The percolation properties and permeability of a group of anisotropic three-dimensional fracture networks are studied numerically. Finite-size scaling is used to extrapolate the percolation thresholds of infinite networks in three spatial directions, i.e., X , Y , and Z directions. The influence of the angular dispersion parameter of fracture orientations on percolation thresholds is analyzed. In this analysis, we considered a family of fractures in a three-dimensional space that are oriented around the Z axis based on the Fisher distribution. We revealed that increased anisotropy leads to decreased percolation thresholds in both X and Y directions, and in these two directions percolation thresholds in anisotropic networks demonstrate a declining trend as anisotropy goes up. However, in the Z direction the trend is the opposite. The fracture networks are triangulated via an advancing front technique and the macroscopic permeability of the networks is determined by solving the two-dimensional Darcy equation in each fracture. We found that the macroscopic permeability in the X and Y directions is higher than the associated permeability of isotropic fracture networks, and this property for anisotropic networks in the Z direction is lower compared with that of the isotropic case. Furthermore, as the anisotropy of networks increases the differences become more remarkable.
In this paper, for the aim of increasing the production rate of highly aligned nanofibers, electrocentrifuge spinning (ECS) technique was modified by equipping it with two nozzles as the spinneret. This new setup obviously doubles the production rate of nanofibers relative to the conventional ECS. To investigate the effect of this modification on the degree of nanofibers alignment (DeNA), the values of DeNA were measured for 30 distinctive experiments and the results were compared with that of ECS setup with a single nozzle. The originality of this work has lain in the fact that for these 30 experiments, which were designed by Design Expert Software (DES), the DeNA of the new ECS was the same as the conventional setup. Additionally, a spinneret with four nozzles was employed to evaluate the influence of number of nozzles on the DeNA. Lastly, the optimum values of voltage, polymer concentration, spinneret rotational speed and collector diameter were determined in order to maximize the DeNA of the modified ECS setup.
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