This study investigates the nonlinear behavior of flow passing through 28 crack topographies in concrete at various pressure gradients using water permeability test. Artificial cracks were generated and quantified by point-cloud matching technique. Results indicate Darcy's law becomes biased for calculating an apparent transmissivity of cracked concrete at a high Reynolds number. As an alternative, Forchheimer's parabolic equation is employed to model the flow rates at different pressure gradients, constructing an equivalent energy conversion model to calculate inertial and viscous pressure gradients and determine intrinsic transmissivity. A numerical model is proposed in which transport efficiency is represented as a function of dimensionless parameter of pressure gradient. The model is validated by experimental data and further used to explore the onset of nonlinear flow. It is observed that the flow exhibits a significant nonlinear behavior once the transport efficiency reaches 0.9305. This threshold is utilized to delimit the flow regimes and construct a Moody chart for permeability assessment of concrete in practice. It provides an effective way to characterize the behaviors of water flow in concrete and evaluate its transport properties.

中文翻译：

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通过透水性试验探索流过裂缝混凝土的非线性行为

本研究利用透水性测试研究了在不同压力梯度下流过混凝土中 28 个裂缝地形的水流的非线性行为。通过点云匹配技术生成并量化人工裂纹。结果表明，达西定律在计算高雷诺数下裂纹混凝土的表观透射率时会出现偏差。作为替代方案，采用 Forchheimer 抛物线方程对不同压力梯度下的流速进行建模，构建等效能量转换模型来计算惯性和粘性压力梯度并确定固有透射率。提出了一种数值模型，其中传输效率表示为压力梯度无量纲参数的函数。该模型通过实验数据进行验证，并进一步用于探索非线性流的发生。据观察，一旦传输效率达到 0.9305，流动就会表现出显着的非线性行为。该阈值用于界定流动状态并构建穆迪图以在实践中评估混凝土的渗透性。它提供了一种表征混凝土中水流行为并评估其传输特性的有效方法。