that the time scale for sucrose transport is reduced when adding TD for low Munch number (defined by the ratio of axial to membrane resistance) whereas its effect will decrease for high Munch number. Comparisons with published laboratory experiments suggest that the inclusion of TD improves the prediction of sucrose transport speed. [Preview Abstract] |
Sunday, November 24, 2019 5:19PM - 5:32PM |
G32.00008: Oil-water separation using synthetic trees Viverjita Umashankar, Arun Kota, Jonathan Boreyko In the world's tallest trees, water evaporating from leaves generates enough suction to lift water over 100 m high. Transpiration can similarly be attained in synthetic trees by coupling nanoporous ``leaves'' with conduits mimicking xylem capillaries. Here, we demonstrate that by adding filters to the free ends of the xylem conduits, the hydraulic load generated by transpiration can be used for oil-water separation. Our synthetic tree was comprised of a vertical array of glass tubes of millimetric diameter, whose upper ends were embedded within a nanoporous ceramic disk and whose lower ends were attached to pre-wet cellulose acetate membranes supported by stainless-steel meshes. After saturating the synthetic tree with degassed water, its synthetic roots (filters) were submerged in a reservoir containing a hexadecane-in-water emulsion. The separation efficiency of liquid entering into the tree was quantified by density and contact angle measurements of permeate extracted from the glass tubes. [Preview Abstract] |
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