Aregawi Wondwosen A, Abera Metadel K, Fanta Solomon W, Verboven Pieter, Nicolai Bart
MeBioS, Department of Biosystems, University of Leuven, 3001 Heverlee, Belgium.
J Phys Condens Matter. 2014 Nov 19;26(46):464111. doi: 10.1088/0953-8984/26/46/464111. Epub 2014 Oct 27.
A two-dimensional multiscale water transport and mechanical model was developed to predict the water loss and deformation of apple tissue (Malus × domestica Borkh. cv. 'Jonagold') during dehydration. At the macroscopic level, a continuum approach was used to construct a coupled water transport and mechanical model. Water transport in the tissue was simulated using a phenomenological approach using Fick's second law of diffusion. Mechanical deformation due to shrinkage was based on a structural mechanics model consisting of two parts: Yeoh strain energy functions to account for non-linearity and Maxwell's rheological model of visco-elasticity. Apparent parameters of the macroscale model were computed from a microscale model. The latter accounted for water exchange between different microscopic structures of the tissue (intercellular space, the cell wall network and cytoplasm) using transport laws with the water potential as the driving force for water exchange between different compartments of tissue. The microscale deformation mechanics were computed using a model where the cells were represented as a closed thin walled structure. The predicted apparent water transport properties of apple cortex tissue from the microscale model showed good agreement with the experimentally measured values. Deviations between calculated and measured mechanical properties of apple tissue were observed at strains larger than 3%, and were attributed to differences in water transport behavior between the experimental compression tests and the simulated dehydration-deformation behavior. Tissue dehydration and deformation in the high relative humidity range ( > 97% RH) could, however, be accurately predicted by the multiscale model. The multiscale model helped to understand the dynamics of the dehydration process and the importance of the different microstructural compartments (intercellular space, cell wall, membrane and cytoplasm) for water transport and mechanical deformation.
建立了一个二维多尺度水分传输与力学模型，以预测苹果组织（苹果属× domestica Borkh. 品种‘乔纳金’）在脱水过程中的水分损失和变形。在宏观层面，采用连续介质方法构建了耦合的水分传输与力学模型。利用基于菲克第二扩散定律的唯象方法模拟组织中的水分传输。由于收缩引起的机械变形基于一个由两部分组成的结构力学模型：用于考虑非线性的Yeoh应变能函数和粘弹性的麦克斯韦流变模型。宏观模型的表观参数由微观模型计算得出。后者利用以水势作为组织不同隔室间水分交换驱动力的传输定律，考虑了组织不同微观结构（细胞间隙、细胞壁网络和细胞质）之间的水分交换。微观变形力学通过一个将细胞表示为封闭薄壁结构的模型进行计算。微观模型预测的苹果皮层组织表观水分传输特性与实验测量值显示出良好的一致性。在应变大于3%时，观察到苹果组织计算力学性能与测量力学性能之间存在偏差，这归因于实验压缩试验与模拟脱水变形行为之间水分传输行为的差异。然而，多尺度模型能够准确预测高相对湿度范围（> 97% RH）内的组织脱水和变形。多尺度模型有助于理解脱水过程的动力学以及不同微观结构隔室（细胞间隙、细胞壁、膜和细胞质）对水分传输和机械变形的重要性。
