Modelling sheet–flow sediment transport in wave–bottom boundary layers using discrete–element modelling
Modelling sheet–flow sediment transport in wave–bottom boundary layers using discrete–element modelling
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DOI：
10.1098/rsta.2004.1427
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
J. Calantoni;K. Todd Holland;T. G. Drake
中科院分区：
文献类型：
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作者：
J. Calantoni;K. Todd Holland;T. G. Drake
振荡边界层中的沉积物输送是驱动沿海地貌变化的过程。近岸地区的大多数床荷输送公式通过参数化颗粒之间的相互作用来包含最小尺度的物理现象。相比之下，我们使用离散元模型直接模拟波底边界层中的颗粒物理，该模型由三维粒子相通过浮力、阻力和附加质量通过牛顿第三定律耦合到一维流体相组成。颗粒沉积物相是使用通过重叠两个球体形成的离散颗粒来模拟的，以近似天然颗粒。这些复合颗粒的每个球体的大小和重叠程度都可以变化，以生成一系列非球形颗粒。对各种形状颗粒的模拟表明，临界角（颗粒堆从静止状态缓慢倾斜时将失效的角度）从球形颗粒的约 26° 增加到哑铃形状的高度非球形复合颗粒的近 39°。使用休止角约为 33° 且 Corey 形状因子大于约 0.8 的复合颗粒进行振荡片流模拟，类似于海滩沙的特性。与使用球形颗粒进行的类似模拟相比，使用复合颗粒进行的层流模拟的结果与实验室测量结果更加一致。研究结果表明，颗粒形状可能是确定床荷通量的重要因素，特别是对于较大的床坡度。
Sediment transport in oscillatory boundary layers is a process that drives coastal geomorphological change. Most formulae for bed–load transport in nearshore regions subsume the smallest–scale physics of the phenomena by parametrizing interactions amongst particles. In contrast, we directly simulate granular physics in the wave–bottom boundary layer using a discrete–element model comprised of a three–dimensional particle phase coupled to a one–dimensional fluid phase via Newton's third law through forces of buoyancy, drag and added mass. The particulate sediment phase is modelled using discrete particles formed to approximate natural grains by overlapping two spheres. Both the size of each sphere and the degree of overlap can be varied for these composite particles to generate a range of non–spherical grains. Simulations of particles having a range of shapes showed that the critical angle—the angle at which a grain pile will fail when tilted slowly from rest—increases from approximately 26° for spherical particles to nearly 39° for highly non–spherical composite particles having a dumbbell shape. Simulations of oscillatory sheet flow were conducted using composite particles with an angle of repose of approximately 33° and a Corey shape factor greater than about 0.8, similar to the properties of beach sand. The results from the sheet–flow simulations with composite particles agreed more closely with laboratory measurements than similar simulations conducted using spherical particles. The findings suggest that particle shape may be an important factor for determining bed–load flux, particularly for larger bed slopes.