The tortuosity of porous solids has been widely used as a basic concept in understanding the fluid flow capacity of these media. Starting from a geometric expression of the tortuosity, different relationships have been developed over time to estimate it from different perspectives as hydraulic, electrical, and molecular diffusion, making necessary an exhaustive analysis of these developments. In this study, evidences for the lack of the true hydrodynamic sense of the conventional expression of tortuosity are shown. As a first sign of its failures, the disparity of results between the different relationships of tortuosity–porosity derived from this conventional expression is shown. Next, the presentation of several examples directly shows that the value obtained with that conventional expression is the same in cases where the actual tortuosity is obviously different. Likewise, a routine physical analysis of the flow in this study shows that the use of the capillary analogue is erroneous for one-dimensional flow analyses. Another inconsistency has been encountered in the widely used equality between the volumetric porosity and the product of free cross-sectional area by the length representing the path of the fluid through the pores. The last key showing the deficiencies of these estimations of the tortuosity is the constraint of the use of constant section ducts in the electrical analogy. As a new expression of tortuosity, an alternative ratio is proposed which can be included in known hydraulic and electrical relationships, in the same way than the conventional tortuosity. This tortuosity ratio constitutes a rethinking of the knowledge and understanding of flow in granular porous media.

多孔固体的曲折度已被广泛用作理解这些介质的流体通过能力的基本概念。从曲折的几何表达开始，随着时间的推移，已经发展出不同的关系，以便从不同的角度对曲折进行估算，例如水力，电和分子扩散，因此有必要对这些发展进行详尽的分析。在这项研究中，显示出缺乏曲折传统表达的真实流体动力意义的证据。作为其失败的第一个迹象，显示了从该常规表达式得出的曲折-孔隙度的不同关系之间的结果差异。下一个，几个例子的表述直接表明，在实际曲折度明显不同的情况下，使用传统表达式获得的值是相同的。同样，在这项研究中，对流动的常规物理分析表明，对于一维流动分析，毛细管类似物的使用是错误的。在广泛使用的体积孔隙率与自由截面积乘以代表流体通过孔的路径的长度的乘积之间的相等性方面，还遇到了另一个矛盾之处。显示曲折度这些估计的缺陷的最后一个关键是在电气类比中使用恒定截面管道的约束。作为曲折性的一种新表达，提出了一种可替代的比率，该比率可以包含在已知的水力和电气关系中，以与传统曲折相同的方式。该曲折率构成了对粒状多孔介质中流动的知识和理解的重新思考。