| Water is an important component of plant cell, raw material of photosynthesis and respiration. It is also a media of physiological and biochemical reaction and material transport. To participate in these physiological and biochemical processes water transport from plant roots along the xylem channel to canopy, and water transport efficiency of plant xylem has a direct effect on the growth and development of plant. Therefore, water transportation in plants has been an important issue in plant physiology and ecophysiology.The research on the water transport in plants is mainly through the botanical anatomy and observation experiment. Because of the small size and complex structure of water conducting tissue in plants, the flow patterns of water in plant xylem, is not easily perceived by means of plant physiology. In this paper, the water transport in plant xylem was studied from the point of view of fluid mechanics. By means of fluid modeling, numerical simulation and experimental research, the rules of influences of tissue structure on flow resistance was achieved, flow field inside vessels and tracheids was analyzed. The work of this paper provides an important theoretical basis for the further study of the mechanism of water transport in plants.The main research contents of this dissertation are as follows:(1) Based on the structure characteristics and hydrodynamic characteristics of conducting tissue of xylem vessels and tracheids, on-way resistance and local resistance, the influence effects of flow performance of xylem vessels and tracheids, were analyzed. The effects of pipe diameter and cross section shape on the flow resistance characteristics of the vessel and tracheid were researched.(2) The aim of this study was to investigate the hydrodynamic properties and the detailed flow patterns occurring in xylem vessels and tracheids in order to obtain a functional interpretation of these structures. For this purpose, the Bernoulli mathematical model of the tissue structure of xylem such as wall thickening, perforation plate and pit was established based on the energy conservation law, the relationship between structural parameters and flow resistance coefficient was analyzed. The relationship between the resistance coefficient and by means of numerical simulation study of internal flow field, pressure drop, and structure were researched using numerical method.(3) With the aim to study the stress and deformation characteristics of border pit under the fluid-structure interaction, the flow field and membrane structure were cooperatively solved based on the bidirectional synchronization solving method. Dynamic characteristics of flow field in border pit, stress and deformation of the membrane were researched under different inlet pressures, and effect of fluid solid coupling(FSI) on pit flow was discussed.(4) According to the fluid similarity theory, we built a simulation test device for water transport in plant tissue. The model of the internal structure of the vessel and the tracheid is formed based on SLS(Selective Laser Sintering, a kind of rapid prototyping technology). The flow resistance characteristics of vessel(tracheid) wall thickness, perforation plate and pit are analyzed by test results, and the results are compared with the numerical simulation results. |
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