Shock waves in rapid flows of dense granular materials: theoretical predictions and experimental results.
Shock waves in rapid flows of dense granular materials: theoretical predictions and experimental results.
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DOI：
10.1103/physreve.78.041308
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发表时间：
2008-10
期刊：
影响因子：
--
通讯作者：
S. Pudasaini;C. Kröner
中科院分区：
文献类型：
--
作者：
S. Pudasaini;C. Kröner
对快速稠密颗粒流中的强激波进行了理论研究和详细分析，并与基准实验数据进行了比较。实验数据包括干颗粒流从筒仓连续释放后的粒子图像测速仪测量。沿着溜槽快速移动的材料撞击在竖立在长而陡峭的通道末端的障碍壁上。撞击导致流动状态发生突变，从快速移动的超临界薄层转变为厚度可变的停滞厚堆。这种流动结构特别有趣，因为它类似于一些水力和空气动力学的情况。我们给出了关于深度和速度演化的结果，并将它们与包含各向异性压力条件的摩擦颗粒流方程的理论预测进行了比较。这些流动方程通过实施高分辨率无振荡中心差分总变差递减格式来积分。我们将详细讨论流动的动力学和几何效应。包括超临界和亚临界流动的几何演化和沉积，冲击速度、冲击速度、位置和演化，数值限制器的选择，以及摩擦角对动力学和沉积的影响。理论预测和实验观测之间的良好一致性将被证明。这些结果可用于估计雪崩对航道沿线和冲突区防御结构或基础设施施加的冲击压力，并可用于研究障碍物周围的复杂流动动力学和质量突然停止时的沉积。重要的是，当颗粒流中发生强激波时，这些结果可以为数值模拟的校准提供基础。
Strong shocks in rapid dense granular flows are studied theoretically and analyzed in detail to compare with benchmark experimental data. The experimental data includes particle image velocimetry measurements of dry granular flow following its continuous release from a silo. The rapidly moving material down the chute impinges on an obstruction wall erected perpendicular at the end of a long and steep channel. Impact leads to a sudden change in the flow regime from a fast moving supercritical thin layer to a stagnant thick heap with variable thickness. This flow configuration is particularly interesting because it is analogous to some hydraulic and aerodynamic situations. We present results about the depth and the velocity evolution and their comparisons with theoretical predictions associated with frictional granular flow equations incorporating anisotropic pressure conditions. These flow equations are integrated by implementing high-resolution nonoscillatory central differencing total variation diminishing schemes. The dynamical and geometrical effects of the flow will be discussed in detail. These include geometry evolution and depositions at supercritical and subcritical flows, the impact velocity, shock speed, its position and evolution, choice of numerical limiters, and the influence of friction angles on the dynamics and depositions. An excellent agreement between theoretical predictions and experimental observations will be demonstrated. These results can be applied to estimate impact pressures exerted by avalanches on defense structures or infrastructure along the channel and in the run-out zones, and to study the complex flow dynamics around the obstacles and in depositions when the mass comes suddenly to a standstill. Importantly, these results can form a basis for calibration of numerical simulations when strong shocks occur in granular flows.