Taylor dispersion in osmotically driven laminar flows in phloem
Taylor dispersion in osmotically driven laminar flows in phloem
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DOI：
10.1017/jfm.2021.56
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发表时间：
2021-03-02
影响因子：
3.7
通讯作者：
Katul, G.
中科院分区：
文献类型：
--
作者：
Nakad, M.;Witelski, T.;Katul, G.
蔗糖是光合作用的主要产物之一，被认为是植物生长和生存所必需的。它产生于叶片的叶肉细胞，并通过韧皮部转移到植物的不同部位。在理解这一运输过程的进展仍然充满了实验困难，从而促进理论方法和实验室研究的兴趣。Munch压力和质量流模型是描述蔗糖在韧皮部中运输的物理学的公认假设之一。它基于渗透作用，在源和汇之间产生能量势能差。假定响应于该势能的流动为层流，并由哈根-普瓦勒方程描述。本研究重新审视了这种粘性驱动的流动与膜壁管包括泰勒色散对质量传输的影响。这一效应在韧皮部流动研究中被忽视。泰勒色散可以通过增加表观扩散系数来增加溶质的有效传输。结果表明，除了传统的扩散校正不渗透管壁，一个新的调整，平均平流项出现，因为渗透效应。由于蔗糖在水中的分子施密特数非常大，因此对于不同的Munch数范围，蔗糖的前沿速度和行进时间直接依赖于Peclet数。这项研究建立了上限预期泰勒分散增强蔗糖运输。
Sucrose is among the main products of photosynthesis that are deemed necessary for plant growth and survival. It is produced in the mesophyll cells of leaves and translocated to different parts of the plant through the phloem. Progress in understanding this transport process remains fraught with experimental difficulties, thereby prompting interest in theoretical approaches and laboratory studies. The Munch pressure and mass flow model is one of the accepted hypotheses describing the physics of sucrose transport in the phloem. It is based on osmosis creating an energy potential difference between the source and the sink. The flow responding to this energy potential is assumed laminar and described by the Hagen-Poiseuille equation. This study revisits such osmotically driven flows in tubes with membrane walls by including the effects of Taylor dispersion on mass transport. This effect has been overlooked in phloem flow studies. Taylor dispersion can increase the effective transport of solutes by increasing the apparent diffusion coefficient. It is shown that, in addition to the conventional diffusive correction derived for impermeable tube walls, a new adjustment to the mean advective terms arises because of osmotic effects. Because the molecular Schmidt number is very large for sucrose in water, the sucrose front speed and travel times have a direct dependence on the Peclet number for different ranges of the Munch number. This study establishes upper limits on expected Taylor dispersion enhancement of sucrose transport.