重新审视摩擦系数在颗粒坍塌中的作用：三维非光滑模拟与实验的对比
Revisiting the role of friction coefficients in granular collapses: confrontation of 3-D non-smooth simulations with experiments
AI总结：
本文通过三维非光滑连续颗粒模型与实验对比，证明将摩擦系数设为雪崩角可高保真再现颗粒坍塌，并重新验证了最终堆积形态的标度律，同时考察了侧壁摩擦影响并探讨了滞回模型扩展。
摘要：
本文对瞬态颗粒流进行了数值和实验研究。模拟采用 Daviet & Bertails-Descoubes (2016) 中引入的连续三维颗粒模型，该模型将颗粒介质表示为在稠密状态下受 Drucker-Prager 屈服准则约束的非弹性可膨胀连续体。该数值模型的一个显著特点是在没有任何正则化的情况下求解这种非光滑流变。我们表明，这一依赖恒定摩擦系数的非光滑模型能够高保真地再现倾斜可侵蚀床层上的各种实验性颗粒坍塌，前提是将摩擦系数设置为雪崩角，而不是通常所采用的停止角。为了更好地刻画完全塑性流变在瞬态摩擦流中的适用范围，我们进一步重新审视了将最终坍塌堆积体形状与初始柱体纵横比联系起来的标度律，并准确恢复了纵横比高达 10 量级的已建立的幂律依赖关系。随后，通过不同通道宽度下的实验和模拟坍塌，考察了侧壁摩擦的影响。有效流动厚度根据通道宽度进行估计，从而对先前关于其估计的假设提出了挑战。最后，我们讨论了用滞回模型扩展恒定系数模型的潜力，以改进对早期坍塌动力学的预测，说明了此类唯象学对瞬态流动的影响，并为更精细的分析铺平了道路。
英文摘要：
In this paper, transient granular flows are examined both numerically and experimentally. Simulations are performed using the continuous 3D granular model introduced in Daviet & Bertails-Descoubes (2016), which represents the granular medium as an inelastic and dilatable continuum subject to the Drucker-Prager yield criterion in the dense regime. One notable feature of this numerical model is to resolve such a non-smooth rheology without any regularisation. We show that this non-smooth model, which relies on a constant friction coefficient, is able to reproduce with high fidelity various experimental granular collapses over inclined erodible beds, provided the friction coefficient is set to the avalanche angle - and not to the stop angle, as generally done. In order to better characterise the range of validity of the fully plastic rheology in the context of transient frictional flows, we further revisit scaling laws relating the shape of the final collapse deposit to the initial column aspect ratio, and accurately recover established power-law dependences up to aspect ratios in the order of 10. The influence of sidewall friction is then examined through experimental and simulated collapses with varying channel widths. The effective flow thickness is estimated in relation to the channel width, thereby challenging previously held assumptions on its estimation. Finally, we discuss the potential extension of the constant coefficient model with a hysteretic model to refine predictions of early-stage collapse dynamics, illustrating the impact of such phenomenology on transient flows and paving the way to more elaborate analysis.
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