A full description of generalized drag in mixture mass flows
A full description of generalized drag in mixture mass flows
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DOI：
10.1016/j.enggeo.2019.105429
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发表时间：
2020-02
影响因子：
7.4
通讯作者：
S. Pudasaini
中科院分区：
文献类型：
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作者：
S. Pudasaini
阻力在粘性流体和固体颗粒组成的混合物流动中起着重要的作用。这种流动经常发生在环境和工程问题中。我们已经解析推导出一个增强的广义阻力，完全描述了任何固体体积分数的混合物质量流的阻力。这为动态演化的复杂阻力提供了完整的解析解和物理基础。以前的阻力公式受到限制，并产生奇异值的固体体积分数大。我们的新模型消除了现有模型继承的奇异性。分析模型显示出不同的行为为较大和较小的值的固体体积分数，并揭示了一个平滑的变化的阻力系数的固体体积分数的演变过程中的流动。密集的混合物中的颗粒，质量通量和材料参数，包括颗粒和流体密度，稀分布的特点，新的扩展模型，强烈地确定阻力曲线。与以前的模型相比，这些模型往往表现出奇异性，新的阻力函数的最重要的方面是，对于任何值的固体分数，它是足够光滑的。我们强调新的增强广义阻力模型的重要性，通过与现有的模型进行比较。一个惊人的新认识是，对于某些固体体积分数值，阻力取其最大值，然后在该特定值的两侧减小。根据从稀流到密流的不同，出现了两种根本不同的非对称阻力曲线族.我们已经解释了这些特殊的阻力行为背后的物理原理。与基准模拟，我们表明，新的增强阻力提供了一个很好的机会，更好的和完整的动态模拟范围广泛的混合物质量流。由于新的广义阻力揭示了许多基本的物理现象，这可以适用于适当地解决一些具有挑战性的环境和工程问题，涉及复杂的多相混合物质量流，包括滑坡和泥石流。
Drag plays an important role in the dynamics of mixture mass flows composed of viscous fluid and solid particles. Such flows often take place in environmental and engineering problems. We have analytically derived an enhanced generalized drag that completely describes the drag for any solid volume fraction in mixture mass flows. This provides a full analytical solution and physical basis for the dynamically evolving complex drag. Previous drag formulations were restricted, and produced singularities for large values of the solid volume fraction. Our new model removes singularity inherited by existing models. The analytical model shows different behavior for larger and smaller values of the solid volume fraction, and reveals a smooth variation of the drag coefficient as the solid volume fraction evolves during the flow. Dense to dilute distribution of particles in the mixture, mass flux and material parameters, including particle and fluid densities, characterize the new extended model that strongly determine the drag curve. In contrast to the previous models which tend to show singularity, the most important aspect of the new drag function is that, for any value of the solid fraction, it is sufficiently smooth. We highlight the importance of the new enhanced generalized drag model by comparing it with existing models. A strikingly new understanding is that for some values of the solid volume fraction, the drag takes its maximum, and then, decreases on either side of that particular value. Depending on the dilute to dense flows, two fundamentally different families of asymmetrical drag curves emerge. We have explained the physics behind these special behaviors of drag. With a benchmark simulation, we show that the new enhanced drag offers a great opportunity for the better and full dynamical simulation of a wide range of mixture mass flows. As the new generalized drag reveals many essential physical phenomena, this can be applied in appropriately solving some challenging environmental and engineering problems related to complex multi-phase mixture mass flows including landslide and debris flows.