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Investigation of influence of an obstacle on granular flows by virtue of a depth-integrated theory
European Journal of Mechanics - B/Fluids ( IF 2.6 ) Pub Date : 2020-07-02 , DOI: 10.1016/j.euromechflu.2020.06.014
Xiannan Meng , Yongqi Wang , Min-Ching Chiou , Yunlai Zhou

Understanding granular flows past an obstacle is very important to most possibly avoid damage to human properties and infrastructures. The present paper investigates the influence of an obstacle on dry and fluid-saturated granular flows to gain insights into physics behind them. To this end, we extend the existing depth-integrated theory by considering additional effects from the pore fluid pressure and the granular dilatancy. We revisit a large-scale experiment to validate the extended theory. The good agreement between numerical results and experimental data reveals that the granular dilatancy plays a crucial role in the mobility and peak depth. Furthermore, we investigate the influence of obstacles on dynamics of dry granular flows by comparing numerical results with experimental data. It is shown that shock waves, dead zones and vacuum (grain-free zone) well observed in the experiments can be captured. Additionally, a fluid-saturated granular flow past the same obstacle is numerically simulated to interpret the role of the interstitial fluid, especially the pore fluid pressure, in the fluid-granular mixture causing distinct dynamic behaviours from those of a dry granular flow. It is also found that the granular dilatancy has a significant influence on the pore fluid pressure which can mitigate the granular friction. This is consistent with many experimental observations. Additionally, it is demonstrated that the pore fluid pressure is prone to elevate in front of a cuboid dam (but not in front of a forward-facing tetrahedral wedge), which in turn mitigates the granular friction. The findings are helpful to understand complex behaviours encountered in geophysical flows and industrial processes.



中文翻译:

深度集成理论研究障碍物对颗粒流的影响

了解越过障碍的颗粒状流对于最有可能避免损害人类财产和基础设施非常重要。本文研究了障碍物对干燥和流体饱和的颗粒流的影响,以了解其背后的物理现象。为此,我们通过考虑孔隙流体压力和颗粒膨胀的附加影响,扩展了现有的深度积分理论。我们重新审视大型实验以验证扩展理论。数值结果和实验数据之间的良好一致性表明,颗粒膨胀率在迁移率和峰深度中起着至关重要的作用。此外,我们通过将数值结果与实验数据进行比较,研究了障碍物对干燥颗粒流动力学的影响。结果表明,冲击波 可以捕获在实验中观察到的死区和真空(无颗粒区)。另外,数值模拟了经过相同障碍物的饱和流体流,以解释间隙流体,特别是孔隙流体压力在流体-颗粒混合物中的作用,从而引起与干燥颗粒流不同的动态行为。还发现颗粒膨胀率对孔隙流体压力具有显着影响,其可以减轻颗粒摩擦。这与许多实验观察结果一致。另外,已经证明,在长方体坝的前面(而不是在向前的四面体楔形的前面),孔隙流体的压力容易升高,从而减轻了颗粒摩擦。

更新日期:2020-07-02
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