Discrete particle model for sheet flow sediment transport in the nearshore
Discrete particle model for sheet flow sediment transport in the nearshore
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DOI：
10.1029/2000jc000611
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发表时间：
2001-09
影响因子：
--
通讯作者：
T. G. Drake;J. Calantoni
中科院分区：
文献类型：
--
作者：
T. G. Drake;J. Calantoni
全三维离散粒子计算机模拟的高浓度片流运输振荡流量化的影响，流体加速度推移质运输在近岸海洋环境中的典型的高度不稳定流。一个简单的冲量动量方法解释了模拟结果，并形成了广泛使用的能量输沙公式的基础上增加了一个加速度相关的条款。当波浪形状接近碎波带钻孔的剖面特征时，由加速度项预测的输运变得越来越重要。模拟集成F = ma和每个球体的扭矩的相应方程组。接触颗粒之间的法向力和切向力分别是球心之间的距离和接触点处的相对切向位移的线性函数;颗粒之间的相互作用是非弹性和摩擦的。由表面重力波的通过产生的压力梯度力驱动薄水平流体层的堆叠中的流体和颗粒运动，所述薄水平流体层交换动量并对颗粒施加流体阻力、附加质量和浮力。模拟的颗粒流体组合的传输特性是强大的颗粒的材料特性的大的变化。模拟的输运率同意与现有的实验数据不稳定的粗砂输运的推移质运动，推移质颗粒的分散，颗粒分离的大小和密度的模式是定性一致的，与现有的颗粒尺度观测天然颗粒推移质输运。
Fully three-dimensional discrete particle computer simulations of high-concentration sheet flow transport in oscillatory flows quantify the effect of fluid acceleration on bed load transport in highly unsteady flows typical of nearshore marine environments. A simple impulse-momentum approach explains simulation results and forms the basis for adding an acceleration-related term to widely used energetics sediment transport formulae. Transport predicted by the acceleration term becomes increasingly significant as wave shape approaches the sawtooth profile characteristic of surf zone bores. Simulations integrate F = ma and a corresponding set of equations for the torques for each sphere. Normal and tangential forces between contacting particles are linear functions of the distance between sphere centers and the relative tangential displacement at the contact point, respectively; particle interactions are both inelastic and frictional. Pressure gradient forces generated by the passage of surface gravity waves drive fluid and particle motion in a stack of thin horizontal fluid layers that exchange momentum and exert fluid drag, added mass, and buoyancy forces on particles. Transport properties of the simulated granular-fluid assemblage are robust to large variations in material properties of the particles. Simulated transport rates agree with available experimental data for unsteady transport of coarse sands; the mode of bed load motion, dispersion of bed load particles, and particle segregation by size and density are qualitatively consistent with available particle-scale observations of bed load transport of natural particles.