三维圆柱型颗粒堆坍塌问题的全相态数值模拟
NUMERICAL SIMULATION OF FULL PHASES OF COLLAPSE OF THREE-DIMENSIONAL CYLINDRICAL GRANULAR PILE
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摘要: 静态颗粒堆在重力作用下的坍塌问题, 是认识和理解许多人为过程和自然现象的基础. 采用传统方法进行模拟存在单颗粒追踪数量大、宏观模拟流变特性明显和相态演变复杂等计算难点. 本文从颗粒介质表现出不同相态的物理机理出发, 对全相态概念进行了定义并进行了区域划分. 根据颗粒介质的应力-应变关系及体积分数的不同, 通过确定不同相态之间的耦合关系和转化准则, 将描述各相态的现有理论有效结合起来, 建立了描述颗粒介质经历全部相态的耦合模型理论. 采用光滑离散颗粒流体动力学方法和离散单元法相耦合的策略, 对颗粒介质物理模型求解, 实现了对不同长径比下的三维圆柱型颗粒堆坍塌过程的数值模拟. 计算结果与实验结果吻合较好, 同时与离散单元法相比, 计算量得到了控制. 不仅捕捉到了不同参数影响下颗粒堆坍塌后沉积的不同现象, 同时获得了不同条件参数对颗粒堆坍塌后铺展特性的影响规律, 为揭示工业和自然界中广泛存在的颗粒介质复杂运动机理提供有效的支撑.Abstract: The collapse of static granular pile under gravity is the basis for understanding many human processes and natural phenomena. There are some difficulties for the traditional simulation methods, such as large number of single particle tracking, obvious rheological characteristics, and complex phase evolution of macro simulation. Based on the physical mechanism of different phases in granular media, the concept of full phases is defined and divided into three regions. According to the stress-strain relationship and volume fraction of granular media, the existing theories describing each phase are effectively combined by determining the coupling relationship and transformation criteria between different phases, and the coupling model theory describing all phase states of granular media is established. Then the physical model of granular media is solved with the strategy of coupling smoothed discrete particle hydrodynamics and discrete element method. The coupling and transformation algorithm between different phase particles is clarified and the particle size independence of the diameter selection of the initial SDPH particles is tested. The numerical simulation of collapse process of granular pile under different aspect ratio is realized. The calculated results are in good agreement with the experimental results. At the same time, compared with the discrete element method, the amount of calculation is controlled. It not only captures the different phenomena of deposition after granular pile collapse under the influence of different parameters, but also obtains the effects of different conditions and parameters on the spreading characteristics of granular pile after collapse are obtained, which provides effective support for revealing the complex motion mechanism of granular media widely existing in industry and nature.