Politecnico di Milano, 20133 Milano, Italy.
Università di Trento, 38123 Trento, Italy.
Phys Rev Lett. 2015 Nov 6;115(19):194501. doi: 10.1103/PhysRevLett.115.194501. Epub 2015 Nov 3.
We reanalyze previous experimental measurements of solid volume fraction, mean velocity, and velocity fluctuations in collisional suspensions of plastic cylinders and water flowing over inclined, erodible beds. We show that the particle pressure scales with the granular temperature, as predicted by kinetic theory of granular gases. The assumption that the particle shear stress is also well predicted by kinetic theory permits us to determine the fluid shear stress and the effective fluid viscosity from the experiments. The fluid viscosity can be decomposed into turbulent and granularlike components: the turbulent viscosity can be modeled using a mixing length, which is a decreasing function of the local volume fraction and does not depend upon the distance from the bed; the granularlike viscosity, associated with the transfer of momentum due to the conjugate motion of the fluid mass added to the particles, can be modeled by replacing the particle density with the density of the added fluid mass in the viscosity of kinetic theory.
我们重新分析了先前关于塑料圆柱碰撞悬浮液和水在倾斜侵蚀床面上流动的固相体积分数、平均速度和速度波动的实验测量结果。我们表明，颗粒压力与颗粒温度按颗粒气体动理论预测的那样成比例。颗粒切应力也由动理论很好地预测的假设，使得我们能够从实验中确定流体切应力和有效流体粘度。流体粘度可以分解为湍流和类似颗粒的成分：湍流粘度可以使用混合长度来建模，混合长度是局部体积分数的递减函数，并且不依赖于距床面的距离；与由于添加到颗粒的流体质量的共轭运动引起的动量传递相关的类似颗粒的粘度，可以通过用添加到流体质量的密度代替动理论粘度中的颗粒密度来建模。
