CAJ | 학술논문

针对植物木质部导管壁面增厚结构对流动阻力特性的影响问题，提出一种基于计算流体动力学（computational fluid dynamics，CFD）的植物导管流体建模方法。建立了导管内壁增厚结构的伯努利数学模型，分析导管内径、增厚纹宽、纹高、纹间距和倾斜角等几何结构与导管流阻系数之间的关系；基于剪切应力传输（shear stress transport，SST）k-ω湍流模型建立了螺纹与环纹导管流场仿真模型，对不同几何结构的增厚导管内部水分流动的流场进行了数值模拟。结果表明，导管内径，增厚纹间距和纹高等结构对流体阻力影响显著，增厚纹宽、倾斜角等结构的变化对流体阻力影响较小；壁面增厚结构对小导管的流动阻力影响更加明显，纹高为2.3μm时，在内径为16μm的导管中增厚结构产生的结构流阻占总流阻的57.0%，而内径50μm的导管中增厚结构流阻只占总流阻的27.2%；具有相同结构参数的环纹导管与螺纹导管的水分传输效率接近，且随着导管内径增大两者压降越来越接近（相差小于0.5%）。研究结果为深入研究植物导管水动力学传输特性提供理论依据。
침대식물목질부도관벽면증후결구대류동조력특성적영향문제，제출일충기우계산류체동역학（computational fluid dynamics，CFD）적식물도관류체건모방법。건립료도관내벽증후결구적백노리수학모형，분석도관내경、증후문관、문고、문간거화경사각등궤하결구여도관류조계수지간적관계；기우전절응력전수（shear stress transport，SST）k-ω단류모형건립료라문여배문도관류장방진모형，대불동궤하결구적증후도관내부수분류동적류장진행료수치모의。결과표명，도관내경，증후문간거화문고등결구대류체조력영향현저，증후문관、경사각등결구적변화대류체조력영향교소；벽면증후결구대소도관적류동조력영향경가명현，문고위2.3μm시，재내경위16μm적도관중증후결구산생적결구류조점총류조적57.0%，이내경50μm적도관중증후결구류조지점총류조적27.2%；구유상동결구삼수적배문도관여라문도관적수분전수효솔접근，차수착도관내경증대량자압강월래월접근（상차소우0.5%）。연구결과위심입연구식물도관수동역학전수특성제공이론의거。
Water transportation in plants has been an important issue in plant physiology and ecophysiology.Limited by experimental conditions, the flow patterns of water through xylem vessels, especially through the vessels with wall thickenings, is not easily perceived, and it is critical to understand the water transportation through plants. The aim of this study was to investigate the hydrodynamic properties and the detailed flow patterns occurring in xylem vessels with annular (helical) thickenings in order to obtain a functional interpretation of these structures. For this purpose, the flow of water through xylem vessels with wall thickenings was studied by adopting a computational fluid dynamics (CFD) approach here. For the computation approach, the Bernoulli mathematical model of the annular vessel was established based on the energy conservation law. According to the obtained mathematical model, the geometrical structures of vessel, such as the inner diameter of vessel, the distance between the thickenings, the height of thickenings, the width of thickenings and the inclination of thickenings, were the main factors that affected the vessel flow resistance. Numerical calculations based on shear stress transport (SST)k-ω turbulence model were implemented to simulate the flow in xylem vessels with various wall thickening structures. In the simulation experiments, we studied and analyzed various aspects, such as influences of inner diameter, distances among thickenings, heights and widths of thickenings, and inclinations of thickenings to the flow resistance coefficient. The results showed that the fluid resistances depended largely on vessel diameters, distances among the thickenings, and heights of thickenings. When other parameters were initialized, with the increase of vessel inner diameter, the average flow raised, while the pressure drop and flow resistance coefficient decreased, for instance, the flow resistance coefficients ranged from 21050.1 to 811.9. With the increase of the distance among thickenings, the average flow remained unchanged, while the pressure drop and flow resistance coefficient decreased, for instance, the flow resistance coefficients ranged from 10078.9 to 2369.9. With the increase of heights of thickenings, the average flow remained unchanged, while the pressure drop and flow resistance coefficient increased, for instance, the flow resistance coefficients ranged from 2032.6 to 20452.1. In contrast, the width and inclination of thickenings had little effect on the fluid resistance of vessel. It was noteworthy that the wall thickenings in small vessels contributed a large fraction of resistance to flow, whereas the wall thickenings in vessels with larger diameter contributed a relatively small fraction of resistance to flow. For example, the flow fraction of resistance generated by the thickenings was 57.0% in a vessel with an inner diameter of 16μm when given the thickening height of 2.3μm, while it was reduced to 27.2% in a vessel with an inner diameter of 50μm. Under the same condition of structural parameters, the flow resistance of annular vessels was closed to that of helical vessels, and the flow resistance difference between annular vessel and helical vessels was less than 0.5% with the increase of the vessel diameter. The results above suggested that it was appropriate for the proposed mathematical model to consider the structures with complex geometries, and it was suitable for the CFD model based on SSTk-ω turbulence model to simulate the flow through wall thickening structures in plant vessel, and to acquire the flow field parameters for which it was difficult to obtain by experiments. The proposed numerical simulation method provides a valid tool for further studies on the hydrodynamic characteristics of the plant vessels. Further studies on the properties of vessel structures are required in order to obtain detailed information about the interaction between wall thickenings and other functionally structures such as pits, and perforation plates.