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Using PIV to measure granular temperature in saturated unsteady polydisperse granular flows

机译：使用PIV测量饱和非稳态多分散颗粒流中的颗粒温度

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摘要

The motion of debris flows, gravity-driven fast moving mixtures of rock, soil and water can be interpreted using the theories developed to describe the shearing motion of highly concentrated granular fluid flows. Frictional, collisional and viscous stress transfer between particles and fluid characterizes the mechanics of debris flows. To quantify the influence of collisional stress transfer, kinetic models have been proposed. Collisions among particles result in random fluctuations in their velocity that can be represented by their granular temperature, T. In this paper particle image velocimetry, PIV, is used to measure the instantaneous velocity field found internally to a physical model of an unsteady debris flow created by using "transparent soil"-i.e. a mixture of graded glass particles and a refractively matched fluid. The ensemble possesses bulk properties similar to that of real soil-pore fluid mixtures, but has the advantage of giving optical access to the interior of the flow by use of plane laser induced fluorescence, PLIF. The relationship between PIV patch size and particle size distribution for the front and tail of the flows is examined in order to assess their influences on the measured granular temperature of the system. We find that while PIV can be used to ascertain values of granular temperature in dense granular flows, due to increasing spatial correlation with widening gradation, a technique proposed to infer the true granular temperature may be limited to flows of relatively uniform particle size or large bulk.
机译：可以使用为描述高浓度颗粒状流体的剪切运动而开发的理论来解释泥石流的运动，重力驱动的岩石，土壤和水的快速移动混合物。颗粒与流体之间的摩擦，碰撞和粘性应力传递是泥石流力学的特征。为了量化碰撞应力传递的影响，提出了动力学模型。粒子之间的碰撞会导致其速度随机波动，可以用粒子温度T来表示。在本文中，粒子图像测速仪PIV用于测量在内部非恒定泥石流物理模型中发现的瞬时速度场通过使用“透明土壤”，即渐变玻璃颗粒和折射匹配的液体的混合物。该集合体具有与真实的土壤-孔隙流体混合物类似的整体性质，但是具有通过使用平面激光诱导的荧光PLIF光学进入流体内部的优势。检查PIV贴片大小与流动前后的粒径分布之间的关系，以评估它们对系统测得的颗粒温度的影响。我们发现，虽然PIV可以用于确定稠密颗粒流中的颗粒温度值，但是由于空间相关性随逐渐变大的梯度而增加，建议的用于推断真实颗粒温度的技术可能仅限于粒径相对均匀或体积较大的流。

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