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中国物理学会期刊

圆柱体在颗粒介质中上升时的阻力机制

Resistance mechanism of a cylinder ascending in granular media

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  • 为探究物体在颗粒介质中垂直提升过程中的阻力机制,针对以往实验研究多限于二维体系、且对完整阻力曲线的定量分析较为缺乏的问题,本文采用三维模拟与实验相结合的方法,对圆柱体从颗粒介质中垂直提升过程进行了数值模拟,获得了宏观阻力演变规律与微观颗粒尺度信息。研究发现,圆柱所受阻力呈现显著的三段式演化特征:在初始上升阶段,阻力迅速增加至峰值;随后急剧下降;最终进入缓慢减小并伴有平稳波动的阶段。微观分析表明,峰值后阻力的剧烈变化来源于颗粒体系发生大规模重排;而当提升至约22mm后,稳定剪切带的形成使上方颗粒构成持续承载结构,此时阻力波动主要由剪切带内的摩擦行为主导。通过对颗粒速度场、力链网络演化以及平均法向压力与等效剪切应力比值分布的系统分析,进一步明确了剪切带的空间位置以及颗粒由静态承载向流动状态转变的细观过程。在此基础上,建立了同时考虑圆柱侧面摩擦阻力与上方颗粒压力的定量力学模型,模型计算结果与模拟曲线吻合良好。本研究为颗粒介质中运动物体的阻力估算提供了简明的理论框架与定量方法,在土木工程与地质灾害防治等领域具有潜在应用价值。后续研究可进一步考虑颗粒材料特性、物体几何形态及提升速度动态变化等因素的影响。

    To investigate the resistance mechanism of an object during vertical upward movement in granular media, to address the limitations of previous experimental studies that were largely confined to two-dimensional systems and lacked comprehensive quantitative characterization of the complete resistance curve, this paper adopts a combined method of three-dimensional simulation and experiment to numerically simulate the vertical lifting process of a cylinder from granular media. The macroscopic evolution of resistance and microscopic grain-scale information are acquired. The results show that the resistance acting on the cylinder exhibits a distinct three-stage evolution: in the initial lifting stage, the resistance rises rapidly to a peak; subsequently, it decreases sharply; and finally, it enters a stage of slow decline accompanied by minor fluctuations. Microscopic analysis reveals that the sharp change after the peak stems fromlarge-scale granular rearrangement, whereas after lifting about 22 mm, the formation of a stable shear band enables the grains above to form a stable load-bearing structure that can sustain loads, with subsequent resistance fluctuations primarily dominated by frictional behavior within the shear band. Through systematic analysis of the grain velocity field, force chain network evolution, and the distribution of the ratio of average normal pressure to equivalent shear stress, the spatial location of the shear band and the mesoscale grain transition from a static bearing state to a flowing state are further elucidated. Based on these findings, a quantitative mechanical model that simultaneously considers the frictional resistance on the cylinder surface and the pressure from the overlying grains is developed. The calculated results are in good agreement with the simulation curves. This study provides a concise theoretical framework and quantitative method for estimating the resistance of objects moving in granular media, which holds potential application value in fields such as civil engineering and bio-inspired engineering. Future research could further explore the effects of granular material properties, object geometry, and dynamic lifting rates.

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